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x86/unwind/orc: Fix ORC for newly forked tasks

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The ORC unwinder fails to unwind newly forked tasks which haven't yet
run on the CPU.  It correctly reads the 'ret_from_fork' instruction
pointer from the stack, but it incorrectly interprets that value as a
call stack address rather than a "signal" one, so the address gets
incorrectly decremented in the call to orc_find(), resulting in bad ORC
data.

Fix it by forcing 'ret_from_fork' frames to be signal frames.

Reported-by: Wang ShaoBo <bobo.shaobowang@huawei.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Wang ShaoBo <bobo.shaobowang@huawei.com>
Link: https://lkml.kernel.org/r/f91a8778dde8aae7f71884b5df2b16d552040441.1594994374.git.jpoimboe@redhat.com
This commit is contained in:
Josh Poimboeuf 2020-07-17 09:04:25 -05:00 committed by Thomas Gleixner
parent de2b41be8f
commit 372a8eaa05
1 changed files with 6 additions and 2 deletions
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8
arch/x86/kernel/unwind_orc.c
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@ -440,8 +440,11 @@ bool unwind_next_frame(struct unwind_state *state)
/*
* Find the orc_entry associated with the text address.
*
* Decrement call return addresses by one so they work for sibling
* calls and calls to noreturn functions.
* For a call frame (as opposed to a signal frame), state->ip points to
* the instruction after the call. That instruction's stack layout
* could be different from the call instruction's layout, for example
* if the call was to a noreturn function. So get the ORC data for the
* call instruction itself.
*/
orc = orc_find(state->signal ? state->ip : state->ip - 1);
if (!orc) {
@ -662,6 +665,7 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task,
state->sp = task->thread.sp;
state->bp = READ_ONCE_NOCHECK(frame->bp);
state->ip = READ_ONCE_NOCHECK(frame->ret_addr);
state->signal = (void *)state->ip == ret_from_fork;
}
if (get_stack_info((unsigned long *)state->sp, state->task,