| Message ID | 20220718134418.354114-1-mpe@ellerman.id.au (mailing list archive) |
|---|---|
| State | Mainlined |
| Commit | be640317a1d0b9cf42fedb2debc2887a7cfa38de |
| Headers | show |
| Series | powerpc/64s: Disable stack variable initialisation for prom_init | expand |
On Mon, Jul 18, 2022 at 2:44 PM Michael Ellerman <mpe@ellerman.id.au> wrote: > > With GCC 12 allmodconfig prom_init fails to build: > > Error: External symbol 'memset' referenced from prom_init.c > make[2]: *** [arch/powerpc/kernel/Makefile:204: arch/powerpc/kernel/prom_init_check] Error 1 > <snip> > > Reported-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com> > Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> And, this has fixed the build failure. Thanks Michael.
On Mon, Jul 18, 2022 at 6:44 AM Michael Ellerman <mpe@ellerman.id.au> wrote: > > With GCC 12, allmodconfig enables CONFIG_INIT_STACK_ALL_PATTERN, which > causes the compiler to emit memset calls to initialise on-stack > variables with a pattern. Ahh, and that explains why "volatile" made no difference. That did seem very odd. Thanks for figuring it out, Linus
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile index f91f0f29a566..c8cf924bf9c0 100644 --- a/arch/powerpc/kernel/Makefile +++ b/arch/powerpc/kernel/Makefile @@ -20,6 +20,7 @@ CFLAGS_prom.o += $(DISABLE_LATENT_ENTROPY_PLUGIN) CFLAGS_prom_init.o += -fno-stack-protector CFLAGS_prom_init.o += -DDISABLE_BRANCH_PROFILING CFLAGS_prom_init.o += -ffreestanding +CFLAGS_prom_init.o += $(call cc-option, -ftrivial-auto-var-init=uninitialized) ifdef CONFIG_FUNCTION_TRACER # Do not trace early boot code
With GCC 12 allmodconfig prom_init fails to build: Error: External symbol 'memset' referenced from prom_init.c make[2]: *** [arch/powerpc/kernel/Makefile:204: arch/powerpc/kernel/prom_init_check] Error 1 The allmodconfig build enables KASAN, so all calls to memset in prom_init should be converted to __memset by the #ifdefs in asm/string.h, because prom_init must use the non-KASAN instrumented versions. The build failure happens because there's a call to memset that hasn't been caught by the pre-processor and converted to __memset. Typically that's because it's a memset generated by the compiler itself, and that is the case here. With GCC 12, allmodconfig enables CONFIG_INIT_STACK_ALL_PATTERN, which causes the compiler to emit memset calls to initialise on-stack variables with a pattern. Because prom_init is non-user-facing boot-time only code, as a workaround just disable stack variable initialisation to unbreak the build. Reported-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> --- arch/powerpc/kernel/Makefile | 1 + 1 file changed, 1 insertion(+)