[PATCH AUTOSEL 5.10 2/7] powerpc/64s: Disable stack variable initialisation for prom_init
Sasha Levin
sashal at kernel.org
Tue Aug 2 05:02:56 AEST 2022
From: Michael Ellerman <mpe at ellerman.id.au>
[ Upstream commit be640317a1d0b9cf42fedb2debc2887a7cfa38de ]
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 at gmail.com>
Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>
Link: https://lore.kernel.org/r/20220718134418.354114-1-mpe@ellerman.id.au
Signed-off-by: Sasha Levin <sashal at kernel.org>
---
arch/powerpc/kernel/Makefile | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index 376104c166fc..db2bdc4cec64 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
--
2.35.1
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