tree 7fe30b8fc61a207980fefa6d9828d4f9bfb25eec
parent d8dd25a461e4eec7190cb9d66616aceacc5110ad
author Josh Poimboeuf <jpoimboe@redhat.com> 1587808981 -0500
committer Ingo Molnar <mingo@kernel.org> 1587810147 +0200

x86/entry/64: Fix unwind hints in register clearing code

The PUSH_AND_CLEAR_REGS macro zeroes each register immediately after
pushing it.  If an NMI or exception hits after a register is cleared,
but before the UNWIND_HINT_REGS annotation, the ORC unwinder will
wrongly think the previous value of the register was zero.  This can
confuse the unwinding process and cause it to exit early.

Because ORC is simpler than DWARF, there are a limited number of unwind
annotation states, so it's not possible to add an individual unwind hint
after each push/clear combination.  Instead, the register clearing
instructions need to be consolidated and moved to after the
UNWIND_HINT_REGS annotation.

Fixes: 3f01daecd545 ("x86/entry/64: Introduce the PUSH_AND_CLEAN_REGS macro")
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Dave Jones <dsj@fb.com>
Cc: Jann Horn <jannh@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Link: https://lore.kernel.org/r/68fd3d0bc92ae2d62ff7879d15d3684217d51f08.1587808742.git.jpoimboe@redhat.com