From: Rich Felker Date: Fri, 27 Sep 2019 13:57:54 +0000 (-0400) Subject: clean up mips (32-bit, o32) syscall asm constraints X-Git-Tag: v1.1.24~9 X-Git-Url: https://git.librecmc.org/?a=commitdiff_plain;h=604f8d3d8b08ee4f548de193050ef93a7753c2e0;p=oweals%2Fmusl.git clean up mips (32-bit, o32) syscall asm constraints analogous to commit ddc7c4f936c7a90781072f10dbaa122007e939d0 for mips64 and n32, remove the hack to load the syscall number into $2 via asm, and use a constraint to let the compiler load it instead. now, only $4, $5, and $6 are potential input-only registers. $2 is always input and output, and $7 is both when it's an argument, otherwise output-only. previously, $7 was treated as an input (with a "1" constraint matching its output position) even when it was not an input, which was arguably undefined behavior (asm input from indeterminate value). this is corrected. as before, $8, $9, and $10 are conditionally input-output registers for 5-, 6-, and 7-argument syscalls. their role in input is carrying in the values that will be stored on the stack for arguments 5-7. their role in output is carrying back whatever the kernel has clobbered them with, so that the compiler cannot assume they still contain the input values. --- diff --git a/arch/mips/syscall_arch.h b/arch/mips/syscall_arch.h index 808aa41d..6ea73437 100644 --- a/arch/mips/syscall_arch.h +++ b/arch/mips/syscall_arch.h @@ -18,10 +18,11 @@ static inline long __syscall0(long n) { register long r7 __asm__("$7"); - register long r2 __asm__("$2"); + register long r2 __asm__("$2") = n; __asm__ __volatile__ ( - "addu $2,$0,%2 ; syscall" - : "=&r"(r2), "=r"(r7) : "ir"(n), "0"(r2), "1"(r7) + "syscall" + : "+r"(r2), "=r"(r7) + : : SYSCALL_CLOBBERLIST, "$8", "$9", "$10"); return r7 ? -r2 : r2; } @@ -30,11 +31,11 @@ static inline long __syscall1(long n, long a) { register long r4 __asm__("$4") = a; register long r7 __asm__("$7"); - register long r2 __asm__("$2"); + register long r2 __asm__("$2") = n; __asm__ __volatile__ ( - "addu $2,$0,%2 ; syscall" - : "=&r"(r2), "=r"(r7) : "ir"(n), "0"(r2), "1"(r7), - "r"(r4) + "syscall" + : "+r"(r2), "=r"(r7) + : "r"(r4) : SYSCALL_CLOBBERLIST, "$8", "$9", "$10"); return r7 ? -r2 : r2; } @@ -44,11 +45,11 @@ static inline long __syscall2(long n, long a, long b) register long r4 __asm__("$4") = a; register long r5 __asm__("$5") = b; register long r7 __asm__("$7"); - register long r2 __asm__("$2"); + register long r2 __asm__("$2") = n; __asm__ __volatile__ ( - "addu $2,$0,%2 ; syscall" - : "=&r"(r2), "=r"(r7) : "ir"(n), "0"(r2), "1"(r7), - "r"(r4), "r"(r5) + "syscall" + : "+r"(r2), "=r"(r7) + : "r"(r4), "r"(r5) : SYSCALL_CLOBBERLIST, "$8", "$9", "$10"); return r7 ? -r2 : r2; } @@ -59,11 +60,11 @@ static inline long __syscall3(long n, long a, long b, long c) register long r5 __asm__("$5") = b; register long r6 __asm__("$6") = c; register long r7 __asm__("$7"); - register long r2 __asm__("$2"); + register long r2 __asm__("$2") = n; __asm__ __volatile__ ( - "addu $2,$0,%2 ; syscall" - : "=&r"(r2), "=r"(r7) : "ir"(n), "0"(r2), "1"(r7), - "r"(r4), "r"(r5), "r"(r6) + "syscall" + : "+r"(r2), "=r"(r7) + : "r"(r4), "r"(r5), "r"(r6) : SYSCALL_CLOBBERLIST, "$8", "$9", "$10"); return r7 ? -r2 : r2; } @@ -74,11 +75,11 @@ static inline long __syscall4(long n, long a, long b, long c, long d) register long r5 __asm__("$5") = b; register long r6 __asm__("$6") = c; register long r7 __asm__("$7") = d; - register long r2 __asm__("$2"); + register long r2 __asm__("$2") = n; __asm__ __volatile__ ( - "addu $2,$0,%2 ; syscall" - : "=&r"(r2), "=r"(r7) : "ir"(n), "0"(r2), "1"(r7), - "r"(r4), "r"(r5), "r"(r6) + "syscall" + : "+r"(r2), "+r"(r7) + : "r"(r4), "r"(r5), "r"(r6) : SYSCALL_CLOBBERLIST, "$8", "$9", "$10"); return r7 ? -r2 : r2; } @@ -90,13 +91,13 @@ static inline long __syscall5(long n, long a, long b, long c, long d, long e) register long r6 __asm__("$6") = c; register long r7 __asm__("$7") = d; register long r8 __asm__("$8") = e; - register long r2 __asm__("$2"); + register long r2 __asm__("$2") = n; __asm__ __volatile__ ( "subu $sp,$sp,32 ; sw $8,16($sp) ; " - "addu $2,$0,%3 ; syscall ;" + "syscall ;" "addu $sp,$sp,32" - : "=&r"(r2), "=r"(r7), "+r"(r8) - : "ir"(n), "0"(r2), "1"(r7), "r"(r4), "r"(r5), "r"(r6) + : "+r"(r2), "+r"(r7), "+r"(r8) + : "r"(r4), "r"(r5), "r"(r6) : SYSCALL_CLOBBERLIST, "$9", "$10"); return r7 ? -r2 : r2; } @@ -109,13 +110,13 @@ static inline long __syscall6(long n, long a, long b, long c, long d, long e, lo register long r7 __asm__("$7") = d; register long r8 __asm__("$8") = e; register long r9 __asm__("$9") = f; - register long r2 __asm__("$2"); + register long r2 __asm__("$2") = n; __asm__ __volatile__ ( "subu $sp,$sp,32 ; sw $8,16($sp) ; sw $9,20($sp) ; " - "addu $2,$0,%4 ; syscall ;" + "syscall ;" "addu $sp,$sp,32" - : "=&r"(r2), "=r"(r7), "+r"(r8), "+r"(r9) - : "ir"(n), "0"(r2), "1"(r7), "r"(r4), "r"(r5), "r"(r6) + : "+r"(r2), "+r"(r7), "+r"(r8), "+r"(r9) + : "r"(r4), "r"(r5), "r"(r6) : SYSCALL_CLOBBERLIST, "$10"); return r7 ? -r2 : r2; } @@ -129,13 +130,13 @@ static inline long __syscall7(long n, long a, long b, long c, long d, long e, lo register long r8 __asm__("$8") = e; register long r9 __asm__("$9") = f; register long r10 __asm__("$10") = g; - register long r2 __asm__("$2"); + register long r2 __asm__("$2") = n; __asm__ __volatile__ ( "subu $sp,$sp,32 ; sw $8,16($sp) ; sw $9,20($sp) ; sw $10,24($sp) ; " - "addu $2,$0,%5 ; syscall ;" + "syscall ;" "addu $sp,$sp,32" - : "=&r"(r2), "=r"(r7), "+r"(r8), "+r"(r9), "+r"(r10) - : "ir"(n), "0"(r2), "1"(r7), "r"(r4), "r"(r5), "r"(r6) + : "+r"(r2), "+r"(r7), "+r"(r8), "+r"(r9), "+r"(r10) + : "r"(r4), "r"(r5), "r"(r6) : SYSCALL_CLOBBERLIST); return r7 ? -r2 : r2; }