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| author | Zhangjin Wu <falcon@tinylab.org> | 2023-07-15 21:18:54 +0300 |
|---|---|---|
| committer | Willy Tarreau <w@1wt.eu> | 2023-08-23 05:40:22 +0300 |
| commit | bff60150f7c464d80d86f289c056c2ad2afb3c05 (patch) | |
| tree | df1827acbd23bf0a92c9d7a08a7b4ee11abaaeed /tools/include/nolibc/arch-riscv.h | |
| parent | 20233498359a29f7b2ff4e8fbdb0a1a7c8d5744c (diff) | |
| download | linux-bff60150f7c464d80d86f289c056c2ad2afb3c05.tar.xz | |
tools/nolibc: fix up startup failures for -O0 under gcc < 11.1.0
As gcc doc [1] shows:
Most optimizations are completely disabled at -O0 or if an -O level is
not set on the command line, even if individual optimization flags are
specified.
Test result [2] shows, gcc>=11.1.0 deviates from the above description,
but before gcc 11.1.0, "-O0" still forcely uses frame pointer in the
_start function even if the individual optimize("omit-frame-pointer")
flag is specified.
The frame pointer related operations will change the stack pointer (e.g.
In x86_64, an extra "push %rbp" will be inserted at the beginning of
_start) and make it differs from the one we expected, as a result, break
the whole startup function.
To fix up this issue, as suggested by Thomas, the individual "Os" and
"omit-frame-pointer" optimize flags are used together on _start function
to disable frame pointer completely even if the -O0 is set on the
command line.
[1]: https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html
[2]: https://lore.kernel.org/lkml/20230714094723.140603-1-falcon@tinylab.org/
Suggested-by: Thomas Weißschuh <linux@weissschuh.net>
Link: https://lore.kernel.org/lkml/34b21ba5-7b59-4b3b-9ed6-ef9a3a5e06f7@t-8ch.de/
Fixes: 7f8548589661 ("tools/nolibc: make compiler and assembler agree on the section around _start")
Signed-off-by: Zhangjin Wu <falcon@tinylab.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Diffstat (limited to 'tools/include/nolibc/arch-riscv.h')
| -rw-r--r-- | tools/include/nolibc/arch-riscv.h | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/tools/include/nolibc/arch-riscv.h b/tools/include/nolibc/arch-riscv.h index 1dd7083c2ac8..322c96f4acdb 100644 --- a/tools/include/nolibc/arch-riscv.h +++ b/tools/include/nolibc/arch-riscv.h @@ -180,7 +180,7 @@ char **environ __attribute__((weak)); const unsigned long *_auxv __attribute__((weak)); /* startup code */ -void __attribute__((weak, noreturn, optimize("omit-frame-pointer"))) __no_stack_protector _start(void) +void __attribute__((weak, noreturn, optimize("Os", "omit-frame-pointer"))) __no_stack_protector _start(void) { __asm__ volatile ( ".option push\n" |