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Commit 32344d29 authored by Josh Poimboeuf's avatar Josh Poimboeuf Committed by Greg Kroah-Hartman
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x86/unwind/orc: Fix ORC for newly forked tasks 



[ Upstream commit 372a8eaa05998cd45b3417d0e0ffd3a70978211a ]

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: default avatarWang ShaoBo <bobo.shaobowang@huawei.com>
Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Tested-by: default avatarWang ShaoBo <bobo.shaobowang@huawei.com>
Link: https://lkml.kernel.org/r/f91a8778dde8aae7f71884b5df2b16d552040441.1594994374.git.jpoimboe@redhat.com


Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent a14d6a9d

arch/x86/kernel/unwind_orc.c

+6 −2
Original line number Diff line number Diff line
@@ -431,8 +431,11 @@ 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) {
@@ -653,6 +656,7 @@ 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,