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From: Szabolcs Nagy <nsz@port70.net>
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Subject: Re: [PATCH] MIPS big endian and *stat syscalls return value
Date: Tue, 7 Apr 2015 13:58:21 +0200
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* Eugene <e.yudin@ndmsystems.com> [2015-04-07 12:25:45 +0300]:
> 
> The reason of the problem is that the function __stat_fix rewrites register
> $v0, which is not stored in the parent function.
> 

ouch

>  static inline long __syscall2(long n, long a, long b)
>  {
> +	long t;
>  	register long r4 __asm__("$4") = a;
>  	register long r5 __asm__("$5") = b;
>  	register long r7 __asm__("$7");
>  	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)
>  		: "$1", "$3", "$8", "$9", "$10", "$11", "$12", "$13",
>  		  "$14", "$15", "$24", "$25", "hi", "lo", "memory");
> +
>  	if (r7) return -r2;
> +	t = r2;
>  	if (n == SYS_stat64 || n == SYS_fstat64 || n == SYS_lstat64) __stat_fix(b);
> -	return r2;
> +
> +	return t;
>  }
>  

looks ok to me
(other than the newline changes)

i wonder if __stat_fix could be inlined in a way that the
compiler knows it shouldnt clobber r2.

same for __syscall3 and __syscall4