x86: Rewrite ret_from_fork() in C

[linux-2.6-block.git] / arch / x86 / kernel / process.c

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index ff9b80a0e3e3bc7f86f02b3c459d96e133f815e7..72015dba72ab4c09fc750e8a66a40adfbf043b4e 100644 (file)
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -28,6 +28,7 @@
 #include <linux/static_call.h>
 #include <trace/events/power.h>
 #include <linux/hw_breakpoint.h>
+#include <linux/entry-common.h>
 #include <asm/cpu.h>
 #include <asm/apic.h>
 #include <linux/uaccess.h>
@@ -134,6 +135,25 @@ static int set_new_tls(struct task_struct *p, unsigned long tls)
                return do_set_thread_area_64(p, ARCH_SET_FS, tls);
 }
 
+__visible void ret_from_fork(struct task_struct *prev, struct pt_regs *regs,
+                                    int (*fn)(void *), void *fn_arg)
+{
+       schedule_tail(prev);
+
+       /* Is this a kernel thread? */
+       if (unlikely(fn)) {
+               fn(fn_arg);
+               /*
+                * A kernel thread is allowed to return here after successfully
+                * calling kernel_execve().  Exit to userspace to complete the
+                * execve() syscall.
+                */
+               regs->ax = 0;
+       }
+
+       syscall_exit_to_user_mode(regs);
+}
+
 int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 {
        unsigned long clone_flags = args->flags;
@@ -149,7 +169,7 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
        frame = &fork_frame->frame;
 
        frame->bp = encode_frame_pointer(childregs);
-       frame->ret_addr = (unsigned long) ret_from_fork;
+       frame->ret_addr = (unsigned long) ret_from_fork_asm;
        p->thread.sp = (unsigned long) fork_frame;
        p->thread.io_bitmap = NULL;
        p->thread.iopl_warn = 0;