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946c191161
With frame pointers, when a task is interrupted, its stack is no longer completely reliable because the function could have been interrupted before it had a chance to save the previous frame pointer on the stack. So the caller of the interrupted function could get skipped by a stack trace. This is problematic for live patching, which needs to know whether a stack trace of a sleeping task can be relied upon. There's currently no way to detect if a sleeping task was interrupted by a page fault exception or preemption before it went to sleep. Another issue is that when dumping the stack of an interrupted task, the unwinder has no way of knowing where the saved pt_regs registers are, so it can't print them. This solves those issues by encoding the pt_regs pointer in the frame pointer on entry from an interrupt or an exception. This patch also updates the unwinder to be able to decode it, because otherwise the unwinder would be broken by this change. Note that this causes a change in the behavior of the unwinder: each instance of a pt_regs on the stack is now considered a "frame". So callers of unwind_get_return_address() will now get an occasional 'regs->ip' address that would have previously been skipped over. Suggested-by: Andy Lutomirski <luto@amacapital.net> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/8b9f84a21e39d249049e0547b559ff8da0df0988.1476973742.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org> |
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| Makefile_32.cpu | ||