Merge tag 'x86-urgent-2020-10-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 fixes from Thomas Gleixner:
 "A couple of x86 fixes which missed rc1 due to my stupidity:

   - Drop lazy TLB mode before switching to the temporary address space
     for text patching.

     text_poke() switches to the temporary mm which clears the lazy mode
     and restores the original mm afterwards. Due to clearing lazy mode
     this might restore a already dead mm if exit_mmap() runs in
     parallel on another CPU.

   - Document the x32 syscall design fail vs. syscall numbers 512-547
     properly.

   - Fix the ORC unwinder to handle the inactive task frame correctly.

     This was unearthed due to the slightly different code generation of
     gcc-10.

   - Use an up to date screen_info for the boot params of kexec instead
     of the possibly stale and invalid version which happened to be
     valid when the kexec kernel was loaded"

* tag 'x86-urgent-2020-10-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/alternative: Don't call text_poke() in lazy TLB mode
  x86/syscalls: Document the fact that syscalls 512-547 are a legacy mistake
  x86/unwind/orc: Fix inactive tasks with stack pointer in %sp on GCC 10 compiled kernels
  hyperv_fb: Update screen_info after removing old framebuffer
  x86/kexec: Use up-to-dated screen_info copy to fill boot params

1 files changed, 1 insertions, 8 deletions

diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c
index 6a339ce328e0..73f800100066 100644
--- a/arch/x86/kernel/unwind_orc.c
+++ b/arch/x86/kernel/unwind_orc.c
@@ -321,19 +321,12 @@ EXPORT_SYMBOL_GPL(unwind_get_return_address);
 
 unsigned long *unwind_get_return_address_ptr(struct unwind_state *state)
 {
-	struct task_struct *task = state->task;
-
 	if (unwind_done(state))
 		return NULL;
 
 	if (state->regs)
 		return &state->regs->ip;
 
-	if (task != current && state->sp == task->thread.sp) {
-		struct inactive_task_frame *frame = (void *)task->thread.sp;
-		return &frame->ret_addr;
-	}
-
 	if (state->sp)
 		return (unsigned long *)state->sp - 1;
 
@@ -663,7 +656,7 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task,
 	} else {
 		struct inactive_task_frame *frame = (void *)task->thread.sp;
 
-		state->sp = task->thread.sp;
+		state->sp = task->thread.sp + sizeof(*frame);
 		state->bp = READ_ONCE_NOCHECK(frame->bp);
 		state->ip = READ_ONCE_NOCHECK(frame->ret_addr);
 		state->signal = (void *)state->ip == ret_from_fork;