s390x/kvm: hw debugging support via guest PER facility

This patch makes use of the hw debugging support in kvm (provided by the guest's
PER facility) on s390. It enables the following features, available using the
gdbserver:
- single-stepping
- hw breakpoints
- hw watchpoints

Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Jens Freimann <jfrei@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>

1 files changed, 143 insertions, 3 deletions

diff --git a/target-s390x/kvm.c b/target-s390x/kvm.c
index 6d47637d78..7a07f9d753 100644
--- a/target-s390x/kvm.c
+++ b/target-s390x/kvm.c
@@ -36,6 +36,7 @@
 #include "sysemu/device_tree.h"
 #include "qapi/qmp/qjson.h"
 #include "monitor/monitor.h"
+#include "exec/gdbstub.h"
 #include "trace.h"
 
 /* #define DEBUG_KVM */
@@ -86,6 +87,14 @@
 #define ICPT_CPU_STOP                   0x28
 #define ICPT_IO                         0x40
 
+static CPUWatchpoint hw_watchpoint;
+/*
+ * We don't use a list because this structure is also used to transmit the
+ * hardware breakpoints to the kernel.
+ */
+static struct kvm_hw_breakpoint *hw_breakpoints;
+static int nb_hw_breakpoints;
+
 const KVMCapabilityInfo kvm_arch_required_capabilities[] = {
     KVM_CAP_LAST_INFO
 };
@@ -351,24 +360,126 @@ int kvm_arch_remove_sw_breakpoint(CPUState *cs, struct kvm_sw_breakpoint *bp)
     return 0;
 }
 
+static struct kvm_hw_breakpoint *find_hw_breakpoint(target_ulong addr,
+                                                    int len, int type)
+{
+    int n;
+
+    for (n = 0; n < nb_hw_breakpoints; n++) {
+        if (hw_breakpoints[n].addr == addr && hw_breakpoints[n].type == type &&
+            (hw_breakpoints[n].len == len || len == -1)) {
+            return &hw_breakpoints[n];
+        }
+    }
+
+    return NULL;
+}
+
+static int insert_hw_breakpoint(target_ulong addr, int len, int type)
+{
+    int size;
+
+    if (find_hw_breakpoint(addr, len, type)) {
+        return -EEXIST;
+    }
+
+    size = (nb_hw_breakpoints + 1) * sizeof(struct kvm_hw_breakpoint);
+
+    if (!hw_breakpoints) {
+        nb_hw_breakpoints = 0;
+        hw_breakpoints = (struct kvm_hw_breakpoint *)g_try_malloc(size);
+    } else {
+        hw_breakpoints =
+            (struct kvm_hw_breakpoint *)g_try_realloc(hw_breakpoints, size);
+    }
+
+    if (!hw_breakpoints) {
+        nb_hw_breakpoints = 0;
+        return -ENOMEM;
+    }
+
+    hw_breakpoints[nb_hw_breakpoints].addr = addr;
+    hw_breakpoints[nb_hw_breakpoints].len = len;
+    hw_breakpoints[nb_hw_breakpoints].type = type;
+
+    nb_hw_breakpoints++;
+
+    return 0;
+}
+
 int kvm_arch_insert_hw_breakpoint(target_ulong addr,
                                   target_ulong len, int type)
 {
-    return -ENOSYS;
+    switch (type) {
+    case GDB_BREAKPOINT_HW:
+        type = KVM_HW_BP;
+        break;
+    case GDB_WATCHPOINT_WRITE:
+        if (len < 1) {
+            return -EINVAL;
+        }
+        type = KVM_HW_WP_WRITE;
+        break;
+    default:
+        return -ENOSYS;
+    }
+    return insert_hw_breakpoint(addr, len, type);
 }
 
 int kvm_arch_remove_hw_breakpoint(target_ulong addr,
                                   target_ulong len, int type)
 {
-    return -ENOSYS;
+    int size;
+    struct kvm_hw_breakpoint *bp = find_hw_breakpoint(addr, len, type);
+
+    if (bp == NULL) {
+        return -ENOENT;
+    }
+
+    nb_hw_breakpoints--;
+    if (nb_hw_breakpoints > 0) {
+        /*
+         * In order to trim the array, move the last element to the position to
+         * be removed - if necessary.
+         */
+        if (bp != &hw_breakpoints[nb_hw_breakpoints]) {
+            *bp = hw_breakpoints[nb_hw_breakpoints];
+        }
+        size = nb_hw_breakpoints * sizeof(struct kvm_hw_breakpoint);
+        hw_breakpoints =
+             (struct kvm_hw_breakpoint *)g_realloc(hw_breakpoints, size);
+    } else {
+        g_free(hw_breakpoints);
+        hw_breakpoints = NULL;
+    }
+
+    return 0;
 }
 
 void kvm_arch_remove_all_hw_breakpoints(void)
 {
+    nb_hw_breakpoints = 0;
+    g_free(hw_breakpoints);
+    hw_breakpoints = NULL;
 }
 
 void kvm_arch_update_guest_debug(CPUState *cpu, struct kvm_guest_debug *dbg)
 {
+    int i;
+
+    if (nb_hw_breakpoints > 0) {
+        dbg->arch.nr_hw_bp = nb_hw_breakpoints;
+        dbg->arch.hw_bp = hw_breakpoints;
+
+        for (i = 0; i < nb_hw_breakpoints; ++i) {
+            hw_breakpoints[i].phys_addr = s390_cpu_get_phys_addr_debug(cpu,
+                                                       hw_breakpoints[i].addr);
+        }
+        dbg->control |= KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_USE_HW_BP;
+    } else {
+        dbg->arch.nr_hw_bp = 0;
+        dbg->arch.hw_bp = NULL;
+    }
 }
 
 void kvm_arch_pre_run(CPUState *cpu, struct kvm_run *run)
@@ -853,7 +964,36 @@ static int handle_tsch(S390CPU *cpu)
 
 static int kvm_arch_handle_debug_exit(S390CPU *cpu)
 {
-    return -ENOSYS;
+    CPUState *cs = CPU(cpu);
+    struct kvm_run *run = cs->kvm_run;
+
+    int ret = 0;
+    struct kvm_debug_exit_arch *arch_info = &run->debug.arch;
+
+    switch (arch_info->type) {
+    case KVM_HW_WP_WRITE:
+        if (find_hw_breakpoint(arch_info->addr, -1, arch_info->type)) {
+            cs->watchpoint_hit = &hw_watchpoint;
+            hw_watchpoint.vaddr = arch_info->addr;
+            hw_watchpoint.flags = BP_MEM_WRITE;
+            ret = EXCP_DEBUG;
+        }
+        break;
+    case KVM_HW_BP:
+        if (find_hw_breakpoint(arch_info->addr, -1, arch_info->type)) {
+            ret = EXCP_DEBUG;
+        }
+        break;
+    case KVM_SINGLESTEP:
+        if (cs->singlestep_enabled) {
+            ret = EXCP_DEBUG;
+        }
+        break;
+    default:
+        ret = -ENOSYS;
+    }
+
+    return ret;
 }
 
 int kvm_arch_handle_exit(CPUState *cs, struct kvm_run *run)