Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/signal

Pull generic execve() changes from Al Viro:
 "This introduces the generic kernel_thread() and kernel_execve()
  functions, and switches x86, arm, alpha, um and s390 over to them."

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/signal: (26 commits)
  s390: convert to generic kernel_execve()
  s390: switch to generic kernel_thread()
  s390: fold kernel_thread_helper() into ret_from_fork()
  s390: fold execve_tail() into start_thread(), convert to generic sys_execve()
  um: switch to generic kernel_thread()
  x86, um/x86: switch to generic sys_execve and kernel_execve
  x86: split ret_from_fork
  alpha: introduce ret_from_kernel_execve(), switch to generic kernel_execve()
  alpha: switch to generic kernel_thread()
  alpha: switch to generic sys_execve()
  arm: get rid of execve wrapper, switch to generic execve() implementation
  arm: optimized current_pt_regs()
  arm: introduce ret_from_kernel_execve(), switch to generic kernel_execve()
  arm: split ret_from_fork, simplify kernel_thread() [based on patch by rmk]
  generic sys_execve()
  generic kernel_execve()
  new helper: current_pt_regs()
  preparation for generic kernel_thread()
  um: kill thread->forking
  um: let signal_delivered() do SIGTRAP on singlestepping into handler
  ...

1 files changed, 25 insertions, 49 deletions

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 44531acd9a81..cdc790c78f32 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -554,7 +554,7 @@ 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
@@ -562,6 +562,16 @@ 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)
 
@@ -862,7 +872,6 @@ ENTRY(stub_execve)
         PARTIAL_FRAME 0
         SAVE_REST
         FIXUP_TOP_OF_STACK %r11
-        movq %rsp, %rcx
         call sys_execve
         RESTORE_TOP_OF_STACK %r11
         movq %rax,RAX(%rsp)
@@ -912,8 +921,7 @@ ENTRY(stub_x32_execve)
         PARTIAL_FRAME 0
         SAVE_REST
         FIXUP_TOP_OF_STACK %r11
-        movq %rsp, %rcx
-        call sys32_execve
+        call compat_sys_execve
         RESTORE_TOP_OF_STACK %r11
         movq %rax,RAX(%rsp)
         RESTORE_REST
@@ -1318,51 +1326,19 @@ 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.
- *
- * C extern interface:
- *       extern long execve(const char *name, char **argv, char **envp)
- *
- * asm input arguments:
- *      rdi: name, rsi: argv, rdx: envp
- *
- * We want to fallback into:
- *      extern long sys_execve(const char *name, char **argv,char **envp, struct pt_regs *regs)
- *
- * do_sys_execve asm fallback arguments:
- *      rdi: name, rsi: argv, rdx: envp, rcx: fake frame on the stack
- */
-ENTRY(kernel_execve)
-        CFI_STARTPROC
-        FAKE_STACK_FRAME $0
-        SAVE_ALL
-        movq %rsp,%rcx
-        call sys_execve
-        movq %rax, RAX(%rsp)
-        RESTORE_REST
-        testq %rax,%rax
-        je int_ret_from_sys_call
-        RESTORE_ARGS
-        UNFAKE_STACK_FRAME
-        ret
-        CFI_ENDPROC
-END(kernel_execve)
+ENTRY(ret_from_kernel_execve)
+        movq %rdi, %rsp
+        movl $0, RAX(%rsp)
+        // RESTORE_REST
+        movq 0*8(%rsp), %r15
+        movq 1*8(%rsp), %r14
+        movq 2*8(%rsp), %r13
+        movq 3*8(%rsp), %r12
+        movq 4*8(%rsp), %rbp
+        movq 5*8(%rsp), %rbx
+        addq $(6*8), %rsp
+        jmp int_ret_from_sys_call
+END(ret_from_kernel_execve)
 
 /* Call softirq on interrupt stack. Interrupts are off. */
 ENTRY(call_softirq)