This is a note to let you know that I've just added the patch titled
powerpc/64s: Disable stack variable initialisation for prom_init
to the 5.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
powerpc-64s-disable-stack-variable-initialisation-fo.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit e67c09ba122a2e4f72a720e8003c13f3588b62f1
Author: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Date: Mon Jul 18 23:44:18 2022 +1000
powerpc/64s: Disable stack variable initialisation for prom_init
[ 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@xxxxxxxxx>
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20220718134418.354114-1-mpe@xxxxxxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
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
