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

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

File Facts

System
Linux kernel
Corpus path
tools/testing/selftests/bpf/progs/test_ksyms_btf_write_check.c
Extension
.c
Size
824 bytes
Lines
45
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

// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2021 Google */

#include "vmlinux.h"

#include <bpf/bpf_helpers.h>

extern const int bpf_prog_active __ksym; /* int type global var. */

SEC("raw_tp/sys_enter")
int handler1(const void *ctx)
{
	int *active;
	__u32 cpu;

	cpu = bpf_get_smp_processor_id();
	active = (int *)bpf_per_cpu_ptr(&bpf_prog_active, cpu);
	if (active) {
		/* Kernel memory obtained from bpf_{per,this}_cpu_ptr
		 * is read-only, should _not_ pass verification.
		 */
		/* WRITE_ONCE */
		*(volatile int *)active = -1;
	}

	return 0;
}

__noinline int write_active(int *p)
{
	return p ? (*p = 42) : 0;
}

SEC("raw_tp/sys_enter")
int handler2(const void *ctx)
{
	int *active;

	active = bpf_this_cpu_ptr(&bpf_prog_active);
	write_active(active);
	return 0;
}

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

Annotation

Implementation Notes