diff options
| author | Matthias Maennich <maennich@google.com> | 2019-09-06 11:32:26 +0100 |
|---|---|---|
| committer | Jessica Yu <jeyu@kernel.org> | 2019-09-10 10:30:09 +0200 |
| commit | ed13fc33f763035a7c290f11c7111877c3a5daab (patch) | |
| tree | 40cc79e8871ff027f7063ba38dd9f25790feace0 /include/asm-generic/export.h | |
| parent | c5e4a062fe661806ab291a7576dc4a41613adb86 (diff) | |
export: explicitly align struct kernel_symbol
This change allows growing struct kernel_symbol without wasting bytes to
alignment. It also concretized the alignment of ksymtab entries if
relative references are used for ksymtab entries.
struct kernel_symbol was already implicitly being aligned to the word
size, except on x86_64 and m68k, where it is aligned to 16 and 2 bytes,
respectively.
As far as I can tell there is no requirement for aligning struct
kernel_symbol to 16 bytes on x86_64, but gcc aligns structs to their
size, and the linker aligns the custom __ksymtab sections to the largest
data type contained within, so setting KSYM_ALIGN to 16 was necessary to
stay consistent with the code generated for non-ASM EXPORT_SYMBOL(). Now
that non-ASM EXPORT_SYMBOL() explicitly aligns to word size (8),
KSYM_ALIGN is no longer necessary.
In case of relative references, the alignment has been changed
accordingly to not waste space when adding new struct members.
As for m68k, struct kernel_symbol is aligned to 2 bytes even though the
structure itself is 8 bytes; using a 4-byte alignment shouldn't hurt.
I manually verified the output of the __ksymtab sections didn't change
on x86, x86_64, arm, arm64 and m68k. As expected, the section contents
didn't change, and the ELF section alignment only changed on x86_64 and
m68k. Feedback from other archs more than welcome.
Co-developed-by: Martijn Coenen <maco@android.com>
Signed-off-by: Martijn Coenen <maco@android.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Matthias Maennich <maennich@google.com>
Signed-off-by: Jessica Yu <jeyu@kernel.org>
Diffstat (limited to 'include/asm-generic/export.h')
| -rw-r--r-- | include/asm-generic/export.h | 8 |
1 files changed, 3 insertions, 5 deletions
diff --git a/include/asm-generic/export.h b/include/asm-generic/export.h index 294d6ae785d4..63f54907317b 100644 --- a/include/asm-generic/export.h +++ b/include/asm-generic/export.h @@ -4,15 +4,13 @@ #ifndef KSYM_FUNC #define KSYM_FUNC(x) x #endif -#ifdef CONFIG_64BIT -#ifndef KSYM_ALIGN +#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS +#define KSYM_ALIGN 4 +#elif defined(CONFIG_64BIT) #define KSYM_ALIGN 8 -#endif #else -#ifndef KSYM_ALIGN #define KSYM_ALIGN 4 #endif -#endif #ifndef KCRC_ALIGN #define KCRC_ALIGN 4 #endif |