20 files changed, 90 insertions, 180 deletions

diff --git a/arch/Kconfig b/arch/Kconfig
index 26a28419cafc..a79a1ad8bb96 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -274,6 +274,9 @@ config ARCH_WANT_OLD_COMPAT_IPC
 config GENERIC_KERNEL_THREAD
         bool
 
+config GENERIC_KERNEL_EXECVE
+        bool
+
 config HAVE_ARCH_SECCOMP_FILTER
         bool
         help
diff --git a/arch/alpha/Kconfig b/arch/alpha/Kconfig
index 7da91246e279..7a08cfb80ee8 100644
--- a/arch/alpha/Kconfig
+++ b/arch/alpha/Kconfig
@@ -21,6 +21,7 @@ config ALPHA
         select GENERIC_STRNCPY_FROM_USER
         select GENERIC_STRNLEN_USER
         select GENERIC_KERNEL_THREAD
+        select GENERIC_KERNEL_EXECVE
         help
           The Alpha is a 64-bit general-purpose processor designed and
           marketed by the Digital Equipment Corporation of blessed memory,
diff --git a/arch/alpha/include/asm/unistd.h b/arch/alpha/include/asm/unistd.h
index 3cb6c1188984..7826e227e4d0 100644
--- a/arch/alpha/include/asm/unistd.h
+++ b/arch/alpha/include/asm/unistd.h
@@ -482,7 +482,6 @@
 #define __ARCH_WANT_SYS_SIGPENDING
 #define __ARCH_WANT_SYS_RT_SIGSUSPEND
 #define __ARCH_WANT_SYS_EXECVE
-#define __ARCH_WANT_KERNEL_EXECVE
 
 /* "Conditional" syscalls.  What we want is
 
diff --git a/arch/alpha/kernel/entry.S b/arch/alpha/kernel/entry.S
index 2a359c9ee3cd..a7607832dd4f 100644
--- a/arch/alpha/kernel/entry.S
+++ b/arch/alpha/kernel/entry.S
@@ -311,7 +311,7 @@ entSys:
 
         .align  4
 ret_from_sys_call:
-        cmovne  $26, 0, $19             /* $19 = 0 => non-restartable */
+        cmovne  $26, 0, $18             /* $18 = 0 => non-restartable */
         ldq     $0, SP_OFF($sp)
         and     $0, 8, $0
         beq     $0, ret_to_kernel
@@ -320,8 +320,8 @@ ret_to_user:
                 sampling and the rti.  */
         lda     $16, 7
         call_pal PAL_swpipl
-        ldl     $5, TI_FLAGS($8)
-        and     $5, _TIF_WORK_MASK, $2
+        ldl     $17, TI_FLAGS($8)
+        and     $17, _TIF_WORK_MASK, $2
         bne     $2, work_pending
 restore_all:
         RESTORE_ALL
@@ -341,10 +341,10 @@ $syscall_error:
          * frame to indicate that a negative return value wasn't an
          * error number..
          */
-        ldq     $19, 0($sp)     /* old syscall nr (zero if success) */
-        beq     $19, $ret_success
+        ldq     $18, 0($sp)     /* old syscall nr (zero if success) */
+        beq     $18, $ret_success
 
-        ldq     $20, 72($sp)    /* .. and this a3 */
+        ldq     $19, 72($sp)    /* .. and this a3 */
         subq    $31, $0, $0     /* with error in v0 */
         addq    $31, 1, $1      /* set a3 for errno return */
         stq     $0, 0($sp)
@@ -362,51 +362,35 @@ $ret_success:
  * Do all cleanup when returning from all interrupts and system calls.
  *
  * Arguments:
- *       $5: TI_FLAGS.
  *       $8: current.
- *      $19: The old syscall number, or zero if this is not a return
+ *      $17: TI_FLAGS.
+ *      $18: The old syscall number, or zero if this is not a return
  *           from a syscall that errored and is possibly restartable.
- *      $20: The old a3 value
+ *      $19: The old a3 value
  */
 
         .align  4
         .ent    work_pending
 work_pending:
-        and     $5, _TIF_NEED_RESCHED, $2
-        beq     $2, $work_notifysig
+        and     $17, _TIF_NOTIFY_RESUME | _TIF_SIGPENDING, $2
+        bne     $2, $work_notifysig
 
 $work_resched:
-        subq    $sp, 16, $sp
-        stq     $19, 0($sp)              /* save syscall nr */
-        stq     $20, 8($sp)              /* and error indication (a3) */
+        /*
+         * We can get here only if we returned from syscall without SIGPENDING
+         * or got through work_notifysig already.  Either case means no syscall
+         * restarts for us, so let $18 and $19 burn.
+         */
         jsr     $26, schedule
-        ldq     $19, 0($sp)
-        ldq     $20, 8($sp)
-        addq    $sp, 16, $sp
-        /* Make sure need_resched and sigpending don't change between
-                sampling and the rti.  */
-        lda     $16, 7
-        call_pal PAL_swpipl
-        ldl     $5, TI_FLAGS($8)
-        and     $5, _TIF_WORK_MASK, $2
-        beq     $2, restore_all
-        and     $5, _TIF_NEED_RESCHED, $2
-        bne     $2, $work_resched
+        mov     0, $18
+        br      ret_to_user
 
 $work_notifysig:
         mov     $sp, $16
         bsr     $1, do_switch_stack
-        mov     $sp, $17
-        mov     $5, $18
-        mov     $19, $9         /* save old syscall number */
-        mov     $20, $10        /* save old a3 */
-        and     $5, _TIF_SIGPENDING, $2
-        cmovne  $2, 0, $9       /* we don't want double syscall restarts */
-        jsr     $26, do_notify_resume
-        mov     $9, $19
-        mov     $10, $20
+        jsr     $26, do_work_pending
         bsr     $1, undo_switch_stack
-        br      ret_to_user
+        br      restore_all
 .end work_pending
 
 /*
@@ -454,9 +438,9 @@ $strace_success:
 
         .align  3
 $strace_error:
-        ldq     $19, 0($sp)     /* old syscall nr (zero if success) */
-        beq     $19, $strace_success
-        ldq     $20, 72($sp)    /* .. and this a3 */
+        ldq     $18, 0($sp)     /* old syscall nr (zero if success) */
+        beq     $18, $strace_success
+        ldq     $19, 72($sp)    /* .. and this a3 */
 
         subq    $31, $0, $0     /* with error in v0 */
         addq    $31, 1, $1      /* set a3 for errno return */
@@ -464,11 +448,11 @@ $strace_error:
         stq     $1, 72($sp)     /* a3 for return */
 
         bsr     $1, do_switch_stack
-        mov     $19, $9         /* save old syscall number */
-        mov     $20, $10        /* save old a3 */
+        mov     $18, $9         /* save old syscall number */
+        mov     $19, $10        /* save old a3 */
         jsr     $26, syscall_trace_leave
-        mov     $9, $19
-        mov     $10, $20
+        mov     $9, $18
+        mov     $10, $19
         bsr     $1, undo_switch_stack
 
         mov     $31, $26        /* tell "ret_from_sys_call" we can restart */
@@ -619,24 +603,9 @@ ret_from_kernel_thread:
         mov     $9, $27
         mov     $10, $16
         jsr     $26, ($9)
-        ldgp    $gp, 0($26)
-        mov     $0, $16
-        mov     $31, $26
-        jmp     $31, sys_exit
-.end ret_from_kernel_thread
-
-        .globl  ret_from_kernel_execve
-        .align  4
-        .ent    ret_from_kernel_execve
-ret_from_kernel_execve:
-        mov     $16, $sp
-        /* Avoid the HAE being gratuitously wrong, to avoid restoring it.  */
-        ldq     $2, alpha_mv+HAE_CACHE
-        stq     $2, 152($sp)            /* HAE */
         mov     $31, $19                /* to disable syscall restarts */
         br      $31, ret_to_user
-
-.end    ret_from_kernel_execve
+.end ret_from_kernel_thread
 
 
 /*
diff --git a/arch/alpha/kernel/signal.c b/arch/alpha/kernel/signal.c
index a8c97d42ec8e..32575f85507d 100644
--- a/arch/alpha/kernel/signal.c
+++ b/arch/alpha/kernel/signal.c
@@ -298,8 +298,9 @@ get_sigframe(struct k_sigaction *ka, unsigned long sp, size_t frame_size)
 
 static long
 setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs, 
-                 struct switch_stack *sw, unsigned long mask, unsigned long sp)
+                 unsigned long mask, unsigned long sp)
 {
+        struct switch_stack *sw = (struct switch_stack *)regs - 1;
         long i, err = 0;
 
         err |= __put_user(on_sig_stack((unsigned long)sc), &sc->sc_onstack);
@@ -354,7 +355,7 @@ setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs,
 
 static int
 setup_frame(int sig, struct k_sigaction *ka, sigset_t *set,
-            struct pt_regs *regs, struct switch_stack * sw)
+            struct pt_regs *regs)
 {
         unsigned long oldsp, r26, err = 0;
         struct sigframe __user *frame;
@@ -364,7 +365,7 @@ setup_frame(int sig, struct k_sigaction *ka, sigset_t *set,
         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
                 return -EFAULT;
 
-        err |= setup_sigcontext(&frame->sc, regs, sw, set->sig[0], oldsp);
+        err |= setup_sigcontext(&frame->sc, regs, set->sig[0], oldsp);
         if (err)
                 return -EFAULT;
 
@@ -401,7 +402,7 @@ setup_frame(int sig, struct k_sigaction *ka, sigset_t *set,
 
 static int
 setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
-               sigset_t *set, struct pt_regs *regs, struct switch_stack * sw)
+               sigset_t *set, struct pt_regs *regs)
 {
         unsigned long oldsp, r26, err = 0;
         struct rt_sigframe __user *frame;
@@ -420,7 +421,7 @@ setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
         err |= __put_user(current->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
         err |= __put_user(sas_ss_flags(oldsp), &frame->uc.uc_stack.ss_flags);
         err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
-        err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, sw,
+        err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, 
                                 set->sig[0], oldsp);
         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
         if (err)
@@ -464,15 +465,15 @@ setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
  */
 static inline void
 handle_signal(int sig, struct k_sigaction *ka, siginfo_t *info,
-              struct pt_regs * regs, struct switch_stack *sw)
+              struct pt_regs * regs)
 {
         sigset_t *oldset = sigmask_to_save();
         int ret;
 
         if (ka->sa.sa_flags & SA_SIGINFO)
-                ret = setup_rt_frame(sig, ka, info, oldset, regs, sw);
+                ret = setup_rt_frame(sig, ka, info, oldset, regs);
         else
-                ret = setup_frame(sig, ka, oldset, regs, sw);
+                ret = setup_frame(sig, ka, oldset, regs);
 
         if (ret) {
                 force_sigsegv(sig, current);
@@ -519,8 +520,7 @@ syscall_restart(unsigned long r0, unsigned long r19,
  * all (if we get here from anything but a syscall return, it will be 0)
  */
 static void
-do_signal(struct pt_regs * regs, struct switch_stack * sw,
-          unsigned long r0, unsigned long r19)
+do_signal(struct pt_regs *regs, unsigned long r0, unsigned long r19)
 {
         siginfo_t info;
         int signr;
@@ -537,7 +537,7 @@ do_signal(struct pt_regs * regs, struct switch_stack * sw,
                 /* Whee!  Actually deliver the signal.  */
                 if (r0)
                         syscall_restart(r0, r19, regs, &ka);
-                handle_signal(signr, &ka, &info, regs, sw);
+                handle_signal(signr, &ka, &info, regs);
                 if (single_stepping) 
                         ptrace_set_bpt(current); /* re-set bpt */
                 return;
@@ -568,15 +568,23 @@ do_signal(struct pt_regs * regs, struct switch_stack * sw,
 }
 
 void
-do_notify_resume(struct pt_regs *regs, struct switch_stack *sw,
-                 unsigned long thread_info_flags,
+do_work_pending(struct pt_regs *regs, unsigned long thread_flags,
                  unsigned long r0, unsigned long r19)
 {
-        if (thread_info_flags & _TIF_SIGPENDING)
-                do_signal(regs, sw, r0, r19);
-
-        if (thread_info_flags & _TIF_NOTIFY_RESUME) {
-                clear_thread_flag(TIF_NOTIFY_RESUME);
-                tracehook_notify_resume(regs);
-        }
+        do {
+                if (thread_flags & _TIF_NEED_RESCHED) {
+                        schedule();
+                } else {
+                        local_irq_enable();
+                        if (thread_flags & _TIF_SIGPENDING) {
+                                do_signal(regs, r0, r19);
+                                r0 = 0;
+                        } else {
+                                clear_thread_flag(TIF_NOTIFY_RESUME);
+                                tracehook_notify_resume(regs);
+                        }
+                }
+                local_irq_disable();
+                thread_flags = current_thread_info()->flags;
+        } while (thread_flags & _TIF_WORK_MASK);
 }
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 767aae8277fa..431c3753145a 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -53,6 +53,7 @@ config ARM
         select GENERIC_STRNLEN_USER
         select DCACHE_WORD_ACCESS if (CPU_V6 || CPU_V6K || CPU_V7) && !CPU_BIG_ENDIAN
         select GENERIC_KERNEL_THREAD
+        select GENERIC_KERNEL_EXECVE
         help
           The ARM series is a line of low-power-consumption RISC chip designs
           licensed by ARM Ltd and targeted at embedded applications and
diff --git a/arch/arm/include/asm/unistd.h b/arch/arm/include/asm/unistd.h
index f259921edfe9..91819ad54424 100644
--- a/arch/arm/include/asm/unistd.h
+++ b/arch/arm/include/asm/unistd.h
@@ -479,7 +479,6 @@
 #define __ARCH_WANT_SYS_SOCKETCALL
 #endif
 #define __ARCH_WANT_SYS_EXECVE
-#define __ARCH_WANT_KERNEL_EXECVE
 
 /*
  * "Conditional" syscalls
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index e340fa1db203..417bac1846bd 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -86,35 +86,14 @@ ENDPROC(ret_to_user)
  */
 ENTRY(ret_from_fork)
         bl      schedule_tail
+        cmp     r5, #0
+        movne   r0, r4
+        movne   lr, pc
+        movne   pc, r5
         get_thread_info tsk
-        mov     why, #1
         b       ret_slow_syscall
 ENDPROC(ret_from_fork)
 
-ENTRY(ret_from_kernel_thread)
- UNWIND(.fnstart)
- UNWIND(.cantunwind)
-        bl      schedule_tail
-        mov     r0, r4
-        adr     lr, BSYM(1f)    @ kernel threads should not exit
-        mov     pc, r5
-1:      bl      do_exit
-        nop
- UNWIND(.fnend)
-ENDPROC(ret_from_kernel_thread)
-
-/*
- * turn a kernel thread into userland process
- * use: ret_from_kernel_execve(struct pt_regs *normal)
- */
-ENTRY(ret_from_kernel_execve)
-        mov     why, #0                 @ not a syscall
-        str     why, [r0, #S_R0]        @ ... and we want 0 in ->ARM_r0 as well
-        get_thread_info tsk             @ thread structure
-        mov     sp, r0                  @ stack pointer just under pt_regs
-        b       ret_slow_syscall
-ENDPROC(ret_from_kernel_execve)
-
         .equ NR_syscalls,0
 #define CALL(x) .equ NR_syscalls,NR_syscalls+1
 #include "calls.S"
diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
index f98c17ff1957..90084a6de35a 100644
--- a/arch/arm/kernel/process.c
+++ b/arch/arm/kernel/process.c
@@ -373,7 +373,6 @@ void release_thread(struct task_struct *dead_task)
 }
 
 asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");
-asmlinkage void ret_from_kernel_thread(void) __asm__("ret_from_kernel_thread");
 
 int
 copy_thread(unsigned long clone_flags, unsigned long stack_start,
@@ -388,13 +387,13 @@ copy_thread(unsigned long clone_flags, unsigned long stack_start,
                 *childregs = *regs;
                 childregs->ARM_r0 = 0;
                 childregs->ARM_sp = stack_start;
-                thread->cpu_context.pc = (unsigned long)ret_from_fork;
         } else {
+                memset(childregs, 0, sizeof(struct pt_regs));
                 thread->cpu_context.r4 = stk_sz;
                 thread->cpu_context.r5 = stack_start;
-                thread->cpu_context.pc = (unsigned long)ret_from_kernel_thread;
                 childregs->ARM_cpsr = SVC_MODE;
         }
+        thread->cpu_context.pc = (unsigned long)ret_from_fork;
         thread->cpu_context.sp = (unsigned long)childregs;
 
         clear_ptrace_hw_breakpoint(p);
diff --git a/arch/powerpc/platforms/pseries/eeh_event.c b/arch/powerpc/platforms/pseries/eeh_event.c
index 51faaac8abe6..185bedd926df 100644
--- a/arch/powerpc/platforms/pseries/eeh_event.c
+++ b/arch/powerpc/platforms/pseries/eeh_event.c
@@ -23,6 +23,7 @@
 #include <linux/pci.h>
 #include <linux/slab.h>
 #include <linux/workqueue.h>
+#include <linux/kthread.h>
 #include <asm/eeh_event.h>
 #include <asm/ppc-pci.h>
 
@@ -59,8 +60,6 @@ static int eeh_event_handler(void * dummy)
         struct eeh_event *event;
         struct eeh_pe *pe;
 
-        set_task_comm(current, "eehd");
-
         spin_lock_irqsave(&eeh_eventlist_lock, flags);
         event = NULL;
 
@@ -108,7 +107,7 @@ static int eeh_event_handler(void * dummy)
  */
 static void eeh_thread_launcher(struct work_struct *dummy)
 {
-        if (kernel_thread(eeh_event_handler, NULL, CLONE_KERNEL) < 0)
+        if (IS_ERR(kthread_run(eeh_event_handler, NULL, "eehd")))
                 printk(KERN_ERR "Failed to start EEH daemon\n");
 }
 
diff --git a/arch/um/include/asm/processor-generic.h b/arch/um/include/asm/processor-generic.h
index 1e82e954e978..c03cd5a02364 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 44883049c11d..95feaa47a2fb 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 ab019c7f0b57..3a8ece7d09ca 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 30629783b3e0..b6d699cdd557 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 162bea3d91b2..b8f34c9e53ae 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 42d2c35a5bbd..70071b19eb98 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -109,6 +109,7 @@ config X86
         select HAVE_RCU_USER_QS if X86_64
         select HAVE_IRQ_TIME_ACCOUNTING
         select GENERIC_KERNEL_THREAD
+        select GENERIC_KERNEL_EXECVE
 
 config INSTRUCTION_DECODER
         def_bool y
diff --git a/arch/x86/include/asm/unistd.h b/arch/x86/include/asm/unistd.h
index 55d155560fdf..16f3fc6ebf2e 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 2c6340796fe9..a1193aef6d7d 100644
--- a/arch/x86/kernel/entry_32.S
+++ b/arch/x86/kernel/entry_32.S
@@ -299,12 +299,20 @@ 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
@@ -1015,21 +1023,6 @@ 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 cdc790c78f32..0c58952d64e8 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -563,15 +563,13 @@ 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)
 
@@ -1326,20 +1324,6 @@ 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 30c4eec033af..9fa950df80e5 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"