mirror of
https://github.com/torvalds/linux
synced 2024-09-06 18:01:05 +00:00
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>
This commit is contained in:
parent
c5e4a062fe
commit
ed13fc33f7
|
@ -1,3 +1,2 @@
|
|||
#define KSYM_ALIGN 2
|
||||
#define KCRC_ALIGN 2
|
||||
#include <asm-generic/export.h>
|
||||
|
|
|
@ -4,14 +4,12 @@
|
|||
#ifndef KSYM_FUNC
|
||||
#define KSYM_FUNC(x) x
|
||||
#endif
|
||||
#ifdef CONFIG_64BIT
|
||||
#ifndef KSYM_ALIGN
|
||||
#define KSYM_ALIGN 8
|
||||
#endif
|
||||
#else
|
||||
#ifndef KSYM_ALIGN
|
||||
#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
|
||||
#define KSYM_ALIGN 4
|
||||
#elif defined(CONFIG_64BIT)
|
||||
#define KSYM_ALIGN 8
|
||||
#else
|
||||
#define KSYM_ALIGN 4
|
||||
#endif
|
||||
#endif
|
||||
#ifndef KCRC_ALIGN
|
||||
#define KCRC_ALIGN 4
|
||||
|
|
|
@ -52,7 +52,7 @@ extern struct module __this_module;
|
|||
#define __KSYMTAB_ENTRY(sym, sec) \
|
||||
__ADDRESSABLE(sym) \
|
||||
asm(" .section \"___ksymtab" sec "+" #sym "\", \"a\" \n" \
|
||||
" .balign 8 \n" \
|
||||
" .balign 4 \n" \
|
||||
"__ksymtab_" #sym ": \n" \
|
||||
" .long " #sym "- . \n" \
|
||||
" .long __kstrtab_" #sym "- . \n" \
|
||||
|
@ -66,6 +66,7 @@ struct kernel_symbol {
|
|||
#define __KSYMTAB_ENTRY(sym, sec) \
|
||||
static const struct kernel_symbol __ksymtab_##sym \
|
||||
__attribute__((section("___ksymtab" sec "+" #sym), used)) \
|
||||
__aligned(sizeof(void *)) \
|
||||
= { (unsigned long)&sym, __kstrtab_##sym }
|
||||
|
||||
struct kernel_symbol {
|
||||
|
|
Loading…
Reference in a new issue