From c8f9e946bc2a0a42e84b5f97f272932de6485b54 Mon Sep 17 00:00:00 2001 From: Kevin Cernekee Date: Tue, 5 Jun 2012 15:05:20 -0700 Subject: [PATCH] MIPS: Use $a0 instead of $v0 for __syscall_error() argument $a0 is saved across _dl_runtime_resolve(); $v0 is not. Unfortunately, __syscall_error() uses $v0 for its argument, not $a0 as is the MIPS ABI standard. This means that if lazy binding was used for __syscall_error(), the errno value in $v0 could get corrupted. The problem can be easily seen in testcases where syscalls in librt fail; when librt tries to call __syscall_error() in libc, the argument gets lost and errno gets set to a bogus value: # ./tst-mqueue1 ; echo $? mq_receive on O_WRONLY mqd_t did not fail with EBADF: Unknown error 2004684208 1 # ./tst-mqueue2 ; echo $? mq_timedreceive with too small msg_len did not fail with EMSGSIZE: Unknown error 1997360560 1 # ./tst-mqueue4 ; echo $? mq_timedsend did not fail with ETIMEDOUT: Unknown error 2008747440 1 When _dl_runtime_resolve() was taken out of the equation, the same test cases passed: # LD_BIND_NOW=y ./tst-mqueue1 ; echo $? 0 # LD_BIND_NOW=y ./tst-mqueue2 ; echo $? 0 # LD_BIND_NOW=y ./tst-mqueue4 ; echo $? 0 Changing __syscall_error() to look at $a0 instead of $v0 fixed the problem. (Note that there is also a "__syscall_error.c" file which presumably uses the standard C calling conventions, but I do not think it is used on MIPS.) Signed-off-by: Kevin Cernekee Signed-off-by: Bernhard Reutner-Fischer --- libc/sysdeps/linux/mips/syscall_error.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/libc/sysdeps/linux/mips/syscall_error.S b/libc/sysdeps/linux/mips/syscall_error.S index 51a8efa..0cc20da 100644 --- a/libc/sysdeps/linux/mips/syscall_error.S +++ b/libc/sysdeps/linux/mips/syscall_error.S @@ -43,7 +43,7 @@ ENTRY(__syscall_error) #ifdef __PIC__ SAVE_GP(GPOFF) #endif - REG_S v0, V0OFF(sp) + REG_S a0, V0OFF(sp) REG_S ra, RAOFF(sp) /* Find our per-thread errno address */ -- 1.7.10.4