x86, entry: Switch stacks on a paranoid entry from userspace

[mirror_ubuntu-focal-kernel.git] / arch / x86 / kernel / traps.c

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 88900e288021f23a2f22aebf739e25070f456971..28f3e5ffc55ddce45e19570fed420c090acfdb6f 100644 (file)
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -466,27 +466,14 @@ NOKPROBE_SYMBOL(do_int3);
 
 #ifdef CONFIG_X86_64
 /*
- * Help handler running on IST stack to switch back to user stack
- * for scheduling or signal handling. The actual stack switch is done in
- * entry.S
+ * Help handler running on IST stack to switch off the IST stack if the
+ * interrupted code was in user mode. The actual stack switch is done in
+ * entry_64.S
  */
 asmlinkage __visible notrace struct pt_regs *sync_regs(struct pt_regs *eregs)
 {
-       struct pt_regs *regs = eregs;
-       /* Did already sync */
-       if (eregs == (struct pt_regs *)eregs->sp)
-               ;
-       /* Exception from user space */
-       else if (user_mode(eregs))
-               regs = task_pt_regs(current);
-       /*
-        * Exception from kernel and interrupts are enabled. Move to
-        * kernel process stack.
-        */
-       else if (eregs->flags & X86_EFLAGS_IF)
-               regs = (struct pt_regs *)(eregs->sp -= sizeof(struct pt_regs));
-       if (eregs != regs)
-               *regs = *eregs;
+       struct pt_regs *regs = task_pt_regs(current);
+       *regs = *eregs;
        return regs;
 }
 NOKPROBE_SYMBOL(sync_regs);