Hi Andrey, On Tue, 13 Oct 2015 18:28:07 +0300 Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx> wrote: > > Some code may perform racy by design memory reads. This could be harmless, > yet such code may produce KASAN warnings. > > To hide such accesses from KASAN this patch introduces READ_ONCE_NOCHECK() > macro. KASAN will not check the memory accessed by READ_ONCE_NOCHECK(). > > This patch creates __read_once_size_nocheck() a clone of > __read_once_size_check() (renamed __read_once_size()). > The only difference between them is 'no_sanitized_address' attribute > appended to '*_nocheck' function. This attribute tells the compiler that > instrumentation of memory accesses should not be applied to that function. > We declare it as static '__maybe_unsed' because GCC is not capable to > inline such function: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368 > > With KASAN=n READ_ONCE_NOCHECK() is just a clone of READ_ONCE(). > > Signed-off-by: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx> > --- > include/linux/compiler-gcc.h | 13 ++++++++++ > include/linux/compiler.h | 60 ++++++++++++++++++++++++++++++++++---------- > 2 files changed, 60 insertions(+), 13 deletions(-) I am pretty sure that this patch is causing quite a bit of compile breakage in linux-next today. During the day I compile with gcc 4.9.0 and did not see any problems with c86_64 allmodconfig, or i386 defconfig etc, but overnight we compile with older compilers (gcc 4.6.3 in particular) and are getting quite a few errors: >From an i386 allnoconfig build: arch/x86/entry/vdso/vdso32.so.dbg: undefined symbols found /home/kisskb/slave/src/arch/x86/entry/vdso/Makefile:154: recipe for target 'arch/x86/entry/vdso/vdso32.so.dbg' failed >From an x86_64 allnoconfig build: arch/x86/entry/vdso/vclock_gettime.o: In function `__read_once_size_check': vclock_gettime.c:(.text+0x5f): undefined reference to `memcpy' arch/x86/entry/vdso/vgetcpu.o: In function `__read_once_size_check': vgetcpu.c:(.text+0x2f): undefined reference to `memcpy' and several others ... -- Cheers, Stephen Rothwell sfr@xxxxxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-next" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
