selftests: vDSO: fix vDSO symbols lookup for powerpc64

selftests: vDSO: fix vDSO symbols lookup for powerpc64

On powerpc64, following tests fail locating vDSO functions:

  ~ # ./vdso_test_abi
  TAP version 13
  1..16
  # [vDSO kselftest] VDSO_VERSION: LINUX_2.6.15
  # Couldn't find __kernel_gettimeofday
  ok 1 # SKIP __kernel_gettimeofday
  # clock_id: CLOCK_REALTIME
  # Couldn't find __kernel_clock_gettime
  ok 2 # SKIP __kernel_clock_gettime CLOCK_REALTIME
  # Couldn't find __kernel_clock_getres
  ok 3 # SKIP __kernel_clock_getres CLOCK_REALTIME
  ...
  # Couldn't find __kernel_time
  ok 16 # SKIP __kernel_time
  # Totals: pass:0 fail:0 xfail:0 xpass:0 skip:16 error:0

  ~ # ./vdso_test_getrandom
  __kernel_getrandom is missing!

  ~ # ./vdso_test_gettimeofday
  Could not find __kernel_gettimeofday

  ~ # ./vdso_test_getcpu
  Could not find __kernel_getcpu

On powerpc64, as shown below by readelf, vDSO functions symbols have
type NOTYPE, so also accept that type when looking for symbols.

$ powerpc64-linux-gnu-readelf -a arch/powerpc/kernel/vdso/vdso64.so.dbg
ELF Header:
  Magic:   7f 45 4c 46 02 02 01 00 00 00 00 00 00 00 00 00
  Class:                             ELF64
  Data:                              2's complement, big endian
  Version:                           1 (current)
  OS/ABI:                            UNIX - System V
  ABI Version:                       0
  Type:                              DYN (Shared object file)
  Machine:                           PowerPC64
  Version:                           0x1
...

Symbol table '.dynsym' contains 12 entries:
   Num:    Value          Size Type    Bind   Vis      Ndx Name
     0: 0000000000000000     0 NOTYPE  LOCAL  DEFAULT  UND
     1: 0000000000000524    84 NOTYPE  GLOBAL DEFAULT    8 __[...]@@LINUX_2.6.15
     2: 00000000000005f0    36 NOTYPE  GLOBAL DEFAULT    8 __[...]@@LINUX_2.6.15
     3: 0000000000000578    68 NOTYPE  GLOBAL DEFAULT    8 __[...]@@LINUX_2.6.15
     4: 0000000000000000     0 OBJECT  GLOBAL DEFAULT  ABS LINUX_2.6.15
     5: 00000000000006c0    48 NOTYPE  GLOBAL DEFAULT    8 __[...]@@LINUX_2.6.15
     6: 0000000000000614   172 NOTYPE  GLOBAL DEFAULT    8 __[...]@@LINUX_2.6.15
     7: 00000000000006f0    84 NOTYPE  GLOBAL DEFAULT    8 __[...]@@LINUX_2.6.15
     8: 000000000000047c    84 NOTYPE  GLOBAL DEFAULT    8 __[...]@@LINUX_2.6.15
     9: 0000000000000454    12 NOTYPE  GLOBAL DEFAULT    8 __[...]@@LINUX_2.6.15
    10: 00000000000004d0    84 NOTYPE  GLOBAL DEFAULT    8 __[...]@@LINUX_2.6.15
    11: 00000000000005bc    52 NOTYPE  GLOBAL DEFAULT    8 __[...]@@LINUX_2.6.15

Symbol table '.symtab' contains 56 entries:
   Num:    Value          Size Type    Bind   Vis      Ndx Name
...
    45: 0000000000000000     0 OBJECT  GLOBAL DEFAULT  ABS LINUX_2.6.15
    46: 00000000000006c0    48 NOTYPE  GLOBAL DEFAULT    8 __kernel_getcpu
    47: 0000000000000524    84 NOTYPE  GLOBAL DEFAULT    8 __kernel_clock_getres
    48: 00000000000005f0    36 NOTYPE  GLOBAL DEFAULT    8 __kernel_get_tbfreq
    49: 000000000000047c    84 NOTYPE  GLOBAL DEFAULT    8 __kernel_gettimeofday
    50: 0000000000000614   172 NOTYPE  GLOBAL DEFAULT    8 __kernel_sync_dicache
    51: 00000000000006f0    84 NOTYPE  GLOBAL DEFAULT    8 __kernel_getrandom
    52: 0000000000000454    12 NOTYPE  GLOBAL DEFAULT    8 __kernel_sigtram[...]
    53: 0000000000000578    68 NOTYPE  GLOBAL DEFAULT    8 __kernel_time
    54: 00000000000004d0    84 NOTYPE  GLOBAL DEFAULT    8 __kernel_clock_g[...]
    55: 00000000000005bc    52 NOTYPE  GLOBAL DEFAULT    8 __kernel_get_sys[...]

Fixes: 98eedc3a9dbf ("Document the vDSO and add a reference parser")
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Acked-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>