releases/3.11.6/arc-ignore-ptrace-setregset-request-for-synthetic-register-stop_pc.patch

   1 From 5b24282846c064ee90d40fcb3a8f63b8e754fd28 Mon Sep 17 00:00:00 2001
   2 From: Vineet Gupta <vgupta@synopsys.com>
   3 Date: Thu, 10 Oct 2013 19:33:57 +0530
   4 Subject: ARC: Ignore ptrace SETREGSET request for synthetic register "stop_pc"
   5
   6 From: Vineet Gupta <vgupta@synopsys.com>
   7
   8 commit 5b24282846c064ee90d40fcb3a8f63b8e754fd28 upstream.
   9
  10 ARCompact TRAP_S insn used for breakpoints, commits before exception is
  11 taken (updating architectural PC). So ptregs->ret contains next-PC and
  12 not the breakpoint PC itself. This is different from other restartable
  13 exceptions such as TLB Miss where ptregs->ret has exact faulting PC.
  14 gdb needs to know exact-PC hence ARC ptrace GETREGSET provides for
  15 @stop_pc which returns ptregs->ret vs. EFA depending on the
  16 situation.
  17
  18 However, writing stop_pc (SETREGSET request), which updates ptregs->ret
  19 doesn't makes sense stop_pc doesn't always correspond to that reg as
  20 described above.
  21
  22 This was not an issue so far since user_regs->ret / user_regs->stop_pc
  23 had same value and both writing to ptregs->ret was OK, needless, but NOT
  24 broken, hence not observed.
  25
  26 With gdb "jump", they diverge, and user_regs->ret updating ptregs is
  27 overwritten immediately with stop_pc, which this patch fixes.
  28
  29 Reported-by: Anton Kolesov <akolesov@synopsys.com>
  30 Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
  31 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  32
  33 ---
  34  arch/arc/kernel/ptrace.c |    2 +-
  35  1 file changed, 1 insertion(+), 1 deletion(-)
  36
  37 --- a/arch/arc/kernel/ptrace.c
  38 +++ b/arch/arc/kernel/ptrace.c
  39 @@ -102,7 +102,7 @@ static int genregs_set(struct task_struc
  40         REG_IGNORE_ONE(pad2);
  41         REG_IN_CHUNK(callee, efa, cregs);       /* callee_regs[r25..r13] */
  42         REG_IGNORE_ONE(efa);                    /* efa update invalid */
  43 -       REG_IN_ONE(stop_pc, &ptregs->ret);      /* stop_pc: PC update */
  44 +       REG_IGNORE_ONE(stop_pc);                        /* PC updated via @ret */
  45
  46         return ret;
  47  }