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tools/nolibc: compiler: use attribute((naked)) if available

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The current entrypoint attributes optimize("Os", "omit-frame-pointer")
are intended to avoid all compiler generated code, like function
porologue and epilogue.
This is the exact usecase implemented by the attribute "naked".

Unfortunately this is not implemented by GCC for all targets,
so only use it where available.
This also provides compatibility with clang, which recognizes the
"naked" attribute but not the previously used attribute "optimized".

Acked-by: Willy Tarreau <w@1wt.eu>
Link: https://lore.kernel.org/r/20240807-nolibc-llvm-v2-6-c20f2f5fc7c2@weissschuh.net
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
This commit is contained in:
Thomas Weißschuh 2024-08-07 23:51:42 +02:00
parent ef32e9b6a3
commit e098eebb63
1 changed files with 7 additions and 2 deletions
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9
tools/include/nolibc/compiler.h
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@ -12,8 +12,13 @@
# define __nolibc_has_attribute(attr) 0
#endif
#define __nolibc_entrypoint __attribute__((optimize("Os", "omit-frame-pointer")))
#define __nolibc_entrypoint_epilogue() __builtin_unreachable()
#if __nolibc_has_attribute(naked)
# define __nolibc_entrypoint __attribute__((naked))
# define __nolibc_entrypoint_epilogue()
#else
# define __nolibc_entrypoint __attribute__((optimize("Os", "omit-frame-pointer")))
# define __nolibc_entrypoint_epilogue() __builtin_unreachable()
#endif /* __nolibc_has_attribute(naked) */
#if defined(__SSP__) || defined(__SSP_STRONG__) || defined(__SSP_ALL__) || defined(__SSP_EXPLICIT__)