On Mon, Jul 30, 2018 at 11:39 AM Nathan Chancellor <natechancellor@xxxxxxxxx> wrote: > > On Mon, Jul 30, 2018 at 10:06:20AM -0700, Nick Desaulniers wrote: > > Starting with Clang-7.0, _THIS_IP_ generates -Wreturn-stack-address > > warnings for almost every translation unit. In general, I'd prefer to > > leave this on (returning the address of a stack allocated variable is in > > general a bad idea) and disable it only at whitelisted call sites. > > > > We can't do something like: > > #pragma clang diagnostic push > > #pragma clang diagnostic ignored "-Wreturn-stack-address" > > <code> > > #pragma clang diagnostic pop > > > > in a GNU Statement Expression or macro, hence we use _Pragma, which is > > its raison d'être: https://gcc.gnu.org/onlinedocs/cpp/Pragmas.html > > > > Cc: stable@xxxxxxxxxxxxxxx # 4.17, 4.14, 4.9, 4.4 > > Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> > > --- > > include/linux/kernel.h | 10 +++++++++- > > 1 file changed, 9 insertions(+), 1 deletion(-) > > > > diff --git a/include/linux/kernel.h b/include/linux/kernel.h > > index 941dc0a5a877..5906f5727f90 100644 > > --- a/include/linux/kernel.h > > +++ b/include/linux/kernel.h > > @@ -168,7 +168,15 @@ > > > > > > #define _RET_IP_ (unsigned long)__builtin_return_address(0) > > -#define _THIS_IP_ ({ __label__ __here; __here: (unsigned long)&&__here; }) > > +#define _THIS_IP_ ( \ > > +{ \ > > + _Pragma("clang diagnostic push") \ > > + _Pragma("clang diagnostic ignored \"-Wreturn-stack-address\"") \ > > + __label__ __here; \ > > +__here: (unsigned long)&&__here; \ > > + _Pragma("clang diagnostic pop") \ > > +} \ > > +) > > > > #ifdef CONFIG_LBDAF > > # include <asm/div64.h> > > -- > > 2.18.0.233.g985f88cf7e-goog > > > > This generates a ton of warnings with GCC: > > In file included from ./include/linux/spinlock.h:58, > from ./include/linux/mmzone.h:8, > from ./include/linux/gfp.h:6, > from ./include/linux/slab.h:15, > from ./include/linux/crypto.h:24, > from arch/x86/kernel/asm-offsets.c:9: > ./include/linux/bottom_half.h: In function ‘local_bh_disable’: > ./include/linux/bottom_half.h:19: error: ignoring #pragma clang diagnostic [-Werror=unknown-pragmas] > __local_bh_disable_ip(_THIS_IP_, SOFTIRQ_DISABLE_OFFSET); > > ./include/linux/bottom_half.h:19: error: ignoring #pragma clang diagnostic [-Werror=unknown-pragmas] > ./include/linux/bottom_half.h:19: error: ignoring #pragma clang diagnostic [-Werror=unknown-pragmas] > ./include/linux/bottom_half.h: In function ‘local_bh_enable’: > ./include/linux/bottom_half.h:32: error: ignoring #pragma clang diagnostic [-Werror=unknown-pragmas] > __local_bh_enable_ip(_THIS_IP_, SOFTIRQ_DISABLE_OFFSET); > > ./include/linux/bottom_half.h:32: error: ignoring #pragma clang diagnostic [-Werror=unknown-pragmas] > ./include/linux/bottom_half.h:32: error: ignoring #pragma clang diagnostic [-Werror=unknown-pragmas] > cc1: all warnings being treated as errors > make[1]: *** [Kbuild:56: arch/x86/kernel/asm-offsets.s] Error 1 > make: *** [Makefile:1081: prepare0] Error 2 Ah, good catch. I thought I had tested locally with gcc-8, but it seems that it was likely only godbolt. I do see the errors locally when building with gcc-8. > > A proper solution is probably going to involve what was done for the > -Wattribute-alias warnings from GCC 8 in commits 8793bb7f4a9d ("kbuild: > add macro for controlling warnings to linux/compiler.h") and > bee20031772a ("disable -Wattribute-alias warning for SYSCALL_DEFINEx()") > > I'll take a look at it in a bit unless someone beats me to it. I'll fix this up, triple check with gcc-8, and attribute you in the Suggested-by tag. Thank you for verifying. -- Thanks, ~Nick Desaulniers
