fix riscv64 syscall asm constraint

having "+r"(a0) is redundant with "0"(a0) in syscalls with at least 1
arg, which is arguably a constraint violation (clang treats it as
such), and an invalid input with indeterminate value in the 0-arg
case. use the "=r"(a0) form instead.

diff --git a/arch/riscv64/syscall_arch.h b/arch/riscv64/syscall_arch.h
index 1aaeb63138d59598d6c280b564bfdbe36d34693a..3e0804efe37fe8413081e54005e0d8638935f8a2 100644 (file)
--- a/arch/riscv64/syscall_arch.h
+++ b/arch/riscv64/syscall_arch.h
@@ -3,7 +3,7 @@
 
 #define __asm_syscall(...) \
        __asm__ __volatile__ ("ecall\n\t" \
-       : "+r"(a0) : __VA_ARGS__ : "memory"); \
+       : "=r"(a0) : __VA_ARGS__ : "memory"); \
        return a0; \
 
 static inline long __syscall0(long n)