Re: [PATCH v6 00/29] Warn on orphan section placement
On Tue, Sep 1, 2020 at 4:18 PM Kees Cook wrote:
>
> On Tue, Sep 01, 2020 at 11:02:02AM -0700, Nick Desaulniers wrote:
> > Uh oh, the ppc vdso uses cc-ldoption which was removed! (I think by
> > me; let me send patches) How is that not an error? Yes, guilty,
> > officer.
> > commit 055efab3120b ("kbuild: drop support for cc-ldoption").
> > Did I not know how to use grep, or? No, it is
> > commit f2af201002a8 ("powerpc/build: vdso linker warning for orphan
> > sections")
> > that is wrong.
>
> Eek, yeah, the vdso needs fixing; whoops. Lucky for my series, I only need
> ld-option! ;)
>
I didn't cc everyone here on that thread, but here's the series I sent
for it:
https://lore.kernel.org/lkml/20200901222523.1941988-1-ndesaulni...@google.com/T/#u
.
--
Thanks,
~Nick Desaulniers
Re: [PATCH v6 00/29] Warn on orphan section placement
On Tue, Sep 01, 2020 at 11:02:02AM -0700, Nick Desaulniers wrote:
> On Tue, Sep 1, 2020 at 8:17 AM Kees Cook wrote:
> >
> > On Tue, Sep 01, 2020 at 10:16:47AM +0200, Ingo Molnar wrote:
> > > > This is with:
> > > >
> > > > GNU ld version 2.25-17.fc23
> >
> > (At best, this is from 2015 ... but yes, min binutils in 2.23.)
>
> Ah, crap! Indeed arch/powerpc/Makefile wraps this in ld-option.
Yeah, I totally missed that too. :)
> Uh oh, the ppc vdso uses cc-ldoption which was removed! (I think by
> me; let me send patches) How is that not an error? Yes, guilty,
> officer.
> commit 055efab3120b ("kbuild: drop support for cc-ldoption").
> Did I not know how to use grep, or? No, it is
> commit f2af201002a8 ("powerpc/build: vdso linker warning for orphan sections")
> that is wrong.
Eek, yeah, the vdso needs fixing; whoops. Lucky for my series, I only need
ld-option! ;)
(Doing test builds now...)
--
Kees Cook
Re: [PATCH v6 00/29] Warn on orphan section placement
On Tue, Sep 1, 2020 at 8:17 AM Kees Cook wrote:
>
> On Tue, Sep 01, 2020 at 10:16:47AM +0200, Ingo Molnar wrote:
> >
> > * Ingo Molnar wrote:
> >
> > >
> > > * Ingo Molnar wrote:
> > >
> > > >
> > > > * Kees Cook wrote:
> > > >
> > > > > On Fri, Aug 21, 2020 at 12:42:41PM -0700, Kees Cook wrote:
> > > > > > Hi Ingo,
> > > > > >
> > > > > > Based on my testing, this is ready to go. I've reviewed the
> > > > > > feedback on
> > > > > > v5 and made a few small changes, noted below.
> > > > >
> > > > > If no one objects, I'll pop this into my tree for -next. I'd prefer it
> > > > > go via -tip though! :)
> > > > >
> > > > > Thanks!
> > > >
> > > > I'll pick it up today, it all looks very good now!
> > >
> > > One thing I found in testing is that it doesn't handler older LD
> > > versions well enough:
> > >
> > > ld: unrecognized option '--orphan-handling=warn'
>
> Oh! Uhm, yikes. Thanks for noticing this.
>
> > > Could we just detect the availability of this flag, and emit a warning
> > > if it doesn't exist but otherwise not abort the build?
>
> Yeah, I'll respin those patches.
>
> > > This is with:
> > >
> > > GNU ld version 2.25-17.fc23
>
> (At best, this is from 2015 ... but yes, min binutils in 2.23.)
Ah, crap! Indeed arch/powerpc/Makefile wraps this in ld-option.
Uh oh, the ppc vdso uses cc-ldoption which was removed! (I think by
me; let me send patches) How is that not an error? Yes, guilty,
officer.
commit 055efab3120b ("kbuild: drop support for cc-ldoption").
Did I not know how to use grep, or? No, it is
commit f2af201002a8 ("powerpc/build: vdso linker warning for orphan sections")
that is wrong.
--
Thanks,
~Nick Desaulniers
Re: [PATCH v6 00/29] Warn on orphan section placement
On Tue, Sep 01, 2020 at 10:16:47AM +0200, Ingo Molnar wrote: > > * Ingo Molnar wrote: > > > > > * Ingo Molnar wrote: > > > > > > > > * Kees Cook wrote: > > > > > > > On Fri, Aug 21, 2020 at 12:42:41PM -0700, Kees Cook wrote: > > > > > Hi Ingo, > > > > > > > > > > Based on my testing, this is ready to go. I've reviewed the feedback > > > > > on > > > > > v5 and made a few small changes, noted below. > > > > > > > > If no one objects, I'll pop this into my tree for -next. I'd prefer it > > > > go via -tip though! :) > > > > > > > > Thanks! > > > > > > I'll pick it up today, it all looks very good now! > > > > One thing I found in testing is that it doesn't handler older LD > > versions well enough: > > > > ld: unrecognized option '--orphan-handling=warn' Oh! Uhm, yikes. Thanks for noticing this. > > Could we just detect the availability of this flag, and emit a warning > > if it doesn't exist but otherwise not abort the build? Yeah, I'll respin those patches. > > This is with: > > > > GNU ld version 2.25-17.fc23 (At best, this is from 2015 ... but yes, min binutils in 2.23.) > > I've resolved this for now by not applying the 5 patches that add the > actual orphan section warnings: > > arm64/build: Warn on orphan section placement > arm/build: Warn on orphan section placement > arm/boot: Warn on orphan section placement > x86/build: Warn on orphan section placement > x86/boot/compressed: Warn on orphan section placement > > The new asserts plus the actual fixes/enhancements are enough changes > to test for now in any case. :-) Yup! I'll respin the enabling patches. Thanks again! -- Kees Cook
Re: [PATCH v6 00/29] Warn on orphan section placement
* Ingo Molnar wrote: > > * Ingo Molnar wrote: > > > > > * Kees Cook wrote: > > > > > On Fri, Aug 21, 2020 at 12:42:41PM -0700, Kees Cook wrote: > > > > Hi Ingo, > > > > > > > > Based on my testing, this is ready to go. I've reviewed the feedback on > > > > v5 and made a few small changes, noted below. > > > > > > If no one objects, I'll pop this into my tree for -next. I'd prefer it > > > go via -tip though! :) > > > > > > Thanks! > > > > I'll pick it up today, it all looks very good now! > > One thing I found in testing is that it doesn't handler older LD > versions well enough: > > ld: unrecognized option '--orphan-handling=warn' > > Could we just detect the availability of this flag, and emit a warning > if it doesn't exist but otherwise not abort the build? > > This is with: > > GNU ld version 2.25-17.fc23 I've resolved this for now by not applying the 5 patches that add the actual orphan section warnings: arm64/build: Warn on orphan section placement arm/build: Warn on orphan section placement arm/boot: Warn on orphan section placement x86/build: Warn on orphan section placement x86/boot/compressed: Warn on orphan section placement The new asserts plus the actual fixes/enhancements are enough changes to test for now in any case. :-) Thanks, Ingo
Re: [PATCH v6 00/29] Warn on orphan section placement
* Ingo Molnar wrote: > > * Kees Cook wrote: > > > On Fri, Aug 21, 2020 at 12:42:41PM -0700, Kees Cook wrote: > > > Hi Ingo, > > > > > > Based on my testing, this is ready to go. I've reviewed the feedback on > > > v5 and made a few small changes, noted below. > > > > If no one objects, I'll pop this into my tree for -next. I'd prefer it > > go via -tip though! :) > > > > Thanks! > > I'll pick it up today, it all looks very good now! One thing I found in testing is that it doesn't handler older LD versions well enough: ld: unrecognized option '--orphan-handling=warn' Could we just detect the availability of this flag, and emit a warning if it doesn't exist but otherwise not abort the build? This is with: GNU ld version 2.25-17.fc23 Thanks, Ingo
Re: [PATCH v6 00/29] Warn on orphan section placement
* Kees Cook wrote: > On Fri, Aug 21, 2020 at 12:42:41PM -0700, Kees Cook wrote: > > Hi Ingo, > > > > Based on my testing, this is ready to go. I've reviewed the feedback on > > v5 and made a few small changes, noted below. > > If no one objects, I'll pop this into my tree for -next. I'd prefer it > go via -tip though! :) > > Thanks! I'll pick it up today, it all looks very good now! Thanks, Ingo
Re: [PATCH v6 00/29] Warn on orphan section placement
On Fri, Aug 21, 2020 at 12:42:41PM -0700, Kees Cook wrote:
> Hi Ingo,
>
> Based on my testing, this is ready to go. I've reviewed the feedback on
> v5 and made a few small changes, noted below.
If no one objects, I'll pop this into my tree for -next. I'd prefer it
go via -tip though! :)
Thanks!
-Kees
>
>
> https://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git/log/?h=linker/orphans/warn/v6
>
> v6:
> - rebase to -tip x86/boot
> - remove 0-sized NOLOAD
> - move .got.plt to end with INFO (NOLOAD warns)
> - add Reviewed-bys
> v5:
> https://lore.kernel.org/lkml/20200731230820.1742553-1-keesc...@chromium.org/
> v4:
> https://lore.kernel.org/lkml/20200629061840.4065483-1-keesc...@chromium.org/
> v3:
> https://lore.kernel.org/lkml/20200624014940.1204448-1-keesc...@chromium.org/
> v2:
> https://lore.kernel.org/lkml/20200622205815.2988115-1-keesc...@chromium.org/
> v1: https://lore.kernel.org/lkml/20200228002244.15240-1-keesc...@chromium.org/
>
> A recent bug[1] was solved for builds linked with ld.lld, and tracking
> it down took way longer than it needed to (a year). Ultimately, it
> boiled down to differences between ld.bfd and ld.lld's handling of
> orphan sections. Similar situation have continued to recur, and it's
> clear the kernel build needs to be much more explicit about linker
> sections. Similarly, the recent FGKASLR series brought up orphan section
> handling too[2]. In all cases, it would have been nice if the linker was
> running with --orphan-handling=warn so that surprise sections wouldn't
> silently get mapped into the kernel image at locations up to the whim
> of the linker's orphan handling logic. Instead, all desired sections
> should be explicitly identified in the linker script (to be either kept,
> discarded, or verified to be zero-sized) with any orphans throwing a
> warning. The powerpc architecture has actually been doing this for some
> time, so this series just extends that coverage to x86, arm, and arm64.
>
> This has gotten sucecssful build testing under the following matrix:
>
> compiler/linker: gcc+ld.bfd, clang+ld.lld
> targets: defconfig, allmodconfig
> architectures: x86, i386, arm64, arm
> versions: -tip x86/boot
>
> All three architectures depend on the first several commits to
> vmlinux.lds.h. x86 depends on Arvind's GOT series (in -tip x86/boot now).
> arm64 depends on the efi/libstub patch. As such, I'd like to land this
> series as a whole. Ingo has suggested he'd take it into -tip.
>
> Thanks!
>
> -Kees
>
> [1] https://github.com/ClangBuiltLinux/linux/issues/282
> [2] https://lore.kernel.org/lkml/202002242122.AA4D1B8@keescook/
>
> Kees Cook (28):
> vmlinux.lds.h: Create COMMON_DISCARDS
> vmlinux.lds.h: Add .gnu.version* to COMMON_DISCARDS
> vmlinux.lds.h: Avoid KASAN and KCSAN's unwanted sections
> vmlinux.lds.h: Split ELF_DETAILS from STABS_DEBUG
> vmlinux.lds.h: Add .symtab, .strtab, and .shstrtab to ELF_DETAILS
> efi/libstub: Disable -mbranch-protection
> arm64/mm: Remove needless section quotes
> arm64/kernel: Remove needless Call Frame Information annotations
> arm64/build: Remove .eh_frame* sections due to unwind tables
> arm64/build: Use common DISCARDS in linker script
> arm64/build: Add missing DWARF sections
> arm64/build: Assert for unwanted sections
> arm64/build: Warn on orphan section placement
> arm/build: Refactor linker script headers
> arm/build: Explicitly keep .ARM.attributes sections
> arm/build: Add missing sections
> arm/build: Assert for unwanted sections
> arm/build: Warn on orphan section placement
> arm/boot: Handle all sections explicitly
> arm/boot: Warn on orphan section placement
> x86/asm: Avoid generating unused kprobe sections
> x86/build: Enforce an empty .got.plt section
> x86/build: Assert for unwanted sections
> x86/build: Warn on orphan section placement
> x86/boot/compressed: Reorganize zero-size section asserts
> x86/boot/compressed: Remove, discard, or assert for unwanted sections
> x86/boot/compressed: Add missing debugging sections to output
> x86/boot/compressed: Warn on orphan section placement
>
> Nick Desaulniers (1):
> vmlinux.lds.h: add PGO and AutoFDO input sections
>
> arch/alpha/kernel/vmlinux.lds.S | 1 +
> arch/arc/kernel/vmlinux.lds.S | 1 +
> arch/arm/Makefile | 4 ++
> arch/arm/boot/compressed/Makefile | 2 +
> arch/arm/boot/compressed/vmlinux.lds.S| 20 +++
> .../arm/{kernel => include/asm}/vmlinux.lds.h | 30 --
> arch/arm/kernel/vmlinux-xip.lds.S | 8 ++-
> arch/arm/kernel/vmlinux.lds.S | 8 ++-
> arch/arm64/Makefile | 9 ++-
> arch/arm64/kernel/smccc-call.S| 2 -
> arch/arm64/kernel/vmlinux.lds.S | 28 +++--
> arch/arm64/mm/mmu.c | 2 +-
> arch/csky/kernel/vmlinux.lds.S| 1 +
>
[PATCH v6 00/29] Warn on orphan section placement
Hi Ingo,
Based on my testing, this is ready to go. I've reviewed the feedback on
v5 and made a few small changes, noted below.
https://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git/log/?h=linker/orphans/warn/v6
v6:
- rebase to -tip x86/boot
- remove 0-sized NOLOAD
- move .got.plt to end with INFO (NOLOAD warns)
- add Reviewed-bys
v5: https://lore.kernel.org/lkml/20200731230820.1742553-1-keesc...@chromium.org/
v4: https://lore.kernel.org/lkml/20200629061840.4065483-1-keesc...@chromium.org/
v3: https://lore.kernel.org/lkml/20200624014940.1204448-1-keesc...@chromium.org/
v2: https://lore.kernel.org/lkml/20200622205815.2988115-1-keesc...@chromium.org/
v1: https://lore.kernel.org/lkml/20200228002244.15240-1-keesc...@chromium.org/
A recent bug[1] was solved for builds linked with ld.lld, and tracking
it down took way longer than it needed to (a year). Ultimately, it
boiled down to differences between ld.bfd and ld.lld's handling of
orphan sections. Similar situation have continued to recur, and it's
clear the kernel build needs to be much more explicit about linker
sections. Similarly, the recent FGKASLR series brought up orphan section
handling too[2]. In all cases, it would have been nice if the linker was
running with --orphan-handling=warn so that surprise sections wouldn't
silently get mapped into the kernel image at locations up to the whim
of the linker's orphan handling logic. Instead, all desired sections
should be explicitly identified in the linker script (to be either kept,
discarded, or verified to be zero-sized) with any orphans throwing a
warning. The powerpc architecture has actually been doing this for some
time, so this series just extends that coverage to x86, arm, and arm64.
This has gotten sucecssful build testing under the following matrix:
compiler/linker: gcc+ld.bfd, clang+ld.lld
targets: defconfig, allmodconfig
architectures: x86, i386, arm64, arm
versions: -tip x86/boot
All three architectures depend on the first several commits to
vmlinux.lds.h. x86 depends on Arvind's GOT series (in -tip x86/boot now).
arm64 depends on the efi/libstub patch. As such, I'd like to land this
series as a whole. Ingo has suggested he'd take it into -tip.
Thanks!
-Kees
[1] https://github.com/ClangBuiltLinux/linux/issues/282
[2] https://lore.kernel.org/lkml/202002242122.AA4D1B8@keescook/
Kees Cook (28):
vmlinux.lds.h: Create COMMON_DISCARDS
vmlinux.lds.h: Add .gnu.version* to COMMON_DISCARDS
vmlinux.lds.h: Avoid KASAN and KCSAN's unwanted sections
vmlinux.lds.h: Split ELF_DETAILS from STABS_DEBUG
vmlinux.lds.h: Add .symtab, .strtab, and .shstrtab to ELF_DETAILS
efi/libstub: Disable -mbranch-protection
arm64/mm: Remove needless section quotes
arm64/kernel: Remove needless Call Frame Information annotations
arm64/build: Remove .eh_frame* sections due to unwind tables
arm64/build: Use common DISCARDS in linker script
arm64/build: Add missing DWARF sections
arm64/build: Assert for unwanted sections
arm64/build: Warn on orphan section placement
arm/build: Refactor linker script headers
arm/build: Explicitly keep .ARM.attributes sections
arm/build: Add missing sections
arm/build: Assert for unwanted sections
arm/build: Warn on orphan section placement
arm/boot: Handle all sections explicitly
arm/boot: Warn on orphan section placement
x86/asm: Avoid generating unused kprobe sections
x86/build: Enforce an empty .got.plt section
x86/build: Assert for unwanted sections
x86/build: Warn on orphan section placement
x86/boot/compressed: Reorganize zero-size section asserts
x86/boot/compressed: Remove, discard, or assert for unwanted sections
x86/boot/compressed: Add missing debugging sections to output
x86/boot/compressed: Warn on orphan section placement
Nick Desaulniers (1):
vmlinux.lds.h: add PGO and AutoFDO input sections
arch/alpha/kernel/vmlinux.lds.S | 1 +
arch/arc/kernel/vmlinux.lds.S | 1 +
arch/arm/Makefile | 4 ++
arch/arm/boot/compressed/Makefile | 2 +
arch/arm/boot/compressed/vmlinux.lds.S| 20 +++
.../arm/{kernel => include/asm}/vmlinux.lds.h | 30 --
arch/arm/kernel/vmlinux-xip.lds.S | 8 ++-
arch/arm/kernel/vmlinux.lds.S | 8 ++-
arch/arm64/Makefile | 9 ++-
arch/arm64/kernel/smccc-call.S| 2 -
arch/arm64/kernel/vmlinux.lds.S | 28 +++--
arch/arm64/mm/mmu.c | 2 +-
arch/csky/kernel/vmlinux.lds.S| 1 +
arch/hexagon/kernel/vmlinux.lds.S | 1 +
arch/ia64/kernel/vmlinux.lds.S| 1 +
arch/mips/kernel/vmlinux.lds.S| 1 +
arch/nds32/kernel/vmlinux.lds.S | 1 +
arch/nios2/kernel/vmlinux.lds.S | 1 +
arch/openrisc/kernel/vmlinux.lds.S| 1 +
arch/parisc/boot/compressed/vmlinux.lds.S | 1 +
