Messages in this thread | | | From | Geert Uytterhoeven <> | Date | Thu, 1 Feb 2018 12:55:47 +0100 | Subject | Re: [PATCH 2/3] compiler-gcc.h: __nostackprotector needs gcc-4.4 and up |
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Hi Arnd,
On Thu, Feb 1, 2018 at 12:46 PM, Arnd Bergmann <arnd@arndb.de> wrote: > On Thu, Feb 1, 2018 at 11:21 AM, Geert Uytterhoeven > <geert@linux-m68k.org> wrote: >> Gcc versions before 4.4 do not recognize the __optimize__ compiler >> attribute: >> >> warning: ‘__optimize__’ attribute directive ignored >> >> Fixes: 7375ae3a0b79ea07 ("compiler-gcc.h: Introduce __nostackprotector function attribute") >> Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org> >> --- >> Can anyone please verify this? >> Apparently __nostackprotector is used on x86 only, which is usually >> served by modern compilers. > > I've checked that __optimize("no-stack-protector") is accepted by exactly those > compilers that your 40400 version check tests for, across all architectures, so > that's fine.
Thanks!
> However, looking at commit 91cfc88c66bf ("x86: Use __nostackprotect for > sme_encrypt_kernel"), I suspect that gcc-4.1 through 4.3 will now cause > a runtime failure in sme_encrypt_kernel() without a compile-time warning.
So having this functionality is a hard requirement. Oops...
> I would leave __nostackprotector unchanged here, so we at least get > a warning for functions that need to disable the stack protector to work > correctly.
Agreed.
> We might want to add an #ifdef CONFIG_CC_STACKPROTECTOR around > the __nostackprotector definition, so that we only warn if stackprotector > is globally enabled.
And we might want to remove the dummy in include/linux/compiler_types.h:
#ifndef __nostackprotector # define __nostackprotector #endif
BTW, how does this work with non-gcc compilers?
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
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
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