x86, um: convert to saner kernel_execve() semantics

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

10 files changed, 21 insertions, 68 deletions

diff --git a/arch/um/include/asm/processor-generic.h b/arch/um/include/asm/processor-generic.h
index 5d9ab0c4f48..62435a00e70 100644
--- a/arch/um/include/asm/processor-generic.h
+++ b/arch/um/include/asm/processor-generic.h
@@ -26,7 +26,6 @@ struct thread_struct {
         jmp_buf *fault_catcher;
         struct task_struct *prev_sched;
         unsigned long temp_stack;
-        jmp_buf *exec_buf;
         struct arch_thread arch;
         jmp_buf switch_buf;
         int mm_count;
@@ -54,7 +53,6 @@ struct thread_struct {
         .fault_addr             = NULL, \
         .prev_sched             = NULL, \
         .temp_stack             = 0, \
-        .exec_buf               = NULL, \
         .arch                   = INIT_ARCH_THREAD, \
         .request                = { 0 } \
 }
diff --git a/arch/um/include/shared/os.h b/arch/um/include/shared/os.h
index 89b686c1a3e..25dbd372d32 100644
--- a/arch/um/include/shared/os.h
+++ b/arch/um/include/shared/os.h
@@ -191,7 +191,6 @@ extern int os_getpid(void);
 extern int os_getpgrp(void);
 
 extern void init_new_thread_signals(void);
-extern int run_kernel_thread(int (*fn)(void *), void *arg, jmp_buf **jmp_ptr);
 
 extern int os_map_memory(void *virt, int fd, unsigned long long off,
                          unsigned long len, int r, int w, int x);
diff --git a/arch/um/kernel/exec.c b/arch/um/kernel/exec.c
index e427301f55d..565ca396d83 100644
--- a/arch/um/kernel/exec.c
+++ b/arch/um/kernel/exec.c
@@ -47,8 +47,3 @@ void start_thread(struct pt_regs *regs, unsigned long eip, unsigned long esp)
 #endif
 }
 EXPORT_SYMBOL(start_thread);
-
-void __noreturn ret_from_kernel_execve(struct pt_regs *unused)
-{
-        UML_LONGJMP(current->thread.exec_buf, 1);
-}
diff --git a/arch/um/kernel/process.c b/arch/um/kernel/process.c
index a1b50add48a..94b0d8b9810 100644
--- a/arch/um/kernel/process.c
+++ b/arch/um/kernel/process.c
@@ -135,14 +135,10 @@ void new_thread_handler(void)
         arg = current->thread.request.u.thread.arg;
 
         /*
-         * The return value is 1 if the kernel thread execs a process,
-         * 0 if it just exits
+         * callback returns only if the kernel thread execs a process
          */
-        n = run_kernel_thread(fn, arg, &current->thread.exec_buf);
-        if (n == 1)
-                userspace(&current->thread.regs.regs);
-        else
-                do_exit(0);
+        n = fn(arg);
+        userspace(&current->thread.regs.regs);
 }
 
 /* Called magically, see new_thread_handler above */
diff --git a/arch/um/os-Linux/process.c b/arch/um/os-Linux/process.c
index 307f173e7f8..a04ec167a9c 100644
--- a/arch/um/os-Linux/process.c
+++ b/arch/um/os-Linux/process.c
@@ -244,16 +244,3 @@ void init_new_thread_signals(void)
         signal(SIGWINCH, SIG_IGN);
         signal(SIGTERM, SIG_DFL);
 }
-
-int run_kernel_thread(int (*fn)(void *), void *arg, jmp_buf **jmp_ptr)
-{
-        jmp_buf buf;
-        int n;
-
-        *jmp_ptr = &buf;
-        n = UML_SETJMP(&buf);
-        if (n != 0)
-                return n;
-        (*fn)(arg);
-        return 0;
-}
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index d93eb9d1bb9..45edcba41e3 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -98,6 +98,7 @@ config X86
         select GENERIC_STRNCPY_FROM_USER
         select GENERIC_STRNLEN_USER
         select GENERIC_KERNEL_THREAD
+        select GENERIC_KERNEL_EXECVE
 
 config INSTRUCTION_DECODER
         def_bool (KPROBES || PERF_EVENTS || UPROBES)
diff --git a/arch/x86/include/asm/unistd.h b/arch/x86/include/asm/unistd.h
index 55d155560fd..16f3fc6ebf2 100644
--- a/arch/x86/include/asm/unistd.h
+++ b/arch/x86/include/asm/unistd.h
@@ -51,7 +51,6 @@
 # define __ARCH_WANT_SYS_UTIME
 # define __ARCH_WANT_SYS_WAITPID
 # define __ARCH_WANT_SYS_EXECVE
-# define __ARCH_WANT_KERNEL_EXECVE
 
 /*
  * "Conditional" syscalls
diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
index fe4cc305d8d..91d295908c3 100644
--- a/arch/x86/kernel/entry_32.S
+++ b/arch/x86/kernel/entry_32.S
@@ -298,12 +298,20 @@ ENTRY(ret_from_fork)
         CFI_ENDPROC
 END(ret_from_fork)
 
-ENTRY(ret_from_kernel_execve)
-        movl %eax, %esp
-        movl $0,PT_EAX(%esp)
+ENTRY(ret_from_kernel_thread)
+        CFI_STARTPROC
+        pushl_cfi %eax
+        call schedule_tail
         GET_THREAD_INFO(%ebp)
+        popl_cfi %eax
+        pushl_cfi $0x0202               # Reset kernel eflags
+        popfl_cfi
+        movl PT_EBP(%esp),%eax
+        call *PT_EBX(%esp)
+        movl $0,PT_EAX(%esp)
         jmp syscall_exit
-END(ret_from_kernel_execve)
+        CFI_ENDPROC
+ENDPROC(ret_from_kernel_thread)
 
 /*
  * Interrupt exit functions should be protected against kprobes
@@ -994,21 +1002,6 @@ END(spurious_interrupt_bug)
  */
         .popsection
 
-ENTRY(ret_from_kernel_thread)
-        CFI_STARTPROC
-        pushl_cfi %eax
-        call schedule_tail
-        GET_THREAD_INFO(%ebp)
-        popl_cfi %eax
-        pushl_cfi $0x0202               # Reset kernel eflags
-        popfl_cfi
-        movl PT_EBP(%esp),%eax
-        call *PT_EBX(%esp)
-        call do_exit
-        ud2                     # padding for call trace
-        CFI_ENDPROC
-ENDPROC(ret_from_kernel_thread)
-
 #ifdef CONFIG_XEN
 /* Xen doesn't set %esp to be precisely what the normal sysenter
    entrypoint expects, so fix it up before using the normal path. */
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 053c9552ffd..e1f98c22003 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -459,15 +459,13 @@ ENTRY(ret_from_fork)
         jmp ret_from_sys_call                   # go to the SYSRET fastpath
 
 1:
-        subq $REST_SKIP, %rsp   # move the stack pointer back
+        subq $REST_SKIP, %rsp   # leave space for volatiles
         CFI_ADJUST_CFA_OFFSET   REST_SKIP
         movq %rbp, %rdi
         call *%rbx
-        # exit
-        mov %eax, %edi
-        call do_exit
-        ud2                     # padding for call trace
-
+        movl $0, RAX(%rsp)
+        RESTORE_REST
+        jmp int_ret_from_sys_call
         CFI_ENDPROC
 END(ret_from_fork)
 
@@ -1214,20 +1212,6 @@ bad_gs:
         jmp  2b
         .previous
 
-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)
         CFI_STARTPROC
diff --git a/arch/x86/um/Kconfig b/arch/x86/um/Kconfig
index da85b6fc8e8..cab8eb88dd2 100644
--- a/arch/x86/um/Kconfig
+++ b/arch/x86/um/Kconfig
@@ -14,6 +14,7 @@ config UML_X86
         def_bool y
         select GENERIC_FIND_FIRST_BIT
         select GENERIC_KERNEL_THREAD
+        select GENERIC_KERNEL_EXECVE
 
 config 64BIT
         bool "64-bit kernel" if SUBARCH = "x86"