[PATCH 5/6] kselftest: alloc_tag: add kselftest for ioctl interface

[Abhishek Bapat]

Introduce a kselftest to verify the new IOCTL-based interface for
/proc/allocinfo. The test covers:

1. Validation of the filename filter.
2. Validation of the function filter.

The first test validates the functionality of the filename filter. Using
"mm/memory.c" as the candidate filename filter, it retrieves filtered
entries from both procfs and ioctl and matches the first VEC_MAX_ENTRIES
entries.

The second test validates the functionality of the function filter.
It uses "dup_mm" as the candidate function as we do not expect this
function name to change frequently and hence won't be needing to modify
this test often.

Note that both the tests match line no, function name and file name
fields. Bytes allocated and calls are not matched as those values may
change in the time when the data is being read from procfs and ioctl and
hence can lead to false negatives.

Signed-off-by: Abhishek Bapat <abhishekbapat@xxxxxxxxxx>
---
 tools/testing/selftests/alloc_tag/Makefile    |   9 +
 .../alloc_tag/allocinfo_ioctl_test.c          | 316 ++++++++++++++++++
 2 files changed, 325 insertions(+)
 create mode 100644 tools/testing/selftests/alloc_tag/Makefile
 create mode 100644 tools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c

diff --git a/tools/testing/selftests/alloc_tag/Makefile b/tools/testing/selftests/alloc_tag/Makefile
new file mode 100644
index 000000000000..f2b8fc022c3b
--- /dev/null
+++ b/tools/testing/selftests/alloc_tag/Makefile
@@ -0,0 +1,9 @@
+# SPDX-License-Identifier: GPL-2.0
+
+TEST_GEN_PROGS := allocinfo_ioctl_test
+
+CFLAGS += -Wall
+CFLAGS += -I../../../../usr/include
+
+include ../lib.mk
+
diff --git a/tools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c b/tools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c
new file mode 100644
index 000000000000..543023ca3d27
--- /dev/null
+++ b/tools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c
@@ -0,0 +1,316 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+/* kselftest for allocinfo ioctl
+ * allocinfo ioctl retrives allocinfo data through ioctl
+ * Copyright (C) 2026 Google, Inc.
+ */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdbool.h>
+#include <unistd.h>
+#include <sys/ioctl.h>
+#include <linux/types.h>
+#include <linux/alloc_tag.h>
+#include "../kselftest.h"
+
+#define MAX_LINE_LEN		512
+#define ALLOCINFO_PROC		"/proc/allocinfo"
+
+enum ioctl_ret {
+	IOCTL_SUCCESS = 0,
+	IOCTL_FAILURE = 1,
+	IOCTL_INVALID_DATA = 2,
+};
+
+#define VEC_MAX_ENTRIES 32
+
+struct allocinfo_tag_data_vec {
+	struct allocinfo_tag_data tag[VEC_MAX_ENTRIES];
+	__u64 count;
+};
+
+static inline int __allocinfo_get_content_id(int dev_fd, struct allocinfo_content_id *params)
+{
+	return ioctl(dev_fd, ALLOCINFO_IOC_CONTENT_ID, params);
+}
+
+static inline int __allocinfo_get_at(int dev_fd, struct allocinfo_get_at *params)
+{
+	return ioctl(dev_fd, ALLOCINFO_IOC_GET_AT, params);
+}
+
+static inline int __allocinfo_get_next(int dev_fd, struct allocinfo_tag_data *params)
+{
+	return ioctl(dev_fd, ALLOCINFO_IOC_GET_NEXT, params);
+}
+
+static bool match_entry(const struct allocinfo_tag_data *procfs_entry,
+			const struct allocinfo_tag_data *tag_data,
+			bool match_bytes, bool match_calls, bool match_lineno,
+			bool match_function, bool match_filename)
+{
+	if (match_bytes && tag_data->counter.bytes != procfs_entry->counter.bytes) {
+		ksft_print_msg("size retrieved through ioctl does not match procfs\n");
+		return false;
+	}
+
+	if (match_calls && tag_data->counter.calls != procfs_entry->counter.calls) {
+		ksft_print_msg("call count retrieved through ioctl does not match procfs\n");
+		return false;
+	}
+
+	if (match_lineno && tag_data->tag.lineno != procfs_entry->tag.lineno) {
+		ksft_print_msg("lineno retrieved through ioctl does not match procfs\n");
+		return false;
+	}
+
+	if (match_function &&
+	    strncmp(tag_data->tag.function, procfs_entry->tag.function, ALLOCINFO_STR_SIZE)) {
+		ksft_print_msg("function retrieved through ioctl does not match procfs\n");
+		return false;
+	}
+
+	if (match_filename &&
+	    strncmp(tag_data->tag.filename, procfs_entry->tag.filename, ALLOCINFO_STR_SIZE)) {
+		ksft_print_msg("filename retrieved through ioctl does not match procfs\n");
+		return false;
+	}
+	return true;
+}
+
+static bool match_entries(const struct allocinfo_tag_data_vec *procfs_entries,
+			  const struct allocinfo_tag_data_vec *tags,
+			  bool match_bytes, bool match_calls, bool match_lineno,
+			  bool match_function, bool match_filename)
+{
+	__u64 i;
+
+	if (procfs_entries->count != tags->count) {
+		ksft_print_msg("Entry count mismatch. ioctl entries: %llu, proc entries: %llu\n",
+			       tags->count, procfs_entries->count);
+		return false;
+	}
+	for (i = 0; i < procfs_entries->count; i++) {
+		if (!match_entry(&procfs_entries->tag[i], &tags->tag[i],
+				 match_bytes, match_calls, match_lineno,
+				 match_function, match_filename)) {
+			ksft_print_msg("%lluth entry does not match.\n", i);
+			return false;
+		}
+	}
+	return true;
+}
+
+static int get_filtered_procfs_entries(struct allocinfo_tag_data_vec *procfs_entries,
+				       const struct allocinfo_filter *filter, int fd)
+{
+	FILE *fp = fdopen(fd, "r");
+	char line[MAX_LINE_LEN];
+	int matches, skip_lines = 2;
+	struct allocinfo_tag_data procfs_entry;
+
+	if (!fp) {
+		ksft_print_msg("Failed to open " ALLOCINFO_PROC " for reading\n");
+		return 1;
+	}
+	memset(procfs_entries, 0, sizeof(*procfs_entries));
+	while (fgets(line, sizeof(line), fp) && procfs_entries->count < VEC_MAX_ENTRIES) {
+		/*The first two procfs entries are for the header, so we skip them.*/
+		if (skip_lines-- > 0)
+			continue;
+
+		memset(&procfs_entry, 0, sizeof(procfs_entry));
+		matches = sscanf(line, "%llu %llu %[^:]:%llu func:%s",
+				 &procfs_entry.counter.bytes,
+				 &procfs_entry.counter.calls,
+				 procfs_entry.tag.filename,
+				 &procfs_entry.tag.lineno,
+				 procfs_entry.tag.function);
+
+		if (matches != 5)
+			continue;
+
+		if (filter->mask & ALLOCINFO_FILTER_MASK_FILENAME) {
+			if (strncmp(procfs_entry.tag.filename,
+				    filter->fields.filename, ALLOCINFO_STR_SIZE))
+				continue;
+		}
+		if (filter->mask & ALLOCINFO_FILTER_MASK_FUNCTION) {
+			if (strncmp(procfs_entry.tag.function,
+				    filter->fields.function, ALLOCINFO_STR_SIZE))
+				continue;
+		}
+		if (filter->mask & ALLOCINFO_FILTER_MASK_LINENO) {
+			if (procfs_entry.tag.lineno != filter->fields.lineno)
+				continue;
+		}
+		if (filter->mask & ALLOCINFO_FILTER_MASK_MIN_SIZE) {
+			if (procfs_entry.counter.bytes < filter->fields.min_size)
+				continue;
+		}
+		if (filter->mask & ALLOCINFO_FILTER_MASK_MAX_SIZE) {
+			if (procfs_entry.counter.bytes > filter->fields.max_size)
+				continue;
+		}
+
+		memcpy(&procfs_entries->tag[procfs_entries->count++], &procfs_entry,
+		       sizeof(procfs_entry));
+	}
+	return 0;
+}
+
+static enum ioctl_ret get_filtered_ioctl_entries(struct allocinfo_tag_data_vec *tags,
+						 const struct allocinfo_filter *filter, int fd,
+						 __u64 start_pos)
+{
+	struct allocinfo_content_id start_cont_id, end_cont_id;
+	struct allocinfo_get_at get_at_params;
+	const int max_retries = 10;
+	int retry_count = 0;
+	int status;
+
+	/*
+	 * __allocinfo_get_content_id may return different values if a kernel module was loaded
+	 * between the two calls. If that happens, the data gathered cannot be considered consistent
+	 * and hence needs to be fetched again to avoid flakiness.
+	 */
+	do {
+		if (__allocinfo_get_content_id(fd, &start_cont_id)) {
+			ksft_print_msg("allocinfo_get_content_id failed\n");
+			return IOCTL_FAILURE;
+		}
+
+		memset(tags, 0, sizeof(*tags));
+		memset(&get_at_params, 0, sizeof(get_at_params));
+		memcpy(&get_at_params.filter, filter, sizeof(*filter));
+		get_at_params.pos = start_pos;
+		if (__allocinfo_get_at(fd, &get_at_params)) {
+			ksft_print_msg("allocinfo_get_at failed\n");
+			return IOCTL_FAILURE;
+		}
+		memcpy(&tags->tag[tags->count++], &get_at_params.data, sizeof(get_at_params.data));
+
+		while (tags->count < VEC_MAX_ENTRIES &&
+		       __allocinfo_get_next(fd, &tags->tag[tags->count]) == 0)
+			tags->count++;
+
+		if (__allocinfo_get_content_id(fd, &end_cont_id)) {
+			ksft_print_msg("allocinfo_get_content_id failed\n");
+			return IOCTL_FAILURE;
+		}
+
+		if (start_cont_id.id == end_cont_id.id) {
+			status = IOCTL_SUCCESS;
+		} else {
+			ksft_print_msg("allocinfo_get_content_id mismatch, retrying...\n");
+			status = IOCTL_INVALID_DATA;
+		}
+	} while (status == IOCTL_INVALID_DATA && retry_count++ < max_retries);
+
+	return status;
+}
+
+static int run_filter_test(const struct allocinfo_filter *filter)
+{
+	int fd;
+	struct allocinfo_tag_data_vec *tags = malloc(sizeof(*tags));
+	struct allocinfo_tag_data_vec *procfs_entries = malloc(sizeof(*procfs_entries));
+	int ioctl_status;
+	int ret = KSFT_PASS;
+
+	if (!tags || !procfs_entries) {
+		ksft_print_msg("Memory allocation failed.\n");
+		ret = KSFT_FAIL;
+		goto freemem;
+	}
+
+	fd = open(ALLOCINFO_PROC, O_RDONLY);
+	if (fd < 0) {
+		ksft_exit_skip("Failed to open " ALLOCINFO_PROC ": %s\n", strerror(errno));
+		ret = KSFT_FAIL;
+		goto freemem;
+	}
+
+	if (get_filtered_procfs_entries(procfs_entries, filter, fd)) {
+		ksft_print_msg("Error retrieving entries from " ALLOCINFO_PROC "\n");
+		ret = KSFT_FAIL;
+		goto exit;
+	}
+
+	if (procfs_entries->count == 0) {
+		ksft_print_msg("No entries found in " ALLOCINFO_PROC ", skipping test\n");
+		ret = KSFT_SKIP;
+		goto exit;
+	}
+
+	ioctl_status = get_filtered_ioctl_entries(tags, filter, fd, 0);
+	if (ioctl_status == IOCTL_INVALID_DATA) {
+		ksft_print_msg("Trouble retrieving valid IOCTL entries, skipping.\n");
+		ret = KSFT_SKIP;
+		goto exit;
+	}
+	if (ioctl_status == IOCTL_FAILURE) {
+		ksft_print_msg("Error retrieving IOCTL entries.\n");
+		ret = KSFT_FAIL;
+		goto exit;
+	}
+
+	if (!match_entries(procfs_entries, tags, false, false, true, true, true))
+		ret = KSFT_FAIL;
+
+exit:
+	close(fd);
+freemem:
+	free(tags);
+	free(procfs_entries);
+	return ret;
+}
+
+static int test_filename_filter(void)
+{
+	struct allocinfo_filter filter;
+	const char *target_filename = "mm/memory.c";
+
+	memset(&filter, 0, sizeof(filter));
+	filter.mask |= ALLOCINFO_FILTER_MASK_FILENAME;
+	strncpy(filter.fields.filename, target_filename, ALLOCINFO_STR_SIZE);
+
+	return run_filter_test(&filter);
+}
+
+static int test_function_filter(void)
+{
+	struct allocinfo_filter filter;
+	const char *target_function = "dup_mm";
+
+	memset(&filter, 0, sizeof(filter));
+	filter.mask |= ALLOCINFO_FILTER_MASK_FUNCTION;
+	strncpy(filter.fields.function, target_function, ALLOCINFO_STR_SIZE);
+
+	return run_filter_test(&filter);
+}
+
+int main(int argc, char *argv[])
+{
+	int ret;
+
+	ksft_set_plan(2);
+
+	ret = test_filename_filter();
+	if (ret == KSFT_SKIP)
+		ksft_test_result_skip("Skipping test_filename_filter\n");
+	else
+		ksft_test_result(ret == KSFT_PASS, "test_filename_filter\n");
+
+	ret = test_function_filter();
+	if (ret == KSFT_SKIP)
+		ksft_test_result_skip("Skipping test_function_filter\n");
+	else
+		ksft_test_result(ret == KSFT_PASS, "test_function_filter\n");
+
+	ksft_finished();
+}
-- 
2.54.0.545.g6539524ca2-goog