Subject: Re: [PATCH v3 02/11] kselftest: arm64: adds first test and common utils

From: Cristian Marussi <[email-masked]>
Date: Fri, 9 Aug 2019 13:20:45 +0100

Hi

On 8/9/19 12:16 PM, Dave Martin wrote:
> On Fri, Aug 09, 2019 at 11:54:06AM +0100, Cristian Marussi wrote:
>> Hi
>>
>> On 8/2/19 6:02 PM, Cristian Marussi wrote:
>>> Added some arm64/signal specific boilerplate and utility code to help
>>> further testcase development.
>>>
>>> A simple testcase and related helpers are also introduced in this commit:
>>> mangle_pstate_invalid_compat_toggle is a simple mangle testcase which
>>> messes with the ucontext_t from within the sig_handler, trying to toggle
>>> PSTATE state bits to switch the system between 32bit/64bit execution state.
>>> Expects SIGSEGV on test PASS.
>>>
>>> Signed-off-by: Cristian Marussi <[email-masked]>
>>> ---
>>> A few fixes:
>>> - test_arm64_signals.sh runner script generation has been reviewed in order to
>>>    be safe against the .gitignore
>>> - using kselftest.h officially provided defines for tests' return values
>>> - removed SAFE_WRITE()/dump_uc()
>>> - looking for si_code==SEGV_ACCERR on SEGV test cases to better understand if
>>>    the sigfault had been directly triggered by Kernel
>>> ---
>>>   tools/testing/selftests/arm64/Makefile        |   2 +-
>>>   .../testing/selftests/arm64/signal/.gitignore |   6 +
>>>   tools/testing/selftests/arm64/signal/Makefile |  88 ++++++
>>>   tools/testing/selftests/arm64/signal/README   |  59 ++++
>>>   .../arm64/signal/test_arm64_signals.src_shell |  55 ++++
>>>   .../selftests/arm64/signal/test_signals.c     |  26 ++
>>>   .../selftests/arm64/signal/test_signals.h     | 137 +++++++++
>>>   .../arm64/signal/test_signals_utils.c         | 261 ++++++++++++++++++
>>>   .../arm64/signal/test_signals_utils.h         |  13 +
>>>   .../arm64/signal/testcases/.gitignore         |   1 +
>>>   .../mangle_pstate_invalid_compat_toggle.c     |  25 ++
>>>   .../arm64/signal/testcases/testcases.c        | 150 ++++++++++
>>>   .../arm64/signal/testcases/testcases.h        |  83 ++++++
>>>   13 files changed, 905 insertions(+), 1 deletion(-)
>>>   create mode 100644 tools/testing/selftests/arm64/signal/.gitignore
>>>   create mode 100644 tools/testing/selftests/arm64/signal/Makefile
>>>   create mode 100644 tools/testing/selftests/arm64/signal/README
>>>   create mode 100755 tools/testing/selftests/arm64/signal/test_arm64_signals.src_shell
>>>   create mode 100644 tools/testing/selftests/arm64/signal/test_signals.c
>>>   create mode 100644 tools/testing/selftests/arm64/signal/test_signals.h
>>>   create mode 100644 tools/testing/selftests/arm64/signal/test_signals_utils.c
>>>   create mode 100644 tools/testing/selftests/arm64/signal/test_signals_utils.h
>>>   create mode 100644 tools/testing/selftests/arm64/signal/testcases/.gitignore
>>>   create mode 100644 tools/testing/selftests/arm64/signal/testcases/mangle_pstate_invalid_compat_toggle.c
>>>   create mode 100644 tools/testing/selftests/arm64/signal/testcases/testcases.c
>>>   create mode 100644 tools/testing/selftests/arm64/signal/testcases/testcases.h
>>>
>>
>> A few more compilation warnings triggered by GCC-8 ONLY when compiling via the top kselftest Makefile/target
>> (due to some additional -W passed down and an awkward use of snprintf on my side...)
>>
>>
>> test_signals_utils.c: In function ‘feats_to_string’:
>> test_signals_utils.c:38:13: warning: passing argument 1 to restrict-qualified parameter aliases with argument 4 [-Wrestrict]
>>      snprintf(feats_string, MAX_FEATS_SZ - 1, "%s %s ",
>>               ^~~~~~~~~~~~
>> test_signals_utils.c: In function ‘default_handler’:
>> test_signals_utils.c:192:19: warning: format ‘%p’ expects argument of type ‘void *’, but argument 3 has type ‘long long unsigned int’ [-Wformat=]
>>      "SIG_OK -- SP:%p  si_addr@:0x%p  si_code:%d  token@:0x%p  offset:%ld\n",
>>                    ~^
>>
>> will be fixed in V4 as:
>>
>>
>> diff --git a/tools/testing/selftests/arm64/signal/test_signals_utils.c b/tools/testing/selftests/arm64/signal/test_signals_utils.c
>> index 31788a1d33a4..c0f3cd1b560a 100644
>> --- a/tools/testing/selftests/arm64/signal/test_signals_utils.c
>> +++ b/tools/testing/selftests/arm64/signal/test_signals_utils.c
>> @@ -23,21 +23,25 @@ extern struct tdescr *current;
>>   static int sig_copyctx = SIGTRAP;
>>   static char *feats_store[FMAX_END] = {
>> -       "SSBS",
>> -       "PAN",
>> -       "UAO",
>> +       " SSBS ",
>> +       " PAN ",
>> +       " UAO ",
>>   };
>>   #define MAX_FEATS_SZ   128
>> +static char feats_string[MAX_FEATS_SZ];
>> +
>>   static inline char *feats_to_string(unsigned long feats)
>>   {
>> -       static char feats_string[MAX_FEATS_SZ];
>> +       for (int i = 0; i < FMAX_END; i++) {
>> +               size_t tlen = 0;
>> -       for (int i = 0; i < FMAX_END && feats_store[i][0]; i++) {
>> -               if (feats & 1UL << i)
>> -                       snprintf(feats_string, MAX_FEATS_SZ - 1, "%s %s ",
>> -                                feats_string, feats_store[i]);
>> +               if (feats & 1UL << i) {
>> +                       strncat(feats_string, feats_store[i],
> 
> Should this be feats_string + tlen?
>

strncat appends to the end of a NULL terminated string overwriting the NULL itself and
appending its own NULL (as long as dest and src do not overlap and fits the max size param),
so it must be fed the start of the dest string to which we are appending
  
>> +                               MAX_FEATS_SZ - 1 - tlen);
> 
> An assert(tlen <= MAX_FEATS_SZ - 1) is probably a good idea here,
> in case more features are added to feats_store[] someday.
> 

Yes in fact...if not it would be simply truncated silently

>> +                       tlen += strlen(feats_store[i]);
>> +               }
> 
> Don't we need to initialise tlen outside the loop?  Otherwise we just
> zero it again after the +=.

..and that's a bug :<

> 
>>          }
>>          return feats_string;
>> @@ -190,7 +194,7 @@ static void default_handler(int signum, siginfo_t *si, void *uc)
>>                  /* it's a bug in the test code when this assert fail */
>>                  assert(!current->sig_trig || current->triggered);
>>                  fprintf(stderr,
>> -                       "SIG_OK -- SP:%p  si_addr@:0x%p  si_code:%d  token@:0x%p  offset:%ld\n",
>> +                       "SIG_OK -- SP:%llX  si_addr@:0x%p  si_code:%d  token@:0x%p  offset:%ld\n",
> 
> For consistency, can we have a "0x" prefix?
> 
> I think %p usually generates a "0x" prefix by itself, so 0x%p might give
> a double prefix.
> 

Yes you are right.

Moreover I'm in doubt what to do generally with all these stderr output, because I optionally discard to null
testing standalone, but this is not what the KSFT framework runner script does, so arm64/signal tests
end up being overly verbose when run from the framework (even if tests use anyway the KSFT exit codes
conventions so all the results are correctly reported); but I suppose I'll receive a clear indication on this matter
from the maintainers at the end...
  
Cheers

Cristian

> [...]
> Cheers
> ---Dave

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