Re: [PATCH v5 5/6] kselftest: alloc_tag: add kselftest for ioctl interface

[Abhishek Bapat]

On Mon, Jun 15, 2026 at 11:01 PM Hao Ge <hao.ge@xxxxxxxxx> wrote:
>
> Hi Abhishek
>
>
> On 2026/6/16 07:04, Abhishek Bapat wrote:
> > 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>
> > ---
> >   MAINTAINERS                                   |   1 +
> >   tools/testing/selftests/alloc_tag/Makefile    |   9 +
> >   .../alloc_tag/allocinfo_ioctl_test.c          | 331 ++++++++++++++++++
> >   3 files changed, 341 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/MAINTAINERS b/MAINTAINERS
> > index 019cc4c285a3..6610dd42e484 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -16715,6 +16715,7 @@ F:    include/linux/alloc_tag.h
> >   F:  include/linux/pgalloc_tag.h
> >   F:  include/uapi/linux/alloc_tag.h
> >   F:  lib/alloc_tag.c
> > +F:   tools/testing/selftests/alloc_tag/
> >
> >   MEMORY CONTROLLER DRIVERS
> >   M:  Krzysztof Kozlowski <krzk@xxxxxxxxxx>
> > 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
>
>
> I think we should replace -I../../../../usr/include with $(KHDR_INCLUDES).
>
>
> > +
> > +include ../lib.mk
> > +
>
>
> We would also introduce an extra field in the parent directory,
>
> allowing our alloc_tag target to be built when running make
>
> within /home/linux/tools/testing/selftests.
>
> like this:
>
> --- a/tools/testing/selftests/Makefile
> +++ b/tools/testing/selftests/Makefile
> @@ -1,5 +1,6 @@
>   # SPDX-License-Identifier: GPL-2.0
>   TARGETS += acct
> +TARGETS += alloc_tag
>   TARGETS += alsa
>   TARGETS += amd-pstate
>   TARGETS += arm64
>
> Below is the relevant build log:
>
> [root@localhost selftests]# make -j8
>    CC       acct_syscall
>    CC       allocinfo_ioctl_test
>
> Below is the log from running make clean:
>
> [root@localhost selftests]# make clean
> rm -f -r /home/linux/tools/testing/selftests/acct/acct_syscall
> rm -f -r /home/linux/tools/testing/selftests/alloc_tag/allocinfo_ioctl_test
>
>
> (Sorry about this inconvenience. I had limited experience with the
> kselftest framework,
>
> so I reached out to my teammates to sort out the relevant build logic.
>
> It's my fault for not catching this issue in prior reviews
>
> and forcing you to send a revised patch.)
>
>
Before writing this patch, I had discussed this with Suren and he was
of the opinion that this should be done later in a separate patch. So
I'll let Suren answer this further.

> > 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..62d5a488a04d
> > --- /dev/null
> > +++ b/tools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c
> > @@ -0,0 +1,331 @@
> > +// 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>
>
>
> errno.h is unused and may be dropped.
>
>
> > +#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 const char *allocinfo_str(const char *str)
> > +{
> > +     size_t len = strlen(str);
> > +
> > +     if (len >= ALLOCINFO_STR_SIZE)
> > +             str += (len - ALLOCINFO_STR_SIZE) + 1;
> > +     return str;
> > +}
> > +
> > +static void allocinfo_copy_str(char *dest, const char *src)
> > +{
> > +     strncpy(dest, allocinfo_str(src), ALLOCINFO_STR_SIZE - 1);
> > +     dest[ALLOCINFO_STR_SIZE - 1] = '\0';
> > +}
> > +
> > +static int get_filtered_procfs_entries(struct allocinfo_tag_data_vec *procfs_entries,
> > +                                    const struct allocinfo_filter *filter)
> > +{
> > +     FILE *fp = fopen(ALLOCINFO_PROC, "r");
> > +     char line[MAX_LINE_LEN];
> > +     int matches;
> > +     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) {
> > +             char filename[MAX_LINE_LEN];
> > +             char function[MAX_LINE_LEN];
> > +
> > +             memset(&procfs_entry, 0, sizeof(procfs_entry));
> > +             matches = sscanf(line, "%llu %llu %[^:]:%llu func:%s",
> > +                              &procfs_entry.counter.bytes,
> > +                              &procfs_entry.counter.calls,
> > +                              filename,
> > +                              &procfs_entry.tag.lineno,
> > +                              function);
> > +
> > +             if (matches != 5)
> > +                     continue;
> > +
> > +             allocinfo_copy_str(procfs_entry.tag.filename, filename);
> > +             allocinfo_copy_str(procfs_entry.tag.function, function);
> > +
> > +             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->min_size)
> > +                             continue;
> > +             }
> > +             if (filter->mask & ALLOCINFO_FILTER_MASK_MAX_SIZE) {
> > +                     if (procfs_entry.counter.bytes > filter->max_size)
> > +                             continue;
> > +             }
> > +
> > +             memcpy(&procfs_entries->tag[procfs_entries->count++], &procfs_entry,
> > +                    sizeof(procfs_entry));
> > +     }
> > +     fclose(fp);
> > +     return 0;
> > +}
> > +
> > +static enum ioctl_ret get_filtered_ioctl_entries(struct allocinfo_tag_data_vec *tags,
> > +                                              const struct allocinfo_filter *filter,
> > +                                              __u64 start_pos)
> > +{
> > +     int fd = open(ALLOCINFO_PROC, O_RDONLY);
> > +
> > +     if (fd < 0) {
> > +             ksft_print_msg("Failed to open " ALLOCINFO_PROC " for IOCTL\n");
> > +             return IOCTL_FAILURE;
> > +     }
> > +     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;
>
> Sashiko pointed out the fd leak in get_filtered_ioctl_entries().
>
> Since we already need to update the patch to fix the missing
>
> TARGETS entry in the top-level Makefile, we might as well fix
>
> this at the same time.
>
>
> Thanks
>
> Best Regards
>
> Hao
>

Ahh I missed this code path interestingly. Ack, I'll remove these
return statements here.

> > +             }
> > +
> > +             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);
> > +
> > +     close(fd);
> > +     return status;
> > +}
> > +
> > +static int run_filter_test(const struct allocinfo_filter *filter)
> > +{
> > +     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 exit;
> > +     }
> > +
> > +     if (get_filtered_procfs_entries(procfs_entries, filter)) {
> > +             ksft_print_msg("Error retrieving entries from " ALLOCINFO_PROC "\n");
> > +             ret = KSFT_SKIP;
> > +             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, 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:
> > +     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();
> > +}