commit 854e67fea6a6f181163a5467fc9ba04de8d181bb
author Thomas Huth <thuth@redhat.com> Fri Jan 13 13:12:35 2017 +0100
committer Dr. David Alan Gilbert <dgilbert@redhat.com> Tue Feb 21 18:29:01 2017 +0000
tree 95528d10774a6b5021083310dee65c7bbe376274
parent 5fc00480ab1ce767f1c6c63ae644e960295fed2c

monitor: Fix crashes when using HMP commands without CPU

When running certain HMP commands ("info registers", "info cpustats",
"info tlb", "nmi", "memsave" or dumping virtual memory) with the "none"
machine, QEMU crashes with a segmentation fault. This happens because the
"none" machine does not have any CPUs by default, but these HMP commands
did not check for a valid CPU pointer yet. Add such checks now, so we get
an error message about the missing CPU instead.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Message-Id: <1484309555-1935-1-git-send-email-thuth@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Acked-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

monitor.c

diff --git a/monitor.c b/monitor.c
index 3cd72a9..5953fc9 100644
--- a/monitor.c
+++ b/monitor.c
@@ -1026,6 +1026,9 @@
 CPUState *mon_get_cpu(void)
 {
     if (!cur_mon->mon_cpu) {
+        if (!first_cpu) {
+            return NULL;
+        }
         monitor_set_cpu(first_cpu->cpu_index);
     }
     cpu_synchronize_state(cur_mon->mon_cpu);
@@ -1034,17 +1037,27 @@
 
 CPUArchState *mon_get_cpu_env(void)
 {
-    return mon_get_cpu()->env_ptr;
+    CPUState *cs = mon_get_cpu();
+
+    return cs ? cs->env_ptr : NULL;
 }
 
 int monitor_get_cpu_index(void)
 {
-    return mon_get_cpu()->cpu_index;
+    CPUState *cs = mon_get_cpu();
+
+    return cs ? cs->cpu_index : UNASSIGNED_CPU_INDEX;
 }
 
 static void hmp_info_registers(Monitor *mon, const QDict *qdict)
 {
-    cpu_dump_state(mon_get_cpu(), (FILE *)mon, monitor_fprintf, CPU_DUMP_FPU);
+    CPUState *cs = mon_get_cpu();
+
+    if (!cs) {
+        monitor_printf(mon, "No CPU available\n");
+        return;
+    }
+    cpu_dump_state(cs, (FILE *)mon, monitor_fprintf, CPU_DUMP_FPU);
 }
 
 static void hmp_info_jit(Monitor *mon, const QDict *qdict)
@@ -1077,7 +1090,13 @@
 
 static void hmp_info_cpustats(Monitor *mon, const QDict *qdict)
 {
-    cpu_dump_statistics(mon_get_cpu(), (FILE *)mon, &monitor_fprintf, 0);
+    CPUState *cs = mon_get_cpu();
+
+    if (!cs) {
+        monitor_printf(mon, "No CPU available\n");
+        return;
+    }
+    cpu_dump_statistics(cs, (FILE *)mon, &monitor_fprintf, 0);
 }
 
 static void hmp_info_trace_events(Monitor *mon, const QDict *qdict)
@@ -1236,6 +1255,12 @@
     int l, line_size, i, max_digits, len;
     uint8_t buf[16];
     uint64_t v;
+    CPUState *cs = mon_get_cpu();
+
+    if (!cs && (format == 'i' || !is_physical)) {
+        monitor_printf(mon, "Can not dump without CPU\n");
+        return;
+    }
 
     if (format == 'i') {
         int flags = 0;
@@ -1265,7 +1290,7 @@
         flags = msr_le << 16;
         flags |= env->bfd_mach;
 #endif
-        monitor_disas(mon, mon_get_cpu(), addr, count, is_physical, flags);
+        monitor_disas(mon, cs, addr, count, is_physical, flags);
         return;
     }
 
@@ -1304,7 +1329,7 @@
         if (is_physical) {
             cpu_physical_memory_read(addr, buf, l);
         } else {
-            if (cpu_memory_rw_debug(mon_get_cpu(), addr, buf, l, 0) < 0) {
+            if (cpu_memory_rw_debug(cs, addr, buf, l, 0) < 0) {
                 monitor_printf(mon, " Cannot access memory\n");
                 break;
             }
@@ -2189,11 +2214,12 @@
 static int get_monitor_def(target_long *pval, const char *name)
 {
     const MonitorDef *md = target_monitor_defs();
+    CPUState *cs = mon_get_cpu();
     void *ptr;
     uint64_t tmp = 0;
     int ret;
 
-    if (md == NULL) {
+    if (cs == NULL || md == NULL) {
         return -1;
     }
 
@@ -2220,7 +2246,7 @@
         }
     }
 
-    ret = target_get_monitor_def(mon_get_cpu(), name, &tmp);
+    ret = target_get_monitor_def(cs, name, &tmp);
     if (!ret) {
         *pval = (target_long) tmp;
     }