From: Lai Jiangshan <la...@linux.alibaba.com>
Directly copy pt_regs to kernel stack when .Lerror_bad_iret.
Directly switch to kernel stack when .Lerror_bad_iret.
We can see that entry_64.S do the following things back to back
when .Lerror_bad_iret:
call fixup_bad_iret(), switch to sp0 stack with pt_regs copied
call sync_regs(), switch to kernel stack with pt_regs copied
So we can do the all things together in fixup_bad_iret().
After this patch, fixup_bad_iret() is restored to the behavior before
7f2590a110b8("x86/entry/64: Use a per-CPU trampoline stack for IDT entries")
Signed-off-by: Lai Jiangshan <la...@linux.alibaba.com>
---
arch/x86/entry/entry_64.S | 13 ++-----------
arch/x86/kernel/traps.c | 9 ++++-----
2 files changed, 6 insertions(+), 16 deletions(-)
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 1a7715430da3..911cfa0da637 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -965,16 +965,6 @@ SYM_CODE_START_LOCAL(error_entry)
ENCODE_FRAME_POINTER 8
ret
-.Lerror_entry_from_usermode_after_swapgs:
- /* Put us onto the real thread stack. */
- popq %r12 /* save return addr in %12 */
- movq %rsp, %rdi /* arg0 = pt_regs pointer */
- call sync_regs
- movq %rax, %rsp /* switch stack */
- ENCODE_FRAME_POINTER
- pushq %r12
- ret
-
.Lerror_entry_done_lfence:
FENCE_SWAPGS_KERNEL_ENTRY
.Lerror_entry_done:
@@ -1028,7 +1018,8 @@ SYM_CODE_START_LOCAL(error_entry)
mov %rsp, %rdi
call fixup_bad_iret
mov %rax, %rsp
- jmp .Lerror_entry_from_usermode_after_swapgs
+ ENCODE_FRAME_POINTER 8
+ ret
SYM_CODE_END(error_entry)
SYM_CODE_START_LOCAL(error_return)
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 1f66d2d1e998..852de6f1bf88 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -684,13 +684,12 @@ struct bad_iret_stack *fixup_bad_iret(struct
bad_iret_stack *s)
/*
* This is called from entry_64.S early in handling a fault
* caused by a bad iret to user mode. To handle the fault
- * correctly, we want to move our stack frame to where it would
- * be had we entered directly on the entry stack (rather than
- * just below the IRET frame) and we want to pretend that the
- * exception came from the IRET target.
+ * correctly, we want to move our stack frame to kernel stack
+ * (rather than just below the IRET frame) and we want to
+ * pretend that the exception came from the IRET target.
*/
struct bad_iret_stack tmp, *new_stack =
- (struct bad_iret_stack
*)__this_cpu_read(cpu_tss_rw.x86_tss.sp0) - 1;
+ (struct bad_iret_stack
*)__this_cpu_read(cpu_current_top_of_stack) - 1;
/* Copy the IRET target to the temporary storage. */
__memcpy(&tmp.regs.ip, (void *)s->regs.sp, 5*8);
--
2.19.1.6.gb485710b
