Re: [PATCH v2] linux-user/strace: Add missing signal strings

[Helge Deller]

On 21.11.19 19:43, Aleksandar Markovic wrote:
> On Wed, Nov 20, 2019 at 3:57 PM Helge Deller <address@hidden> wrote:
>>
>> Add the textual representations of some missing target signals.
>>
>> Signed-off-by: Helge Deller <address@hidden>
>>
>> diff --git a/linux-user/strace.c b/linux-user/strace.c
>> index 3d4d684450..de43238fa4 100644
>> --- a/linux-user/strace.c
>> +++ b/linux-user/strace.c
>> @@ -146,6 +146,19 @@ print_signal(abi_ulong arg, int last)
>>      case TARGET_SIGSTOP: signal_name = "SIGSTOP"; break;
>>      case TARGET_SIGTTIN: signal_name = "SIGTTIN"; break;
>>      case TARGET_SIGTTOU: signal_name = "SIGTTOU"; break;
>> +    case TARGET_SIGIO: signal_name = "SIGIO"; break;
>> +    case TARGET_SIGBUS: signal_name = "SIGBUS"; break;
>> +    case TARGET_SIGPWR: signal_name = "SIGPWR"; break;
>> +    case TARGET_SIGURG: signal_name = "SIGURG"; break;
>> +    case TARGET_SIGSYS: signal_name = "SIGSYS"; break;
>> +    case TARGET_SIGTRAP: signal_name = "SIGTRAP"; break;
>> +    case TARGET_SIGXCPU: signal_name = "SIGXCPU"; break;
>> +    case TARGET_SIGPROF: signal_name = "SIGPROF"; break;
>> +    case TARGET_SIGTSTP: signal_name = "SIGTSTP"; break;
>> +    case TARGET_SIGXFSZ: signal_name = "SIGXFSZ"; break;
>> +    case TARGET_SIGWINCH: signal_name = "SIGWINCH"; break;
>> +    case TARGET_SIGVTALRM: signal_name = "SIGVTALRM"; break;
>> +    case TARGET_SIGSTKFLT: signal_name = "SIGSTKFLT"; break;
>
> What about TARGET_SIGEMT, TARGET_SIGIOT ? Those are missing from
> MIPS-specific list of signals, and they won't be printed as strings. I
> think you should add:
>
> #if defined TARGET_SIGEMT
>     case TARGET_SIGEMT: signal_name = "SIGEMT"; break;
> #endif
> case TARGET_SIGIOT: signal_name = "SIGIOT"; break;

Please see my first version of the patch.
There I added the TARGET_SIGIOT as comment.
I assume there is a build issue if you add a case
for TARGET_SIGIOT, since it probably conflicts with TARGET_SIGABRT.
That's probably why TARGET_SIGIOT is commented out in linux-user/signal.c
as well?

For SIGEMT I don't know.
It's only defined for MIPS, and I can't test-compile it.
I'm happy to add the #ifdef mentioned above if you could test it.

> (I believe "#if defined"s is needed only for SIG_EMT, but doublecheck.)

Yes, it's not defined for any other arch.

> Without this, this patch favors other platforms over MIPS, which is
> certainly not a good/fair thing.

Everyone loves the own baby :-)
> There might be some similar case or two for other platforms too
> (alpha, sparc perhaps).

I think I checked with the table in linux-user/signal.c before sending.

> Your reference should be kernel files:
> arch/<platform>/include/uapi/asm/sighal.h.
>
> In fact, there is some peace of kernell code that exactly deal with
> the same problem - getting the names of the signals. It is in
> security/apparmor/include/sig_names.h
>
> ( 
> https://elixir.bootlin.com/linux/v5.4-rc8/source/security/apparmor/include/sig_names.h
> )
>
> Since the file is short, I am inserting the whole content here:
>
> #include <linux/signal.h>
>
> #define SIGUNKNOWN 0
> #define MAXMAPPED_SIG 35
> #define MAXMAPPED_SIGNAME (MAXMAPPED_SIG + 1)
> #define SIGRT_BASE 128
>
> /* provide a mapping of arch signal to internal signal # for mediation
>  * those that are always an alias SIGCLD for SIGCLHD and SIGPOLL for SIGIO
>  * map to the same entry those that may/or may not get a separate entry
>  */
> static const int sig_map[MAXMAPPED_SIG] = {
> [0] = MAXMAPPED_SIG, /* existence test */
> [SIGHUP] = 1,
> [SIGINT] = 2,
> [SIGQUIT] = 3,
> [SIGILL] = 4,
> [SIGTRAP] = 5, /* -, 5, - */
> [SIGABRT] = 6, /*  SIGIOT: -, 6, - */
> [SIGBUS] = 7, /* 10, 7, 10 */
> [SIGFPE] = 8,
> [SIGKILL] = 9,
> [SIGUSR1] = 10, /* 30, 10, 16 */
> [SIGSEGV] = 11,
> [SIGUSR2] = 12, /* 31, 12, 17 */
> [SIGPIPE] = 13,
> [SIGALRM] = 14,
> [SIGTERM] = 15,
> #ifdef SIGSTKFLT
> [SIGSTKFLT] = 16, /* -, 16, - */
> #endif
> [SIGCHLD] = 17, /* 20, 17, 18.  SIGCHLD -, -, 18 */
> [SIGCONT] = 18, /* 19, 18, 25 */
> [SIGSTOP] = 19, /* 17, 19, 23 */
> [SIGTSTP] = 20, /* 18, 20, 24 */
> [SIGTTIN] = 21, /* 21, 21, 26 */
> [SIGTTOU] = 22, /* 22, 22, 27 */
> [SIGURG] = 23, /* 16, 23, 21 */
> [SIGXCPU] = 24, /* 24, 24, 30 */
> [SIGXFSZ] = 25, /* 25, 25, 31 */
> [SIGVTALRM] = 26, /* 26, 26, 28 */
> [SIGPROF] = 27, /* 27, 27, 29 */
> [SIGWINCH] = 28, /* 28, 28, 20 */
> [SIGIO] = 29, /* SIGPOLL: 23, 29, 22 */
> [SIGPWR] = 30, /* 29, 30, 19.  SIGINFO 29, -, - */
> #ifdef SIGSYS
> [SIGSYS] = 31, /* 12, 31, 12. often SIG LOST/UNUSED */
> #endif
> #ifdef SIGEMT
> [SIGEMT] = 32, /* 7, - , 7 */
> #endif
> #if defined(SIGLOST) && SIGPWR != SIGLOST /* sparc */
> [SIGLOST] = 33, /* unused on Linux */
> #endif
> #if defined(SIGUNUSED) && \
>     defined(SIGLOST) && defined(SIGSYS) && SIGLOST != SIGSYS
> [SIGUNUSED] = 34, /* -, 31, - */
> #endif
> };
>
> /* this table is ordered post sig_map[sig] mapping */
> static const char *const sig_names[MAXMAPPED_SIGNAME] = {
> "unknown",
> "hup",
> "int",
> "quit",
> "ill",
> "trap",
> "abrt",
> "bus",
> "fpe",
> "kill",
> "usr1",
> "segv",
> "usr2",
> "pipe",
> "alrm",
> "term",
> "stkflt",
> "chld",
> "cont",
> "stop",
> "stp",
> "ttin",
> "ttou",
> "urg",
> "xcpu",
> "xfsz",
> "vtalrm",
> "prof",
> "winch",
> "io",
> "pwr",
> "sys",
> "emt",
> "lost",
> "unused",
>
> "exists", /* always last existence test mapped to MAXMAPPED_SIG */
> };
>
> I think you should mirror the functionality from that file.

Simply mirroring files isn't good IMHO.
The copy from bootlin above might not have all cases/fixes for all platforms
(e.g. s390x, parisc, sparc, ...)?

Helge