LoongArch: Wire up memfd_secret system call

LoongArch supports ARCH_HAS_SET_DIRECT_MAP, therefore wire up the
memfd_secret system call, which just depends on it.

Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Acked-by: David Hildenbrand (Red Hat) <david@kernel.org>
Signed-off-by: Lain "Fearyncess" Yang <fearyncess@aosc.io>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: maoxiaochuan <maoxiaochuan@loongson.cn>

arch/loongarch/include/asm/unistd.h

@@ -10,5 +10,6 @@
 
 #define __ARCH_WANT_NEW_STAT
 #define __ARCH_WANT_SYS_CLONE
+#define __ARCH_WANT_MEMFD_SECRET
 
 #define NR_syscalls (__NR_syscalls)

arch/loongarch/kernel/Makefile.syscalls

@@ -1,4 +1,4 @@
 # SPDX-License-Identifier: GPL-2.0
 
 # No special ABIs on loongarch so far
-syscall_abis_64 +=
+syscall_abis_64 += memfd_secret

tools/testing/selftests/mm/Makefile

@@ -53,7 +53,7 @@ TEST_GEN_FILES += madv_populate
 TEST_GEN_FILES += map_fixed_noreplace
 TEST_GEN_FILES += map_hugetlb
 TEST_GEN_FILES += map_populate
-ifneq (,$(filter $(ARCH),arm64 riscv riscv64 x86 x86_64))
+ifneq (,$(filter $(ARCH),arm64 riscv riscv64 x86 x86_64 loongarch64))
 TEST_GEN_FILES += memfd_secret
 endif
 TEST_GEN_FILES += migration