[PATCH 1/3] powerpc: Fix stack protector Kconfig test for clang

[Nathan Chancellor <nathan@kernel.org>]

Clang's in-progress per-task stack protector support [1] does not work
with the current Kconfig checks because '-mstack-protector-guard-offset'
is not provided, unlike all other architecture Kconfig checks.

  $ fd Kconfig -x rg -l mstack-protector-guard-offset
  ./arch/arm/Kconfig
  ./arch/riscv/Kconfig
  ./arch/arm64/Kconfig

This produces an error from clang, which is interpreted as the flags not
being supported at all when they really are.

  $ clang --target=powerpc64-linux-gnu \
          -mstack-protector-guard=tls \
          -mstack-protector-guard-reg=r13 \
          -c -o /dev/null -x c /dev/null
  clang: error: '-mstack-protector-guard=tls' is used without '-mstack-protector-guard-offset', and there is no default

This argument will always be provided by the build system, so mirror
other architectures and use '-mstack-protector-guard-offset=0' for
testing support, which fixes the issue for clang and does not regress
support with GCC.

Link: https://github.com/llvm/llvm-project/pull/110928 [1]
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---
 arch/powerpc/Kconfig | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 8094a01974cca1d27002720e706f66bec2a2d035..eb98050b8c016bb23887a9d669d29e69d933c9c8 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -275,8 +275,8 @@ config PPC
 	select HAVE_RSEQ
 	select HAVE_SETUP_PER_CPU_AREA		if PPC64
 	select HAVE_SOFTIRQ_ON_OWN_STACK
-	select HAVE_STACKPROTECTOR		if PPC32 && $(cc-option,-mstack-protector-guard=tls -mstack-protector-guard-reg=r2)
-	select HAVE_STACKPROTECTOR		if PPC64 && $(cc-option,-mstack-protector-guard=tls -mstack-protector-guard-reg=r13)
+	select HAVE_STACKPROTECTOR		if PPC32 && $(cc-option,-mstack-protector-guard=tls -mstack-protector-guard-reg=r2 -mstack-protector-guard-offset=0)
+	select HAVE_STACKPROTECTOR		if PPC64 && $(cc-option,-mstack-protector-guard=tls -mstack-protector-guard-reg=r13 -mstack-protector-guard-offset=0)
 	select HAVE_STATIC_CALL			if PPC32
 	select HAVE_SYSCALL_TRACEPOINTS
 	select HAVE_VIRT_CPU_ACCOUNTING

-- 
2.47.0