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 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. Thanks! Nathan
