mips64 fstatat broken

[Rich Felker <dalias@libc.org>]

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The mips64 port requires 'struct stat' conversion due to incorrect
32-bit fields where time_t should be in the kernel version of the
structure. The mips64 port performs the correct translation for stat,
fstat, and lstat syscalls, but omits any special handling for fstatat.
I'm planning to commit the attached patch to fix it; casual testing
(linking toybox against the resulting libc and running toybox ls)
seems to show it works.

I also plan to remove (in a separate commit) the old __clang__ check
that suppresses inline syscalls on mips and mips64; it seems the
relevant bug in clang was fixed long before clang was safe for
compiling musl.

Rich

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diff --git a/arch/mips64/syscall_arch.h b/arch/mips64/syscall_arch.h
index 1bd6c18..bb73dc3 100644
--- a/arch/mips64/syscall_arch.h
+++ b/arch/mips64/syscall_arch.h
@@ -149,13 +149,15 @@ static inline long __syscall4(long n, long a, long b, long c, long d)
 	register long r7 __asm__("$7");
 	register long r2 __asm__("$2");
 
+	r4 = a;
 	r5 = b;
+	r6 = c;
+	r7 = d;
 	if (n == SYS_stat || n == SYS_fstat || n == SYS_lstat)
 		r5 = (long) &kst;
+	if (n == SYS_newfstatat)
+		r6 = (long) &kst;
 
-	r4 = a;
-	r6 = c;
-	r7 = d;
 	__asm__ __volatile__ (
 		"daddu $2,$0,%2 ; syscall"
 		: "=&r"(r2), "=r"(r7) : "ir"(n), "0"(r2), "1"(r7),
@@ -168,6 +170,8 @@ static inline long __syscall4(long n, long a, long b, long c, long d)
 
 	if (n == SYS_stat || n == SYS_fstat || n == SYS_lstat)
 		__stat_fix(&kst, (struct stat *)b);
+	if (n == SYS_newfstatat)
+		__stat_fix(&kst, (struct stat *)c);
 
 	return ret;
 }
@@ -224,16 +228,21 @@ static inline long __syscall4(long n, long a, long b, long c, long d)
 {
 	long r2;
 	long old_b = b;
+	long old_c = c;
 	struct kernel_stat kst;
 
 	if (n == SYS_stat || n == SYS_fstat || n == SYS_lstat)
 		b = (long) &kst;
+	if (n == SYS_newfstatat)
+		c = (long) &kst;
 
 	r2 = (__syscall)(n, a, b, c, d);
 	if (r2 > -4096UL) return r2;
 
 	if (n == SYS_stat || n == SYS_fstat || n == SYS_lstat)
 		__stat_fix(&kst, (struct stat *)old_b);
+	if (n == SYS_newfstatat)
+		__stat_fix(&kst, (struct stat *)old_c);
 
 	return r2;
 }
@@ -244,16 +253,21 @@ 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;
 
 	if (n == SYS_stat || n == SYS_fstat || n == SYS_lstat)
 		b = (long) &kst;
+	if (n == SYS_newfstatat)
+		c = (long) &kst;
 
 	r2 = (__syscall)(n, a, b, c, d, e);
 	if (r2 > -4096UL) return r2;
 
 	if (n == SYS_stat || n == SYS_fstat || n == SYS_lstat)
 		__stat_fix(&kst, (struct stat *)old_b);
+	if (n == SYS_newfstatat)
+		__stat_fix(&kst, (struct stat *)old_c);
 
 	return r2;
 }
@@ -262,16 +276,21 @@ static inline long __syscall6(long n, long a, long b, long c, long d, long e, lo
 {
 	long r2;
 	long old_b = b;
+	long old_c = c;
 	struct kernel_stat kst;
 
 	if (n == SYS_stat || n == SYS_fstat || n == SYS_lstat)
 		b = (long) &kst;
+	if (n == SYS_newfstatat)
+		c = (long) &kst;
 
 	r2 = (__syscall)(n, a, b, c, d, e, f);
 	if (r2 > -4096UL) return r2;
 
 	if (n == SYS_stat || n == SYS_fstat || n == SYS_lstat)
 		__stat_fix(&kst, (struct stat *)old_b);
+	if (n == SYS_newfstatat)
+		__stat_fix(&kst, (struct stat *)old_c);
 
 	return r2;
 }