syscall_exit is going away, and return tracing is just a function
call now, so open-code the two non-syscall 32-bit users.

While we're at it, update the big register layout comment.

Signed-off-by: Andy Lutomirski <[email protected]>
---
 arch/x86/entry/entry_32.S | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index a08ded481aba..36b6beb181f6 100644
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -3,7 +3,7 @@
  *
  * entry_32.S contains the system-call and low-level fault and trap handling 
routines.
  *
- * Stack layout in 'syscall_exit':
+ * Stack layout while running C code:
  *     ptrace needs to have all registers on the stack.
  *     If the order here is changed, it needs to be
  *     updated in fork.c:copy_process(), signal.c:do_signal(),
@@ -211,7 +211,11 @@ ENTRY(ret_from_fork)
        popl    %eax
        pushl   $0x0202                         # Reset kernel eflags
        popfl
-       jmp     syscall_exit
+
+       /* When we fork, we trace the syscall return in the child, too. */
+       movl    %esp, %eax
+       call    syscall_return_slowpath
+       jmp     restore_all
 END(ret_from_fork)
 
 ENTRY(ret_from_kernel_thread)
@@ -224,7 +228,15 @@ ENTRY(ret_from_kernel_thread)
        movl    PT_EBP(%esp), %eax
        call    *PT_EBX(%esp)
        movl    $0, PT_EAX(%esp)
-       jmp     syscall_exit
+
+       /*
+        * Kernel threads return to userspace as if returning from a syscall.
+        * We should check whether anything actually uses this path and, if so,
+        * consider switching it over to ret_from_fork.
+        */
+       movl    %esp, %eax
+       call    syscall_return_slowpath
+       jmp     restore_all
 ENDPROC(ret_from_kernel_thread)
 
 /*
-- 
2.4.3

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