Re: [Qemu-devel] [Qemu-ppc] [PATCH] qemu/target-ppc: software breakpoint support

[Madhavan Srinivasan <maddy@linux.vnet.ibm.com>]

On Monday 16 June 2014 03:22 PM, Bharat.Bhushan@freescale.com wrote:
> 
> 
>> -----Original Message-----
>> From: qemu-ppc-bounces+bharat.bhushan=freescale.com@nongnu.org [mailto:qemu-ppc-
>> bounces+bharat.bhushan=freescale.com@nongnu.org] On Behalf Of Madhavan
>> Srinivasan
>> Sent: Sunday, June 15, 2014 2:38 AM
>> To: agraf@suse.de; paulus@samba.org
>> Cc: Madhavan Srinivasan; qemu-ppc@nongnu.org; qemu-devel@nongnu.org
>> Subject: [Qemu-ppc] [PATCH] qemu/target-ppc: software breakpoint support
>>
>> This patch adds software breakpoint support for ppc. Patch
>> allows to insert and remove sw breakpoints using Qemu
>> gdbserver on ppc.
>>
>> Patch use "abs" instruction as sw breakpoint instruction.
>> This instruction with primary opcode 31 and extended opcode 360
>> has been dropped from PowerISA (in v2.01) and will generate an
>> Emulation assistance interrupt in hypervisor when executed.
>> KVM also has to be updated with this to make use of sw breakpoint.
> 
> There are already a patch "ppc debug: Add debug stub support" in review which implements software breakpoint

My bad. Should have checked for it. Will look at the patchset posted.

> In addition this patch also implements h/w breakpoints/watchpoints for BOOKE. But I actually do not know how h/w breakpoints works on BOOK3S and you can help me figuring out what can be shared between booke and book3s.
> 
Sure will update you on this soon.

>>
>> Signed-off-by: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
>> ---
>>  target-ppc/kvm.c | 38 +++++++++++++++++++++++++++++++++++---
>>  1 file changed, 35 insertions(+), 3 deletions(-)
>>
>> diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c
>> index 9974b10..fa4b4ec 100644
>> --- a/target-ppc/kvm.c
>> +++ b/target-ppc/kvm.c
>> @@ -1201,6 +1201,17 @@ static int kvmppc_handle_dcr_write(CPUPPCState *env,
>> uint32_t dcrn, uint32_t dat
>>      return 0;
>>  }
>>
>> +static int kvmppc_handle_debug(CPUState *cs, struct kvm_debug_exit_arch
>> *arch_info)
>> +{
>> +	int ret = -1;
>> +
>> +	if (kvm_find_sw_breakpoint(cs, arch_info->address)) {
>> +		ret = EXCP_DEBUG;
>> +	}
>> +
>> +	return ret;
>> +}
>> +
>>  int kvm_arch_handle_exit(CPUState *cs, struct kvm_run *run)
>>  {
>>      PowerPCCPU *cpu = POWERPC_CPU(cs);
>> @@ -1240,7 +1251,10 @@ int kvm_arch_handle_exit(CPUState *cs, struct kvm_run
>> *run)
>>          watchdog_perform_action();
>>          ret = 0;
>>          break;
>> -
>> +    case KVM_EXIT_DEBUG:
>> +        DPRINTF("handle debug exit pc = 0x%lx\n", run->debug.arch.address);
>> +        ret = kvmppc_handle_debug(cs, &run->debug.arch);
>> +        break;
>>      default:
>>          fprintf(stderr, "KVM: unknown exit reason %d\n", run->exit_reason);
>>          ret = -1;
>> @@ -1901,14 +1915,29 @@ void kvm_arch_init_irq_routing(KVMState *s)
>>  {
>>  }
>>
>> +static const uint8_t dbg_int[] = { 0x7c, 0x00, 0x02, 0xd0};
> 
> This should not be hardcoded but we should get this from KVM. Please refer to patch "ppc debug: Add debug stub support" to know how to get debug instruction.
> 
Sure Will do

> Thanks
> -Bharat
> 

Thanks for review.
Regards
Maddy

>>  int kvm_arch_insert_sw_breakpoint(CPUState *cpu, struct kvm_sw_breakpoint *bp)
>>  {
>> -    return -EINVAL;
>> +	if( cpu_memory_rw_debug(cpu, bp->pc, (uint8_t *)&bp->saved_insn,
>> sizeof(dbg_int), 0) ||
>> +	    cpu_memory_rw_debug(cpu, bp->pc, (uint8_t *)dbg_int, sizeof(dbg_int),
>> 1) ){
>> +		return -EINVAL;
>> +	}
>> +	return 0;
>>  }
>>
>>  int kvm_arch_remove_sw_breakpoint(CPUState *cpu, struct kvm_sw_breakpoint *bp)
>>  {
>> -    return -EINVAL;
>> +	uint8_t tmp[4];
>> +
>> +	if (cpu_memory_rw_debug(cpu, bp->pc, tmp, sizeof(dbg_int), 0)) {
>> +		return -EINVAL;
>> +	} else if (memcmp(tmp, dbg_int, sizeof(dbg_int))) {
>> +		return -EINVAL;
>> +	} else if (cpu_memory_rw_debug(cpu, bp->pc, (uint8_t *)&bp->saved_insn,
>> sizeof(dbg_int), 1)) {
>> +		return -EINVAL;
>> +	}
>> +
>> +	return 0;
>>  }
>>
>>  int kvm_arch_insert_hw_breakpoint(target_ulong addr, target_ulong len, int
>> type)
>> @@ -1927,6 +1956,9 @@ void kvm_arch_remove_all_hw_breakpoints(void)
>>
>>  void kvm_arch_update_guest_debug(CPUState *cpu, struct kvm_guest_debug *dbg)
>>  {
>> +	if (kvm_sw_breakpoints_active(cpu)) {
>> +		dbg->control |= KVM_GUESTDBG_USE_SW_BP;
>> +	}
>>  }
>>
>>  struct kvm_get_htab_buf {
>> --
>> 1.8.3.1
>>
>