[Qemu-devel] [PULL 3/3] monitor: Fix crashes when using HMP commands without CPU

[Dr. David Alan Gilbert (git)]

From: Thomas Huth <address@hidden>

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 <address@hidden>
Message-Id: <address@hidden>
Reviewed-by: Markus Armbruster <address@hidden>
Acked-by: David Gibson <address@hidden>
Signed-off-by: Dr. David Alan Gilbert <address@hidden>
---
 hmp.c                   |  8 +++++++-
 monitor.c               | 42 ++++++++++++++++++++++++++++++++++--------
 target/i386/monitor.c   | 16 +++++++++++++++-
 target/ppc/monitor.c    |  4 ++++
 target/sh4/monitor.c    |  5 +++++
 target/sparc/monitor.c  |  4 ++++
 target/xtensa/monitor.c |  4 ++++
 7 files changed, 73 insertions(+), 10 deletions(-)

diff --git a/hmp.c b/hmp.c
index 8b0c2b0..aba728f 100644
--- a/hmp.c
+++ b/hmp.c
@@ -1014,8 +1014,14 @@ void hmp_memsave(Monitor *mon, const QDict *qdict)
     const char *filename = qdict_get_str(qdict, "filename");
     uint64_t addr = qdict_get_int(qdict, "val");
     Error *err = NULL;
+    int cpu_index = monitor_get_cpu_index();
 
-    qmp_memsave(addr, size, filename, true, monitor_get_cpu_index(), &err);
+    if (cpu_index < 0) {
+        monitor_printf(mon, "No CPU available\n");
+        return;
+    }
+
+    qmp_memsave(addr, size, filename, true, cpu_index, &err);
     hmp_handle_error(mon, &err);
 }
 
diff --git a/monitor.c b/monitor.c
index 3cd72a9..5953fc9 100644
--- a/monitor.c
+++ b/monitor.c
@@ -1026,6 +1026,9 @@ int monitor_set_cpu(int cpu_index)
 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 @@ CPUState *mon_get_cpu(void)
 
 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_history(Monitor *mon, const QDict 
*qdict)
 
 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 @@ static void memory_dump(Monitor *mon, int count, int 
format, int wsize,
     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 @@ static void memory_dump(Monitor *mon, int count, int 
format, int wsize,
         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 @@ static void memory_dump(Monitor *mon, int count, int 
format, int wsize,
         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 @@ expr_error(Monitor *mon, const char *fmt, ...)
 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 @@ static int get_monitor_def(target_long *pval, const char 
*name)
         }
     }
 
-    ret = target_get_monitor_def(mon_get_cpu(), name, &tmp);
+    ret = target_get_monitor_def(cs, name, &tmp);
     if (!ret) {
         *pval = (target_long) tmp;
     }
diff --git a/target/i386/monitor.c b/target/i386/monitor.c
index 468aa07..77ead60 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 c2d0806..b8f30e9 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 426e5d4..4c7f36c 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 7cc1b0f..f3ca524 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 f3fa4cd..2ee2b5b 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);
 }
-- 
2.9.3