The functions like gmtime(3) expect to cache a GMT time zone. Some
sandboxed programs (like last(1)) use the gmtime function. In case
of last, this function fails to load a proper time zone because it
is called after entering the capability mode.
_open () at _open.S:4 0x00000008011bc5a8 in tzloadbody (name=0x8018b9580 "/usr/share/zoneinfo/Etc/UTC", sp=0x801870140, tzload (name=<optimized out>, sp=0x801870140, doextend=true) 0x00000008011bb8ba in gmtload (sp=0x801870140) at /usr/src/contrib/tzcode/localtime.c:1456 gmtcheck () at /usr/src/contrib/tzcode/localtime.c:1581 0x000000080111f85a in _libc_once (once_control=0x80127c550, init_routine=0x0) _once (once_control=0x80127c550, init_routine=0x0) at /usr/src/lib/libc/gen/_once_stub.c:63 0x00000008011bb9d0 in gmtime_r (timep=0x7fffffffe3a8, tmp=0x80127c568) gmtime (timep=timep@entry=0x7fffffffe3a8) at /usr/src/contrib/tzcode/localtime.c:1865 0x0000000001024cd4 in printentry (bp=bp@entry=0x8018b4800, tt=tt@entry=0x80186a0a0) 0x00000000010245ae in doentry (bp=0x8018b4800) 0x00000000010243a7 in main (argc=1, argv=<optimized out>)
This time zone is not loaded by the tzset(3) function. Because of
that, extend the caph_cache_tzdata(3) function to also include the
GMT time zone. There is no other way to cache this data than
calling gmtime(3) once.