target-arm: kvm - implement software breakpoints

These don't involve messing around with debug registers, just setting
the breakpoint instruction in memory. GDB will not use this mechanism if
it can't access the memory to write the breakpoint.

All the kernel has to do is ensure the hypervisor traps the breakpoint
exceptions and returns to userspace.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-id: 1449599553-24713-3-git-send-email-alex.bennee@linaro.org
[PMM: Fixed typo in comment]
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 24 insertions, 15 deletions

diff --git a/target-arm/kvm.c b/target-arm/kvm.c
index 79ef4c61de..7f44e22f88 100644
--- a/target-arm/kvm.c
+++ b/target-arm/kvm.c
@@ -17,6 +17,7 @@
 
 #include "qemu-common.h"
 #include "qemu/timer.h"
+#include "qemu/error-report.h"
 #include "sysemu/sysemu.h"
 #include "sysemu/kvm.h"
 #include "kvm_arm.h"
@@ -516,9 +517,23 @@ MemTxAttrs kvm_arch_post_run(CPUState *cs, struct kvm_run *run)
     return MEMTXATTRS_UNSPECIFIED;
 }
 
+
 int kvm_arch_handle_exit(CPUState *cs, struct kvm_run *run)
 {
-    return 0;
+    int ret = 0;
+
+    switch (run->exit_reason) {
+    case KVM_EXIT_DEBUG:
+        if (kvm_arm_handle_debug(cs, &run->debug.arch)) {
+            ret = EXCP_DEBUG;
+        } /* otherwise return to guest */
+        break;
+    default:
+        qemu_log_mask(LOG_UNIMP, "%s: un-handled exit reason %d\n",
+                      __func__, run->exit_reason);
+        break;
+    }
+    return ret;
 }
 
 bool kvm_arch_stop_on_emulation_error(CPUState *cs)
@@ -541,16 +556,16 @@ int kvm_arch_on_sigbus(int code, void *addr)
     return 1;
 }
 
+/* The #ifdef protections are until 32bit headers are imported and can
+ * be removed once both 32 and 64 bit reach feature parity.
+ */
 void kvm_arch_update_guest_debug(CPUState *cs, struct kvm_guest_debug *dbg)
 {
-    qemu_log_mask(LOG_UNIMP, "%s: not implemented\n", __func__);
-}
-
-int kvm_arch_insert_sw_breakpoint(CPUState *cs,
-                                  struct kvm_sw_breakpoint *bp)
-{
-    qemu_log_mask(LOG_UNIMP, "%s: not implemented\n", __func__);
-    return -EINVAL;
+#ifdef KVM_GUESTDBG_USE_SW_BP
+    if (kvm_sw_breakpoints_active(cs)) {
+        dbg->control |= KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_USE_SW_BP;
+    }
+#endif
 }
 
 int kvm_arch_insert_hw_breakpoint(target_ulong addr,
@@ -567,12 +582,6 @@ int kvm_arch_remove_hw_breakpoint(target_ulong addr,
     return -EINVAL;
 }
 
-int kvm_arch_remove_sw_breakpoint(CPUState *cs,
-                                  struct kvm_sw_breakpoint *bp)
-{
-    qemu_log_mask(LOG_UNIMP, "%s: not implemented\n", __func__);
-    return -EINVAL;
-}
 
 void kvm_arch_remove_all_hw_breakpoints(void)
 {