Re: [PATCH] Extract initrd free logic from arch-specific code.

[Ingo Molnar]

* Shea Levy  wrote:

> > Please also put it into Documentation/features/.
> 
> I switched this patch series (the latest revision v6 was just posted) to
> using weak symbols instead of Kconfig. Does it still warrant documentation?

Probably not.

Thanks,

Ingo

Re: [PATCH] Extract initrd free logic from arch-specific code.

[Shea Levy]

Hi Ingo,

Ingo Molnar  writes:

> * Shea Levy  wrote:
>
>> Now only those architectures that have custom initrd free requirements
>> need to define free_initrd_mem.
>> 
>> Signed-off-by: Shea Levy 
>
> Please put the Kconfig symbol name this patch introduces both into the title, 
> so 
> that people know what to grep for.
>
>> ---
>>  arch/alpha/mm/init.c  |  8 
>>  arch/arc/mm/init.c|  7 ---
>>  arch/arm/Kconfig  |  1 +
>>  arch/arm64/Kconfig|  1 +
>>  arch/blackfin/Kconfig |  1 +
>>  arch/c6x/mm/init.c|  7 ---
>>  arch/cris/Kconfig |  1 +
>>  arch/frv/mm/init.c| 11 ---
>>  arch/h8300/mm/init.c  |  7 ---
>>  arch/hexagon/Kconfig  |  1 +
>>  arch/ia64/Kconfig |  1 +
>>  arch/m32r/Kconfig |  1 +
>>  arch/m32r/mm/init.c   | 11 ---
>>  arch/m68k/mm/init.c   |  7 ---
>>  arch/metag/Kconfig|  1 +
>>  arch/microblaze/mm/init.c |  7 ---
>>  arch/mips/Kconfig |  1 +
>>  arch/mn10300/Kconfig  |  1 +
>>  arch/nios2/mm/init.c  |  7 ---
>>  arch/openrisc/mm/init.c   |  7 ---
>>  arch/parisc/mm/init.c |  7 ---
>>  arch/powerpc/mm/mem.c |  7 ---
>>  arch/riscv/mm/init.c  |  6 --
>>  arch/s390/Kconfig |  1 +
>>  arch/score/Kconfig|  1 +
>>  arch/sh/mm/init.c |  7 ---
>>  arch/sparc/Kconfig|  1 +
>>  arch/tile/Kconfig |  1 +
>>  arch/um/kernel/mem.c  |  7 ---
>>  arch/unicore32/Kconfig|  1 +
>>  arch/x86/Kconfig  |  1 +
>>  arch/xtensa/Kconfig   |  1 +
>>  init/initramfs.c  |  7 +++
>>  usr/Kconfig   |  4 
>>  34 files changed, 28 insertions(+), 113 deletions(-)
>
> Please also put it into Documentation/features/.
>

I switched this patch series (the latest revision v6 was just posted) to
using weak symbols instead of Kconfig. Does it still warrant documentation?

>
>> diff --git a/usr/Kconfig b/usr/Kconfig
>> index 43658b8a975e..7a94f6df39bf 100644
>> --- a/usr/Kconfig
>> +++ b/usr/Kconfig
>> @@ -233,3 +233,7 @@ config INITRAMFS_COMPRESSION
>>  default ".lzma" if RD_LZMA
>>  default ".bz2"  if RD_BZIP2
>>  default ""
>> +
>> +config HAVE_ARCH_FREE_INITRD_MEM
>> +bool
>> +default n
>
> Help text would be nice, to tell arch maintainers what the purpose of this 
> switch 
> is.
>
> Also, a nit, I think this should be named "ARCH_HAS_FREE_INITRD_MEM", which 
> is the 
> dominant pattern:
>
> triton:~/tip> git grep 'select.*ARCH' arch/x86/Kconfig* | cut -f2 | cut -d_ 
> -f1-2 | sort | uniq -c | sort -n
> ...
>   2 select ARCH_USES
>   2 select ARCH_WANTS
>   3 select ARCH_MIGHT
>   3 select ARCH_WANT
>   4 select ARCH_SUPPORTS
>   4 select ARCH_USE
>  16 select HAVE_ARCH
>  23 select ARCH_HAS
>
> It also reads nicely in English:
>
>   "arch has free_initrd_mem()"
>
> While the other makes little sense:
>
>   "have arch free_initrd_mem()"
>
> ?
>
> Thanks,
>
>   Ingo

Thanks,
Shea


signature.asc
Description: PGP signature

Re: [PATCH] Extract initrd free logic from arch-specific code.

[Ingo Molnar]

* Shea Levy  wrote:

> Now only those architectures that have custom initrd free requirements
> need to define free_initrd_mem.
> 
> Signed-off-by: Shea Levy 

Please put the Kconfig symbol name this patch introduces both into the title, 
so 
that people know what to grep for.

> ---
>  arch/alpha/mm/init.c  |  8 
>  arch/arc/mm/init.c|  7 ---
>  arch/arm/Kconfig  |  1 +
>  arch/arm64/Kconfig|  1 +
>  arch/blackfin/Kconfig |  1 +
>  arch/c6x/mm/init.c|  7 ---
>  arch/cris/Kconfig |  1 +
>  arch/frv/mm/init.c| 11 ---
>  arch/h8300/mm/init.c  |  7 ---
>  arch/hexagon/Kconfig  |  1 +
>  arch/ia64/Kconfig |  1 +
>  arch/m32r/Kconfig |  1 +
>  arch/m32r/mm/init.c   | 11 ---
>  arch/m68k/mm/init.c   |  7 ---
>  arch/metag/Kconfig|  1 +
>  arch/microblaze/mm/init.c |  7 ---
>  arch/mips/Kconfig |  1 +
>  arch/mn10300/Kconfig  |  1 +
>  arch/nios2/mm/init.c  |  7 ---
>  arch/openrisc/mm/init.c   |  7 ---
>  arch/parisc/mm/init.c |  7 ---
>  arch/powerpc/mm/mem.c |  7 ---
>  arch/riscv/mm/init.c  |  6 --
>  arch/s390/Kconfig |  1 +
>  arch/score/Kconfig|  1 +
>  arch/sh/mm/init.c |  7 ---
>  arch/sparc/Kconfig|  1 +
>  arch/tile/Kconfig |  1 +
>  arch/um/kernel/mem.c  |  7 ---
>  arch/unicore32/Kconfig|  1 +
>  arch/x86/Kconfig  |  1 +
>  arch/xtensa/Kconfig   |  1 +
>  init/initramfs.c  |  7 +++
>  usr/Kconfig   |  4 
>  34 files changed, 28 insertions(+), 113 deletions(-)

Please also put it into Documentation/features/.

> diff --git a/usr/Kconfig b/usr/Kconfig
> index 43658b8a975e..7a94f6df39bf 100644
> --- a/usr/Kconfig
> +++ b/usr/Kconfig
> @@ -233,3 +233,7 @@ config INITRAMFS_COMPRESSION
>   default ".lzma" if RD_LZMA
>   default ".bz2"  if RD_BZIP2
>   default ""
> +
> +config HAVE_ARCH_FREE_INITRD_MEM
> + bool
> + default n

Help text would be nice, to tell arch maintainers what the purpose of this 
switch 
is.

Also, a nit, I think this should be named "ARCH_HAS_FREE_INITRD_MEM", which is 
the 
dominant pattern:

triton:~/tip> git grep 'select.*ARCH' arch/x86/Kconfig* | cut -f2 | cut -d_ 
-f1-2 | sort | uniq -c | sort -n
...
  2 select ARCH_USES
  2 select ARCH_WANTS
  3 select ARCH_MIGHT
  3 select ARCH_WANT
  4 select ARCH_SUPPORTS
  4 select ARCH_USE
 16 select HAVE_ARCH
 23 select ARCH_HAS

It also reads nicely in English:

  "arch has free_initrd_mem()"

While the other makes little sense:

  "have arch free_initrd_mem()"

?

Thanks,

Ingo

Re: [PATCH] Extract initrd free logic from arch-specific code.

[kbuild test robot]

Hi Shea,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on linus/master]
[also build test WARNING on v4.16-rc7]
[cannot apply to next-20180329]
[if your patch is applied to the wrong git tree, please drop us a note to help 
improve the system]

url:
https://github.com/0day-ci/linux/commits/Shea-Levy/Extract-initrd-free-logic-from-arch-specific-code/20180330-085507
config: m32r-m32104ut_defconfig (attached as .config)
compiler: m32r-linux-gcc (GCC) 7.2.0
reproduce:
wget 
https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O 
~/bin/make.cross
chmod +x ~/bin/make.cross
# save the attached .config to linux build tree
make.cross ARCH=m32r 

All warnings (new ones prefixed by >>):

warning: (M32R) selects HAVE_ARCH_FREE_INITRD_MEM which has unmet direct 
dependencies (BLK_DEV_INITRD)

---
0-DAY kernel test infrastructureOpen Source Technology Center
https://lists.01.org/pipermail/kbuild-all   Intel Corporation


.config.gz
Description: application/gzip

Re: [PATCH] Extract initrd free logic from arch-specific code.

[kbuild test robot]

Hi Shea,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on linus/master]
[also build test WARNING on v4.16-rc7]
[cannot apply to next-20180329]
[if your patch is applied to the wrong git tree, please drop us a note to help 
improve the system]

url:
https://github.com/0day-ci/linux/commits/Shea-Levy/Extract-initrd-free-logic-from-arch-specific-code/20180330-085507
config: ia64-allnoconfig (attached as .config)
compiler: ia64-linux-gcc (GCC) 7.2.0
reproduce:
wget 
https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O 
~/bin/make.cross
chmod +x ~/bin/make.cross
# save the attached .config to linux build tree
make.cross ARCH=ia64 

All warnings (new ones prefixed by >>):

warning: (IA64) selects HAVE_ARCH_FREE_INITRD_MEM which has unmet direct 
dependencies (BLK_DEV_INITRD)

---
0-DAY kernel test infrastructureOpen Source Technology Center
https://lists.01.org/pipermail/kbuild-all   Intel Corporation


.config.gz
Description: application/gzip

Re: [PATCH] Extract initrd free logic from arch-specific code.

[Rob Landley]

On 03/29/2018 10:27 AM, Russell King - ARM Linux wrote:
> On Thu, Mar 29, 2018 at 09:37:52AM +1100, Oliver wrote:
>> On Thu, Mar 29, 2018 at 9:14 AM, Russell King - ARM Linux
>>> LD_DEAD_CODE_DATA_ELIMINATION is a symbol without a prompt, and from
>>> what I can see, nothing selects it.  Therefore, the symbol is always
>>> disabled, and so the feature never gets used in mainline kernels.
>>>
>>> Brings up the obvious question - why is it there if it's completely
>>> unused?  (Maybe to cause confusion, and allowing a justification
>>> for __weak ?)
>>
>> IIRC Nick had some patches to do the arch enablement for powerpc, but
>> I'm not sure what happened to them though. I suspect it just fell down
>> Nick's ever growing TODO list.
> 
> I've given it a go on ARM, marking every linker-built table with KEEP()
> and comparing the System.map files.  The resulting kernel is around
> 150k smaller, which seems good.
> 
> However, it doesn't boot - and I don't know why.  Booting the kernel
> under kvmtool in a VM using virtio-console, I can find no way to get
> any kernel messages out of it.  Using lkvm debug, I can see that the
> PC is stuck inside die(), and that's the only information I have.

qemu-system-arm's "-s" option lets you hook to the hardware with gdb, as if
using one of those jtags that speaks gdbserver protocol. It stops waiting for
you to attach with 'target remote' it, then 'file vmlinux' to load the 
symbols...

The miniconfig and qemu invocation I use for arm64 are attached, tested with
2.11.0 on a 4.14 kernel. You should be able to just "qemu-aarch64.sh -s" and
then probably "target remote 127.0.0.1:1234"? (Been a while since I've used it,
don't have a cross-gdb for arm64 lying around...)

Sigh, I just tried -s and qemu 2.11.0 is _not_ waiting for gdb to attach on
arm64, despite what the docs say:

$ qemu-system-aarch64 --help | grep gdb
-gdb devwait for gdb connection on 'dev'
-s  shorthand for -gdb tcp::1234

Another random regression in qemu, gee what a surprise.

> It dies before bringing up the other CPUs, so it's a very early death.
> 
> I don't think other console types are available under ARM64.

I've often found useful the two line version of:

https://balau82.wordpress.com/2010/02/28/hello-world-for-bare-metal-arm-using-qemu/

Which is generally some variant of:

{char *XX = "blah"; while (*XX) {while (*SERIAL_STATUS_REGISTER & OUT_READY);
*SERIAL_OUT = *XX++;}}

(I.E. balu cheated not spinning checking the ready-for-next-byte bit, because
qemu's always angry.)

That trick lets you cut and paste a print statement into all sorts of early
hardware nonsense, on most architectures. You just have to look up
SERIAL_STATUS_REGISTER, OUT_OK_BIT, and SERIAL_OUT values for the serial port du
jour.

That said I've mostly used it in things like u-boot. I dunno at what point the
kernel's done enough setup that direct banging on registers would stop working.
(Works in the decompresion code, anyway.) And it assumes the port's set to the
right speed (usually left there by the bootloader)...

Rob
# make ARCH=arm64 allnoconfig KCONFIG_ALLCONFIG=aarch64.miniconf
# make ARCH=arm64 -j $(nproc)
# boot arch/arm64/boot/Image


CONFIG_MMU=y
CONFIG_ARCH_MULTI_V7=y
CONFIG_ARCH_VIRT=y
CONFIG_SOC_DRA7XX=y
CONFIG_ARCH_OMAP2PLUS_TYPICAL=y
CONFIG_ARCH_ALPINE=y
CONFIG_ARM_THUMB=y
CONFIG_VDSO=y
CONFIG_CPU_IDLE=y
CONFIG_ARM_CPUIDLE=y
CONFIG_KERNEL_MODE_NEON=y

CONFIG_SERIAL_AMBA_PL011=y
CONFIG_SERIAL_AMBA_PL011_CONSOLE=y

CONFIG_RTC_CLASS=y
CONFIG_RTC_HCTOSYS=y
CONFIG_RTC_DRV_PL031=y

CONFIG_NET_CORE=y
CONFIG_VIRTIO_NET=y

CONFIG_PCI=y
CONFIG_PCI_HOST_GENERIC=y
CONFIG_VIRTIO_BLK=y
CONFIG_VIRTIO_PCI=y
CONFIG_VIRTIO_MMIO=y

CONFIG_ATA=y
CONFIG_ATA_SFF=y
CONFIG_ATA_BMDMA=y
CONFIG_ATA_PIIX=y

CONFIG_PATA_PLATFORM=y
CONFIG_PATA_OF_PLATFORM=y
CONFIG_ATA_GENERIC=y


# CONFIG_EMBEDDED is not set
CONFIG_EARLY_PRINTK=y
CONFIG_BINFMT_ELF=y
CONFIG_BINFMT_SCRIPT=y
CONFIG_NO_HZ=y
CONFIG_HIGH_RES_TIMERS=y

CONFIG_BLK_DEV=y
CONFIG_BLK_DEV_INITRD=y
CONFIG_RD_GZIP=y

CONFIG_BLK_DEV_LOOP=y
CONFIG_EXT4_FS=y
CONFIG_EXT4_USE_FOR_EXT2=y
CONFIG_VFAT_FS=y
CONFIG_FAT_DEFAULT_UTF8=y
CONFIG_MISC_FILESYSTEMS=y
CONFIG_SQUASHFS=y
CONFIG_SQUASHFS_XATTR=y
CONFIG_SQUASHFS_ZLIB=y
CONFIG_DEVTMPFS=y
CONFIG_DEVTMPFS_MOUNT=y
CONFIG_TMPFS=y
CONFIG_TMPFS_POSIX_ACL=y

CONFIG_NET=y
CONFIG_PACKET=y
CONFIG_UNIX=y
CONFIG_INET=y
CONFIG_IPV6=y
CONFIG_NETDEVICES=y
#CONFIG_NET_CORE=y
#CONFIG_NETCONSOLE=y
CONFIG_ETHERNET=y



qemu-aarch64.sh
Description: application/shellscript

Re: [PATCH] Extract initrd free logic from arch-specific code.

[Russell King - ARM Linux]

On Thu, Mar 29, 2018 at 05:53:14PM +0100, Marc Zyngier wrote:
> On Thu, 29 Mar 2018 16:58:27 +0100,
> Russell King - ARM Linux wrote:
> > 
> > On Thu, Mar 29, 2018 at 05:43:47PM +0200, Geert Uytterhoeven wrote:
> > > On Thu, Mar 29, 2018 at 5:27 PM, Russell King - ARM Linux
> > >  wrote:
> > > > On Thu, Mar 29, 2018 at 09:37:52AM +1100, Oliver wrote:
> > > >> On Thu, Mar 29, 2018 at 9:14 AM, Russell King - ARM Linux
> > > >>  wrote:
> > > >> > On Wed, Mar 28, 2018 at 02:04:22PM -0500, Rob Landley wrote:
> > > >> >> On 03/28/2018 11:48 AM, Russell King - ARM Linux wrote:
> > > >> >> > On Wed, Mar 28, 2018 at 10:58:51AM -0500, Rob Landley wrote:
> > > >> >> >> On 03/28/2018 10:26 AM, Shea Levy wrote:
> > > >> >> >>> Now only those architectures that have custom initrd free 
> > > >> >> >>> requirements
> > > >> >> >>> need to define free_initrd_mem.
> > > >> >> >> ...
> > > >> >> >>> --- a/arch/arc/mm/init.c
> > > >> >> >>> +++ b/arch/arc/mm/init.c
> > > >> >> >>> @@ -229,10 +229,3 @@ void __ref free_initmem(void)
> > > >> >> >>>  {
> > > >> >> >>>   free_initmem_default(-1);
> > > >> >> >>>  }
> > > >> >> >>> -
> > > >> >> >>> -#ifdef CONFIG_BLK_DEV_INITRD
> > > >> >> >>> -void __init free_initrd_mem(unsigned long start, unsigned long 
> > > >> >> >>> end)
> > > >> >> >>> -{
> > > >> >> >>> - free_reserved_area((void *)start, (void *)end, -1, "initrd");
> > > >> >> >>> -}
> > > >> >> >>> -#endif
> > > >> >> >>> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> > > >> >> >>> index 3f972e83909b..19d1c5594e2d 100644
> > > >> >> >>> --- a/arch/arm/Kconfig
> > > >> >> >>> +++ b/arch/arm/Kconfig
> > > >> >> >>> @@ -47,6 +47,7 @@ config ARM
> > > >> >> >>>   select HARDIRQS_SW_RESEND
> > > >> >> >>>   select HAVE_ARCH_AUDITSYSCALL if (AEABI && !OABI_COMPAT)
> > > >> >> >>>   select HAVE_ARCH_BITREVERSE if (CPU_32v7M || CPU_32v7) && 
> > > >> >> >>> !CPU_32v6
> > > >> >> >>> + select HAVE_ARCH_FREE_INITRD_MEM
> > > >> >> >>>   select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL && 
> > > >> >> >>> !CPU_ENDIAN_BE32 && MMU
> > > >> >> >>>   select HAVE_ARCH_KGDB if !CPU_ENDIAN_BE32 && MMU
> > > >> >> >>>   select HAVE_ARCH_MMAP_RND_BITS if MMU
> > > >> >> >>
> > > >> >> >> Isn't this why weak symbols were invented?
> > > >> >> >
> > > >> >> > Weak symbols means that we end up with both the weakly-referenced 
> > > >> >> > code
> > > >> >> > and the arch code in the kernel image.  That's fine if the weak 
> > > >> >> > code
> > > >> >> > is small.
> > > >> >>
> > > >> >> The kernel's been able to build with link time garbage collection 
> > > >> >> since 2016:
> > > >> >>
> > > >> >> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b67067f1176d
> > > >> >>
> > > >> >> Wouldn't that remove the unused one?
> > > >> >
> > > >> > Probably, if anyone bothered to use that, which they don't.
> > > >> >
> > > >> > LD_DEAD_CODE_DATA_ELIMINATION is a symbol without a prompt, and from
> > > >> > what I can see, nothing selects it.  Therefore, the symbol is always
> > > >> > disabled, and so the feature never gets used in mainline kernels.
> > > >> >
> > > >> > Brings up the obvious question - why is it there if it's completely
> > > >> > unused?  (Maybe to cause confusion, and allowing a justification
> > > >> > for __weak ?)
> > > >>
> > > >> IIRC Nick had some patches to do the arch enablement for powerpc, but
> > > >> I'm not sure what happened to them though. I suspect it just fell down
> > > >> Nick's ever growing TODO list.
> > > >
> > > > I've given it a go on ARM, marking every linker-built table with KEEP()
> > > > and comparing the System.map files.  The resulting kernel is around
> > > > 150k smaller, which seems good.
> > > >
> > > > However, it doesn't boot - and I don't know why.  Booting the kernel
> > > > under kvmtool in a VM using virtio-console, I can find no way to get
> > > > any kernel messages out of it.  Using lkvm debug, I can see that the
> > > > PC is stuck inside die(), and that's the only information I have.
> > > > It dies before bringing up the other CPUs, so it's a very early death.
> > > >
> > > > I don't think other console types are available under ARM64.
> > > 
> > > earlycon?
> > 
> > Through what - as I say above, I think the only thing that's present is
> > virtio-console, and the virtio stack only get initialised much later in
> > boot.
> > 
> > Eg, there's the memory-based virtio driver which interfaces any virtio
> > driver to a memory-based ring structures for communication with the host
> > (drivers/virtio/virtio_mmio.c) which is initialised at module_init()
> > time, and so isn't available for earlycon.
> > 
> > I don't think merely changing the module_init() calls in the appropriate
> > virtio bits will suffice - it's why I pointed out that it dies before
> > SMP initialisation, which also means that it dies before we start
> > running the initcalls for subsystems and drivers.
> > 
> > I'm not aware of there being an 

Re: [PATCH] Extract initrd free logic from arch-specific code.

[Rob Landley]

On 03/28/2018 05:14 PM, Russell King - ARM Linux wrote:
> On Wed, Mar 28, 2018 at 02:04:22PM -0500, Rob Landley wrote:
>>
>>
>> On 03/28/2018 11:48 AM, Russell King - ARM Linux wrote:
>>> On Wed, Mar 28, 2018 at 10:58:51AM -0500, Rob Landley wrote:
 On 03/28/2018 10:26 AM, Shea Levy wrote:
> Now only those architectures that have custom initrd free requirements
> need to define free_initrd_mem.
 ...
> --- a/arch/arc/mm/init.c
> +++ b/arch/arc/mm/init.c
> @@ -229,10 +229,3 @@ void __ref free_initmem(void)
>  {
>   free_initmem_default(-1);
>  }
> -
> -#ifdef CONFIG_BLK_DEV_INITRD
> -void __init free_initrd_mem(unsigned long start, unsigned long end)
> -{
> - free_reserved_area((void *)start, (void *)end, -1, "initrd");
> -}
> -#endif
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index 3f972e83909b..19d1c5594e2d 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -47,6 +47,7 @@ config ARM
>   select HARDIRQS_SW_RESEND
>   select HAVE_ARCH_AUDITSYSCALL if (AEABI && !OABI_COMPAT)
>   select HAVE_ARCH_BITREVERSE if (CPU_32v7M || CPU_32v7) && !CPU_32v6
> + select HAVE_ARCH_FREE_INITRD_MEM
>   select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL && !CPU_ENDIAN_BE32 && MMU
>   select HAVE_ARCH_KGDB if !CPU_ENDIAN_BE32 && MMU
>   select HAVE_ARCH_MMAP_RND_BITS if MMU

 Isn't this why weak symbols were invented?
>>>
>>> Weak symbols means that we end up with both the weakly-referenced code
>>> and the arch code in the kernel image.  That's fine if the weak code
>>> is small.
>>
>> The kernel's been able to build with link time garbage collection since 2016:
>>
>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b67067f1176d
>>
>> Wouldn't that remove the unused one?
> 
> Probably, if anyone bothered to use that, which they don't.
> 
> LD_DEAD_CODE_DATA_ELIMINATION is a symbol without a prompt, and from
> what I can see, nothing selects it.  Therefore, the symbol is always
> disabled, and so the feature never gets used in mainline kernels.

It looks like there are per-architecture linker scripts that need to be updated?
So if an architecture supports it, it's always done (well, it probes for the
toolchain supporting the flag). And if the architecture doesn't support it, the
linker script needs to be updated to mark sections with "I know nothing seems to
reference this at the ELF level but keep it anyway, we're pulling an assembly
trick".

> Brings up the obvious question - why is it there if it's completely
> unused?  (Maybe to cause confusion, and allowing a justification
> for __weak ?)

Presumably it will become the default on architectures as their linker scripts
are converted. Once they're all converted the config symbol can go away. (Given
the move to requiring gcc 4.7 or whatever it is, there can't be an architecture
depending on a toolchain that _doesn't_ support it after that point. I doubt you
can pair gcc 4.7 with a >12 year old binutils and expect good things...)

Rob

Re: [PATCH] Extract initrd free logic from arch-specific code.

[Marc Zyngier]

On Thu, 29 Mar 2018 18:32:47 +0100,
Russell King - ARM Linux wrote:
> 
> On Thu, Mar 29, 2018 at 05:53:14PM +0100, Marc Zyngier wrote:
> > On Thu, 29 Mar 2018 16:58:27 +0100,
> > Russell King - ARM Linux wrote:

[...]

> > > I'm not aware of there being an emulated UART in the guest's address
> > > space, so serial based stuff doesn't work.
> > 
> > "earlycon=uart,mmio,0x3f8" is what you're looking for:
> 
> Does that also mean that we have a RTC at the standard PC IO addresses
> as well, but in mmio space?

There is one, together with an i8042. Not exposed in the DT though.

M.

-- 
Jazz is not dead, it just smell funny.

Re: [PATCH] Extract initrd free logic from arch-specific code.

[Russell King - ARM Linux]

On Thu, Mar 29, 2018 at 11:39:24AM -0500, Rob Landley wrote:
> 
> 
> On 03/28/2018 05:14 PM, Russell King - ARM Linux wrote:
> > On Wed, Mar 28, 2018 at 02:04:22PM -0500, Rob Landley wrote:
> >>
> >>
> >> On 03/28/2018 11:48 AM, Russell King - ARM Linux wrote:
> >>> On Wed, Mar 28, 2018 at 10:58:51AM -0500, Rob Landley wrote:
>  On 03/28/2018 10:26 AM, Shea Levy wrote:
> > Now only those architectures that have custom initrd free requirements
> > need to define free_initrd_mem.
>  ...
> > --- a/arch/arc/mm/init.c
> > +++ b/arch/arc/mm/init.c
> > @@ -229,10 +229,3 @@ void __ref free_initmem(void)
> >  {
> > free_initmem_default(-1);
> >  }
> > -
> > -#ifdef CONFIG_BLK_DEV_INITRD
> > -void __init free_initrd_mem(unsigned long start, unsigned long end)
> > -{
> > -   free_reserved_area((void *)start, (void *)end, -1, "initrd");
> > -}
> > -#endif
> > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> > index 3f972e83909b..19d1c5594e2d 100644
> > --- a/arch/arm/Kconfig
> > +++ b/arch/arm/Kconfig
> > @@ -47,6 +47,7 @@ config ARM
> > select HARDIRQS_SW_RESEND
> > select HAVE_ARCH_AUDITSYSCALL if (AEABI && !OABI_COMPAT)
> > select HAVE_ARCH_BITREVERSE if (CPU_32v7M || CPU_32v7) && 
> > !CPU_32v6
> > +   select HAVE_ARCH_FREE_INITRD_MEM
> > select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL && !CPU_ENDIAN_BE32 
> > && MMU
> > select HAVE_ARCH_KGDB if !CPU_ENDIAN_BE32 && MMU
> > select HAVE_ARCH_MMAP_RND_BITS if MMU
> 
>  Isn't this why weak symbols were invented?
> >>>
> >>> Weak symbols means that we end up with both the weakly-referenced code
> >>> and the arch code in the kernel image.  That's fine if the weak code
> >>> is small.
> >>
> >> The kernel's been able to build with link time garbage collection since 
> >> 2016:
> >>
> >> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b67067f1176d
> >>
> >> Wouldn't that remove the unused one?
> > 
> > Probably, if anyone bothered to use that, which they don't.
> > 
> > LD_DEAD_CODE_DATA_ELIMINATION is a symbol without a prompt, and from
> > what I can see, nothing selects it.  Therefore, the symbol is always
> > disabled, and so the feature never gets used in mainline kernels.
> 
> It looks like there are per-architecture linker scripts that need to be 
> updated?
> So if an architecture supports it, it's always done (well, it probes for the
> toolchain supporting the flag). And if the architecture doesn't support it, 
> the
> linker script needs to be updated to mark sections with "I know nothing seems 
> to
> reference this at the ELF level but keep it anyway, we're pulling an assembly
> trick".

It looks like it needs much more than just architecture changes as the
reason it fails on ARM is because the init thread structure is missing
due to missing KEEP()s in INIT_TASK_DATA().  Probably means it doesn't
work anywhere.

8<===
From: Russell King 
Subject: [PATCH] Fix LD_DEAD_CODE_DATA_ELIMINATION

LD_DEAD_CODE_DATA_ELIMINATION fails to boot on ARM because the linker
eliminates the init thread data from the bottom of the init threads
stack.  This causes recursive faults that end up overwriting parts
of the kernel before they can print any message.

Signed-off-by: Russell King 
---
 include/asm-generic/vmlinux.lds.h |4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/asm-generic/vmlinux.lds.h 
b/include/asm-generic/vmlinux.lds.h
index 1ab0e520d6fc..41af8a74aae4 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -279,8 +279,8 @@
VMLINUX_SYMBOL(__start_init_task) = .;  \
VMLINUX_SYMBOL(init_thread_union) = .;  \
VMLINUX_SYMBOL(init_stack) = .; \
-   *(.data..init_task) \
-   *(.data..init_thread_info)  \
+   KEEP(*(.data..init_task))   \
+   KEEP(*(.data..init_thread_info))\
. = VMLINUX_SYMBOL(__start_init_task) + THREAD_SIZE;\
VMLINUX_SYMBOL(__end_init_task) = .;
 

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 8.8Mbps down 630kbps up
According to speedtest.net: 8.21Mbps down 510kbps up

Re: [PATCH] Extract initrd free logic from arch-specific code.

[Marc Zyngier]

On Thu, 29 Mar 2018 16:58:27 +0100,
Russell King - ARM Linux wrote:
> 
> On Thu, Mar 29, 2018 at 05:43:47PM +0200, Geert Uytterhoeven wrote:
> > On Thu, Mar 29, 2018 at 5:27 PM, Russell King - ARM Linux
> >  wrote:
> > > On Thu, Mar 29, 2018 at 09:37:52AM +1100, Oliver wrote:
> > >> On Thu, Mar 29, 2018 at 9:14 AM, Russell King - ARM Linux
> > >>  wrote:
> > >> > On Wed, Mar 28, 2018 at 02:04:22PM -0500, Rob Landley wrote:
> > >> >> On 03/28/2018 11:48 AM, Russell King - ARM Linux wrote:
> > >> >> > On Wed, Mar 28, 2018 at 10:58:51AM -0500, Rob Landley wrote:
> > >> >> >> On 03/28/2018 10:26 AM, Shea Levy wrote:
> > >> >> >>> Now only those architectures that have custom initrd free 
> > >> >> >>> requirements
> > >> >> >>> need to define free_initrd_mem.
> > >> >> >> ...
> > >> >> >>> --- a/arch/arc/mm/init.c
> > >> >> >>> +++ b/arch/arc/mm/init.c
> > >> >> >>> @@ -229,10 +229,3 @@ void __ref free_initmem(void)
> > >> >> >>>  {
> > >> >> >>>   free_initmem_default(-1);
> > >> >> >>>  }
> > >> >> >>> -
> > >> >> >>> -#ifdef CONFIG_BLK_DEV_INITRD
> > >> >> >>> -void __init free_initrd_mem(unsigned long start, unsigned long 
> > >> >> >>> end)
> > >> >> >>> -{
> > >> >> >>> - free_reserved_area((void *)start, (void *)end, -1, "initrd");
> > >> >> >>> -}
> > >> >> >>> -#endif
> > >> >> >>> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> > >> >> >>> index 3f972e83909b..19d1c5594e2d 100644
> > >> >> >>> --- a/arch/arm/Kconfig
> > >> >> >>> +++ b/arch/arm/Kconfig
> > >> >> >>> @@ -47,6 +47,7 @@ config ARM
> > >> >> >>>   select HARDIRQS_SW_RESEND
> > >> >> >>>   select HAVE_ARCH_AUDITSYSCALL if (AEABI && !OABI_COMPAT)
> > >> >> >>>   select HAVE_ARCH_BITREVERSE if (CPU_32v7M || CPU_32v7) && 
> > >> >> >>> !CPU_32v6
> > >> >> >>> + select HAVE_ARCH_FREE_INITRD_MEM
> > >> >> >>>   select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL && !CPU_ENDIAN_BE32 
> > >> >> >>> && MMU
> > >> >> >>>   select HAVE_ARCH_KGDB if !CPU_ENDIAN_BE32 && MMU
> > >> >> >>>   select HAVE_ARCH_MMAP_RND_BITS if MMU
> > >> >> >>
> > >> >> >> Isn't this why weak symbols were invented?
> > >> >> >
> > >> >> > Weak symbols means that we end up with both the weakly-referenced 
> > >> >> > code
> > >> >> > and the arch code in the kernel image.  That's fine if the weak code
> > >> >> > is small.
> > >> >>
> > >> >> The kernel's been able to build with link time garbage collection 
> > >> >> since 2016:
> > >> >>
> > >> >> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b67067f1176d
> > >> >>
> > >> >> Wouldn't that remove the unused one?
> > >> >
> > >> > Probably, if anyone bothered to use that, which they don't.
> > >> >
> > >> > LD_DEAD_CODE_DATA_ELIMINATION is a symbol without a prompt, and from
> > >> > what I can see, nothing selects it.  Therefore, the symbol is always
> > >> > disabled, and so the feature never gets used in mainline kernels.
> > >> >
> > >> > Brings up the obvious question - why is it there if it's completely
> > >> > unused?  (Maybe to cause confusion, and allowing a justification
> > >> > for __weak ?)
> > >>
> > >> IIRC Nick had some patches to do the arch enablement for powerpc, but
> > >> I'm not sure what happened to them though. I suspect it just fell down
> > >> Nick's ever growing TODO list.
> > >
> > > I've given it a go on ARM, marking every linker-built table with KEEP()
> > > and comparing the System.map files.  The resulting kernel is around
> > > 150k smaller, which seems good.
> > >
> > > However, it doesn't boot - and I don't know why.  Booting the kernel
> > > under kvmtool in a VM using virtio-console, I can find no way to get
> > > any kernel messages out of it.  Using lkvm debug, I can see that the
> > > PC is stuck inside die(), and that's the only information I have.
> > > It dies before bringing up the other CPUs, so it's a very early death.
> > >
> > > I don't think other console types are available under ARM64.
> > 
> > earlycon?
> 
> Through what - as I say above, I think the only thing that's present is
> virtio-console, and the virtio stack only get initialised much later in
> boot.
> 
> Eg, there's the memory-based virtio driver which interfaces any virtio
> driver to a memory-based ring structures for communication with the host
> (drivers/virtio/virtio_mmio.c) which is initialised at module_init()
> time, and so isn't available for earlycon.
> 
> I don't think merely changing the module_init() calls in the appropriate
> virtio bits will suffice - it's why I pointed out that it dies before
> SMP initialisation, which also means that it dies before we start
> running the initcalls for subsystems and drivers.
> 
> I'm not aware of there being an emulated UART in the guest's address
> space, so serial based stuff doesn't work.

"earlycon=uart,mmio,0x3f8" is what you're looking for:

$ Work/kvmtool/lkvm run -c2 -k zImage -p "earlycon=uart,mmio,0x3f8" --console 
virtio --aarch32
  # lkvm run -k zImage -m 320 -c 2 --name 

Re: [PATCH] Extract initrd free logic from arch-specific code.

[Russell King - ARM Linux]

On Thu, Mar 29, 2018 at 05:43:47PM +0200, Geert Uytterhoeven wrote:
> On Thu, Mar 29, 2018 at 5:27 PM, Russell King - ARM Linux
>  wrote:
> > On Thu, Mar 29, 2018 at 09:37:52AM +1100, Oliver wrote:
> >> On Thu, Mar 29, 2018 at 9:14 AM, Russell King - ARM Linux
> >>  wrote:
> >> > On Wed, Mar 28, 2018 at 02:04:22PM -0500, Rob Landley wrote:
> >> >> On 03/28/2018 11:48 AM, Russell King - ARM Linux wrote:
> >> >> > On Wed, Mar 28, 2018 at 10:58:51AM -0500, Rob Landley wrote:
> >> >> >> On 03/28/2018 10:26 AM, Shea Levy wrote:
> >> >> >>> Now only those architectures that have custom initrd free 
> >> >> >>> requirements
> >> >> >>> need to define free_initrd_mem.
> >> >> >> ...
> >> >> >>> --- a/arch/arc/mm/init.c
> >> >> >>> +++ b/arch/arc/mm/init.c
> >> >> >>> @@ -229,10 +229,3 @@ void __ref free_initmem(void)
> >> >> >>>  {
> >> >> >>>   free_initmem_default(-1);
> >> >> >>>  }
> >> >> >>> -
> >> >> >>> -#ifdef CONFIG_BLK_DEV_INITRD
> >> >> >>> -void __init free_initrd_mem(unsigned long start, unsigned long end)
> >> >> >>> -{
> >> >> >>> - free_reserved_area((void *)start, (void *)end, -1, "initrd");
> >> >> >>> -}
> >> >> >>> -#endif
> >> >> >>> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> >> >> >>> index 3f972e83909b..19d1c5594e2d 100644
> >> >> >>> --- a/arch/arm/Kconfig
> >> >> >>> +++ b/arch/arm/Kconfig
> >> >> >>> @@ -47,6 +47,7 @@ config ARM
> >> >> >>>   select HARDIRQS_SW_RESEND
> >> >> >>>   select HAVE_ARCH_AUDITSYSCALL if (AEABI && !OABI_COMPAT)
> >> >> >>>   select HAVE_ARCH_BITREVERSE if (CPU_32v7M || CPU_32v7) && 
> >> >> >>> !CPU_32v6
> >> >> >>> + select HAVE_ARCH_FREE_INITRD_MEM
> >> >> >>>   select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL && !CPU_ENDIAN_BE32 && 
> >> >> >>> MMU
> >> >> >>>   select HAVE_ARCH_KGDB if !CPU_ENDIAN_BE32 && MMU
> >> >> >>>   select HAVE_ARCH_MMAP_RND_BITS if MMU
> >> >> >>
> >> >> >> Isn't this why weak symbols were invented?
> >> >> >
> >> >> > Weak symbols means that we end up with both the weakly-referenced code
> >> >> > and the arch code in the kernel image.  That's fine if the weak code
> >> >> > is small.
> >> >>
> >> >> The kernel's been able to build with link time garbage collection since 
> >> >> 2016:
> >> >>
> >> >> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b67067f1176d
> >> >>
> >> >> Wouldn't that remove the unused one?
> >> >
> >> > Probably, if anyone bothered to use that, which they don't.
> >> >
> >> > LD_DEAD_CODE_DATA_ELIMINATION is a symbol without a prompt, and from
> >> > what I can see, nothing selects it.  Therefore, the symbol is always
> >> > disabled, and so the feature never gets used in mainline kernels.
> >> >
> >> > Brings up the obvious question - why is it there if it's completely
> >> > unused?  (Maybe to cause confusion, and allowing a justification
> >> > for __weak ?)
> >>
> >> IIRC Nick had some patches to do the arch enablement for powerpc, but
> >> I'm not sure what happened to them though. I suspect it just fell down
> >> Nick's ever growing TODO list.
> >
> > I've given it a go on ARM, marking every linker-built table with KEEP()
> > and comparing the System.map files.  The resulting kernel is around
> > 150k smaller, which seems good.
> >
> > However, it doesn't boot - and I don't know why.  Booting the kernel
> > under kvmtool in a VM using virtio-console, I can find no way to get
> > any kernel messages out of it.  Using lkvm debug, I can see that the
> > PC is stuck inside die(), and that's the only information I have.
> > It dies before bringing up the other CPUs, so it's a very early death.
> >
> > I don't think other console types are available under ARM64.
> 
> earlycon?

Through what - as I say above, I think the only thing that's present is
virtio-console, and the virtio stack only get initialised much later in
boot.

Eg, there's the memory-based virtio driver which interfaces any virtio
driver to a memory-based ring structures for communication with the host
(drivers/virtio/virtio_mmio.c) which is initialised at module_init()
time, and so isn't available for earlycon.

I don't think merely changing the module_init() calls in the appropriate
virtio bits will suffice - it's why I pointed out that it dies before
SMP initialisation, which also means that it dies before we start
running the initcalls for subsystems and drivers.

I'm not aware of there being an emulated UART in the guest's address
space, so serial based stuff doesn't work.

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 8.8Mbps down 630kbps up
According to speedtest.net: 8.21Mbps down 510kbps up

Re: [PATCH] Extract initrd free logic from arch-specific code.

[Geert Uytterhoeven]

On Thu, Mar 29, 2018 at 5:27 PM, Russell King - ARM Linux
 wrote:
> On Thu, Mar 29, 2018 at 09:37:52AM +1100, Oliver wrote:
>> On Thu, Mar 29, 2018 at 9:14 AM, Russell King - ARM Linux
>>  wrote:
>> > On Wed, Mar 28, 2018 at 02:04:22PM -0500, Rob Landley wrote:
>> >> On 03/28/2018 11:48 AM, Russell King - ARM Linux wrote:
>> >> > On Wed, Mar 28, 2018 at 10:58:51AM -0500, Rob Landley wrote:
>> >> >> On 03/28/2018 10:26 AM, Shea Levy wrote:
>> >> >>> Now only those architectures that have custom initrd free requirements
>> >> >>> need to define free_initrd_mem.
>> >> >> ...
>> >> >>> --- a/arch/arc/mm/init.c
>> >> >>> +++ b/arch/arc/mm/init.c
>> >> >>> @@ -229,10 +229,3 @@ void __ref free_initmem(void)
>> >> >>>  {
>> >> >>>   free_initmem_default(-1);
>> >> >>>  }
>> >> >>> -
>> >> >>> -#ifdef CONFIG_BLK_DEV_INITRD
>> >> >>> -void __init free_initrd_mem(unsigned long start, unsigned long end)
>> >> >>> -{
>> >> >>> - free_reserved_area((void *)start, (void *)end, -1, "initrd");
>> >> >>> -}
>> >> >>> -#endif
>> >> >>> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
>> >> >>> index 3f972e83909b..19d1c5594e2d 100644
>> >> >>> --- a/arch/arm/Kconfig
>> >> >>> +++ b/arch/arm/Kconfig
>> >> >>> @@ -47,6 +47,7 @@ config ARM
>> >> >>>   select HARDIRQS_SW_RESEND
>> >> >>>   select HAVE_ARCH_AUDITSYSCALL if (AEABI && !OABI_COMPAT)
>> >> >>>   select HAVE_ARCH_BITREVERSE if (CPU_32v7M || CPU_32v7) && !CPU_32v6
>> >> >>> + select HAVE_ARCH_FREE_INITRD_MEM
>> >> >>>   select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL && !CPU_ENDIAN_BE32 && 
>> >> >>> MMU
>> >> >>>   select HAVE_ARCH_KGDB if !CPU_ENDIAN_BE32 && MMU
>> >> >>>   select HAVE_ARCH_MMAP_RND_BITS if MMU
>> >> >>
>> >> >> Isn't this why weak symbols were invented?
>> >> >
>> >> > Weak symbols means that we end up with both the weakly-referenced code
>> >> > and the arch code in the kernel image.  That's fine if the weak code
>> >> > is small.
>> >>
>> >> The kernel's been able to build with link time garbage collection since 
>> >> 2016:
>> >>
>> >> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b67067f1176d
>> >>
>> >> Wouldn't that remove the unused one?
>> >
>> > Probably, if anyone bothered to use that, which they don't.
>> >
>> > LD_DEAD_CODE_DATA_ELIMINATION is a symbol without a prompt, and from
>> > what I can see, nothing selects it.  Therefore, the symbol is always
>> > disabled, and so the feature never gets used in mainline kernels.
>> >
>> > Brings up the obvious question - why is it there if it's completely
>> > unused?  (Maybe to cause confusion, and allowing a justification
>> > for __weak ?)
>>
>> IIRC Nick had some patches to do the arch enablement for powerpc, but
>> I'm not sure what happened to them though. I suspect it just fell down
>> Nick's ever growing TODO list.
>
> I've given it a go on ARM, marking every linker-built table with KEEP()
> and comparing the System.map files.  The resulting kernel is around
> 150k smaller, which seems good.
>
> However, it doesn't boot - and I don't know why.  Booting the kernel
> under kvmtool in a VM using virtio-console, I can find no way to get
> any kernel messages out of it.  Using lkvm debug, I can see that the
> PC is stuck inside die(), and that's the only information I have.
> It dies before bringing up the other CPUs, so it's a very early death.
>
> I don't think other console types are available under ARM64.

earlycon?

Gr{oetje,eeting}s,

Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds

Re: [PATCH] Extract initrd free logic from arch-specific code.

[Russell King - ARM Linux]

On Thu, Mar 29, 2018 at 09:37:52AM +1100, Oliver wrote:
> On Thu, Mar 29, 2018 at 9:14 AM, Russell King - ARM Linux
>  wrote:
> > On Wed, Mar 28, 2018 at 02:04:22PM -0500, Rob Landley wrote:
> >>
> >>
> >> On 03/28/2018 11:48 AM, Russell King - ARM Linux wrote:
> >> > On Wed, Mar 28, 2018 at 10:58:51AM -0500, Rob Landley wrote:
> >> >> On 03/28/2018 10:26 AM, Shea Levy wrote:
> >> >>> Now only those architectures that have custom initrd free requirements
> >> >>> need to define free_initrd_mem.
> >> >> ...
> >> >>> --- a/arch/arc/mm/init.c
> >> >>> +++ b/arch/arc/mm/init.c
> >> >>> @@ -229,10 +229,3 @@ void __ref free_initmem(void)
> >> >>>  {
> >> >>>   free_initmem_default(-1);
> >> >>>  }
> >> >>> -
> >> >>> -#ifdef CONFIG_BLK_DEV_INITRD
> >> >>> -void __init free_initrd_mem(unsigned long start, unsigned long end)
> >> >>> -{
> >> >>> - free_reserved_area((void *)start, (void *)end, -1, "initrd");
> >> >>> -}
> >> >>> -#endif
> >> >>> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> >> >>> index 3f972e83909b..19d1c5594e2d 100644
> >> >>> --- a/arch/arm/Kconfig
> >> >>> +++ b/arch/arm/Kconfig
> >> >>> @@ -47,6 +47,7 @@ config ARM
> >> >>>   select HARDIRQS_SW_RESEND
> >> >>>   select HAVE_ARCH_AUDITSYSCALL if (AEABI && !OABI_COMPAT)
> >> >>>   select HAVE_ARCH_BITREVERSE if (CPU_32v7M || CPU_32v7) && !CPU_32v6
> >> >>> + select HAVE_ARCH_FREE_INITRD_MEM
> >> >>>   select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL && !CPU_ENDIAN_BE32 && MMU
> >> >>>   select HAVE_ARCH_KGDB if !CPU_ENDIAN_BE32 && MMU
> >> >>>   select HAVE_ARCH_MMAP_RND_BITS if MMU
> >> >>
> >> >> Isn't this why weak symbols were invented?
> >> >
> >> > Weak symbols means that we end up with both the weakly-referenced code
> >> > and the arch code in the kernel image.  That's fine if the weak code
> >> > is small.
> >>
> >> The kernel's been able to build with link time garbage collection since 
> >> 2016:
> >>
> >> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b67067f1176d
> >>
> >> Wouldn't that remove the unused one?
> >
> > Probably, if anyone bothered to use that, which they don't.
> >
> > LD_DEAD_CODE_DATA_ELIMINATION is a symbol without a prompt, and from
> > what I can see, nothing selects it.  Therefore, the symbol is always
> > disabled, and so the feature never gets used in mainline kernels.
> >
> > Brings up the obvious question - why is it there if it's completely
> > unused?  (Maybe to cause confusion, and allowing a justification
> > for __weak ?)
> 
> IIRC Nick had some patches to do the arch enablement for powerpc, but
> I'm not sure what happened to them though. I suspect it just fell down
> Nick's ever growing TODO list.

I've given it a go on ARM, marking every linker-built table with KEEP()
and comparing the System.map files.  The resulting kernel is around
150k smaller, which seems good.

However, it doesn't boot - and I don't know why.  Booting the kernel
under kvmtool in a VM using virtio-console, I can find no way to get
any kernel messages out of it.  Using lkvm debug, I can see that the
PC is stuck inside die(), and that's the only information I have.
It dies before bringing up the other CPUs, so it's a very early death.

I don't think other console types are available under ARM64.

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 8.8Mbps down 630kbps up
According to speedtest.net: 8.21Mbps down 510kbps up

Re: [PATCH] Extract initrd free logic from arch-specific code.

[Wei Yang]

On Wed, Mar 28, 2018 at 09:55:07AM -0700, Kees Cook wrote:
>On Wed, Mar 28, 2018 at 8:26 AM, Shea Levy  wrote:
>> Now only those architectures that have custom initrd free requirements
>> need to define free_initrd_mem.
>>
>> Signed-off-by: Shea Levy 
>
>Yay consolidation! :)
>
>> --- a/usr/Kconfig
>> +++ b/usr/Kconfig
>> @@ -233,3 +233,7 @@ config INITRAMFS_COMPRESSION
>> default ".lzma" if RD_LZMA
>> default ".bz2"  if RD_BZIP2
>> default ""
>> +
>> +config HAVE_ARCH_FREE_INITRD_MEM
>> +   bool
>> +   default n
>
>If you keep the Kconfig, you can leave off "default n", and I'd
>suggest adding a help section just to describe what the per-arch
>responsibilities are when select-ing the config. (See
>HAVE_ARCH_SECCOMP_FILTER for an example.)
>

One question about this change.

The original code would "select" HAVE_ARCH_FREE_INITRD_MEM on those arch.
After this change, we need to manually "select" this?

>-Kees
>
>-- 
>Kees Cook
>Pixel Security

-- 
Wei Yang
Help you, Help me

Re: [PATCH] Extract initrd free logic from arch-specific code.

[Nicholas Piggin]

On Thu, 29 Mar 2018 09:37:52 +1100
Oliver  wrote:

> On Thu, Mar 29, 2018 at 9:14 AM, Russell King - ARM Linux
>  wrote:
> > On Wed, Mar 28, 2018 at 02:04:22PM -0500, Rob Landley wrote:  
> >>
> >>
> >> On 03/28/2018 11:48 AM, Russell King - ARM Linux wrote:  
> >> > On Wed, Mar 28, 2018 at 10:58:51AM -0500, Rob Landley wrote:  
> >> >> On 03/28/2018 10:26 AM, Shea Levy wrote:  
> >> >>> Now only those architectures that have custom initrd free requirements
> >> >>> need to define free_initrd_mem.  
> >> >> ...  
> >> >>> --- a/arch/arc/mm/init.c
> >> >>> +++ b/arch/arc/mm/init.c
> >> >>> @@ -229,10 +229,3 @@ void __ref free_initmem(void)
> >> >>>  {
> >> >>>   free_initmem_default(-1);
> >> >>>  }
> >> >>> -
> >> >>> -#ifdef CONFIG_BLK_DEV_INITRD
> >> >>> -void __init free_initrd_mem(unsigned long start, unsigned long end)
> >> >>> -{
> >> >>> - free_reserved_area((void *)start, (void *)end, -1, "initrd");
> >> >>> -}
> >> >>> -#endif
> >> >>> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> >> >>> index 3f972e83909b..19d1c5594e2d 100644
> >> >>> --- a/arch/arm/Kconfig
> >> >>> +++ b/arch/arm/Kconfig
> >> >>> @@ -47,6 +47,7 @@ config ARM
> >> >>>   select HARDIRQS_SW_RESEND
> >> >>>   select HAVE_ARCH_AUDITSYSCALL if (AEABI && !OABI_COMPAT)
> >> >>>   select HAVE_ARCH_BITREVERSE if (CPU_32v7M || CPU_32v7) && !CPU_32v6
> >> >>> + select HAVE_ARCH_FREE_INITRD_MEM
> >> >>>   select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL && !CPU_ENDIAN_BE32 && MMU
> >> >>>   select HAVE_ARCH_KGDB if !CPU_ENDIAN_BE32 && MMU
> >> >>>   select HAVE_ARCH_MMAP_RND_BITS if MMU  
> >> >>
> >> >> Isn't this why weak symbols were invented?  
> >> >
> >> > Weak symbols means that we end up with both the weakly-referenced code
> >> > and the arch code in the kernel image.  That's fine if the weak code
> >> > is small.  
> >>
> >> The kernel's been able to build with link time garbage collection since 
> >> 2016:
> >>
> >> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b67067f1176d
> >>
> >> Wouldn't that remove the unused one?  
> >
> > Probably, if anyone bothered to use that, which they don't.
> >
> > LD_DEAD_CODE_DATA_ELIMINATION is a symbol without a prompt, and from
> > what I can see, nothing selects it.  Therefore, the symbol is always
> > disabled, and so the feature never gets used in mainline kernels.
> >
> > Brings up the obvious question - why is it there if it's completely
> > unused?  (Maybe to cause confusion, and allowing a justification
> > for __weak ?)  

Well weak symbols have been used long before it was added.

> IIRC Nick had some patches to do the arch enablement for powerpc, but
> I'm not sure what happened to them though. I suspect it just fell down
> Nick's ever growing TODO list.

Yeah I had started some patches for powerpc and x86 that have ended up
on the back burner. There's been some MIPS people playing with it too.

For the kernel, LD_DEAD_CODE_DATA_ELIMINATION is not great. It can save
a little, but you get issues like any exception table entry or bug table
entry in a function will create a reference back to the function, so the
linker can't trim it away even if nothing else references it.

I'll try to take another look at it within the next few months and
remove it if I can't make progress.

Nicolas Pitre has been doing some much better work on dead code using
real LTO.

Thanks,
Nick

Re: [PATCH] Extract initrd free logic from arch-specific code.

[Oliver]

On Thu, Mar 29, 2018 at 9:14 AM, Russell King - ARM Linux
 wrote:
> On Wed, Mar 28, 2018 at 02:04:22PM -0500, Rob Landley wrote:
>>
>>
>> On 03/28/2018 11:48 AM, Russell King - ARM Linux wrote:
>> > On Wed, Mar 28, 2018 at 10:58:51AM -0500, Rob Landley wrote:
>> >> On 03/28/2018 10:26 AM, Shea Levy wrote:
>> >>> Now only those architectures that have custom initrd free requirements
>> >>> need to define free_initrd_mem.
>> >> ...
>> >>> --- a/arch/arc/mm/init.c
>> >>> +++ b/arch/arc/mm/init.c
>> >>> @@ -229,10 +229,3 @@ void __ref free_initmem(void)
>> >>>  {
>> >>>   free_initmem_default(-1);
>> >>>  }
>> >>> -
>> >>> -#ifdef CONFIG_BLK_DEV_INITRD
>> >>> -void __init free_initrd_mem(unsigned long start, unsigned long end)
>> >>> -{
>> >>> - free_reserved_area((void *)start, (void *)end, -1, "initrd");
>> >>> -}
>> >>> -#endif
>> >>> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
>> >>> index 3f972e83909b..19d1c5594e2d 100644
>> >>> --- a/arch/arm/Kconfig
>> >>> +++ b/arch/arm/Kconfig
>> >>> @@ -47,6 +47,7 @@ config ARM
>> >>>   select HARDIRQS_SW_RESEND
>> >>>   select HAVE_ARCH_AUDITSYSCALL if (AEABI && !OABI_COMPAT)
>> >>>   select HAVE_ARCH_BITREVERSE if (CPU_32v7M || CPU_32v7) && !CPU_32v6
>> >>> + select HAVE_ARCH_FREE_INITRD_MEM
>> >>>   select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL && !CPU_ENDIAN_BE32 && MMU
>> >>>   select HAVE_ARCH_KGDB if !CPU_ENDIAN_BE32 && MMU
>> >>>   select HAVE_ARCH_MMAP_RND_BITS if MMU
>> >>
>> >> Isn't this why weak symbols were invented?
>> >
>> > Weak symbols means that we end up with both the weakly-referenced code
>> > and the arch code in the kernel image.  That's fine if the weak code
>> > is small.
>>
>> The kernel's been able to build with link time garbage collection since 2016:
>>
>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b67067f1176d
>>
>> Wouldn't that remove the unused one?
>
> Probably, if anyone bothered to use that, which they don't.
>
> LD_DEAD_CODE_DATA_ELIMINATION is a symbol without a prompt, and from
> what I can see, nothing selects it.  Therefore, the symbol is always
> disabled, and so the feature never gets used in mainline kernels.
>
> Brings up the obvious question - why is it there if it's completely
> unused?  (Maybe to cause confusion, and allowing a justification
> for __weak ?)

IIRC Nick had some patches to do the arch enablement for powerpc, but
I'm not sure what happened to them though. I suspect it just fell down
Nick's ever growing TODO list.

Re: [PATCH] Extract initrd free logic from arch-specific code.

[Russell King - ARM Linux]

On Wed, Mar 28, 2018 at 02:04:22PM -0500, Rob Landley wrote:
> 
> 
> On 03/28/2018 11:48 AM, Russell King - ARM Linux wrote:
> > On Wed, Mar 28, 2018 at 10:58:51AM -0500, Rob Landley wrote:
> >> On 03/28/2018 10:26 AM, Shea Levy wrote:
> >>> Now only those architectures that have custom initrd free requirements
> >>> need to define free_initrd_mem.
> >> ...
> >>> --- a/arch/arc/mm/init.c
> >>> +++ b/arch/arc/mm/init.c
> >>> @@ -229,10 +229,3 @@ void __ref free_initmem(void)
> >>>  {
> >>>   free_initmem_default(-1);
> >>>  }
> >>> -
> >>> -#ifdef CONFIG_BLK_DEV_INITRD
> >>> -void __init free_initrd_mem(unsigned long start, unsigned long end)
> >>> -{
> >>> - free_reserved_area((void *)start, (void *)end, -1, "initrd");
> >>> -}
> >>> -#endif
> >>> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> >>> index 3f972e83909b..19d1c5594e2d 100644
> >>> --- a/arch/arm/Kconfig
> >>> +++ b/arch/arm/Kconfig
> >>> @@ -47,6 +47,7 @@ config ARM
> >>>   select HARDIRQS_SW_RESEND
> >>>   select HAVE_ARCH_AUDITSYSCALL if (AEABI && !OABI_COMPAT)
> >>>   select HAVE_ARCH_BITREVERSE if (CPU_32v7M || CPU_32v7) && !CPU_32v6
> >>> + select HAVE_ARCH_FREE_INITRD_MEM
> >>>   select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL && !CPU_ENDIAN_BE32 && MMU
> >>>   select HAVE_ARCH_KGDB if !CPU_ENDIAN_BE32 && MMU
> >>>   select HAVE_ARCH_MMAP_RND_BITS if MMU
> >>
> >> Isn't this why weak symbols were invented?
> > 
> > Weak symbols means that we end up with both the weakly-referenced code
> > and the arch code in the kernel image.  That's fine if the weak code
> > is small.
> 
> The kernel's been able to build with link time garbage collection since 2016:
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b67067f1176d
> 
> Wouldn't that remove the unused one?

Probably, if anyone bothered to use that, which they don't.

LD_DEAD_CODE_DATA_ELIMINATION is a symbol without a prompt, and from
what I can see, nothing selects it.  Therefore, the symbol is always
disabled, and so the feature never gets used in mainline kernels.

Brings up the obvious question - why is it there if it's completely
unused?  (Maybe to cause confusion, and allowing a justification
for __weak ?)

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 8.8Mbps down 630kbps up
According to speedtest.net: 8.21Mbps down 510kbps up

Re: [PATCH] Extract initrd free logic from arch-specific code.

[Rob Landley]

On 03/28/2018 11:48 AM, Russell King - ARM Linux wrote:
> On Wed, Mar 28, 2018 at 10:58:51AM -0500, Rob Landley wrote:
>> On 03/28/2018 10:26 AM, Shea Levy wrote:
>>> Now only those architectures that have custom initrd free requirements
>>> need to define free_initrd_mem.
>> ...
>>> --- a/arch/arc/mm/init.c
>>> +++ b/arch/arc/mm/init.c
>>> @@ -229,10 +229,3 @@ void __ref free_initmem(void)
>>>  {
>>> free_initmem_default(-1);
>>>  }
>>> -
>>> -#ifdef CONFIG_BLK_DEV_INITRD
>>> -void __init free_initrd_mem(unsigned long start, unsigned long end)
>>> -{
>>> -   free_reserved_area((void *)start, (void *)end, -1, "initrd");
>>> -}
>>> -#endif
>>> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
>>> index 3f972e83909b..19d1c5594e2d 100644
>>> --- a/arch/arm/Kconfig
>>> +++ b/arch/arm/Kconfig
>>> @@ -47,6 +47,7 @@ config ARM
>>> select HARDIRQS_SW_RESEND
>>> select HAVE_ARCH_AUDITSYSCALL if (AEABI && !OABI_COMPAT)
>>> select HAVE_ARCH_BITREVERSE if (CPU_32v7M || CPU_32v7) && !CPU_32v6
>>> +   select HAVE_ARCH_FREE_INITRD_MEM
>>> select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL && !CPU_ENDIAN_BE32 && MMU
>>> select HAVE_ARCH_KGDB if !CPU_ENDIAN_BE32 && MMU
>>> select HAVE_ARCH_MMAP_RND_BITS if MMU
>>
>> Isn't this why weak symbols were invented?
> 
> Weak symbols means that we end up with both the weakly-referenced code
> and the arch code in the kernel image.  That's fine if the weak code
> is small.

The kernel's been able to build with link time garbage collection since 2016:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b67067f1176d

Wouldn't that remove the unused one?

Rob

Re: [PATCH] Extract initrd free logic from arch-specific code.

[Russell King - ARM Linux]

On Wed, Mar 28, 2018 at 10:58:51AM -0500, Rob Landley wrote:
> On 03/28/2018 10:26 AM, Shea Levy wrote:
> > Now only those architectures that have custom initrd free requirements
> > need to define free_initrd_mem.
> ...
> > --- a/arch/arc/mm/init.c
> > +++ b/arch/arc/mm/init.c
> > @@ -229,10 +229,3 @@ void __ref free_initmem(void)
> >  {
> > free_initmem_default(-1);
> >  }
> > -
> > -#ifdef CONFIG_BLK_DEV_INITRD
> > -void __init free_initrd_mem(unsigned long start, unsigned long end)
> > -{
> > -   free_reserved_area((void *)start, (void *)end, -1, "initrd");
> > -}
> > -#endif
> > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> > index 3f972e83909b..19d1c5594e2d 100644
> > --- a/arch/arm/Kconfig
> > +++ b/arch/arm/Kconfig
> > @@ -47,6 +47,7 @@ config ARM
> > select HARDIRQS_SW_RESEND
> > select HAVE_ARCH_AUDITSYSCALL if (AEABI && !OABI_COMPAT)
> > select HAVE_ARCH_BITREVERSE if (CPU_32v7M || CPU_32v7) && !CPU_32v6
> > +   select HAVE_ARCH_FREE_INITRD_MEM
> > select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL && !CPU_ENDIAN_BE32 && MMU
> > select HAVE_ARCH_KGDB if !CPU_ENDIAN_BE32 && MMU
> > select HAVE_ARCH_MMAP_RND_BITS if MMU
> 
> Isn't this why weak symbols were invented?

Weak symbols means that we end up with both the weakly-referenced code
and the arch code in the kernel image.  That's fine if the weak code
is small.

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 8.8Mbps down 630kbps up
According to speedtest.net: 8.21Mbps down 510kbps up

Re: [PATCH] Extract initrd free logic from arch-specific code.

[Shea Levy]

Hi Rob,

Rob Landley  writes:

> On 03/28/2018 10:26 AM, Shea Levy wrote:
>> Now only those architectures that have custom initrd free requirements
>> need to define free_initrd_mem.
> ...
>> --- a/arch/arc/mm/init.c
>> +++ b/arch/arc/mm/init.c
>> @@ -229,10 +229,3 @@ void __ref free_initmem(void)
>>  {
>>  free_initmem_default(-1);
>>  }
>> -
>> -#ifdef CONFIG_BLK_DEV_INITRD
>> -void __init free_initrd_mem(unsigned long start, unsigned long end)
>> -{
>> -free_reserved_area((void *)start, (void *)end, -1, "initrd");
>> -}
>> -#endif
>> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
>> index 3f972e83909b..19d1c5594e2d 100644
>> --- a/arch/arm/Kconfig
>> +++ b/arch/arm/Kconfig
>> @@ -47,6 +47,7 @@ config ARM
>>  select HARDIRQS_SW_RESEND
>>  select HAVE_ARCH_AUDITSYSCALL if (AEABI && !OABI_COMPAT)
>>  select HAVE_ARCH_BITREVERSE if (CPU_32v7M || CPU_32v7) && !CPU_32v6
>> +select HAVE_ARCH_FREE_INITRD_MEM
>>  select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL && !CPU_ENDIAN_BE32 && MMU
>>  select HAVE_ARCH_KGDB if !CPU_ENDIAN_BE32 && MMU
>>  select HAVE_ARCH_MMAP_RND_BITS if MMU
>
> Isn't this why weak symbols were invented?
>

This approach was suggested by Christoph Hellwig upthread, and seems to
have some precedent elsewhere (e.g. strncasecmp), but I agree weak
symbols seem appropriate here. I'm happy to implement either approach!

>
> Confused,
>
> Rob

Thanks,
Shea


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Re: [PATCH] Extract initrd free logic from arch-specific code.

[Rob Landley]

On 03/28/2018 10:26 AM, Shea Levy wrote:
> Now only those architectures that have custom initrd free requirements
> need to define free_initrd_mem.
...
> --- a/arch/arc/mm/init.c
> +++ b/arch/arc/mm/init.c
> @@ -229,10 +229,3 @@ void __ref free_initmem(void)
>  {
>   free_initmem_default(-1);
>  }
> -
> -#ifdef CONFIG_BLK_DEV_INITRD
> -void __init free_initrd_mem(unsigned long start, unsigned long end)
> -{
> - free_reserved_area((void *)start, (void *)end, -1, "initrd");
> -}
> -#endif
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index 3f972e83909b..19d1c5594e2d 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -47,6 +47,7 @@ config ARM
>   select HARDIRQS_SW_RESEND
>   select HAVE_ARCH_AUDITSYSCALL if (AEABI && !OABI_COMPAT)
>   select HAVE_ARCH_BITREVERSE if (CPU_32v7M || CPU_32v7) && !CPU_32v6
> + select HAVE_ARCH_FREE_INITRD_MEM
>   select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL && !CPU_ENDIAN_BE32 && MMU
>   select HAVE_ARCH_KGDB if !CPU_ENDIAN_BE32 && MMU
>   select HAVE_ARCH_MMAP_RND_BITS if MMU

Isn't this why weak symbols were invented?

Confused,

Rob

[PATCH] Extract initrd free logic from arch-specific code.

[Shea Levy]

Now only those architectures that have custom initrd free requirements
need to define free_initrd_mem.

Signed-off-by: Shea Levy 
---
 arch/alpha/mm/init.c  |  8 
 arch/arc/mm/init.c|  7 ---
 arch/arm/Kconfig  |  1 +
 arch/arm64/Kconfig|  1 +
 arch/blackfin/Kconfig |  1 +
 arch/c6x/mm/init.c|  7 ---
 arch/cris/Kconfig |  1 +
 arch/frv/mm/init.c| 11 ---
 arch/h8300/mm/init.c  |  7 ---
 arch/hexagon/Kconfig  |  1 +
 arch/ia64/Kconfig |  1 +
 arch/m32r/Kconfig |  1 +
 arch/m32r/mm/init.c   | 11 ---
 arch/m68k/mm/init.c   |  7 ---
 arch/metag/Kconfig|  1 +
 arch/microblaze/mm/init.c |  7 ---
 arch/mips/Kconfig |  1 +
 arch/mn10300/Kconfig  |  1 +
 arch/nios2/mm/init.c  |  7 ---
 arch/openrisc/mm/init.c   |  7 ---
 arch/parisc/mm/init.c |  7 ---
 arch/powerpc/mm/mem.c |  7 ---
 arch/riscv/mm/init.c  |  6 --
 arch/s390/Kconfig |  1 +
 arch/score/Kconfig|  1 +
 arch/sh/mm/init.c |  7 ---
 arch/sparc/Kconfig|  1 +
 arch/tile/Kconfig |  1 +
 arch/um/kernel/mem.c  |  7 ---
 arch/unicore32/Kconfig|  1 +
 arch/x86/Kconfig  |  1 +
 arch/xtensa/Kconfig   |  1 +
 init/initramfs.c  |  7 +++
 usr/Kconfig   |  4 
 34 files changed, 28 insertions(+), 113 deletions(-)

diff --git a/arch/alpha/mm/init.c b/arch/alpha/mm/init.c
index 9d74520298ab..55f7c8efa962 100644
--- a/arch/alpha/mm/init.c
+++ b/arch/alpha/mm/init.c
@@ -291,11 +291,3 @@ free_initmem(void)
 {
free_initmem_default(-1);
 }
-
-#ifdef CONFIG_BLK_DEV_INITRD
-void
-free_initrd_mem(unsigned long start, unsigned long end)
-{
-   free_reserved_area((void *)start, (void *)end, -1, "initrd");
-}
-#endif
diff --git a/arch/arc/mm/init.c b/arch/arc/mm/init.c
index ba145065c579..7bcf23ab1756 100644
--- a/arch/arc/mm/init.c
+++ b/arch/arc/mm/init.c
@@ -229,10 +229,3 @@ void __ref free_initmem(void)
 {
free_initmem_default(-1);
 }
-
-#ifdef CONFIG_BLK_DEV_INITRD
-void __init free_initrd_mem(unsigned long start, unsigned long end)
-{
-   free_reserved_area((void *)start, (void *)end, -1, "initrd");
-}
-#endif
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 3f972e83909b..19d1c5594e2d 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -47,6 +47,7 @@ config ARM
select HARDIRQS_SW_RESEND
select HAVE_ARCH_AUDITSYSCALL if (AEABI && !OABI_COMPAT)
select HAVE_ARCH_BITREVERSE if (CPU_32v7M || CPU_32v7) && !CPU_32v6
+   select HAVE_ARCH_FREE_INITRD_MEM
select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL && !CPU_ENDIAN_BE32 && MMU
select HAVE_ARCH_KGDB if !CPU_ENDIAN_BE32 && MMU
select HAVE_ARCH_MMAP_RND_BITS if MMU
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index cb03e93f03cf..de93620870af 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -85,6 +85,7 @@ config ARM64
select HAVE_ALIGNED_STRUCT_PAGE if SLUB
select HAVE_ARCH_AUDITSYSCALL
select HAVE_ARCH_BITREVERSE
+   select HAVE_ARCH_FREE_INITRD_MEM
select HAVE_ARCH_HUGE_VMAP
select HAVE_ARCH_JUMP_LABEL
select HAVE_ARCH_KASAN if !(ARM64_16K_PAGES && ARM64_VA_BITS_48)
diff --git a/arch/blackfin/Kconfig b/arch/blackfin/Kconfig
index d9c2866ba618..6c6dae9fe894 100644
--- a/arch/blackfin/Kconfig
+++ b/arch/blackfin/Kconfig
@@ -15,6 +15,7 @@ config BLACKFIN
def_bool y
select HAVE_ARCH_KGDB
select HAVE_ARCH_TRACEHOOK
+   select HAVE_ARCH_FREE_INITRD_MEM
select HAVE_DYNAMIC_FTRACE
select HAVE_FTRACE_MCOUNT_RECORD
select HAVE_FUNCTION_GRAPH_TRACER
diff --git a/arch/c6x/mm/init.c b/arch/c6x/mm/init.c
index 4cc72b0d1c1d..a11cb657182a 100644
--- a/arch/c6x/mm/init.c
+++ b/arch/c6x/mm/init.c
@@ -66,13 +66,6 @@ void __init mem_init(void)
mem_init_print_info(NULL);
 }
 
-#ifdef CONFIG_BLK_DEV_INITRD
-void __init free_initrd_mem(unsigned long start, unsigned long end)
-{
-   free_reserved_area((void *)start, (void *)end, -1, "initrd");
-}
-#endif
-
 void __init free_initmem(void)
 {
free_initmem_default(-1);
diff --git a/arch/cris/Kconfig b/arch/cris/Kconfig
index cd5a0865c97f..5425f77e5664 100644
--- a/arch/cris/Kconfig
+++ b/arch/cris/Kconfig
@@ -76,6 +76,7 @@ config CRIS
select HAVE_DEBUG_BUGVERBOSE if ETRAX_ARCH_V32
select HAVE_NMI
select DMA_DIRECT_OPS if PCI
+   select HAVE_ARCH_FREE_INITRD_MEM
 
 config HZ
int
diff --git a/arch/frv/mm/init.c b/arch/frv/mm/init.c
index cf464100e838..345edc4dc462 100644
--- a/arch/frv/mm/init.c
+++ b/arch/frv/mm/init.c
@@ -131,14 +131,3 @@ void free_initmem(void)
free_initmem_default(-1);
 #endif
 } /* end free_initmem() */
-
-/*/
-/*
- * free the initial ramdisk memory
- */

Re: [PATCH] Extract initrd free logic from arch-specific code.

[Kees Cook]

On Wed, Mar 28, 2018 at 8:26 AM, Shea Levy  wrote:
> Now only those architectures that have custom initrd free requirements
> need to define free_initrd_mem.
>
> Signed-off-by: Shea Levy 

Yay consolidation! :)

> --- a/usr/Kconfig
> +++ b/usr/Kconfig
> @@ -233,3 +233,7 @@ config INITRAMFS_COMPRESSION
> default ".lzma" if RD_LZMA
> default ".bz2"  if RD_BZIP2
> default ""
> +
> +config HAVE_ARCH_FREE_INITRD_MEM
> +   bool
> +   default n

If you keep the Kconfig, you can leave off "default n", and I'd
suggest adding a help section just to describe what the per-arch
responsibilities are when select-ing the config. (See
HAVE_ARCH_SECCOMP_FILTER for an example.)

-Kees

-- 
Kees Cook
Pixel Security