x86-64: merge the standard and compat start_thread() functions

The only thing left that differs between the standard and compat
start_thread functions is the actual segment numbers and the
prototype, so have a single common function which contains the guts
and two very small wrappers.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Acked-by: Suresh Siddha <suresh.b.siddha@intel.com>

1 files changed, 17 insertions, 22 deletions

diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 7cf0a6b6d4bb..eb261c582a44 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -344,18 +344,20 @@ out:
         return err;
 }
 
-void
-start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp)
+static void
+start_thread_common(struct pt_regs *regs, unsigned long new_ip,
+                    unsigned long new_sp,
+                    unsigned int _cs, unsigned int _ss, unsigned int _ds)
 {
         loadsegment(fs, 0);
-        loadsegment(es, 0);
-        loadsegment(ds, 0);
+        loadsegment(es, _ds);
+        loadsegment(ds, _ds);
         load_gs_index(0);
         regs->ip                = new_ip;
         regs->sp                = new_sp;
         percpu_write(old_rsp, new_sp);
-        regs->cs                = __USER_CS;
-        regs->ss                = __USER_DS;
+        regs->cs                = _cs;
+        regs->ss                = _ss;
         regs->flags             = X86_EFLAGS_IF;
         set_fs(USER_DS);
         /*
@@ -363,26 +365,19 @@ start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp)
          */
         free_thread_xstate(current);
 }
-EXPORT_SYMBOL_GPL(start_thread);
+
+void
+start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp)
+{
+        start_thread_common(regs, new_ip, new_sp,
+                            __USER_CS, __USER_DS, 0);
+}
 
 #ifdef CONFIG_IA32_EMULATION
 void start_thread_ia32(struct pt_regs *regs, u32 new_ip, u32 new_sp)
 {
-        loadsegment(fs, 0);
-        loadsegment(ds, __USER32_DS);
-        loadsegment(es, __USER32_DS);
-        load_gs_index(0);
-        regs->ip                = new_ip;
-        regs->sp                = new_sp;
-        percpu_write(old_rsp, new_sp);
-        regs->cs                = __USER32_CS;
-        regs->ss                = __USER32_DS;
-        regs->flags             = X86_EFLAGS_IF;
-        set_fs(USER_DS);
-        /*
-         * Free the old FP and other extended state
-         */
-        free_thread_xstate(current);
+        start_thread_common(regs, new_ip, new_sp,
+                            __USER32_CS, __USER32_DS, __USER32_DS);
 }
 #endif