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From: Konstantin Belousov <kib@FreeBSD.org>
Date: Sun, 28 Aug 2016 00:26:06 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r304931 - head/lib/libc/amd64/sys
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Author: kib
Date: Sun Aug 28 00:26:06 2016
New Revision: 304931
URL: https://svnweb.freebsd.org/changeset/base/304931

Log:
  Follow ABI when calling __error from the ptrace(2) wrapper.
  
  In particular, preserve syscall arguments on stack, since callee is
  not required to preserve arg-passing registers.  Align stack.
  
  Sponsored by:	The FreeBSD Foundation
  MFC after:	1 week

Modified:
  head/lib/libc/amd64/sys/ptrace.S

Modified: head/lib/libc/amd64/sys/ptrace.S
==============================================================================
--- head/lib/libc/amd64/sys/ptrace.S	Sun Aug 28 00:21:24 2016	(r304930)
+++ head/lib/libc/amd64/sys/ptrace.S	Sun Aug 28 00:26:06 2016	(r304931)
@@ -42,11 +42,21 @@ __FBSDID("$FreeBSD$");
 	.type	CNAME(__error),@function
 
 ENTRY(ptrace)
+	pushq	%rdi	/* align stack */
+	pushq	%rdi
+	pushq	%rsi
+	pushq	%rdx
+	pushq	%rcx
 #ifdef PIC
 	callq	PIC_PLT(CNAME(__error))
 #else
 	callq	CNAME(__error)
 #endif
+	popq	%rcx
+	popq	%rdx
+	popq	%rsi
+	popq	%rdi
+	popq	%rdi
 	movl	$0,(%rax)
 	mov	$SYS_ptrace,%eax
 	KERNCALL