fix microblaze syscall register clobbers

the kernel entry point for syscalls on microblaze nominally saves and
restores all registers, and testing on qemu always worked since qemu
behaves this way too. however, the real kernel treats r3:r4 as a
potential 64-bit return value from the syscall function, and copies
both over top of the saved registers before returning to userspace.
thus, we need to treat r4 as always-clobbered.

(cherry picked from commit 91d5aa06572d2660122f9a06ed242fef0383f292)

diff --git a/arch/microblaze/syscall_arch.h b/arch/microblaze/syscall_arch.h
index 70217ffadd3e637be43bff1dc75c87e449be8e02..cab4607d0e5328f77e6d2fbfd8b60b69fc59db93 100644 (file)
--- a/arch/microblaze/syscall_arch.h
+++ b/arch/microblaze/syscall_arch.h
@@ -13,7 +13,7 @@ static __inline long __syscall0(long n)
        register unsigned long r3 __asm__("r3");
        __asm__ __volatile__ ("brki r14, 0x8" : "=r"(r3)
                : "r"(r12)
-               : "memory");
+               : "memory", "r4");
        return r3;
 }
 
@@ -24,7 +24,7 @@ static inline long __syscall1(long n, long a)
        register unsigned long r5 __asm__("r5") = a;
        __asm__ __volatile__ ("brki r14, 0x8" : "=r"(r3)
                : "r"(r12), "r"(r5)
-               : "memory");
+               : "memory", "r4");
        return r3;
 }
 
@@ -36,7 +36,7 @@ static inline long __syscall2(long n, long a, long b)
        register unsigned long r6 __asm__("r6") = b;
        __asm__ __volatile__ ("brki r14, 0x8" : "=r"(r3)
                : "r"(r12), "r"(r5), "r"(r6)
-               : "memory");
+               : "memory", "r4");
        return r3;
 }
 
@@ -49,7 +49,7 @@ static inline long __syscall3(long n, long a, long b, long c)
        register unsigned long r7 __asm__("r7") = c;
        __asm__ __volatile__ ("brki r14, 0x8" : "=r"(r3)
                : "r"(r12), "r"(r5), "r"(r6), "r"(r7)
-               : "memory");
+               : "memory", "r4");
        return r3;
 }
 
@@ -63,7 +63,7 @@ static inline long __syscall4(long n, long a, long b, long c, long d)
        register unsigned long r8 __asm__("r8") = d;
        __asm__ __volatile__ ("brki r14, 0x8" : "=r"(r3)
                : "r"(r12), "r"(r5), "r"(r6), "r"(r7), "r"(r8)
-               : "memory");
+               : "memory", "r4");
        return r3;
 }
 
@@ -78,7 +78,7 @@ static inline long __syscall5(long n, long a, long b, long c, long d, long e)
        register unsigned long r9 __asm__("r9") = e;
        __asm__ __volatile__ ("brki r14, 0x8" : "=r"(r3)
                : "r"(r12), "r"(r5), "r"(r6), "r"(r7), "r"(r8), "r"(r9)
-               : "memory");
+               : "memory", "r4");
        return r3;
 }
 
@@ -94,7 +94,7 @@ static inline long __syscall6(long n, long a, long b, long c, long d, long e, lo
        register unsigned long r10 __asm__("r10") = f;
        __asm__ __volatile__ ("brki r14, 0x8" : "=r"(r3)
                : "r"(r12), "r"(r5), "r"(r6), "r"(r7), "r"(r8), "r"(r9), "r"(r10)
-               : "memory");
+               : "memory", "r4");
        return r3;
 }