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