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.
Even with the first problem addressed, the 32-bit test continues to fail
because Kbuild uses the powerpc64le-linux-gnu target for clang and
nothing flips the target to 32-bit, resulting in an error about an
invalid register valid:
$ clang --target=powerpc64le-linux-gnu \
-mstack-protector-guard=tls
-mstack-protector-guard-reg=r2 \
-mstack-protector-guard-offset=0 \
-x c -c -o /dev/null /dev/null
clang: error: invalid value 'r2' in 'mstack-protector-guard-reg=', expected one of: r13
While GCC allows arbitrary registers, the implementation of
'-mstack-protector-guard=tls' in LLVM shares the same code path as the
user space thread local storage implementation, which uses a fixed
register (2 for 32-bit and 13 for 62-bit), so the command line parsing
enforces this limitation.
Use the Kconfig macro '$(m32-flag)', which expands to '-m32' when
supported, in the stack protector support cc-option call to properly
switch the target to a 32-bit one, which matches what happens in Kbuild.
While the 64-bit macro does not strictly need it, add the equivalent
64-bit option for symmetry.
Cc: stable@xxxxxxxxxxxxxxx # 6.1+
Link: https://github.com/llvm/llvm-project/pull/110928 [1]
Reviewed-by: Keith Packard <keithp@xxxxxxxxxx>
Tested-by: Keith Packard <keithp@xxxxxxxxxx>
Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx>
---
arch/powerpc/Kconfig | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 8094a01974cca1d27002720e706f66bec2a2d035..6aaca48955a34b2a38af1415bfa36f74f35c3f3e 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 && $(cc-option,$(m32-flag) -mstack-protector-guard=tls -mstack-protector-guard-reg=r2 -mstack-protector-guard-offset=0)
+ select HAVE_STACKPROTECTOR if PPC64 && $(cc-option,$(m64-flag) -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
