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>

5 files changed, 32 insertions, 1 deletions

diff --git a/target/i386/monitor.c b/target/i386/monitor.c
index 468aa073bc..77ead60437 100644
--- a/target/i386/monitor.c
+++ b/target/i386/monitor.c
@@ -210,6 +210,10 @@ void hmp_info_tlb(Monitor *mon, const QDict *qdict)
     CPUArchState *env;
 
     env = mon_get_cpu_env();
+    if (!env) {
+        monitor_printf(mon, "No CPU available\n");
+        return;
+    }
 
     if (!(env->cr[0] & CR0_PG_MASK)) {
         monitor_printf(mon, "PG disabled\n");
@@ -529,6 +533,10 @@ void hmp_info_mem(Monitor *mon, const QDict *qdict)
     CPUArchState *env;
 
     env = mon_get_cpu_env();
+    if (!env) {
+        monitor_printf(mon, "No CPU available\n");
+        return;
+    }
 
     if (!(env->cr[0] & CR0_PG_MASK)) {
         monitor_printf(mon, "PG disabled\n");
@@ -624,7 +632,13 @@ const MonitorDef *target_monitor_defs(void)
 
 void hmp_info_local_apic(Monitor *mon, const QDict *qdict)
 {
-    x86_cpu_dump_local_apic_state(mon_get_cpu(), (FILE *)mon, monitor_fprintf,
+    CPUState *cs = mon_get_cpu();
+
+    if (!cs) {
+        monitor_printf(mon, "No CPU available\n");
+        return;
+    }
+    x86_cpu_dump_local_apic_state(cs, (FILE *)mon, monitor_fprintf,
                                   CPU_DUMP_FPU);
 }
 
diff --git a/target/ppc/monitor.c b/target/ppc/monitor.c
index c2d0806dd1..b8f30e9eaf 100644
--- a/target/ppc/monitor.c
+++ b/target/ppc/monitor.c
@@ -62,6 +62,10 @@ void hmp_info_tlb(Monitor *mon, const QDict *qdict)
 {
     CPUArchState *env1 = mon_get_cpu_env();
 
+    if (!env1) {
+        monitor_printf(mon, "No CPU available\n");
+        return;
+    }
     dump_mmu((FILE*)mon, (fprintf_function)monitor_printf, env1);
 }
 
diff --git a/target/sh4/monitor.c b/target/sh4/monitor.c
index 426e5d4914..4c7f36c9cc 100644
--- a/target/sh4/monitor.c
+++ b/target/sh4/monitor.c
@@ -44,6 +44,11 @@ void hmp_info_tlb(Monitor *mon, const QDict *qdict)
     CPUArchState *env = mon_get_cpu_env();
     int i;
 
+    if (!env) {
+        monitor_printf(mon, "No CPU available\n");
+        return;
+    }
+
     monitor_printf (mon, "ITLB:\n");
     for (i = 0 ; i < ITLB_SIZE ; i++)
         print_tlb (mon, i, &env->itlb[i]);
diff --git a/target/sparc/monitor.c b/target/sparc/monitor.c
index 7cc1b0f87f..f3ca524ae9 100644
--- a/target/sparc/monitor.c
+++ b/target/sparc/monitor.c
@@ -32,6 +32,10 @@ void hmp_info_tlb(Monitor *mon, const QDict *qdict)
 {
     CPUArchState *env1 = mon_get_cpu_env();
 
+    if (!env1) {
+        monitor_printf(mon, "No CPU available\n");
+        return;
+    }
     dump_mmu((FILE*)mon, (fprintf_function)monitor_printf, env1);
 }
 
diff --git a/target/xtensa/monitor.c b/target/xtensa/monitor.c
index f3fa4cd278..2ee2b5b23e 100644
--- a/target/xtensa/monitor.c
+++ b/target/xtensa/monitor.c
@@ -31,5 +31,9 @@ void hmp_info_tlb(Monitor *mon, const QDict *qdict)
 {
     CPUArchState *env1 = mon_get_cpu_env();
 
+    if (!env1) {
+        monitor_printf(mon, "No CPU available\n");
+        return;
+    }
     dump_mmu((FILE*)mon, (fprintf_function)monitor_printf, env1);
 }