Re: [Qemu-devel] [PATCH v2 1/3] qemu-io: Add sigraise command

[Max Reitz <mreitz@redhat.com>]

On 2014-12-05 at 10:52, Markus Armbruster wrote:
> Max Reitz <mreitz@redhat.com> writes:
>
>> abort() has the sometimes undesirable side-effect of generating a core
>> dump. If that is not needed, SIGKILL has the same effect of abruptly
>> crash qemu; without a core dump.
>>
>> Thus, -c abort is not always useful to simulate a qemu-io crash;
>> therefore, this patch adds a new sigraise command which allows to raise
>> any Unix signal.
> Nitpick: signals are ISO C, not just UNIX.

Yes, but "Unix signal" is what the Wikipedia article is named, so... ;-)

>> Signed-off-by: Max Reitz <mreitz@redhat.com>
>> ---
>>   qemu-io-cmds.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
>>   1 file changed, 46 insertions(+)
>>
>> diff --git a/qemu-io-cmds.c b/qemu-io-cmds.c
>> index d94fb1e..942b694 100644
>> --- a/qemu-io-cmds.c
>> +++ b/qemu-io-cmds.c
>> @@ -2048,6 +2048,51 @@ static const cmdinfo_t abort_cmd = {
>>          .oneline        = "simulate a program crash using abort(3)",
>>   };
>>   
>> +static void sigraise_help(void)
>> +{
>> +    printf(
>> +"\n"
>> +" raises the given Unix signal\n"
>> +"\n"
>> +" Example:\n"
>> +" 'sigraise 9' - raises SIGKILL\n"
> Assumes SIGKILL is encoded as 9, which is traditionally the case, but
> not actually mandated by POSIX.

Yes, I know. The best would be to parse the signal like kill(1) does, 
but that would have been extra difficult and probably not worth the effort.

Furthermore, I know there is a song called "kill dash nine", so I 
guessed it would be enough (at least it'll have to be enough for test 
039, thanks to "_supported_os Linux").

> You could avoid hardcoding 9 with
>
>      " 'sigraise %d' - raises SIGKILL\n"
>
> with a SIGKILL as argument for %d.

Clever. Will do.

> But then you'd have to face the fact that SIGKILL is POSIX, not ISO C.
> The ISO C signals are SIGABRT, SIGFPE, SIGILL, SIGINT, SIGSEGV, SIGTERM.
> Of these, SIGINT and SIGTERM don't dump core, in case you care.

Good to know. I guess I'll just go with SIGKILL anyway, it's ubiquitous 
enough.

>> +"\n"
>> +" Invokes raise(signal), where \"signal\" is the mandatory integer argument\n"
>> +" given to sigraise.\n"
>> +"\n");
>> +}
>> +
>> +static int sigraise_f(BlockDriverState *bs, int argc, char **argv);
>> +
>> +static const cmdinfo_t sigraise_cmd = {
>> +    .name       = "sigraise",
>> +    .cfunc      = sigraise_f,
>> +    .argmin     = 1,
>> +    .argmax     = 1,
>> +    .flags      = CMD_NOFILE_OK,
>> +    .args       = "signal",
>> +    .oneline    = "raises a Unix signal",
>> +    .help       = sigraise_help,
>> +};
>> +
>> +static int sigraise_f(BlockDriverState *bs, int argc, char **argv)
>> +{
>> +    int sig = cvtnum(argv[1]);
>> +    if (sig < 0) {
>> +        printf("non-numeric signal number argument -- %s\n", argv[1]);
>> +        return 0;
>> +    }
>> +
>> +    /* Using raise() to kill this process does not necessarily flush all open
>> +     * streams. At least stdout and stderr (although the latter should be
>> +     * non-buffered anyway) should be flushed, though. */
>> +    fflush(stdout);
>> +    fflush(stderr);
>> +
>> +    raise(sig);
>> +    return 0;
>> +}
>> +
>>   static void sleep_cb(void *opaque)
>>   {
>>       bool *expired = opaque;
>> @@ -2202,4 +2247,5 @@ static void __attribute((constructor)) init_qemuio_commands(void)
>>       qemuio_add_command(&wait_break_cmd);
>>       qemuio_add_command(&abort_cmd);
>>       qemuio_add_command(&sleep_cmd);
>> +    qemuio_add_command(&sigraise_cmd);
>>   }
> Looks good otherwise.

Thanks :-)

Max