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ARC: Ignore ptrace SETREGSET request for synthetic register "stop_pc"

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ARCompact TRAP_S insn used for breakpoints, commits before exception is
taken (updating architectural PC). So ptregs->ret contains next-PC and
not the breakpoint PC itself. This is different from other restartable
exceptions such as TLB Miss where ptregs->ret has exact faulting PC.
gdb needs to know exact-PC hence ARC ptrace GETREGSET provides for
@stop_pc which returns ptregs->ret vs. EFA depending on the
situation.

However, writing stop_pc (SETREGSET request), which updates ptregs->ret
doesn't makes sense stop_pc doesn't always correspond to that reg as
described above.

This was not an issue so far since user_regs->ret / user_regs->stop_pc
had same value and both writing to ptregs->ret was OK, needless, but NOT
broken, hence not observed.

With gdb "jump", they diverge, and user_regs->ret updating ptregs is
overwritten immediately with stop_pc, which this patch fixes.

Reported-by: Anton Kolesov <akolesov@synopsys.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
This commit is contained in:
Vineet Gupta 2013-10-10 19:33:57 +05:30
parent d0e639c9e0
commit 5b24282846
1 changed files with 1 additions and 1 deletions
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2
arch/arc/kernel/ptrace.c
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@ -102,7 +102,7 @@ static int genregs_set(struct task_struct *target,
REG_IGNORE_ONE(pad2);
REG_IN_CHUNK(callee, efa, cregs); /* callee_regs[r25..r13] */
REG_IGNORE_ONE(efa); /* efa update invalid */
REG_IN_ONE(stop_pc, &ptregs->ret); /* stop_pc: PC update */
REG_IGNORE_ONE(stop_pc); /* PC updated via @ret */
return ret;
}