Cross compiling to aarch32 (for vdso32) using clang correctly
identifies that (the unused) write_sysreg inline asm directive is
illegal in that architectural context:
arch/arm64/include/asm/arch_timer.h: error: invalid input constraint 'rZ' in asm
write_sysreg(cntkctl, cntkctl_el1);
^
arch/arm64/include/asm/sysreg.h: note: expanded from macro 'write_sysreg'
: : "rZ" (__val));
^
GCC normally checks for correctness everywhere. But uniquely for
unused asm, will optimize out and suppress the error report.
Signed-off-by: Mark Salyzyn <saly...@android.com>
Cc: Catalin Marinas <catalin.mari...@arm.com>
Cc: Will Deacon <will.dea...@arm.com>
Cc: Christoffer Dall <cd...@linaro.org>
Cc: Mark Rutland <mark.rutl...@arm.com>
Cc: Marc Zyngier <marc.zyng...@arm.com>
Cc: Suzuki K Poulose <suzuki.poul...@arm.com>
Cc: Stefan Traby <ste...@hello-penguin.com>
Cc: Dave Martin <dave.mar...@arm.com>
Cc: linux-arm-ker...@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
---
arch/arm64/include/asm/sysreg.h | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index f707fed5886f..a7b61c9327db 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -492,11 +492,15 @@ asm(
* The "Z" constraint normally means a zero immediate, but when combined with
* the "%x0" template means XZR.
*/
+#if defined(__aarch64__)
#define write_sysreg(v, r) do { \
u64 __val = (u64)(v); \
asm volatile("msr " __stringify(r) ", %x0" \
: : "rZ" (__val)); \
} while (0)
+#else
+#define write_sysreg(v, r) BUG()
+#endif
/*
* For registers without architectural names, or simply unsupported by
--
2.15.0.403.gc27cc4dac6-goog
