[2/3] tools/testing: add PROCMAP_QUERY helper functions in mm self tests

Commit Message

Lorenzo Stoakes March 17, 2025, 9:15 p.m. UTC

The PROCMAP_QUERY ioctl() is very useful - it allows for binary access to
/proc/$pid/[s]maps data and thus convenient lookup of data contained there.

This patch exposes this for convenient use by mm self tests so the state of
VMAs can easily be queried.

Signed-off-by: Lorenzo Stoakes <[e-mail]>
---
 tools/testing/selftests/mm/vm_util.c | 62 ++++++++++++++++++++++++++++
 tools/testing/selftests/mm/vm_util.h | 21 ++++++++++
 2 files changed, 83 insertions(+)

Comments

Lorenzo Stoakes March 18, 2025, 3:18 p.m. UTC | #1

On Mon, Mar 17, 2025 at 09:15:04PM +0000, Lorenzo Stoakes wrote:
> The PROCMAP_QUERY ioctl() is very useful - it allows for binary access to
> /proc/$pid/[s]maps data and thus convenient lookup of data contained there.
>
> This patch exposes this for convenient use by mm self tests so the state of
> VMAs can easily be queried.
>
> Signed-off-by: Lorenzo Stoakes <[e-mail]>

Quick fix on this:

----8<----
From 02d674de3736e3726a97a27625d4598c3d49d08a Mon Sep 17 00:00:00 2001
From: Lorenzo Stoakes <[e-mail]>
Date: Tue, 18 Mar 2025 15:16:29 +0000
Subject: [PATCH] correctly return errno

---
 tools/testing/selftests/mm/vm_util.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c
index 891ce17453cd..1357e2d6a7b6 100644
--- a/tools/testing/selftests/mm/vm_util.c
+++ b/tools/testing/selftests/mm/vm_util.c
@@ -440,7 +440,7 @@ int open_procmap(pid_t pid, struct procmap_fd *procmap_out)
 	procmap_out->query.size = sizeof(procmap_out->query);
 	procmap_out->fd = open(path, O_RDONLY);
 	if (procmap_out < 0)
-		ret = errno;
+		ret = -errno;

 	return ret;
 }
@@ -451,7 +451,7 @@ int query_procmap(struct procmap_fd *procmap)
 	int ret = 0;

 	if (ioctl(procmap->fd, PROCMAP_QUERY, &procmap->query) == -1)
-		ret = errno;
+		ret = -errno;

 	return ret;
 }
--
2.48.1

Patch

diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c
index a36734fb62f3..891ce17453cd 100644
--- a/tools/testing/selftests/mm/vm_util.c
+++ b/tools/testing/selftests/mm/vm_util.c
@@ -1,5 +1,6 @@ 
 // SPDX-License-Identifier: GPL-2.0
 #include <string.h>
+#include <errno.h>
 #include <fcntl.h>
 #include <dirent.h>
 #include <inttypes.h>
@@ -424,3 +425,64 @@  bool check_vmflag_io(void *addr)
 		flags += flaglen;
 	}
 }
+
+/*
+ * Open an fd at /proc/$pid/maps and configure procmap_out ready for
+ * PROCMAP_QUERY query. Returns 0 on success, or an error code otherwise.
+ */
+int open_procmap(pid_t pid, struct procmap_fd *procmap_out)
+{
+	char path[256];
+	int ret = 0;
+
+	memset(procmap_out, '\0', sizeof(*procmap_out));
+	sprintf(path, "/proc/%d/maps", pid);
+	procmap_out->query.size = sizeof(procmap_out->query);
+	procmap_out->fd = open(path, O_RDONLY);
+	if (procmap_out < 0)
+		ret = errno;
+
+	return ret;
+}
+
+/* Perform PROCMAP_QUERY. Returns 0 on success, or an error code otherwise. */
+int query_procmap(struct procmap_fd *procmap)
+{
+	int ret = 0;
+
+	if (ioctl(procmap->fd, PROCMAP_QUERY, &procmap->query) == -1)
+		ret = errno;
+
+	return ret;
+}
+
+/*
+ * Try to find the VMA at specified address, returns true if found, false if not
+ * found, and the test is failed if any other error occurs.
+ *
+ * On success, procmap->query is populated with the results.
+ */
+bool find_vma_procmap(struct procmap_fd *procmap, void *address)
+{
+	int err;
+
+	procmap->query.query_flags = 0;
+	procmap->query.query_addr = (unsigned long)address;
+	err = query_procmap(procmap);
+	if (!err)
+		return true;
+
+	if (err != -ENOENT)
+		ksft_exit_fail_msg("%s: Error %d on ioctl(PROCMAP_QUERY)\n",
+				   __func__, err);
+	return false;
+}
+
+/*
+ * Close fd used by PROCMAP_QUERY mechanism. Returns 0 on success, or an error
+ * code otherwise.
+ */
+int close_procmap(struct procmap_fd *procmap)
+{
+	return close(procmap->fd);
+}
diff --git a/tools/testing/selftests/mm/vm_util.h b/tools/testing/selftests/mm/vm_util.h
index 0e629586556b..aaea0ef78322 100644
--- a/tools/testing/selftests/mm/vm_util.h
+++ b/tools/testing/selftests/mm/vm_util.h
@@ -5,6 +5,7 @@ 
 #include <err.h>
 #include <strings.h> /* ffsl() */
 #include <unistd.h> /* _SC_PAGESIZE */
+#include <linux/fs.h>
 
 #define BIT_ULL(nr)                   (1ULL << (nr))
 #define PM_SOFT_DIRTY                 BIT_ULL(55)
@@ -18,6 +19,15 @@ 
 extern unsigned int __page_size;
 extern unsigned int __page_shift;
 
+/*
+ * Represents an open fd and PROCMAP_QUERY state for binary (via ioctl)
+ * /proc/$pid/[s]maps lookup.
+ */
+struct procmap_fd {
+	int fd;
+	struct procmap_query query;
+};
+
 static inline unsigned int psize(void)
 {
 	if (!__page_size)
@@ -55,6 +65,17 @@  int uffd_register_with_ioctls(int uffd, void *addr, uint64_t len,
 			      bool miss, bool wp, bool minor, uint64_t *ioctls);
 unsigned long get_free_hugepages(void);
 bool check_vmflag_io(void *addr);
+int open_procmap(pid_t pid, struct procmap_fd *procmap_out);
+int query_procmap(struct procmap_fd *procmap);
+bool find_vma_procmap(struct procmap_fd *procmap, void *address);
+int close_procmap(struct procmap_fd *procmap);
+
+static inline int open_self_procmap(struct procmap_fd *procmap_out)
+{
+	pid_t pid = getpid();
+
+	return open_procmap(pid, procmap_out);
+}
 
 /*
  * On ppc64 this will only work with radix 2M hugepage size