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Re: [patch, avr, sim] PR19401 - Update PC when simulate break instruction
- From: Denis Chertykov <chertykov at gmail dot com>
- To: Pitchumani Sivanupandi <pitchumani dot sivanupandi at atmel dot com>
- Cc: gdb-patches at sourceware dot org, Pedro Alves <palves at redhat dot com>, Mike Frysinger <vapier at gentoo dot org>
- Date: Tue, 19 Jul 2016 09:49:03 +0300
- Subject: Re: [patch, avr, sim] PR19401 - Update PC when simulate break instruction
- Authentication-results: sourceware.org; auth=none
- References: <57769A40.email@example.com> <577F3A79.firstname.lastname@example.org>
2016-07-08 8:30 GMT+03:00 Pitchumani Sivanupandi
> On Friday 01 July 2016 09:58 PM, Pitchumani Sivanupandi wrote:
>> When there is a software breakpoint for avr target, gdb asks remote to
>> write break instruction (0x9598) in the breakpoint location. When target
>> hits breakpoint location the it asks remote to restore the content.
>> Remote will resume from the PC when GDB asks.
>> After executing break instruction AVR MCU's PC will point to next
>> location. It is the remote (gdb-server/ sim) who sets PC to next
>> instruction to be executed (after hitting software breakpoint).
>> So, AVR simulator's PC is expected to point breakpoint location when it
>> hits break insn. Simulator was doing that earlier. It is changed after
>> the commit 9943d3185, which introduces sim_engine_halt to handle break.
>> Since this function jumps to sim_resume using longjmp to sim_resume,
>> code that sets PC (cpu->pc = ipc) is not executed.
>> Following patch will restore the behavior of setting PC on break.
>> diff --git a/sim/avr/interp.c b/sim/avrinterp.c
>> index 31a9940..fcce9b2 100644
>> --- a/sim/avr/interp.c
>> +++ b/sim/avr/interp.c
>> @@ -911,8 +911,7 @@ step_once (SIM_CPU *cpu)
>> case OP_break:
>> /* Stop on this address. */
>> - sim_engine_halt (CPU_STATE (cpu), cpu, NULL, cpu->pc, sim_stopped,
>> - cpu->pc = ipc;
>> + sim_engine_halt (CPU_STATE (cpu), cpu, NULL, ipc, sim_stopped,
>> case OP_bld:
>> If OK, could someone commit please? I don't have commit access.
>> 2016-07-01 Pitchumani Sivanupandi <email@example.com>
>> PR target/ 19401
>> * avr/interp.c (step_once): Pass break instruction address to
>> sim_engine_halt function which writes that to PC. Remove code that
>> follows that function call as it is unreachable.