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Commit 51ec28e1 authored by Andi Kleen's avatar Andi Kleen Committed by Andi Kleen
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[PATCH] x86: Terminate the kernel stacks for the unwinder 



Always make sure RIP/EIP is 0 in the registers stored on the top
of the stack of a kernel thread. This makes sure the unwinder code
won't try a fallback but knows the stack has ended.

AK: this patch is a bit mysterious. in theory they should be terminated
anyways, but it seems to fix at least one crash. Anyways double termination
probably doesn't hurt.

Signed-off-by: default avatarAndi Kleen <ak@suse.de>
parent f015c6c4

arch/i386/kernel/process.c

+5 −1
Original line number Diff line number Diff line
@@ -328,6 +328,7 @@ extern void kernel_thread_helper(void); 
int kernel_thread(int (*fn)(void *), void * arg, unsigned long flags)

{

	struct pt_regs regs;

	int err;



	memset(&regs, 0, sizeof(regs));
@@ -342,7 +343,10 @@ int kernel_thread(int (*fn)(void *), void * arg, unsigned long flags) 
	regs.eflags = X86_EFLAGS_IF | X86_EFLAGS_SF | X86_EFLAGS_PF | 0x2;



	/* Ok, create the new process.. */

	return do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, &regs, 0, NULL, NULL);

	err = do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, &regs, 0, NULL, NULL);

	if (err == 0) /* terminate kernel stack */

		task_pt_regs(current)->eip = 0;

	return err;

}

EXPORT_SYMBOL(kernel_thread);

arch/x86_64/kernel/entry.S

+5 −0
Original line number Diff line number Diff line
@@ -978,6 +978,11 @@ ENTRY(kernel_thread) 
	call do_fork

	movq %rax,RAX(%rsp)

	xorl %edi,%edi

	test %rax,%rax

	jnz  1f

	/* terminate stack in child */

	movq %rdi,RIP(%rsp)

1:



	/*

	 * It isn't worth to check for reschedule here,