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Re: [Qemu-trivial] [Qemu-devel] [PATCH v3] monitor: Fix crashes when usi
From: |
Markus Armbruster |
Subject: |
Re: [Qemu-trivial] [Qemu-devel] [PATCH v3] monitor: Fix crashes when using HMP commands without CPU |
Date: |
Fri, 13 Jan 2017 08:59:34 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/25.1 (gnu/linux) |
Thomas Huth <address@hidden> writes:
> On 12.01.2017 17:22, Markus Armbruster wrote:
>> Thomas Huth <address@hidden> writes:
>>
>>> When running certain HMP commands ("info registers", "info cpustats",
>>> "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.
>>>
>>> Reviewed-by: Dr. David Alan Gilbert <address@hidden>
>>> Signed-off-by: Thomas Huth <address@hidden>
>>> ---
>>> v3:
>>> - Use UNASSIGNED_CPU_INDEX instead of hard-coded -1
>>> v2:
>>> - Added more checks to cover "nmi" and "memsave", too
>>>
>>> hmp.c | 8 +++++++-
>>> monitor.c | 37 +++++++++++++++++++++++++++++++------
>>> 2 files changed, 38 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/hmp.c b/hmp.c
>>> index b869617..b1c503a 100644
>>> --- a/hmp.c
>>> +++ b/hmp.c
>>> @@ -1013,8 +1013,14 @@ 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 0841d43..17121ff 100644
>>> --- a/monitor.c
>>> +++ b/monitor.c
>>> @@ -1025,6 +1025,9 @@ 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);
>>> @@ -1033,17 +1036,27 @@ 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)
>>> @@ -1076,7 +1089,13 @@ 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)
>>> @@ -1235,6 +1254,12 @@ 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;
>>> + }
>>
>> This is basically "if (we're going to dereference cs)". Not so nice, in
>> particular since the dereferences are hidden inside mon_get_cpu_env()
>> calls. I guess it'll do.
>>
>>>
>>> if (format == 'i') {
>>> int flags = 0;
>>> @@ -1264,7 +1289,7 @@ 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;
>>> }
>>>
>>> @@ -1303,7 +1328,7 @@ 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;
>>> }
>>
>> What about get_monitor_def()?
>>
>> $ qemu-system-x86_64 --nodefaults -S -display none -M none -monitor stdio
>> QEMU 2.8.50 monitor - type 'help' for more information
>> (qemu) p $pc
>> Segmentation fault (core dumped)
>
> Oh, I saw that get_monitor_def() uses mon_get_cpu_env(), but I only
> checked with qemu-system-m68k where "p $pc" simply prints "unknown
> register" when you run it with the "none" machine ... that's why I
> assumed that no fixes would be needed here.
>
>> Likewise, info tlb, info mem, ...
>
> These seem to be target specific, too, so I think they could go into a
> separate patch instead. If it's OK for you, I'd like to keep my current
> patch as it is, and add these items to
> http://qemu-project.org/BiteSizedTasks instead - since these are all
> non-urgent problems that should be easy to fix for newcomers, too.
I'm not into rejecting partial fixes to blackmail for more complete
fixes. But let's add a FIXME comment next to mon_get_cpu(), to record
the issue in the source code, and not just the web site.