implement inline 5- and 6-argument syscalls for mipsn32 and mips64

n32 and n64 ABIs add new argument registers vs o32, so that passing on
the stack is not necessary, so it's not clear why the 5- and
6-argument versions were special-cased to begin with; it seems to have
been pattern-copying from arch/mips (o32).

i've treated the new argument registers like the first 4 in terms of
clobber status (non-clobbered). hopefully this is correct.

arch/mips64/syscall_arch.h

 #define __SYSCALL_LL_E(x) (x)
 #define __SYSCALL_LL_O(x) (x)
 
-__attribute__((visibility("hidden")))
-long (__syscall)(long, ...);
-
 #define SYSCALL_RLIM_INFINITY (-1UL/2)
 
 #include <sys/stat.h>
@@ -167,48 +164,71 @@ static inline long __syscall4(long n, long a, long b, long c, long d)
 
 static inline long __syscall5(long n, long a, long b, long c, long d, long e)
 {
-	long r2;
-	long old_b = b;
-	long old_c = c;
 	struct kernel_stat kst;
+	long ret;
+	register long r4 __asm__("$4") = a;
+	register long r5 __asm__("$5") = b;
+	register long r6 __asm__("$6") = c;
+	register long r7 __asm__("$7") = d;
+	register long r8 __asm__("$8") = e;
+	register long r2 __asm__("$2");
 
 	if (n == SYS_stat || n == SYS_fstat || n == SYS_lstat)
-		b = (long) &kst;
+		r5 = (long) &kst;
 	if (n == SYS_newfstatat)
-		c = (long) &kst;
+		r6 = (long) &kst;
 
-	r2 = (__syscall)(n, a, b, c, d, e);
-	if (r2 > -4096UL) return r2;
+	__asm__ __volatile__ (
+		"daddu $2,$0,%2 ; syscall"
+		: "=&r"(r2), "=r"(r7) : "ir"(n), "0"(r2), "1"(r7),
+		  "r"(r4), "r"(r5), "r"(r6), "r"(r8)
+		: "$1", "$3", "$9", "$10", "$11", "$12", "$13",
+		  "$14", "$15", "$24", "$25", "hi", "lo", "memory");
+
+	if (r7) return -r2;
+	ret = r2;
 
 	if (n == SYS_stat || n == SYS_fstat || n == SYS_lstat)
-		__stat_fix(&kst, (struct stat *)old_b);
+		__stat_fix(&kst, (struct stat *)b);
 	if (n == SYS_newfstatat)
-		__stat_fix(&kst, (struct stat *)old_c);
+		__stat_fix(&kst, (struct stat *)c);
 
-	return r2;
+	return ret;
 }
 
 static inline long __syscall6(long n, long a, long b, long c, long d, long e, long f)
 {
-	long r2;
-	long old_b = b;
-	long old_c = c;
 	struct kernel_stat kst;
+	long ret;
+	register long r4 __asm__("$4") = a;
+	register long r5 __asm__("$5") = b;
+	register long r6 __asm__("$6") = c;
+	register long r7 __asm__("$7") = d;
+	register long r8 __asm__("$8") = e;
+	register long r9 __asm__("$9") = f;
+	register long r2 __asm__("$2");
 
 	if (n == SYS_stat || n == SYS_fstat || n == SYS_lstat)
-		b = (long) &kst;
+		r5 = (long) &kst;
 	if (n == SYS_newfstatat)
-		c = (long) &kst;
+		r6 = (long) &kst;
+
+	__asm__ __volatile__ (
+		"daddu $2,$0,%2 ; syscall"
+		: "=&r"(r2), "=r"(r7) : "ir"(n), "0"(r2), "1"(r7),
+		  "r"(r4), "r"(r5), "r"(r6), "r"(r8), "r"(r9)
+		: "$1", "$3", "$10", "$11", "$12", "$13",
+		  "$14", "$15", "$24", "$25", "hi", "lo", "memory");
 
-	r2 = (__syscall)(n, a, b, c, d, e, f);
-	if (r2 > -4096UL) return r2;
+	if (r7) return -r2;
+	ret = r2;
 
 	if (n == SYS_stat || n == SYS_fstat || n == SYS_lstat)
-		__stat_fix(&kst, (struct stat *)old_b);
+		__stat_fix(&kst, (struct stat *)b);
 	if (n == SYS_newfstatat)
-		__stat_fix(&kst, (struct stat *)old_c);
+		__stat_fix(&kst, (struct stat *)c);
 
-	return r2;
+	return ret;
 }
 
 #define VDSO_USEFUL

arch/mipsn32/syscall_arch.h

 #define __SYSCALL_LL_E(x) (x)
 #define __SYSCALL_LL_O(x) (x)
 
-hidden long (__syscall)(long, ...);
-
 #define SYSCALL_RLIM_INFINITY (-1UL/2)
 
 #if _MIPSEL || __MIPSEL || __MIPSEL__
@@ -102,8 +100,18 @@ static inline long __syscall4(long n, long a, long b, long c, long d)
 
 static inline long __syscall5(long n, long a, long b, long c, long d, long e)
 {
-	long r2 = (__syscall)(n, a, b, c, d, e);
-	if (r2 > -4096UL) return r2;
+	register long r4 __asm__("$4") = a;
+	register long r5 __asm__("$5") = b;
+	register long r6 __asm__("$6") = c;
+	register long r7 __asm__("$7") = d;
+	register long r8 __asm__("$8") = e;
+	register long r2 __asm__("$2");
+	__asm__ __volatile__ (
+		"addu $2,$0,%2 ; syscall"
+		: "=&r"(r2), "=r"(r7) : "ir"(n), "0"(r2), "1"(r7),
+		  "r"(r4), "r"(r5), "r"(r6), "r"(r8)
+		: "$1", "$3", "$9", "$10", "$11", "$12", "$13",
+		  "$14", "$15", "$24", "$25", "hi", "lo", "memory");
 	if (n == SYS_stat || n == SYS_fstat || n == SYS_lstat) __stat_fix(b);
 	if (n == SYS_newfstatat) __stat_fix(c);
 	return r2;
@@ -111,8 +119,19 @@ static inline long __syscall5(long n, long a, long b, long c, long d, long e)
 
 static inline long __syscall6(long n, long a, long b, long c, long d, long e, long f)
 {
-	long r2 = (__syscall)(n, a, b, c, d, e, f);
-	if (r2 > -4096UL) return r2;
+	register long r4 __asm__("$4") = a;
+	register long r5 __asm__("$5") = b;
+	register long r6 __asm__("$6") = c;
+	register long r7 __asm__("$7") = d;
+	register long r8 __asm__("$8") = e;
+	register long r8 __asm__("$9") = f;
+	register long r2 __asm__("$2");
+	__asm__ __volatile__ (
+		"addu $2,$0,%2 ; syscall"
+		: "=&r"(r2), "=r"(r7) : "ir"(n), "0"(r2), "1"(r7),
+		  "r"(r4), "r"(r5), "r"(r6), "r"(r8), "r"(r9)
+		: "$1", "$3", "$10", "$11", "$12", "$13",
+		  "$14", "$15", "$24", "$25", "hi", "lo", "memory");
 	if (n == SYS_stat || n == SYS_fstat || n == SYS_lstat) __stat_fix(b);
 	if (n == SYS_newfstatat) __stat_fix(c);
 	return r2;