[PATCH] x86_64: Regularize exception stack handling
This fixes various issues in the return path for "paranoid"
handlers (= running on a private exception stack that act like NMIs).
Generalize previous hack to switch back to process stack for
scheduling/signal handling purposes.
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/arch/x86_64/kernel/entry.S b/arch/x86_64/kernel/entry.S
index 12a3071..3e888c2 100644
--- a/arch/x86_64/kernel/entry.S
+++ b/arch/x86_64/kernel/entry.S
@@ -579,6 +579,7 @@
movq ORIG_RAX(%rsp),%rsi
movq $-1,ORIG_RAX(%rsp)
call \sym
+ cli
.endm
/*
@@ -794,10 +795,6 @@
pushq $0
CFI_ADJUST_CFA_OFFSET 8
paranoidentry do_debug
- /* switch back to process stack to restore the state ptrace touched */
- movq %rax,%rsp
- testl $3,CS(%rsp)
- jnz paranoid_userspace
jmp paranoid_exit
CFI_ENDPROC
@@ -807,35 +804,49 @@
pushq $-1
CFI_ADJUST_CFA_OFFSET 8
paranoidentry do_nmi
+ /*
+ * "Paranoid" exit path from exception stack.
+ * Paranoid because this is used by NMIs and cannot take
+ * any kernel state for granted.
+ * We don't do kernel preemption checks here, because only
+ * NMI should be common and it does not enable IRQs and
+ * cannot get reschedule ticks.
+ */
/* ebx: no swapgs flag */
paranoid_exit:
testl %ebx,%ebx /* swapgs needed? */
jnz paranoid_restore
+ testl $3,CS(%rsp)
+ jnz paranoid_userspace
paranoid_swapgs:
- cli
swapgs
paranoid_restore:
RESTORE_ALL 8
iretq
paranoid_userspace:
- cli
GET_THREAD_INFO(%rcx)
- movl threadinfo_flags(%rcx),%edx
- testl $_TIF_WORK_MASK,%edx
+ movl threadinfo_flags(%rcx),%ebx
+ andl $_TIF_WORK_MASK,%ebx
jz paranoid_swapgs
- testl $_TIF_NEED_RESCHED,%edx
- jnz paranoid_resched
+ movq %rsp,%rdi /* &pt_regs */
+ call sync_regs
+ movq %rax,%rsp /* switch stack for scheduling */
+ testl $_TIF_NEED_RESCHED,%ebx
+ jnz paranoid_schedule
+ movl %ebx,%edx /* arg3: thread flags */
sti
- xorl %esi,%esi /* oldset */
- movq %rsp,%rdi /* &pt_regs */
+ xorl %esi,%esi /* arg2: oldset */
+ movq %rsp,%rdi /* arg1: &pt_regs */
call do_notify_resume
- jmp paranoid_exit
-paranoid_resched:
+ cli
+ jmp paranoid_userspace
+paranoid_schedule:
sti
call schedule
- jmp paranoid_exit
+ cli
+ jmp paranoid_userspace
CFI_ENDPROC
-
+
ENTRY(int3)
zeroentry do_int3
@@ -858,9 +869,6 @@
ENTRY(double_fault)
CFI_STARTPROC
paranoidentry do_double_fault
- movq %rax,%rsp
- testl $3,CS(%rsp)
- jnz paranoid_userspace
jmp paranoid_exit
CFI_ENDPROC
@@ -874,9 +882,6 @@
ENTRY(stack_segment)
CFI_STARTPROC
paranoidentry do_stack_segment
- movq %rax,%rsp
- testl $3,CS(%rsp)
- jnz paranoid_userspace
jmp paranoid_exit
CFI_ENDPROC