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

Source file repositories/reference/linux-study-clean/tools/testing/selftests/bpf/progs/file_reader.c

File Facts

System
Linux kernel
Corpus path
tools/testing/selftests/bpf/progs/file_reader.c
Extension
.c
Size
3567 bytes
Lines
146
Domain
Support Tooling And Documentation
Bucket
tools
Inferred role
Support Tooling And Documentation: implementation source
Status
source implementation candidate

Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

Dependency Surface

Detected Declarations

Annotated Snippet

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, user_buf_sz, 0);
	if (local_err == -EFAULT || local_err == 0) { /* Expect page fault or success */
		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);
	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)
	{

Annotation

Implementation Notes