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

[address@hidden]

> -----Original Message-----
> From: address@hidden [mailto:qemu-ppc-
> address@hidden On Behalf Of Madhavan
> Srinivasan
> Sent: Sunday, June 15, 2014 2:38 AM
> To: address@hidden; address@hidden
> Cc: Madhavan Srinivasan; address@hidden; address@hidden
> 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
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.

> 
> Signed-off-by: Madhavan Srinivasan <address@hidden>
> ---
>  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.

Thanks
-Bharat

>  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
>