On Fri, 7 Jun 2019 09:36:02 -0400 Josh Poimboeuf <[email protected]> wrote:
> On Fri, Jun 07, 2019 at 10:02:10PM +0900, Masami Hiramatsu wrote: > > On Wed, 05 Jun 2019 15:07:56 +0200 > > Peter Zijlstra <[email protected]> wrote: > > > > > The kprobe trampolines have a FRAME_POINTER annotation that makes no > > > sense. It marks the frame in the middle of pt_regs, at the place of > > > saving BP. > > > > commit ee213fc72fd67 introduced this code, and this is for unwinder which > > uses frame pointer. I think current code stores the address of previous > > (original context's) frame pointer into %rbp. So with that, if unwinder > > tries to decode frame pointer, it can get the original %rbp value, > > instead of &pt_regs from current %rbp. > > > > > > > > Change it to mark the pt_regs frame as per the ENCODE_FRAME_POINTER > > > from the respective entry_*.S. > > > > > > > With this change, I think stack unwinder can not get the original %rbp > > value. Peter, could you check the above commit? > > The unwinder knows how to decode the encoded frame pointer. So it can > find regs by decoding the new rbp value, and it also knows that regs->bp > is the original rbp value. > > Reviewed-by: Josh Poimboeuf <[email protected]> > Ah, OK. My misunderstood. So this encode framepointer as same as other interrupt entry stack. Then, it looks good to me too. Acked-by: Masami Hiramatsu <[email protected]> Thank you Josh! > -- > Josh -- Masami Hiramatsu <[email protected]>
