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Commit a31f8dd7 authored by Roland McGrath's avatar Roland McGrath Committed by Ingo Molnar
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x86: ptrace vs -ENOSYS 



When we're stopped at syscall entry tracing, ptrace can change the %rax
value from -ENOSYS to something else.  If no system call is actually made
because the syscall number (now in orig_rax) is bad, then we now always
reset %rax to -ENOSYS again.

This changes it to leave the return value alone after entry tracing.
That way, the %rax value set by ptrace is there to be seen in user mode
(or in syscall exit tracing).  This is consistent with what the 32-bit
kernel does.

Signed-off-by: default avatarRoland McGrath <roland@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 8ab32bb8

arch/x86/kernel/entry_64.S

+3 −5
Original line number Diff line number Diff line
@@ -319,19 +319,17 @@ badsys: 
	/* Do syscall tracing */

tracesys:			 

	SAVE_REST

	movq $-ENOSYS,RAX(%rsp)

	movq $-ENOSYS,RAX(%rsp) /* ptrace can change this for a bad syscall */

	FIXUP_TOP_OF_STACK %rdi

	movq %rsp,%rdi

	call syscall_trace_enter

	LOAD_ARGS ARGOFFSET  /* reload args from stack in case ptrace changed it */

	RESTORE_REST

	cmpq $__NR_syscall_max,%rax

	movq $-ENOSYS,%rcx

	cmova %rcx,%rax

	ja  1f

	ja   int_ret_from_sys_call	/* RAX(%rsp) set to -ENOSYS above */

	movq %r10,%rcx	/* fixup for C */

	call *sys_call_table(,%rax,8)

1:	movq %rax,RAX-ARGOFFSET(%rsp)

	movq %rax,RAX-ARGOFFSET(%rsp)

	/* Use IRET because user could have changed frame */

		

/*