[PATCH v7 6/6] selftests/mm: use PIDFD_SELF in guard pages test

[Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>]

Now we have PIDFD_SELF available for process_madvise(), make use of it in
the guard pages test.

This is both more convenient and asserts that PIDFD_SELF works as expected.

Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
---
 tools/testing/selftests/mm/Makefile      |  4 ++++
 tools/testing/selftests/mm/guard-pages.c | 15 +++------------
 2 files changed, 7 insertions(+), 12 deletions(-)

diff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile
index 63ce39d024bb..ecc4252fa3fe 100644
--- a/tools/testing/selftests/mm/Makefile
+++ b/tools/testing/selftests/mm/Makefile
@@ -225,6 +225,10 @@ $(OUTPUT)/ksm_tests: LDLIBS += -lnuma
 
 $(OUTPUT)/migration: LDLIBS += -lnuma
 
+# We need uapi/pdifd.h but need to work around broken linux/fcntl.h, so
+# explicitly import
+$(OUTPUT)/guard-pages: CFLAGS += -I $(top_srcdir)/tools/include
+
 local_config.mk local_config.h: check_config.sh
 	/bin/sh ./check_config.sh $(CC)
 
diff --git a/tools/testing/selftests/mm/guard-pages.c b/tools/testing/selftests/mm/guard-pages.c
index ece37212a8a2..549653724661 100644
--- a/tools/testing/selftests/mm/guard-pages.c
+++ b/tools/testing/selftests/mm/guard-pages.c
@@ -18,6 +18,7 @@
 #include <sys/syscall.h>
 #include <sys/uio.h>
 #include <unistd.h>
+#include <linux/pidfd.h>
 
 /*
  * Ignore the checkpatch warning, as per the C99 standard, section 7.14.1.1:
@@ -50,11 +51,6 @@ static void handle_fatal(int c)
 	siglongjmp(signal_jmp_buf, c);
 }
 
-static int pidfd_open(pid_t pid, unsigned int flags)
-{
-	return syscall(SYS_pidfd_open, pid, flags);
-}
-
 static ssize_t sys_process_madvise(int pidfd, const struct iovec *iovec,
 				   size_t n, int advice, unsigned int flags)
 {
@@ -370,14 +366,10 @@ TEST_F(guard_pages, multi_vma)
 TEST_F(guard_pages, process_madvise)
 {
 	const unsigned long page_size = self->page_size;
-	pid_t pid = getpid();
-	int pidfd = pidfd_open(pid, 0);
 	char *ptr_region, *ptr1, *ptr2, *ptr3;
 	ssize_t count;
 	struct iovec vec[6];
 
-	ASSERT_NE(pidfd, -1);
-
 	/* Reserve region to map over. */
 	ptr_region = mmap(NULL, 100 * page_size, PROT_NONE,
 			  MAP_ANON | MAP_PRIVATE, -1, 0);
@@ -425,7 +417,7 @@ TEST_F(guard_pages, process_madvise)
 	ASSERT_EQ(munmap(&ptr_region[99 * page_size], page_size), 0);
 
 	/* Now guard in one step. */
-	count = sys_process_madvise(pidfd, vec, 6, MADV_GUARD_INSTALL, 0);
+	count = sys_process_madvise(PIDFD_SELF, vec, 6, MADV_GUARD_INSTALL, 0);
 
 	/* OK we don't have permission to do this, skip. */
 	if (count == -1 && errno == EPERM)
@@ -446,7 +438,7 @@ TEST_F(guard_pages, process_madvise)
 	ASSERT_FALSE(try_read_write_buf(&ptr3[19 * page_size]));
 
 	/* Now do the same with unguard... */
-	count = sys_process_madvise(pidfd, vec, 6, MADV_GUARD_REMOVE, 0);
+	count = sys_process_madvise(PIDFD_SELF, vec, 6, MADV_GUARD_REMOVE, 0);
 
 	/* ...and everything should now succeed. */
 
@@ -463,7 +455,6 @@ TEST_F(guard_pages, process_madvise)
 	ASSERT_EQ(munmap(ptr1, 10 * page_size), 0);
 	ASSERT_EQ(munmap(ptr2, 5 * page_size), 0);
 	ASSERT_EQ(munmap(ptr3, 20 * page_size), 0);
-	close(pidfd);
 }
 
 /* Assert that unmapping ranges does not leave guard markers behind. */
-- 
2.48.1