x86: split ret_from_fork

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 11 insertions, 16 deletions

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 69babd8c834f..5526d17db676 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -450,7 +450,7 @@ ENTRY(ret_from_fork)
         RESTORE_REST
 
         testl $3, CS-ARGOFFSET(%rsp)            # from kernel_thread?
-        jz   retint_restore_args
+        jz   1f
 
         testl $_TIF_IA32, TI_flags(%rcx)        # 32-bit compat task needs IRET
         jnz  int_ret_from_sys_call
@@ -458,6 +458,16 @@ ENTRY(ret_from_fork)
         RESTORE_TOP_OF_STACK %rdi, -ARGOFFSET
         jmp ret_from_sys_call                   # go to the SYSRET fastpath
 
+1:
+        subq $REST_SKIP, %rsp   # move the stack pointer back
+        CFI_ADJUST_CFA_OFFSET   REST_SKIP
+        movq %rbp, %rdi
+        call *%rbx
+        # exit
+        mov %eax, %edi
+        call do_exit
+        ud2                     # padding for call trace
+
         CFI_ENDPROC
 END(ret_from_fork)
 
@@ -1206,21 +1216,6 @@ bad_gs:
         jmp  2b
         .previous
 
-ENTRY(kernel_thread_helper)
-        pushq $0                # fake return address
-        CFI_STARTPROC
-        /*
-         * Here we are in the child and the registers are set as they were
-         * at kernel_thread() invocation in the parent.
-         */
-        call *%rsi
-        # exit
-        mov %eax, %edi
-        call do_exit
-        ud2                     # padding for call trace
-        CFI_ENDPROC
-END(kernel_thread_helper)
-
 /*
  * execve(). This function needs to use IRET, not SYSRET, to set up all state properly.
  *