Commit 6fefb0d1 authored by Andi Kleen's avatar Andi Kleen Committed by Linus Torvalds
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[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: default avatarAndi Kleen <ak@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 11b854b2

arch/x86_64/kernel/entry.S

+27 −22
Original line number Diff line number Diff line
@@ -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
@@ -807,33 +804,47 @@ 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

	sti

	xorl %esi,%esi /* oldset */

	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 			/* 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)
@@ -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

arch/x86_64/kernel/traps.c

+28 −29
Original line number Diff line number Diff line
@@ -488,24 +488,8 @@ DO_ERROR(10, SIGSEGV, "invalid TSS", invalid_TSS) 
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 char reason, struct pt_regs * regs) 
	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 * regs, long error_code) 
	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 * regs, unsigned long error_code) 


	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 * regs, unsigned long error_code) 
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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