pts/seccomp: MIPS register access

MIPS PTRACE_GETREGSET returns an array of register values. Define
ARCH_REGS to reflect this and use the offsets defined in asm/regs.h
to access it.

Incorporates some additional changes from patch by Matt
Redfearn (
- support the O32 syscall which passes the real syscall number in a0.
- Because SYSCALL_NUM and SYSCALL_RET are the same register, it is not
  possible to test modifying the syscall return value when skipping,
  since both would need to set the same register. Therefore modify that
  test case to just detect the skipped test.

Bug: 27484186
Change-Id: I066b01a271bc8f2eecab5e3adb5aa2117fcf5b86
1 file changed