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[PATCH] x86: Terminate the kernel stacks for the unwinder

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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: Andi Kleen <ak@suse.de>
This commit is contained in:
Andi Kleen 2006-10-05 18:47:22 +02:00 committed by Andi Kleen
parent f015c6c4d7
commit 51ec28e1b2
2 changed files with 10 additions and 1 deletions
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6
arch/i386/kernel/process.c
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@ -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);

5
arch/x86_64/kernel/entry.S
View File

@ -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,