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Re: [Qemu-ppc] [PATCH 3/3] ppc debug: Add debug stub support


From: Alexander Graf
Subject: Re: [Qemu-ppc] [PATCH 3/3] ppc debug: Add debug stub support
Date: Wed, 11 Jun 2014 15:04:52 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130910 Thunderbird/17.0.9

On 06/10/2014 05:06 PM, Bharat Bhushan wrote:
This patch adds software breakpoint, hardware breakpoint and
hardware watchpoint support for ppc. If the debug interrupt is
not handled then this is injected to guest.

Signed-off-by: Bharat Bhushan <address@hidden>
---
  hw/ppc/e500.c        |   1 +
  target-ppc/kvm.c     | 304 ++++++++++++++++++++++++++++++++++++++++++++++-----
  target-ppc/kvm_ppc.h |   1 +
  3 files changed, 278 insertions(+), 28 deletions(-)

diff --git a/hw/ppc/e500.c b/hw/ppc/e500.c
index a973c18..514c595 100644
--- a/hw/ppc/e500.c
+++ b/hw/ppc/e500.c
@@ -853,6 +853,7 @@ void ppce500_init(MachineState *machine, PPCE500Params 
*params)
      if (kvm_enabled()) {
          kvmppc_init();
      }
+    kvmppc_e500_hw_breakpoint_init();
  }
static int e500_ccsr_initfn(SysBusDevice *dev)
diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c
index 1d2384d..f5fbec6 100644
--- a/target-ppc/kvm.c
+++ b/target-ppc/kvm.c
@@ -38,6 +38,7 @@
  #include "hw/ppc/ppc.h"
  #include "sysemu/watchdog.h"
  #include "trace.h"
+#include "exec/gdbstub.h"
//#define DEBUG_KVM @@ -768,6 +769,38 @@ static int kvm_put_vpa(CPUState *cs) static int kvmppc_inject_debug_exception(CPUState *cs)
  {
+    PowerPCCPU *cpu = POWERPC_CPU(cs);
+    CPUPPCState *env = &cpu->env;
+    struct kvm_sregs sregs;
+    int ret;
+
+    if (!cap_booke_sregs) {
+        return -1;
+    }
+
+    ret = kvm_vcpu_ioctl(cs, KVM_GET_SREGS, &sregs);
+    if (ret < 0) {
+        return -1;
+    }
+

I don't think any of this code should ever run for non-e500, no?

+    if (sregs.u.e.features & KVM_SREGS_E_ED) {

Hrm - we never seem to set E_ED in kvm?

+        sregs.u.e.dsrr0 = env->nip;
+        sregs.u.e.dsrr1 = env->msr;
+    } else {
+        sregs.u.e.csrr0 = env->nip;
+        sregs.u.e.csrr1 = env->msr;
+    }
+
+    sregs.u.e.update_special = KVM_SREGS_E_UPDATE_DBSR;
+    sregs.u.e.dbsr = env->spr[SPR_BOOKE_DBSR];
+
+    ret = kvm_vcpu_ioctl(cs, KVM_SET_SREGS, &sregs);
+    if (ret < 0) {
+        return -1;
+    }
+
+    env->pending_interrupts &= ~(1 << PPC_INTERRUPT_DEBUG);
+
      return 0;
  }
@@ -1275,6 +1308,239 @@ static int kvmppc_handle_dcr_write(CPUPPCState *env, uint32_t dcrn, uint32_t dat
      return 0;
  }
+int kvm_arch_insert_sw_breakpoint(CPUState *cs, struct kvm_sw_breakpoint *bp)
+{
+    uint32_t sc = tswap32(debug_inst_opcode);

Heh - this will become a lot of fun for real LE host as well as guest systems. For now just remove the tswap and add a comment that this needs fixing for LE.

+
+    if (cpu_memory_rw_debug(cs, bp->pc, (uint8_t *)&bp->saved_insn, 4, 0) ||
+        cpu_memory_rw_debug(cs, bp->pc, (uint8_t *)&sc, 4, 1)) {
+        return -EINVAL;
+    }
+
+    return 0;
+}
+
+int kvm_arch_remove_sw_breakpoint(CPUState *cs, struct kvm_sw_breakpoint *bp)
+{
+    uint32_t sc;
+
+    if (cpu_memory_rw_debug(cs, bp->pc, (uint8_t *)&sc, 4, 0) ||
+        sc != tswap32(debug_inst_opcode) ||

Same here.

In fact, neither of the 2 operations are in a fast path. Can't we just fetch the debug inst opcode on demand in a function here? That will allow for easier byte swapping depending on the guest's MSR.LE setting later as well.

+        cpu_memory_rw_debug(cs, bp->pc, (uint8_t *)&bp->saved_insn, 4, 1)) {
+        return -EINVAL;
+    }
+
+    return 0;
+}
+
+static struct HWBreakpoint {
+    target_ulong addr;
+    int type;
+} hw_breakpoint[6];
+
+static int nb_hw_breakpoint;
+static int nb_hw_watchpoint;
+static int max_hw_breakpoint = 4;
+static int max_hw_watchpoint = 2;
+
+void kvmppc_e500_hw_breakpoint_init(void)
+{
+    max_hw_breakpoint = 2;
+    max_hw_watchpoint = 2;

Can we somehow get this information from kvm and set it in kvm_arch_init? Worst case we'll have to look at the cpu class and derive it from there, but it really should live solely inside the kvm file.

+}
+
+static int find_hw_breakpoint(target_ulong addr, int type)
+{
+    int n;
+
+    for (n = 0; n < nb_hw_breakpoint + nb_hw_watchpoint; n++) {
+        if (hw_breakpoint[n].addr == addr && hw_breakpoint[n].type == type) {
+            return n;
+        }
+    }
+
+    return -1;
+}
+
+static int find_hw_watchpoint(target_ulong addr, int *flag)
+{
+    int n;
+
+    n = find_hw_breakpoint(addr, GDB_WATCHPOINT_ACCESS);
+    if (n >= 0) {
+        *flag = BP_MEM_ACCESS;
+        return n;
+    }
+
+    n = find_hw_breakpoint(addr, GDB_WATCHPOINT_WRITE);
+    if (n >= 0) {
+        *flag = BP_MEM_WRITE;
+        return n;
+    }
+
+    n = find_hw_breakpoint(addr, GDB_WATCHPOINT_READ);
+    if (n >= 0) {
+        *flag = BP_MEM_READ;
+        return n;
+    }
+
+    return -1;
+}
+
+int kvm_arch_insert_hw_breakpoint(target_ulong addr,
+                                  target_ulong len, int type)
+{
+    hw_breakpoint[nb_hw_breakpoint + nb_hw_watchpoint].addr = addr;
+    hw_breakpoint[nb_hw_breakpoint + nb_hw_watchpoint].type = type;
+
+    switch (type) {
+    case GDB_BREAKPOINT_HW:
+        if (nb_hw_breakpoint >= max_hw_breakpoint) {
+            return -ENOBUFS;
+        }
+
+        if (find_hw_breakpoint(addr, type) >= 0) {
+            return -EEXIST;
+        }
+
+        nb_hw_breakpoint++;
+        break;
+
+    case GDB_WATCHPOINT_WRITE:
+    case GDB_WATCHPOINT_READ:
+    case GDB_WATCHPOINT_ACCESS:
+        if (nb_hw_watchpoint >= max_hw_watchpoint) {
+            return -ENOBUFS;
+        }
+
+        if (find_hw_breakpoint(addr, type) >= 0) {
+            return -EEXIST;
+        }
+
+        nb_hw_watchpoint++;
+        break;
+
+    default:
+        return -ENOSYS;
+    }
+
+    return 0;
+}
+
+int kvm_arch_remove_hw_breakpoint(target_ulong addr,
+                                  target_ulong len, int type)
+{
+    int n;
+
+    n = find_hw_breakpoint(addr, type);
+    if (n < 0) {
+        return -ENOENT;
+    }
+
+    switch (type) {
+    case GDB_BREAKPOINT_HW:
+        nb_hw_breakpoint--;
+        break;
+
+    case GDB_WATCHPOINT_WRITE:
+    case GDB_WATCHPOINT_READ:
+    case GDB_WATCHPOINT_ACCESS:
+        nb_hw_watchpoint--;
+        break;
+
+    default:
+        return -ENOSYS;
+    }
+    hw_breakpoint[n] = hw_breakpoint[nb_hw_breakpoint + nb_hw_watchpoint];
+
+    return 0;
+}
+
+void kvm_arch_remove_all_hw_breakpoints(void)
+{
+    nb_hw_breakpoint = nb_hw_watchpoint = 0;
+}
+
+static CPUWatchpoint hw_watchpoint;
+
+
+static int kvm_handle_debug(PowerPCCPU *cpu, struct kvm_run *run)
+{
+    CPUState *cs = CPU(cpu);
+    CPUPPCState *env = &cpu->env;
+    int handle = 0;
+    int n;
+    int flag = 0;
+    struct kvm_debug_exit_arch *arch_info = &run->debug.arch;
+
+    if (cs->singlestep_enabled) {
+        handle = 1;
+    } else if (arch_info->status) {
+        if (arch_info->status & KVMPPC_DEBUG_BREAKPOINT) {
+            n = find_hw_breakpoint(arch_info->address, GDB_BREAKPOINT_HW);
+            if (n >= 0) {
+                handle = 1;
+            }
+        } else if (arch_info->status & (KVMPPC_DEBUG_WATCH_READ |
+                                        KVMPPC_DEBUG_WATCH_WRITE)) {
+            n = find_hw_watchpoint(arch_info->address,  &flag);
+            if (n >= 0) {
+                handle = 1;
+                cs->watchpoint_hit = &hw_watchpoint;
+                hw_watchpoint.vaddr = hw_breakpoint[n].addr;
+                hw_watchpoint.flags = flag;
+            }
+        }
+    } else if (kvm_find_sw_breakpoint(cs, arch_info->address)) {
+        handle = 1;
+    }
+
+    cpu_synchronize_state(cs);
+    if (handle) {
+        env->spr[SPR_BOOKE_DBSR] = 0;

This is pretty e500 specific.


Alex

+    } else {
+       printf("unhandled\n");
+       /* inject guest debug exception */
+       env->pending_interrupts |=  1 << PPC_INTERRUPT_DEBUG;
+     }
+
+    return handle;
+}
+
+void kvm_arch_update_guest_debug(CPUState *cs, struct kvm_guest_debug *dbg)
+{
+    if (kvm_sw_breakpoints_active(cs)) {
+        dbg->control |= KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_USE_SW_BP;
+    }
+
+    if (nb_hw_breakpoint + nb_hw_watchpoint > 0) {
+        int n;
+
+        dbg->control |= KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_USE_HW_BP;
+        memset(dbg->arch.bp, 0, sizeof(dbg->arch.bp));
+        for (n = 0; n < nb_hw_breakpoint + nb_hw_watchpoint; n++) {
+            switch (hw_breakpoint[n].type) {
+            case GDB_BREAKPOINT_HW:
+                dbg->arch.bp[n].type = KVMPPC_DEBUG_BREAKPOINT;
+                break;
+            case GDB_WATCHPOINT_WRITE:
+                dbg->arch.bp[n].type = KVMPPC_DEBUG_WATCH_WRITE;
+                break;
+            case GDB_WATCHPOINT_READ:
+                dbg->arch.bp[n].type = KVMPPC_DEBUG_WATCH_READ;
+                break;
+            case GDB_WATCHPOINT_ACCESS:
+                dbg->arch.bp[n].type = KVMPPC_DEBUG_WATCH_WRITE |
+                                        KVMPPC_DEBUG_WATCH_READ;
+                break;
+            default:
+                cpu_abort(cs, "Unsupported breakpoint type\n");
+            }
+            dbg->arch.bp[n].addr = hw_breakpoint[n].addr;
+        }
+    }
+}
+
  int kvm_arch_handle_exit(CPUState *cs, struct kvm_run *run)
  {
      PowerPCCPU *cpu = POWERPC_CPU(cs);
@@ -1315,6 +1581,16 @@ int kvm_arch_handle_exit(CPUState *cs, struct kvm_run 
*run)
          ret = 0;
          break;
+ case KVM_EXIT_DEBUG:
+        DPRINTF("handle debug exception\n");
+        if (kvm_handle_debug(cpu, run)) {
+            ret = EXCP_DEBUG;
+            break;
+        }
+        /* re-enter, this exception was guest-internal */
+        ret = 0;
+        break;
+
      default:
          fprintf(stderr, "KVM: unknown exit reason %d\n", run->exit_reason);
          ret = -1;
@@ -2002,34 +2278,6 @@ void kvm_arch_init_irq_routing(KVMState *s)
  {
  }
-int kvm_arch_insert_sw_breakpoint(CPUState *cpu, struct kvm_sw_breakpoint *bp)
-{
-    return -EINVAL;
-}
-
-int kvm_arch_remove_sw_breakpoint(CPUState *cpu, struct kvm_sw_breakpoint *bp)
-{
-    return -EINVAL;
-}
-
-int kvm_arch_insert_hw_breakpoint(target_ulong addr, target_ulong len, int 
type)
-{
-    return -EINVAL;
-}
-
-int kvm_arch_remove_hw_breakpoint(target_ulong addr, target_ulong len, int 
type)
-{
-    return -EINVAL;
-}
-
-void kvm_arch_remove_all_hw_breakpoints(void)
-{
-}
-
-void kvm_arch_update_guest_debug(CPUState *cpu, struct kvm_guest_debug *dbg)
-{
-}
-
  struct kvm_get_htab_buf {
      struct kvm_get_htab_header header;
      /*
diff --git a/target-ppc/kvm_ppc.h b/target-ppc/kvm_ppc.h
index 412cc7f..89244e5 100644
--- a/target-ppc/kvm_ppc.h
+++ b/target-ppc/kvm_ppc.h
@@ -30,6 +30,7 @@ int kvmppc_clear_tsr_bits(PowerPCCPU *cpu, uint32_t tsr_bits);
  int kvmppc_or_tsr_bits(PowerPCCPU *cpu, uint32_t tsr_bits);
  int kvmppc_set_tcr(PowerPCCPU *cpu);
  int kvmppc_booke_watchdog_enable(PowerPCCPU *cpu);
+void kvmppc_e500_hw_breakpoint_init(void);
  #ifndef CONFIG_USER_ONLY
  off_t kvmppc_alloc_rma(const char *name, MemoryRegion *sysmem);
  bool kvmppc_spapr_use_multitce(void);




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