x86: Merge kernel_thread()

Signed-off-by: Brian Gerst <brgerst@gmail.com>
LKML-Reference: <1260380084-3707-6-git-send-email-brgerst@gmail.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

1 files changed, 35 insertions, 0 deletions

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index f3c1a6b3a65e..8705ccedd447 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -243,6 +243,41 @@ sys_clone(unsigned long clone_flags, unsigned long newsp,
 	return do_fork(clone_flags, newsp, regs, 0, parent_tid, child_tid);
 }
 
+/*
+ * This gets run with %si containing the
+ * function to call, and %di containing
+ * the "args".
+ */
+extern void kernel_thread_helper(void);
+
+/*
+ * Create a kernel thread
+ */
+int kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
+{
+	struct pt_regs regs;
+
+	memset(&regs, 0, sizeof(regs));
+
+	regs.si = (unsigned long) fn;
+	regs.di = (unsigned long) arg;
+
+#ifdef CONFIG_X86_32
+	regs.ds = __USER_DS;
+	regs.es = __USER_DS;
+	regs.fs = __KERNEL_PERCPU;
+	regs.gs = __KERNEL_STACK_CANARY;
+#endif
+
+	regs.orig_ax = -1;
+	regs.ip = (unsigned long) kernel_thread_helper;
+	regs.cs = __KERNEL_CS | get_kernel_rpl();
+	regs.flags = X86_EFLAGS_IF | 0x2;
+
+	/* Ok, create the new process.. */
+	return do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, &regs, 0, NULL, NULL);
+}
+EXPORT_SYMBOL(kernel_thread);
 
 /*
  * sys_execve() executes a new program.