Commit 784cdf93 authored by Mykyta Yatsenko's avatar Mykyta Yatsenko Committed by Alexei Starovoitov
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selftests/bpf: add file dynptr tests 



Introducing selftests for validating file-backed dynptr works as
expected.
 * validate implementation supports dynptr slice and read operations
 * validate destructors should be paired with initializers
 * validate sleepable progs can page in.

Signed-off-by: default avatarMykyta Yatsenko <yatsenko@meta.com>
Reviewed-by: default avatarEduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20251026203853.135105-11-mykyta.yatsenko5@gmail.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 2c52e894

tools/testing/selftests/bpf/prog_tests/file_reader.c

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// SPDX-License-Identifier: GPL-2.0

/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */



#include <test_progs.h>

#include <network_helpers.h>

#include "file_reader.skel.h"

#include "file_reader_fail.skel.h"

#include <dlfcn.h>

#include <sys/mman.h>



const char *user_ptr = "hello world";

char file_contents[256000];



void *get_executable_base_addr(void)

{

	Dl_info info;



	if (!dladdr((void *)&get_executable_base_addr, &info)) {

		fprintf(stderr, "dladdr failed\n");

		return NULL;

	}



	return info.dli_fbase;

}



static int initialize_file_contents(void)

{

	int fd, page_sz = sysconf(_SC_PAGESIZE);

	ssize_t n = 0, cur, off;

	void *addr;



	fd = open("/proc/self/exe", O_RDONLY);

	if (!ASSERT_OK_FD(fd, "Open /proc/self/exe\n"))

		return 1;



	do {

		cur = read(fd, file_contents + n, sizeof(file_contents) - n);

		if (!ASSERT_GT(cur, 0, "read success"))

			break;

		n += cur;

	} while (n < sizeof(file_contents));



	close(fd);



	if (!ASSERT_EQ(n, sizeof(file_contents), "Read /proc/self/exe\n"))

		return 1;



	addr = get_executable_base_addr();

	if (!ASSERT_NEQ(addr, NULL, "get executable address"))

		return 1;



	/* page-align base file address */

	addr = (void *)((unsigned long)addr & ~(page_sz - 1));



	for (off = 0; off < sizeof(file_contents); off += page_sz) {

		if (!ASSERT_OK(madvise(addr + off, page_sz, MADV_PAGEOUT),

			       "madvise pageout"))

			return errno;

	}



	return 0;

}



static void run_test(const char *prog_name)

{

	struct file_reader *skel;

	struct bpf_program *prog;

	int err, fd;



	err = initialize_file_contents();

	if (!ASSERT_OK(err, "initialize file contents"))

		return;



	skel = file_reader__open();

	if (!ASSERT_OK_PTR(skel, "file_reader__open"))

		return;



	bpf_object__for_each_program(prog, skel->obj) {

		bpf_program__set_autoload(prog, strcmp(bpf_program__name(prog), prog_name) == 0);

	}



	memcpy(skel->bss->user_buf, file_contents, sizeof(file_contents));

	skel->bss->pid = getpid();



	err = file_reader__load(skel);

	if (!ASSERT_OK(err, "file_reader__load"))

		goto cleanup;



	err = file_reader__attach(skel);

	if (!ASSERT_OK(err, "file_reader__attach"))

		goto cleanup;



	fd = open("/proc/self/exe", O_RDONLY);

	if (fd >= 0)

		close(fd);



	ASSERT_EQ(skel->bss->err, 0, "err");

	ASSERT_EQ(skel->bss->run_success, 1, "run_success");

cleanup:

	file_reader__destroy(skel);

}



void test_file_reader(void)

{

	if (test__start_subtest("on_open_expect_fault"))

		run_test("on_open_expect_fault");



	if (test__start_subtest("on_open_validate_file_read"))

		run_test("on_open_validate_file_read");



	if (test__start_subtest("negative"))

		RUN_TESTS(file_reader_fail);

}

tools/testing/selftests/bpf/progs/file_reader.c

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// SPDX-License-Identifier: GPL-2.0

/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */



#include <vmlinux.h>

#include <string.h>

#include <stdbool.h>

#include <bpf/bpf_tracing.h>

#include "bpf_misc.h"

#include "errno.h"



char _license[] SEC("license") = "GPL";



struct {

	__uint(type, BPF_MAP_TYPE_ARRAY);

	__uint(max_entries, 1);

	__type(key, int);

	__type(value, struct elem);

} arrmap SEC(".maps");



struct elem {

	struct file *file;

	struct bpf_task_work tw;

};



char user_buf[256000];

char tmp_buf[256000];



int pid = 0;

int err, run_success = 0;



static int validate_file_read(struct file *file);

static int task_work_callback(struct bpf_map *map, void *key, void *value);



SEC("lsm/file_open")

int on_open_expect_fault(void *c)

{

	struct bpf_dynptr dynptr;

	struct file *file;

	int local_err = 1;

	__u32 user_buf_sz = sizeof(user_buf);



	if (bpf_get_current_pid_tgid() >> 32 != pid)

		return 0;



	file = bpf_get_task_exe_file(bpf_get_current_task_btf());

	if (!file)

		return 0;



	if (bpf_dynptr_from_file(file, 0, &dynptr))

		goto out;



	local_err = bpf_dynptr_read(tmp_buf, user_buf_sz, &dynptr, 0, 0);

	if (local_err == -EFAULT) { /* Expect page fault */

		local_err = 0;

		run_success = 1;

	}

out:

	bpf_dynptr_file_discard(&dynptr);

	if (local_err)

		err = local_err;

	bpf_put_file(file);

	return 0;

}



SEC("lsm/file_open")

int on_open_validate_file_read(void *c)

{

	struct task_struct *task = bpf_get_current_task_btf();

	struct elem *work;

	int key = 0;



	if (bpf_get_current_pid_tgid() >> 32 != pid)

		return 0;



	work = bpf_map_lookup_elem(&arrmap, &key);

	if (!work) {

		err = 1;

		return 0;

	}

	bpf_task_work_schedule_signal(task, &work->tw, &arrmap, task_work_callback, NULL);

	return 0;

}



/* Called in a sleepable context, read 256K bytes, cross check with user space read data */

static int task_work_callback(struct bpf_map *map, void *key, void *value)

{

	struct task_struct *task = bpf_get_current_task_btf();

	struct file *file = bpf_get_task_exe_file(task);



	if (!file)

		return 0;



	err = validate_file_read(file);

	if (!err)

		run_success = 1;

	bpf_put_file(file);

	return 0;

}



static int verify_dynptr_read(struct bpf_dynptr *ptr, u32 off, char *user_buf, u32 len)

{

	int i;



	if (bpf_dynptr_read(tmp_buf, len, ptr, off, 0))

		return 1;



	/* Verify file contents read from BPF is the same as the one read from userspace */

	bpf_for(i, 0, len)

	{

		if (tmp_buf[i] != user_buf[i])

			return 1;

	}

	return 0;

}



static int validate_file_read(struct file *file)

{

	struct bpf_dynptr dynptr;

	int loc_err = 1, off;

	__u32 user_buf_sz = sizeof(user_buf);



	if (bpf_dynptr_from_file(file, 0, &dynptr))

		goto cleanup;



	loc_err = verify_dynptr_read(&dynptr, 0, user_buf, user_buf_sz);

	off = 1;

	loc_err = loc_err ?: verify_dynptr_read(&dynptr, off, user_buf + off, user_buf_sz - off);

	off = user_buf_sz - 1;

	loc_err = loc_err ?: verify_dynptr_read(&dynptr, off, user_buf + off, user_buf_sz - off);

	/* Read file with random offset and length */

	off = 4097;

	loc_err = loc_err ?: verify_dynptr_read(&dynptr, off, user_buf + off, 100);



	/* Adjust dynptr, verify read */

	loc_err = loc_err ?: bpf_dynptr_adjust(&dynptr, off, off + 1);

	loc_err = loc_err ?: verify_dynptr_read(&dynptr, 0, user_buf + off, 1);

	/* Can't read more than 1 byte */

	loc_err = loc_err ?: verify_dynptr_read(&dynptr, 0, user_buf + off, 2) == 0;

	/* Can't read with far offset */

	loc_err = loc_err ?: verify_dynptr_read(&dynptr, 1, user_buf + off, 1) == 0;



cleanup:

	bpf_dynptr_file_discard(&dynptr);

	return loc_err;

}

tools/testing/selftests/bpf/progs/file_reader_fail.c

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// SPDX-License-Identifier: GPL-2.0

/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */



#include <vmlinux.h>

#include <string.h>

#include <stdbool.h>

#include <bpf/bpf_tracing.h>

#include "bpf_misc.h"



char _license[] SEC("license") = "GPL";



int err;

void *user_ptr;



SEC("lsm/file_open")

__failure

__msg("Unreleased reference id=")

int on_nanosleep_unreleased_ref(void *ctx)

{

	struct task_struct *task = bpf_get_current_task_btf();

	struct file *file = bpf_get_task_exe_file(task);

	struct bpf_dynptr dynptr;



	if (!file)

		return 0;



	err = bpf_dynptr_from_file(file, 0, &dynptr);

	return err ? 1 : 0;

}



SEC("xdp")

__failure

__msg("Expected a dynptr of type file as arg #0")

int xdp_wrong_dynptr_type(struct xdp_md *xdp)

{

	struct bpf_dynptr dynptr;



	bpf_dynptr_from_xdp(xdp, 0, &dynptr);

	bpf_dynptr_file_discard(&dynptr);

	return 0;

}



SEC("xdp")

__failure

__msg("Expected an initialized dynptr as arg #0")

int xdp_no_dynptr_type(struct xdp_md *xdp)

{

	struct bpf_dynptr dynptr;



	bpf_dynptr_file_discard(&dynptr);

	return 0;

}