Commit 7c95d8893fb5 ("powerpc: Change calling convention for
create_branch() et. al.") complexified the frame of function
do_feature_fixups(), leading to GCC setting up a stack
guard when CONFIG_STACKPROTECTOR is selected.
The problem is that do_feature_fixups() is called very early
while 'current' in r2 is not set up yet and the code is still
not at the final address used at link time.
So, like other instrumentation, stack protection needs to be
deactivated for feature-fixups.c and code-patching.c
Reported-by: Jonathan Neuschaefer <[email protected]>
Fixes: 7c95d8893fb5 ("powerpc: Change calling convention for create_branch() et. al.")
Signed-off-by: Christophe Leroy <[email protected]>
---
arch/powerpc/lib/Makefile | 3 +++
1 file changed, 3 insertions(+)
diff --git a/arch/powerpc/lib/Makefile b/arch/powerpc/lib/Makefile
index f2c690ee75d1..cc1a8a0f311e 100644
--- a/arch/powerpc/lib/Makefile
+++ b/arch/powerpc/lib/Makefile
@@ -5,6 +5,9 @@
ccflags-$(CONFIG_PPC64) := $(NO_MINIMAL_TOC)
+CFLAGS_code-patching.o += -fno-stack-protector
+CFLAGS_feature-fixups.o += -fno-stack-protector
+
CFLAGS_REMOVE_code-patching.o = $(CC_FLAGS_FTRACE)
CFLAGS_REMOVE_feature-fixups.o = $(CC_FLAGS_FTRACE)
--
2.25.0
On Thu, Apr 29, 2021 at 04:52:09PM +0000, Christophe Leroy wrote:
> Commit 7c95d8893fb5 ("powerpc: Change calling convention for
> create_branch() et. al.") complexified the frame of function
> do_feature_fixups(), leading to GCC setting up a stack
> guard when CONFIG_STACKPROTECTOR is selected.
>
> The problem is that do_feature_fixups() is called very early
> while 'current' in r2 is not set up yet and the code is still
> not at the final address used at link time.
>
> So, like other instrumentation, stack protection needs to be
> deactivated for feature-fixups.c and code-patching.c
>
> Reported-by: Jonathan Neuschaefer <[email protected]>
> Fixes: 7c95d8893fb5 ("powerpc: Change calling convention for create_branch() et. al.")
> Signed-off-by: Christophe Leroy <[email protected]>
> ---
Thank you for looking into this issue. This patch does indeed fix my
issue.
Tested-by: Jonathan Neuschaefer <[email protected]>
Thanks again,
Jonathan