| Message ID | 20210730223815.1382706-1-nathan@kernel.org |
|---|---|
| State | Accepted |
| Commit | 848378812e40152abe9b9baf58ce2004f76fb988 |
| Headers | show |
| Series | vmlinux.lds.h: Handle clang's module.{c,d}tor sections | expand |
On 7/30/2021 3:59 PM, Fangrui Song wrote: > On 2021-07-30, Nick Desaulniers wrote: >> On Fri, Jul 30, 2021 at 3:38 PM Nathan Chancellor <nathan@kernel.org> >> wrote: >>> >>> A recent change in LLVM causes module_{c,d}tor sections to appear when >>> CONFIG_K{A,C}SAN are enabled, which results in orphan section warnings >>> because these are not handled anywhere: >>> >>> ld.lld: warning: >>> arch/x86/pci/built-in.a(legacy.o):(.text.asan.module_ctor) is being >>> placed in '.text.asan.module_ctor' >>> ld.lld: warning: >>> arch/x86/pci/built-in.a(legacy.o):(.text.asan.module_dtor) is being >>> placed in '.text.asan.module_dtor' >>> ld.lld: warning: >>> arch/x86/pci/built-in.a(legacy.o):(.text.tsan.module_ctor) is being >>> placed in '.text.tsan.module_ctor' >> >> ^ .text.tsan.* > > I was wondering why the orphan section warning only arose recently. > Now I see: the function asan.module_ctor has the SHF_GNU_RETAIN flag, so > it is in a separate section even with -fno-function-sections (default). Thanks for the explanation, I will add this to the commit message. > It seems that with -ffunction-sections the issue should have been caught > much earlier. > >>> >>> Place them in the TEXT_TEXT section so that these technologies continue >>> to work with the newer compiler versions. All of the KASAN and KCSAN >>> KUnit tests continue to pass after this change. >>> >>> Cc: stable@vger.kernel.org >>> Link: https://github.com/ClangBuiltLinux/linux/issues/1432 >>> Link: >>> https://github.com/llvm/llvm-project/commit/7b789562244ee941b7bf2cefeb3fc08a59a01865 >>> >>> Signed-off-by: Nathan Chancellor <nathan@kernel.org> >>> --- >>> include/asm-generic/vmlinux.lds.h | 1 + >>> 1 file changed, 1 insertion(+) >>> >>> diff --git a/include/asm-generic/vmlinux.lds.h >>> b/include/asm-generic/vmlinux.lds.h >>> index 17325416e2de..3b79b1e76556 100644 >>> --- a/include/asm-generic/vmlinux.lds.h >>> +++ b/include/asm-generic/vmlinux.lds.h >>> @@ -586,6 +586,7 @@ >>> >>> NOINSTR_TEXT \ >>> >>> *(.text..refcount) \ >>> >>> *(.ref.text) \ >>> + *(.text.asan >>> .text.asan.*) \ >> >> Will this match .text.tsan.module_ctor? No, I forgot to test CONFIG_KCSAN with this version, rather than the prior one I had on GitHub so I will send v2 shortly. > asan.module_ctor is the only function AddressSanitizer synthesizes in > the instrumented translation unit. > There is no function called "asan". > > (Even if a function "asan" exists due to -ffunction-sections > -funique-section-names, TEXT_MAIN will match .text.asan, so the > .text.asan pattern will match nothing.) Sounds good, I will update it to remove the .text.asan and replace it with .text.tsan.* >> Do we want to add these conditionally on >> CONFIG_KASAN_GENERIC/CONFIG_KCSAN like we do for SANITIZER_DISCARDS? I do not think there is a point in doing so but I can if others feel strongly. Thank you both for the comments for the comments! Cheers, Nathan
On Sat, 31 Jul 2021 at 04:33, Nathan Chancellor <nathan@kernel.org> wrote: > A recent change in LLVM causes module_{c,d}tor sections to appear when > CONFIG_K{A,C}SAN are enabled, which results in orphan section warnings > because these are not handled anywhere: > > ld.lld: warning: arch/x86/pci/built-in.a(legacy.o):(.text.asan.module_ctor) is being placed in '.text.asan.module_ctor' > ld.lld: warning: arch/x86/pci/built-in.a(legacy.o):(.text.asan.module_dtor) is being placed in '.text.asan.module_dtor' > ld.lld: warning: arch/x86/pci/built-in.a(legacy.o):(.text.tsan.module_ctor) is being placed in '.text.tsan.module_ctor' > > Fangrui explains: "the function asan.module_ctor has the SHF_GNU_RETAIN > flag, so it is in a separate section even with -fno-function-sections > (default)". > > Place them in the TEXT_TEXT section so that these technologies continue > to work with the newer compiler versions. All of the KASAN and KCSAN > KUnit tests continue to pass after this change. > > Cc: stable@vger.kernel.org > Link: https://github.com/ClangBuiltLinux/linux/issues/1432 > Link: https://github.com/llvm/llvm-project/commit/7b789562244ee941b7bf2cefeb3fc08a59a01865 > Signed-off-by: Nathan Chancellor <nathan@kernel.org> Acked-by: Marco Elver <elver@google.com> For KASAN module_ctors are very much required to support detecting globals out-of-bounds: https://reviews.llvm.org/D81390 For KASAN the test would have revealed that at the latest. KCSAN does not yet have much use for the module_ctors, but it may change in future, so keeping them all was the right call. Thanks, -- Marco > --- > > v1 -> v2: > > * Fix inclusion of .text.tsan.* (Nick) > > * Drop .text.asan as it does not exist plus it would be handled by a > different line (Fangrui) > > * Add Fangrui's explanation about why the LLVM commit caused these > sections to appear. > > include/asm-generic/vmlinux.lds.h | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h > index 17325416e2de..62669b36a772 100644 > --- a/include/asm-generic/vmlinux.lds.h > +++ b/include/asm-generic/vmlinux.lds.h > @@ -586,6 +586,7 @@ > NOINSTR_TEXT \ > *(.text..refcount) \ > *(.ref.text) \ > + *(.text.asan.* .text.tsan.*) \ > TEXT_CFI_JT \ > MEM_KEEP(init.text*) \ > MEM_KEEP(exit.text*) \ > > base-commit: 4669e13cd67f8532be12815ed3d37e775a9bdc16 > -- > 2.32.0.264.g75ae10bc75 >
On Fri, Jul 30, 2021 at 7:33 PM Nathan Chancellor <nathan@kernel.org> wrote: > > A recent change in LLVM causes module_{c,d}tor sections to appear when > CONFIG_K{A,C}SAN are enabled, which results in orphan section warnings > because these are not handled anywhere: > > ld.lld: warning: arch/x86/pci/built-in.a(legacy.o):(.text.asan.module_ctor) is being placed in '.text.asan.module_ctor' > ld.lld: warning: arch/x86/pci/built-in.a(legacy.o):(.text.asan.module_dtor) is being placed in '.text.asan.module_dtor' > ld.lld: warning: arch/x86/pci/built-in.a(legacy.o):(.text.tsan.module_ctor) is being placed in '.text.tsan.module_ctor' > > Fangrui explains: "the function asan.module_ctor has the SHF_GNU_RETAIN > flag, so it is in a separate section even with -fno-function-sections > (default)". > > Place them in the TEXT_TEXT section so that these technologies continue > to work with the newer compiler versions. All of the KASAN and KCSAN > KUnit tests continue to pass after this change. > > Cc: stable@vger.kernel.org > Link: https://github.com/ClangBuiltLinux/linux/issues/1432 > Link: https://github.com/llvm/llvm-project/commit/7b789562244ee941b7bf2cefeb3fc08a59a01865 > Signed-off-by: Nathan Chancellor <nathan@kernel.org> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> > --- > > v1 -> v2: > > * Fix inclusion of .text.tsan.* (Nick) > > * Drop .text.asan as it does not exist plus it would be handled by a > different line (Fangrui) > > * Add Fangrui's explanation about why the LLVM commit caused these > sections to appear. > > include/asm-generic/vmlinux.lds.h | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h > index 17325416e2de..62669b36a772 100644 > --- a/include/asm-generic/vmlinux.lds.h > +++ b/include/asm-generic/vmlinux.lds.h > @@ -586,6 +586,7 @@ > NOINSTR_TEXT \ > *(.text..refcount) \ > *(.ref.text) \ > + *(.text.asan.* .text.tsan.*) \ > TEXT_CFI_JT \ > MEM_KEEP(init.text*) \ > MEM_KEEP(exit.text*) \ > > base-commit: 4669e13cd67f8532be12815ed3d37e775a9bdc16 > -- > 2.32.0.264.g75ae10bc75 > -- Thanks, ~Nick Desaulniers
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index 17325416e2de..3b79b1e76556 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -586,6 +586,7 @@ NOINSTR_TEXT \ *(.text..refcount) \ *(.ref.text) \ + *(.text.asan .text.asan.*) \ TEXT_CFI_JT \ MEM_KEEP(init.text*) \ MEM_KEEP(exit.text*) \
A recent change in LLVM causes module_{c,d}tor sections to appear when CONFIG_K{A,C}SAN are enabled, which results in orphan section warnings because these are not handled anywhere: ld.lld: warning: arch/x86/pci/built-in.a(legacy.o):(.text.asan.module_ctor) is being placed in '.text.asan.module_ctor' ld.lld: warning: arch/x86/pci/built-in.a(legacy.o):(.text.asan.module_dtor) is being placed in '.text.asan.module_dtor' ld.lld: warning: arch/x86/pci/built-in.a(legacy.o):(.text.tsan.module_ctor) is being placed in '.text.tsan.module_ctor' Place them in the TEXT_TEXT section so that these technologies continue to work with the newer compiler versions. All of the KASAN and KCSAN KUnit tests continue to pass after this change. Cc: stable@vger.kernel.org Link: https://github.com/ClangBuiltLinux/linux/issues/1432 Link: https://github.com/llvm/llvm-project/commit/7b789562244ee941b7bf2cefeb3fc08a59a01865 Signed-off-by: Nathan Chancellor <nathan@kernel.org> --- include/asm-generic/vmlinux.lds.h | 1 + 1 file changed, 1 insertion(+) base-commit: 4669e13cd67f8532be12815ed3d37e775a9bdc16