Hi Ard,
On Tue, Oct 27, 2020 at 9:57 PM Ard Biesheuvel <[email protected]> wrote:
> Commit 3193c0836f203 ("bpf: Disable GCC -fgcse optimization for
> ___bpf_prog_run()") introduced a __no_fgcse macro that expands to a
> function scope __attribute__((optimize("-fno-gcse"))), to disable a
> GCC specific optimization that was causing trouble on x86 builds, and
> was not expected to have any positive effect in the first place.
>
> However, as the GCC manual documents, __attribute__((optimize))
> is not for production use, and results in all other optimization
> options to be forgotten for the function in question. This can
> cause all kinds of trouble, but in one particular reported case,
> it causes -fno-asynchronous-unwind-tables to be disregarded,
> resulting in .eh_frame info to be emitted for the function
> inadvertently.
>
> This reverts commit 3193c0836f203, and instead, it disables the -fgcse
> optimization for the entire source file, but only when building for
> X86.
>
> Cc: Nick Desaulniers <[email protected]>
> Cc: Arvind Sankar <[email protected]>
> Cc: Randy Dunlap <[email protected]>
> Cc: Josh Poimboeuf <[email protected]>
> Cc: Thomas Gleixner <[email protected]>
> Cc: Alexei Starovoitov <[email protected]>
> Cc: Daniel Borkmann <[email protected]>
> Cc: Peter Zijlstra (Intel) <[email protected]>
> Cc: Geert Uytterhoeven <[email protected]>
> Cc: Kees Cook <[email protected]>
> Fixes: 3193c0836f203 ("bpf: Disable GCC -fgcse optimization for
> ___bpf_prog_run()")
> Signed-off-by: Ard Biesheuvel <[email protected]>
Thanks, this gets rid of the following warning, which you may
want to quote in the patch description:
aarch64-linux-gnu-ld: warning: orphan section `.eh_frame' from
`kernel/bpf/core.o' being placed in section `.eh_frame'
Tested-by: Geert Uytterhoeven <[email protected]>
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected]
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
