Re: [discuss] [RFC] [PATCH] Double syscall exit traces on x86_64

[Andi Kleen]

On Friday 26 May 2006 05:24, Jeff Dike wrote:
> We are seeing double ptrace notifications of system call returns on recent
> x86_64 kernels.  This breaks UML and at least one other app.

I believe this patch is the correct fix. Can you confirm it works for you? 

-Andi

Don't do syscall exit tracing twice

int_ret_from_syscall already does syscall exit tracing, so 
no need to do it again in the caller.

This caused problems for UML and some other special programs doing
syscall interception.

Signed-off-by: Andi Kleen <ak@xxxxxxx>

Index: linux/arch/x86_64/kernel/entry.S
===================================================================
--- linux.orig/arch/x86_64/kernel/entry.S
+++ linux/arch/x86_64/kernel/entry.S
@@ -282,12 +282,7 @@ tracesys:			 
 	ja  1f
 	movq %r10,%rcx	/* fixup for C */
 	call *sys_call_table(,%rax,8)
-	movq %rax,RAX-ARGOFFSET(%rsp)
-1:	SAVE_REST
-	movq %rsp,%rdi
-	call syscall_trace_leave
-	RESTORE_TOP_OF_STACK %rbx
-	RESTORE_REST
+1:	movq %rax,RAX-ARGOFFSET(%rsp)
 	/* Use IRET because user could have changed frame */
 	jmp int_ret_from_sys_call
 	CFI_ENDPROC
-
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