From: Michael Ellerman <mpe@ellerman.id.au>
To: <linuxppc-dev@lists.ozlabs.org>
Cc: linux-kernel@vger.kernel.org, torvalds@linux-foundation.org,
linux-hardening@vger.kernel.org, sudipm.mukherjee@gmail.com,
keescook@chromium.org
Subject: [PATCH] powerpc/64s: Disable stack variable initialisation for prom_init
Date: Mon, 18 Jul 2022 23:44:18 +1000 [thread overview]
Message-ID: <20220718134418.354114-1-mpe@ellerman.id.au> (raw)
In-Reply-To: <87cze3docs.fsf@mpe.ellerman.id.au>
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(+)
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
--
2.35.3
next prev parent reply other threads:[~2022-07-18 13:45 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-14 8:55 mainline build failure of powerpc allmodconfig for prom_init_check Sudip Mukherjee (Codethink)
2022-07-17 9:12 ` Sudip Mukherjee
2022-07-17 14:44 ` Linus Torvalds
2022-07-17 19:54 ` Segher Boessenkool
2022-07-18 3:52 ` Michael Ellerman
2022-07-18 14:56 ` Segher Boessenkool
2022-07-17 20:25 ` Sudip Mukherjee
2022-07-17 20:29 ` Linus Torvalds
2022-07-17 20:38 ` Sudip Mukherjee
2022-07-17 20:56 ` Linus Torvalds
2022-07-17 20:56 ` Segher Boessenkool
2022-07-17 21:11 ` Linus Torvalds
2022-07-17 21:45 ` Segher Boessenkool
2022-07-18 1:38 ` Linus Torvalds
2022-07-18 4:41 ` Michael Ellerman
2022-07-18 7:51 ` David Laight
2022-07-18 13:44 ` Michael Ellerman [this message]
2022-07-18 15:03 ` [PATCH] powerpc/64s: Disable stack variable initialisation for prom_init Sudip Mukherjee
2022-07-18 18:34 ` Linus Torvalds
2022-07-27 12:02 ` Michael Ellerman
2022-07-18 19:06 ` mainline build failure of powerpc allmodconfig for prom_init_check Linus Torvalds
2022-07-18 22:08 ` Segher Boessenkool
2022-07-18 22:55 ` Linus Torvalds
2022-07-19 13:35 ` Michael Ellerman
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