From 51ec28e1b2cb267a09a0b8eac1ccf8d61b7268bf Mon Sep 17 00:00:00 2001 From: Andi Kleen Date: Thu, 5 Oct 2006 18:47:22 +0200 Subject: [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: Andi Kleen --- arch/i386/kernel/process.c | 6 +++++- arch/x86_64/kernel/entry.S | 5 +++++ 2 files changed, 10 insertions(+), 1 deletion(-) diff --git a/arch/i386/kernel/process.c b/arch/i386/kernel/process.c index dad02a9..b0a0780 100644 --- a/arch/i386/kernel/process.c +++ b/arch/i386/kernel/process.c @@ -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(®s, 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, ®s, 0, NULL, NULL); + err = do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, ®s, 0, NULL, NULL); + if (err == 0) /* terminate kernel stack */ + task_pt_regs(current)->eip = 0; + return err; } EXPORT_SYMBOL(kernel_thread); diff --git a/arch/x86_64/kernel/entry.S b/arch/x86_64/kernel/entry.S index b8285cf..ab9b2c4 100644 --- a/arch/x86_64/kernel/entry.S +++ b/arch/x86_64/kernel/entry.S @@ -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, -- cgit v1.1