| Message ID | 1517480520-4465-2-git-send-email-geert@linux-m68k.org (mailing list archive) |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
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. 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. 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. We might want to add an #ifdef CONFIG_CC_STACKPROTECTOR around the __nostackprotector definition, so that we only warn if stackprotector is globally enabled. Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-sparse" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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 -- To unsubscribe from this list: send the line "unsubscribe linux-sparse" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, Feb 1, 2018 at 12:55 PM, Geert Uytterhoeven <geert@linux-m68k.org> wrote: > 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: > > 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? clang should in theory accept the same flags, and it pretends to be an older version of gcc. I don't think anyone cares about ICC or any other compiler. Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-sparse" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h index 0a278a527944ad2f..73bc63e0a1c4b664 100644 --- a/include/linux/compiler-gcc.h +++ b/include/linux/compiler-gcc.h @@ -167,8 +167,6 @@ #if GCC_VERSION >= 40100 # define __compiletime_object_size(obj) __builtin_object_size(obj, 0) - -#define __nostackprotector __attribute__((__optimize__("no-stack-protector"))) #endif #if GCC_VERSION >= 40300 @@ -198,6 +196,7 @@ #if GCC_VERSION >= 40400 #define __optimize(level) __attribute__((__optimize__(level))) +#define __nostackprotector __optimize("no-stack-protector") #endif /* GCC_VERSION >= 40400 */ #if GCC_VERSION >= 40500
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. --- include/linux/compiler-gcc.h | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)