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x86/unwind/orc: Fix ORC for newly forked tasks
[ Upstream commit 372a8eaa05
]
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
Signed-off-by: Sasha Levin <sashal@kernel.org>
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1 changed files with 6 additions and 2 deletions
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@ -431,8 +431,11 @@ bool unwind_next_frame(struct unwind_state *state)
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/*
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* Find the orc_entry associated with the text address.
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*
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* Decrement call return addresses by one so they work for sibling
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* calls and calls to noreturn functions.
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* For a call frame (as opposed to a signal frame), state->ip points to
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* the instruction after the call. That instruction's stack layout
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* could be different from the call instruction's layout, for example
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* if the call was to a noreturn function. So get the ORC data for the
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* call instruction itself.
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*/
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orc = orc_find(state->signal ? state->ip : state->ip - 1);
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if (!orc) {
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@ -653,6 +656,7 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task,
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state->sp = task->thread.sp;
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state->bp = READ_ONCE_NOCHECK(frame->bp);
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state->ip = READ_ONCE_NOCHECK(frame->ret_addr);
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state->signal = (void *)state->ip == ret_from_fork;
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}
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if (get_stack_info((unsigned long *)state->sp, state->task,
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