Re: [PATCH] libselinux: rename gettid() to something which never conflicts with the libc

[Petr Lautrbach <plautrba@redhat.com>]

Petr Lautrbach <plautrba@redhat.com> writes:

> Nicolas Iooss <nicolas.iooss@m4x.org> writes:
>
>> Musl recently added a wrapper for gettid() syscall. There is no way to
>> detect this new version in a reliable way, so rename our gettid()
>> wrapper to a non-conflicting name.
>>
>> Introduce a new function which, when using a libc known to provide a
>> wrapper for gettid(), calls it, and which, otherwise, performs the
>> syscall directly.
>>
>> Anyway this function is only used on systems where /proc/thread-self
>> does not exist, which are therefore running Linux<3.17.
>>
>> Fixes: https://github.com/SELinuxProject/selinux/issues/282
>> Signed-off-by: Nicolas Iooss <nicolas.iooss@m4x.org>
>
> Tested on Fedora with musl-1.2.22 scratch build
> https://koji.fedoraproject.org/koji/taskinfo?taskID=62214131 :
>
> Before
> ^&^ musl-gcc -D_GNU_SOURCE -I../include procattr.c -c
> procattr.c:38:14: error: static declaration of ‘gettid’ follows non-static declaration
>    38 | static pid_t gettid(void)
>       |              ^~~~~~
> In file included from procattr.c:2:
> /usr/x86_64-linux-musl/include/unistd.h:194:7: note: previous declaration of ‘gettid’ with type ‘pid_t(void)’ {aka ‘int(void)’}
>   194 | pid_t gettid(void);
>       |       ^~~~~~
>
>
> After
> ^&^ musl-gcc -D_GNU_SOURCE -I../include procattr.c -c
>
>
> Seems to work. Thanks!
>
> Acked-by: Petr Lautrbach <plautrba@redhat.com>
>

Merged.


>
>> diff --git a/libselinux/src/procattr.c b/libselinux/src/procattr.c
>> index 1aa67ac53f39..840570525f5f 100644
>> --- a/libselinux/src/procattr.c
>> +++ b/libselinux/src/procattr.c
>> @@ -25,21 +25,23 @@ static __thread char destructor_initialized;
>>  /* Bionic and glibc >= 2.30 declare gettid() system call wrapper in unistd.h and
>>   * has a definition for it */
>>  #ifdef __BIONIC__
>> -  #define OVERRIDE_GETTID 0
>> +  #define HAVE_GETTID 1
>>  #elif !defined(__GLIBC_PREREQ)
>> -  #define OVERRIDE_GETTID 1
>> +  #define HAVE_GETTID 0
>>  #elif !__GLIBC_PREREQ(2,30)
>> -  #define OVERRIDE_GETTID 1
>> +  #define HAVE_GETTID 0
>>  #else
>> -  #define OVERRIDE_GETTID 0
>> +  #define HAVE_GETTID 1
>>  #endif
>>  
>> -#if OVERRIDE_GETTID
>> -static pid_t gettid(void)
>> +static pid_t selinux_gettid(void)
>>  {
>> +#if HAVE_GETTID
>> +	return gettid();
>> +#else
>>  	return syscall(__NR_gettid);
>> -}
>>  #endif
>> +}
>>  
>>  static void procattr_thread_destructor(void __attribute__((unused)) *unused)
>>  {
>> @@ -94,7 +96,7 @@ static int openattr(pid_t pid, const char *attr, int flags)
>>  		if (fd >= 0 || errno != ENOENT)
>>  			goto out;
>>  		free(path);
>> -		tid = gettid();
>> +		tid = selinux_gettid();
>>  		rc = asprintf(&path, "/proc/self/task/%d/attr/%s", tid, attr);
>>  	} else {
>>  		errno = EINVAL;
>> -- 
>> 2.30.0