Re: [PATCH] powerpc/32: Include .branch_lt in data section
Alan Modra writes:
> On Thu, Nov 15, 2018 at 11:47:52PM +1100, Michael Ellerman wrote:
>> Alan Modra writes:
>>
>> > On Wed, Nov 14, 2018 at 01:32:18PM +1030, Joel Stanley wrote:
>> >> I wasn't sure where this should go or if the ordering matters.
>> >
>> > The usual answer is: "Look at where the section goes in the standard
>> > linker scripts." But that doesn't apply here. The section will be
>> > empty for a kernel build so it doesn't matter where it goes.
>>
>> If it's empty why don't we just discard it?
>
> That can be a recipe for finding linker bugs. Not that I'm against
> you finding linker bugs. ;-)
Seems we might have found a linker bug :)
With a binutils 2.29 toolchain discarding .branch_lt causes a segfault
when linking:
http://kisskb.ellerman.id.au/kisskb/buildresult/13618838/log/
/kisskb/src/scripts/link-vmlinux.sh: line 85: 74627 Segmentation fault
(core dumped) ${LD} ${KBUILD_LDFLAGS} ${LDFLAGS_vmlinux} -o ${2} -T ${lds}
${objects}
That toolchain is here:
https://mirrors.edge.kernel.org/pub/tools/crosstool/files/bin/x86_64/5.5.0/x86_64-gcc-5.5.0-nolibc-powerpc64-linux.tar.xz
It seems to be better with binutils 2.30, it doesn't crash but still
doesn't link:
http://kisskb.ellerman.id.au/kisskb/buildresult/13620269/log/
/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/powerpc64-linux/bin/powerpc64-linux-ld:
linkage table error against `0002bf55.xdp_rxq_info_reg_mem_model'
/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/powerpc64-linux/bin/powerpc64-linux-ld:
stubs don't match calculated size
/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/powerpc64-linux/bin/powerpc64-linux-ld:
can not build stubs: Bad value
make[1]: *** [/kisskb/src/Makefile:1036: vmlinux] Error 1
So I guess I'll take this version of the patch for now.
cheers
Re: [PATCH] powerpc/32: Include .branch_lt in data section
On Thu, Nov 15, 2018 at 11:47:52PM +1100, Michael Ellerman wrote: > Alan Modra writes: > > > On Wed, Nov 14, 2018 at 01:32:18PM +1030, Joel Stanley wrote: > >> I wasn't sure where this should go or if the ordering matters. > > > > The usual answer is: "Look at where the section goes in the standard > > linker scripts." But that doesn't apply here. The section will be > > empty for a kernel build so it doesn't matter where it goes. > > If it's empty why don't we just discard it? That can be a recipe for finding linker bugs. Not that I'm against you finding linker bugs. ;-) -- Alan Modra Australia Development Lab, IBM
Re: [PATCH] powerpc/32: Include .branch_lt in data section
Alan Modra writes:
> On Wed, Nov 14, 2018 at 01:32:18PM +1030, Joel Stanley wrote:
>> When building a 32 bit powerpc kernel with Binutils 2.31.1 this warning
>> is emitted:
>>
>> powerpc-linux-gnu-ld: warning: orphan section `.branch_lt' from
>> `arch/powerpc/kernel/head_44x.o' being placed in section `.branch_lt'
>>
>> As of binutils commit 2d7ad24e8726 ("Support PLT16 relocs against local
>> symbols")[1], 32 bit targets can produce .branch_lt sections in their
>> output.
>>
>> Include these symbols in the .data section as the ppc64 kernel does.
>>
>> [1]
>> https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=commitdiff;h=2d7ad24e8726ba4c45c9e67be08223a146a837ce
>> Signed-off-by: Joel Stanley
> Reviewed-by: Alan Modra
>
> Looks fine to me.
>
>> ---
>> I wasn't sure where this should go or if the ordering matters.
>
> The usual answer is: "Look at where the section goes in the standard
> linker scripts." But that doesn't apply here. The section will be
> empty for a kernel build so it doesn't matter where it goes.
If it's empty why don't we just discard it?
cheers
Re: [PATCH] powerpc/32: Include .branch_lt in data section
On Wed, Nov 14, 2018 at 01:32:18PM +1030, Joel Stanley wrote:
> When building a 32 bit powerpc kernel with Binutils 2.31.1 this warning
> is emitted:
>
> powerpc-linux-gnu-ld: warning: orphan section `.branch_lt' from
> `arch/powerpc/kernel/head_44x.o' being placed in section `.branch_lt'
>
> As of binutils commit 2d7ad24e8726 ("Support PLT16 relocs against local
> symbols")[1], 32 bit targets can produce .branch_lt sections in their
> output.
>
> Include these symbols in the .data section as the ppc64 kernel does.
>
> [1]
> https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=commitdiff;h=2d7ad24e8726ba4c45c9e67be08223a146a837ce
> Signed-off-by: Joel Stanley
Reviewed-by: Alan Modra
Looks fine to me.
> ---
> I wasn't sure where this should go or if the ordering matters.
The usual answer is: "Look at where the section goes in the standard
linker scripts." But that doesn't apply here. The section will be
empty for a kernel build so it doesn't matter where it goes.
> ---
> arch/powerpc/kernel/vmlinux.lds.S | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/arch/powerpc/kernel/vmlinux.lds.S
> b/arch/powerpc/kernel/vmlinux.lds.S
> index 434581bcd5b4..6d5fd1b95311 100644
> --- a/arch/powerpc/kernel/vmlinux.lds.S
> +++ b/arch/powerpc/kernel/vmlinux.lds.S
> @@ -313,6 +313,7 @@ SECTIONS
> *(.sdata2)
> *(.got.plt) *(.got)
> *(.plt)
> + *(.branch_lt)
> }
> #else
> .data : AT(ADDR(.data) - LOAD_OFFSET) {
> --
> 2.19.1
--
Alan Modra
Australia Development Lab, IBM
[PATCH] powerpc/32: Include .branch_lt in data section
When building a 32 bit powerpc kernel with Binutils 2.31.1 this warning
is emitted:
powerpc-linux-gnu-ld: warning: orphan section `.branch_lt' from
`arch/powerpc/kernel/head_44x.o' being placed in section `.branch_lt'
As of binutils commit 2d7ad24e8726 ("Support PLT16 relocs against local
symbols")[1], 32 bit targets can produce .branch_lt sections in their
output.
Include these symbols in the .data section as the ppc64 kernel does.
[1]
https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=commitdiff;h=2d7ad24e8726ba4c45c9e67be08223a146a837ce
Signed-off-by: Joel Stanley
---
I wasn't sure where this should go or if the ordering matters.
---
arch/powerpc/kernel/vmlinux.lds.S | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/powerpc/kernel/vmlinux.lds.S
b/arch/powerpc/kernel/vmlinux.lds.S
index 434581bcd5b4..6d5fd1b95311 100644
--- a/arch/powerpc/kernel/vmlinux.lds.S
+++ b/arch/powerpc/kernel/vmlinux.lds.S
@@ -313,6 +313,7 @@ SECTIONS
*(.sdata2)
*(.got.plt) *(.got)
*(.plt)
+ *(.branch_lt)
}
#else
.data : AT(ADDR(.data) - LOAD_OFFSET) {
--
2.19.1
