From: "Andi Kleen" <[email protected]>
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 <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
---
25-akpm/arch/x86_64/kernel/entry.S | 49 +++++++++++++++++--------------
25-akpm/arch/x86_64/kernel/traps.c | 57 ++++++++++++++++++-------------------
2 files changed, 55 insertions(+), 51 deletions(-)
diff -puN arch/x86_64/kernel/entry.S~x86_64-regularize-exception-stack-handling arch/x86_64/kernel/entry.S
--- 25/arch/x86_64/kernel/entry.S~x86_64-regularize-exception-stack-handling 2005-04-12 03:21:22.841664440 -0700
+++ 25-akpm/arch/x86_64/kernel/entry.S 2005-04-12 03:21:22.846663680 -0700
@@ -579,6 +579,7 @@ ENTRY(spurious_interrupt)
movq ORIG_RAX(%rsp),%rsi
movq $-1,ORIG_RAX(%rsp)
call \sym
+ cli
.endm
/*
@@ -794,10 +795,6 @@ ENTRY(debug)
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 @@ ENTRY(nmi)
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(reserved)
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(segment_not_present)
ENTRY(stack_segment)
CFI_STARTPROC
paranoidentry do_stack_segment
- movq %rax,%rsp
- testl $3,CS(%rsp)
- jnz paranoid_userspace
jmp paranoid_exit
CFI_ENDPROC
diff -puN arch/x86_64/kernel/traps.c~x86_64-regularize-exception-stack-handling arch/x86_64/kernel/traps.c
--- 25/arch/x86_64/kernel/traps.c~x86_64-regularize-exception-stack-handling 2005-04-12 03:21:22.842664288 -0700
+++ 25-akpm/arch/x86_64/kernel/traps.c 2005-04-12 03:21:22.847663528 -0700
@@ -488,24 +488,8 @@ DO_ERROR(10, SIGSEGV, "invalid TSS", inv
DO_ERROR(11, SIGBUS, "segment not present", segment_not_present)
DO_ERROR_INFO(17, SIGBUS, "alignment check", alignment_check, BUS_ADRALN, 0)
DO_ERROR(18, SIGSEGV, "reserved", reserved)
-
-#define DO_ERROR_STACK(trapnr, signr, str, name) \
-asmlinkage void *do_##name(struct pt_regs * regs, long error_code) \
-{ \
- struct pt_regs *pr = ((struct pt_regs *)(current->thread.rsp0))-1; \
- if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, signr) \
- == NOTIFY_STOP) \
- return regs; \
- if (regs->cs & 3) { \
- memcpy(pr, regs, sizeof(struct pt_regs)); \
- regs = pr; \
- } \
- do_trap(trapnr, signr, str, regs, error_code, NULL); \
- return regs; \
-}
-
-DO_ERROR_STACK(12, SIGBUS, "stack segment", stack_segment)
-DO_ERROR_STACK( 8, SIGSEGV, "double fault", double_fault)
+DO_ERROR(12, SIGBUS, "stack segment", stack_segment)
+DO_ERROR( 8, SIGSEGV, "double fault", double_fault)
asmlinkage void do_general_protection(struct pt_regs * regs, long error_code)
{
@@ -584,6 +568,8 @@ static void unknown_nmi_error(unsigned c
printk("Do you have a strange power saving mode enabled?\n");
}
+/* Runs on IST stack. This code must keep interrupts off all the time.
+ Nested NMIs are prevented by the CPU. */
asmlinkage void default_do_nmi(struct pt_regs *regs)
{
unsigned char reason = 0;
@@ -629,20 +615,34 @@ asmlinkage void do_int3(struct pt_regs *
return;
}
+/* 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 */
+asmlinkage struct pt_regs *sync_regs(struct pt_regs *eregs)
+{
+ struct pt_regs *regs = eregs;
+ /* Did already sync */
+ if (eregs == (struct pt_regs *)eregs->rsp)
+ ;
+ /* Exception from user space */
+ else if (eregs->cs & 3)
+ regs = ((struct pt_regs *)current->thread.rsp0) - 1;
+ /* Exception from kernel and interrupts are enabled. Move to
+ kernel process stack. */
+ else if (eregs->eflags & X86_EFLAGS_IF)
+ regs = (struct pt_regs *)(eregs->rsp -= sizeof(struct pt_regs));
+ if (eregs != regs)
+ *regs = *eregs;
+ return regs;
+}
+
/* runs on IST stack. */
-asmlinkage void *do_debug(struct pt_regs * regs, unsigned long error_code)
+asmlinkage void do_debug(struct pt_regs * regs, unsigned long error_code)
{
- struct pt_regs *pr;
unsigned long condition;
struct task_struct *tsk = current;
siginfo_t info;
- pr = (struct pt_regs *)(current->thread.rsp0)-1;
- if (regs->cs & 3) {
- memcpy(pr, regs, sizeof(struct pt_regs));
- regs = pr;
- }
-
#ifdef CONFIG_CHECKING
{
/* RED-PEN interaction with debugger - could destroy gs */
@@ -660,7 +660,7 @@ asmlinkage void *do_debug(struct pt_regs
if (notify_die(DIE_DEBUG, "debug", regs, condition, error_code,
SIGTRAP) == NOTIFY_STOP) {
- return regs;
+ return;
}
conditional_sti(regs);
@@ -712,7 +712,7 @@ asmlinkage void *do_debug(struct pt_regs
clear_dr7:
asm volatile("movq %0,%%db7"::"r"(0UL));
notify_die(DIE_DEBUG, "debug", regs, condition, 1, SIGTRAP);
- return regs;
+ return;
clear_TF_reenable:
set_tsk_thread_flag(tsk, TIF_SINGLESTEP);
@@ -722,7 +722,6 @@ clear_TF:
if (notify_die(DIE_DEBUG, "debug2", regs, condition, 1, SIGTRAP)
!= NOTIFY_STOP)
regs->eflags &= ~TF_MASK;
- return regs;
}
static int kernel_math_error(struct pt_regs *regs, char *str)
_
-
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