When enabling CONFIG_TRIM_UNUSED_KSYMS, the linker will warn about the
orphan sections:
(".discard.ksym") is being placed in '".discard.ksym"'
repeatedly when linking vmlinux. This is because the stringification
operator, `#`, in the preprocessor escapes strings. GCC and Clang
differ in how they treat section names that contain \".
The portable solution is to not use a string literal with the
preprocessor stringification operator.
Link: https://bugs.llvm.org/show_bug.cgi?id=42950
Link: https://github.com/ClangBuiltLinux/linux/issues/1166
Fixes: commit bbda5ec671d3 ("kbuild: simplify dependency generation for CONFIG_TRIM_UNUSED_KSYMS")
Reported-by: kbuild test robot <[email protected]>
Suggested-by: Kees Cook <[email protected]>
Signed-off-by: Nick Desaulniers <[email protected]>
---
include/linux/export.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/linux/export.h b/include/linux/export.h
index fceb5e855717..8933ff6ad23a 100644
--- a/include/linux/export.h
+++ b/include/linux/export.h
@@ -130,7 +130,7 @@ struct kernel_symbol {
* discarded in the final link stage.
*/
#define __ksym_marker(sym) \
- static int __ksym_marker_##sym[0] __section(".discard.ksym") __used
+ static int __ksym_marker_##sym[0] __section(.discard.ksym) __used
#define __EXPORT_SYMBOL(sym, sec, ns) \
__ksym_marker(sym); \
--
2.28.0.709.gb0816b6eb0-goog
On Tue, Sep 29, 2020 at 12:07:00PM -0700, Nick Desaulniers wrote:
> When enabling CONFIG_TRIM_UNUSED_KSYMS, the linker will warn about the
> orphan sections:
> (".discard.ksym") is being placed in '".discard.ksym"'
> repeatedly when linking vmlinux. This is because the stringification
> operator, `#`, in the preprocessor escapes strings. GCC and Clang
> differ in how they treat section names that contain \".
>
> The portable solution is to not use a string literal with the
> preprocessor stringification operator.
>
> Link: https://bugs.llvm.org/show_bug.cgi?id=42950
> Link: https://github.com/ClangBuiltLinux/linux/issues/1166
> Fixes: commit bbda5ec671d3 ("kbuild: simplify dependency generation for CONFIG_TRIM_UNUSED_KSYMS")
> Reported-by: kbuild test robot <[email protected]>
> Suggested-by: Kees Cook <[email protected]>
> Signed-off-by: Nick Desaulniers <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
Do these other cases need fixing too?
arch/arm64/mm/mmu.c:u64 __section(".mmuoff.data.write") vabits_actual;
include/linux/srcutree.h: __section("___srcu_struct_ptrs") = &name
-Kees
> ---
> include/linux/export.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/export.h b/include/linux/export.h
> index fceb5e855717..8933ff6ad23a 100644
> --- a/include/linux/export.h
> +++ b/include/linux/export.h
> @@ -130,7 +130,7 @@ struct kernel_symbol {
> * discarded in the final link stage.
> */
> #define __ksym_marker(sym) \
> - static int __ksym_marker_##sym[0] __section(".discard.ksym") __used
> + static int __ksym_marker_##sym[0] __section(.discard.ksym) __used
>
> #define __EXPORT_SYMBOL(sym, sec, ns) \
> __ksym_marker(sym); \
> --
> 2.28.0.709.gb0816b6eb0-goog
>
--
Kees Cook
On Tue, Sep 29, 2020 at 12:07:00PM -0700, Nick Desaulniers wrote:
> When enabling CONFIG_TRIM_UNUSED_KSYMS, the linker will warn about the
> orphan sections:
> (".discard.ksym") is being placed in '".discard.ksym"'
> repeatedly when linking vmlinux. This is because the stringification
> operator, `#`, in the preprocessor escapes strings. GCC and Clang
> differ in how they treat section names that contain \".
>
> The portable solution is to not use a string literal with the
> preprocessor stringification operator.
>
> Link: https://bugs.llvm.org/show_bug.cgi?id=42950
> Link: https://github.com/ClangBuiltLinux/linux/issues/1166
> Fixes: commit bbda5ec671d3 ("kbuild: simplify dependency generation for CONFIG_TRIM_UNUSED_KSYMS")
> Reported-by: kbuild test robot <[email protected]>
> Suggested-by: Kees Cook <[email protected]>
> Signed-off-by: Nick Desaulniers <[email protected]>
Reviewed-by: Nathan Chancellor <[email protected]>
> ---
> include/linux/export.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/export.h b/include/linux/export.h
> index fceb5e855717..8933ff6ad23a 100644
> --- a/include/linux/export.h
> +++ b/include/linux/export.h
> @@ -130,7 +130,7 @@ struct kernel_symbol {
> * discarded in the final link stage.
> */
> #define __ksym_marker(sym) \
> - static int __ksym_marker_##sym[0] __section(".discard.ksym") __used
> + static int __ksym_marker_##sym[0] __section(.discard.ksym) __used
>
> #define __EXPORT_SYMBOL(sym, sec, ns) \
> __ksym_marker(sym); \
> --
> 2.28.0.709.gb0816b6eb0-goog
>
On Tue, Sep 29, 2020 at 9:07 PM 'Nick Desaulniers' via Clang Built
Linux <[email protected]> wrote:
>
> When enabling CONFIG_TRIM_UNUSED_KSYMS, the linker will warn about the
> orphan sections:
> (".discard.ksym") is being placed in '".discard.ksym"'
> repeatedly when linking vmlinux. This is because the stringification
> operator, `#`, in the preprocessor escapes strings. GCC and Clang
> differ in how they treat section names that contain \".
>
> The portable solution is to not use a string literal with the
> preprocessor stringification operator.
>
> Link: https://bugs.llvm.org/show_bug.cgi?id=42950
> Link: https://github.com/ClangBuiltLinux/linux/issues/1166
> Fixes: commit bbda5ec671d3 ("kbuild: simplify dependency generation for CONFIG_TRIM_UNUSED_KSYMS")
> Reported-by: kbuild test robot <[email protected]>
> Suggested-by: Kees Cook <[email protected]>
> Signed-off-by: Nick Desaulniers <[email protected]>
"The return of escaped section names" - soon in your cinema?
Thanks Nick for catching this.
Reviewed-by: Sedat Dilek <[email protected]>
- Sedat -
> ---
> include/linux/export.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/export.h b/include/linux/export.h
> index fceb5e855717..8933ff6ad23a 100644
> --- a/include/linux/export.h
> +++ b/include/linux/export.h
> @@ -130,7 +130,7 @@ struct kernel_symbol {
> * discarded in the final link stage.
> */
> #define __ksym_marker(sym) \
> - static int __ksym_marker_##sym[0] __section(".discard.ksym") __used
> + static int __ksym_marker_##sym[0] __section(.discard.ksym) __used
>
> #define __EXPORT_SYMBOL(sym, sec, ns) \
> __ksym_marker(sym); \
> --
> 2.28.0.709.gb0816b6eb0-goog
>
> --
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