selftests/seccomp: Add LoongArch selftesting support

BPF for LoongArch is supported now, add the selftesting support in
seccomp_bpf.c.
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

tools/testing/selftests/seccomp/seccomp_bpf.c

@@ -128,6 +128,8 @@ struct seccomp_data {
 #  define __NR_seccomp 277
 # elif defined(__csky__)
 #  define __NR_seccomp 277
+# elif defined(__loongarch__)
+#  define __NR_seccomp 277
 # elif defined(__hppa__)
 #  define __NR_seccomp 338
 # elif defined(__powerpc__)
@@ -1753,6 +1755,10 @@ TEST_F(TRACE_poke, getpid_runs_normally)
 				    NT_ARM_SYSTEM_CALL, &__v));	\
 	} while (0)
 # define SYSCALL_RET(_regs)	(_regs).regs[0]
+#elif defined(__loongarch__)
+# define ARCH_REGS		struct user_pt_regs
+# define SYSCALL_NUM(_regs)	(_regs).regs[11]
+# define SYSCALL_RET(_regs)	(_regs).regs[4]
 #elif defined(__riscv) && __riscv_xlen == 64
 # define ARCH_REGS		struct user_regs_struct
 # define SYSCALL_NUM(_regs)	(_regs).a7