x86: Optionally dump code bytes on cpu_dump_state

Introduce the cpu_dump_state flag CPU_DUMP_CODE and implement it for
x86. This writes out the code bytes around the current instruction
pointer. Make use of this feature in KVM to help debugging fatal vm
exits.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

3 files changed, 25 insertions, 2 deletions

diff --git a/cpu-all.h b/cpu-all.h
index 4ce4e83032..ffbd6a4df8 100644
--- a/cpu-all.h
+++ b/cpu-all.h
@@ -765,6 +765,8 @@ int page_check_range(target_ulong start, target_ulong len, int flags);
 CPUState *cpu_copy(CPUState *env);
 CPUState *qemu_get_cpu(int cpu);
 
+#define CPU_DUMP_CODE 0x00010000
+
 void cpu_dump_state(CPUState *env, FILE *f, fprintf_function cpu_fprintf,
                     int flags);
 void cpu_dump_statistics(CPUState *env, FILE *f, fprintf_function cpu_fprintf,
diff --git a/kvm-all.c b/kvm-all.c
index 10e11944b3..41decdeae4 100644
--- a/kvm-all.c
+++ b/kvm-all.c
@@ -832,7 +832,7 @@ static int kvm_handle_internal_error(CPUState *env, struct kvm_run *run)
     if (run->internal.suberror == KVM_INTERNAL_ERROR_EMULATION) {
         fprintf(stderr, "emulation failure\n");
         if (!kvm_arch_stop_on_emulation_error(env)) {
-            cpu_dump_state(env, stderr, fprintf, 0);
+            cpu_dump_state(env, stderr, fprintf, CPU_DUMP_CODE);
             return 0;
         }
     }
@@ -994,7 +994,7 @@ int kvm_cpu_exec(CPUState *env)
     } while (ret > 0);
 
     if (ret < 0) {
-        cpu_dump_state(env, stderr, fprintf, 0);
+        cpu_dump_state(env, stderr, fprintf, CPU_DUMP_CODE);
         vm_stop(0);
         env->exit_request = 1;
     }
diff --git a/target-i386/helper.c b/target-i386/helper.c
index 6dfa27d51b..1217452e71 100644
--- a/target-i386/helper.c
+++ b/target-i386/helper.c
@@ -249,6 +249,9 @@ done:
     cpu_fprintf(f, "\n");
 }
 
+#define DUMP_CODE_BYTES_TOTAL    50
+#define DUMP_CODE_BYTES_BACKWARD 20
+
 void cpu_dump_state(CPUState *env, FILE *f, fprintf_function cpu_fprintf,
                     int flags)
 {
@@ -434,6 +437,24 @@ void cpu_dump_state(CPUState *env, FILE *f, fprintf_function cpu_fprintf,
                 cpu_fprintf(f, " ");
         }
     }
+    if (flags & CPU_DUMP_CODE) {
+        target_ulong base = env->segs[R_CS].base + env->eip;
+        target_ulong offs = MIN(env->eip, DUMP_CODE_BYTES_BACKWARD);
+        uint8_t code;
+        char codestr[3];
+
+        cpu_fprintf(f, "Code=");
+        for (i = 0; i < DUMP_CODE_BYTES_TOTAL; i++) {
+            if (cpu_memory_rw_debug(env, base - offs + i, &code, 1, 0) == 0) {
+                snprintf(codestr, sizeof(codestr), "%02x", code);
+            } else {
+                snprintf(codestr, sizeof(codestr), "??");
+            }
+            cpu_fprintf(f, "%s%s%s%s", i > 0 ? " " : "",
+                        i == offs ? "<" : "", codestr, i == offs ? ">" : "");
+        }
+        cpu_fprintf(f, "\n");
+    }
 }
 
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