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@xxxxxxxxxx>
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@xxxxxxxxxxxxxxx
Link: https://github.com/ClangBuiltLinux/linux/issues/1432
Link:
https://github.com/llvm/llvm-project/commit/7b789562244ee941b7bf2cefeb3fc08a59a01865
Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx>
---
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
