cregit-Linux how code gets into the kernel

Release 4.9 samples/bpf/trace_event_user.c

Directory: samples/bpf
/* Copyright (c) 2016 Facebook
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of version 2 of the GNU General Public
 * License as published by the Free Software Foundation.
 */
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
#include <fcntl.h>
#include <poll.h>
#include <sys/ioctl.h>
#include <linux/perf_event.h>
#include <linux/bpf.h>
#include <signal.h>
#include <assert.h>
#include <errno.h>
#include <sys/resource.h>
#include "libbpf.h"
#include "bpf_load.h"


#define SAMPLE_FREQ 50



static bool sys_read_seen, sys_write_seen;


static void print_ksym(__u64 addr) { struct ksym *sym; if (!addr) return; sym = ksym_search(addr); printf("%s;", sym->name); if (!strcmp(sym->name, "sys_read")) sys_read_seen = true; else if (!strcmp(sym->name, "sys_write")) sys_write_seen = true; }

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static void print_addr(__u64 addr) { if (!addr) return; printf("%llx;", addr); }

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#define TASK_COMM_LEN 16 struct key_t { char comm[TASK_COMM_LEN]; __u32 kernstack; __u32 userstack; };
static void print_stack(struct key_t *key, __u64 count) { __u64 ip[PERF_MAX_STACK_DEPTH] = {}; static bool warned; int i; printf("%3lld %s;", count, key->comm); if (bpf_lookup_elem(map_fd[1], &key->kernstack, ip) != 0) { printf("---;"); } else { for (i = PERF_MAX_STACK_DEPTH - 1; i >= 0; i--) print_ksym(ip[i]); } printf("-;"); if (bpf_lookup_elem(map_fd[1], &key->userstack, ip) != 0) { printf("---;"); } else { for (i = PERF_MAX_STACK_DEPTH - 1; i >= 0; i--) print_addr(ip[i]); } printf("\n"); if (key->kernstack == -EEXIST && !warned) { printf("stackmap collisions seen. Consider increasing size\n"); warned = true; } else if ((int)key->kernstack < 0 && (int)key->userstack < 0) { printf("err stackid %d %d\n", key->kernstack, key->userstack); } }

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static void int_exit(int sig) { kill(0, SIGKILL); exit(0); }

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static void print_stacks(void) { struct key_t key = {}, next_key; __u64 value; __u32 stackid = 0, next_id; int fd = map_fd[0], stack_map = map_fd[1]; sys_read_seen = sys_write_seen = false; while (bpf_get_next_key(fd, &key, &next_key) == 0) { bpf_lookup_elem(fd, &next_key, &value); print_stack(&next_key, value); bpf_delete_elem(fd, &next_key); key = next_key; } if (!sys_read_seen || !sys_write_seen) { printf("BUG kernel stack doesn't contain sys_read() and sys_write()\n"); int_exit(0); } /* clear stack map */ while (bpf_get_next_key(stack_map, &stackid, &next_id) == 0) { bpf_delete_elem(stack_map, &next_id); stackid = next_id; } }

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static void test_perf_event_all_cpu(struct perf_event_attr *attr) { int nr_cpus = sysconf(_SC_NPROCESSORS_CONF); int *pmu_fd = malloc(nr_cpus * sizeof(int)); int i; /* open perf_event on all cpus */ for (i = 0; i < nr_cpus; i++) { pmu_fd[i] = perf_event_open(attr, -1, i, -1, 0); if (pmu_fd[i] < 0) { printf("perf_event_open failed\n"); goto all_cpu_err; } assert(ioctl(pmu_fd[i], PERF_EVENT_IOC_SET_BPF, prog_fd[0]) == 0); assert(ioctl(pmu_fd[i], PERF_EVENT_IOC_ENABLE, 0) == 0); } system("dd if=/dev/zero of=/dev/null count=5000k"); print_stacks(); all_cpu_err: for (i--; i >= 0; i--) close(pmu_fd[i]); free(pmu_fd); }

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static void test_perf_event_task(struct perf_event_attr *attr) { int pmu_fd; /* open task bound event */ pmu_fd = perf_event_open(attr, 0, -1, -1, 0); if (pmu_fd < 0) { printf("perf_event_open failed\n"); return; } assert(ioctl(pmu_fd, PERF_EVENT_IOC_SET_BPF, prog_fd[0]) == 0); assert(ioctl(pmu_fd, PERF_EVENT_IOC_ENABLE, 0) == 0); system("dd if=/dev/zero of=/dev/null count=5000k"); print_stacks(); close(pmu_fd); }

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static void test_bpf_perf_event(void) { struct perf_event_attr attr_type_hw = { .sample_freq = SAMPLE_FREQ, .freq = 1, .type = PERF_TYPE_HARDWARE, .config = PERF_COUNT_HW_CPU_CYCLES, .inherit = 1, }; struct perf_event_attr attr_type_sw = { .sample_freq = SAMPLE_FREQ, .freq = 1, .type = PERF_TYPE_SOFTWARE, .config = PERF_COUNT_SW_CPU_CLOCK, .inherit = 1, }; test_perf_event_all_cpu(&attr_type_hw); test_perf_event_task(&attr_type_hw); test_perf_event_all_cpu(&attr_type_sw); test_perf_event_task(&attr_type_sw); }

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int main(int argc, char **argv) { struct rlimit r = {RLIM_INFINITY, RLIM_INFINITY}; char filename[256]; snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]); setrlimit(RLIMIT_MEMLOCK, &r); signal(SIGINT, int_exit); if (load_kallsyms()) { printf("failed to process /proc/kallsyms\n"); return 1; } if (load_bpf_file(filename)) { printf("%s", bpf_log_buf); return 2; } if (fork() == 0) { read_trace_pipe(); return 0; } test_bpf_perf_event(); int_exit(0); return 0; }

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Directory: samples/bpf