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8d3b7dce86
%s specifier makes bpf program and kernel debugging easier. To make sure that trace_printk won't crash the unsafe string is copied into stack and unsafe pointer is substituted. The following C program: #include <linux/fs.h> int foo(struct pt_regs *ctx, struct filename *filename) { void *name = 0; bpf_probe_read(&name, sizeof(name), &filename->name); bpf_trace_printk("executed %s\n", name); return 0; } when attached to kprobe do_execve() will produce output in /sys/kernel/debug/tracing/trace_pipe : make-13492 [002] d..1 3250.997277: : executed /bin/sh sh-13493 [004] d..1 3250.998716: : executed /usr/bin/gcc gcc-13494 [002] d..1 3250.999822: : executed /usr/lib/gcc/x86_64-linux-gnu/4.7/cc1 gcc-13495 [002] d..1 3251.006731: : executed /usr/bin/as gcc-13496 [002] d..1 3251.011831: : executed /usr/lib/gcc/x86_64-linux-gnu/4.7/collect2 collect2-13497 [000] d..1 3251.012941: : executed /usr/bin/ld Suggested-by: Brendan Gregg <brendan.d.gregg@gmail.com> Signed-off-by: Alexei Starovoitov <ast@plumgrid.com> Signed-off-by: David S. Miller <davem@davemloft.net>
284 lines
6.8 KiB
C
284 lines
6.8 KiB
C
/* Copyright (c) 2011-2015 PLUMgrid, http://plumgrid.com
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of version 2 of the GNU General Public
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* License as published by the Free Software Foundation.
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*/
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#include <linux/kernel.h>
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#include <linux/types.h>
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#include <linux/slab.h>
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#include <linux/bpf.h>
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#include <linux/filter.h>
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#include <linux/uaccess.h>
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#include <linux/ctype.h>
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#include "trace.h"
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static DEFINE_PER_CPU(int, bpf_prog_active);
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/**
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* trace_call_bpf - invoke BPF program
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* @prog: BPF program
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* @ctx: opaque context pointer
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*
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* kprobe handlers execute BPF programs via this helper.
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* Can be used from static tracepoints in the future.
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*
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* Return: BPF programs always return an integer which is interpreted by
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* kprobe handler as:
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* 0 - return from kprobe (event is filtered out)
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* 1 - store kprobe event into ring buffer
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* Other values are reserved and currently alias to 1
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*/
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unsigned int trace_call_bpf(struct bpf_prog *prog, void *ctx)
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{
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unsigned int ret;
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if (in_nmi()) /* not supported yet */
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return 1;
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preempt_disable();
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if (unlikely(__this_cpu_inc_return(bpf_prog_active) != 1)) {
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/*
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* since some bpf program is already running on this cpu,
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* don't call into another bpf program (same or different)
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* and don't send kprobe event into ring-buffer,
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* so return zero here
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*/
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ret = 0;
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goto out;
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}
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rcu_read_lock();
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ret = BPF_PROG_RUN(prog, ctx);
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rcu_read_unlock();
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out:
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__this_cpu_dec(bpf_prog_active);
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preempt_enable();
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return ret;
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}
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EXPORT_SYMBOL_GPL(trace_call_bpf);
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static u64 bpf_probe_read(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
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{
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void *dst = (void *) (long) r1;
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int size = (int) r2;
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void *unsafe_ptr = (void *) (long) r3;
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return probe_kernel_read(dst, unsafe_ptr, size);
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}
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static const struct bpf_func_proto bpf_probe_read_proto = {
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.func = bpf_probe_read,
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.gpl_only = true,
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.ret_type = RET_INTEGER,
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.arg1_type = ARG_PTR_TO_STACK,
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.arg2_type = ARG_CONST_STACK_SIZE,
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.arg3_type = ARG_ANYTHING,
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};
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/*
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* limited trace_printk()
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* only %d %u %x %ld %lu %lx %lld %llu %llx %p %s conversion specifiers allowed
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*/
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static u64 bpf_trace_printk(u64 r1, u64 fmt_size, u64 r3, u64 r4, u64 r5)
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{
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char *fmt = (char *) (long) r1;
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bool str_seen = false;
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int mod[3] = {};
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int fmt_cnt = 0;
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u64 unsafe_addr;
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char buf[64];
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int i;
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/*
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* bpf_check()->check_func_arg()->check_stack_boundary()
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* guarantees that fmt points to bpf program stack,
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* fmt_size bytes of it were initialized and fmt_size > 0
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*/
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if (fmt[--fmt_size] != 0)
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return -EINVAL;
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/* check format string for allowed specifiers */
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for (i = 0; i < fmt_size; i++) {
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if ((!isprint(fmt[i]) && !isspace(fmt[i])) || !isascii(fmt[i]))
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return -EINVAL;
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if (fmt[i] != '%')
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continue;
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if (fmt_cnt >= 3)
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return -EINVAL;
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/* fmt[i] != 0 && fmt[last] == 0, so we can access fmt[i + 1] */
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i++;
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if (fmt[i] == 'l') {
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mod[fmt_cnt]++;
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i++;
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} else if (fmt[i] == 'p' || fmt[i] == 's') {
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mod[fmt_cnt]++;
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i++;
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if (!isspace(fmt[i]) && !ispunct(fmt[i]) && fmt[i] != 0)
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return -EINVAL;
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fmt_cnt++;
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if (fmt[i - 1] == 's') {
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if (str_seen)
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/* allow only one '%s' per fmt string */
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return -EINVAL;
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str_seen = true;
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switch (fmt_cnt) {
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case 1:
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unsafe_addr = r3;
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r3 = (long) buf;
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break;
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case 2:
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unsafe_addr = r4;
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r4 = (long) buf;
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break;
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case 3:
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unsafe_addr = r5;
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r5 = (long) buf;
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break;
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}
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buf[0] = 0;
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strncpy_from_unsafe(buf,
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(void *) (long) unsafe_addr,
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sizeof(buf));
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}
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continue;
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}
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if (fmt[i] == 'l') {
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mod[fmt_cnt]++;
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i++;
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}
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if (fmt[i] != 'd' && fmt[i] != 'u' && fmt[i] != 'x')
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return -EINVAL;
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fmt_cnt++;
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}
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return __trace_printk(1/* fake ip will not be printed */, fmt,
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mod[0] == 2 ? r3 : mod[0] == 1 ? (long) r3 : (u32) r3,
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mod[1] == 2 ? r4 : mod[1] == 1 ? (long) r4 : (u32) r4,
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mod[2] == 2 ? r5 : mod[2] == 1 ? (long) r5 : (u32) r5);
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}
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static const struct bpf_func_proto bpf_trace_printk_proto = {
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.func = bpf_trace_printk,
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.gpl_only = true,
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.ret_type = RET_INTEGER,
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.arg1_type = ARG_PTR_TO_STACK,
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.arg2_type = ARG_CONST_STACK_SIZE,
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};
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const struct bpf_func_proto *bpf_get_trace_printk_proto(void)
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{
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/*
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* this program might be calling bpf_trace_printk,
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* so allocate per-cpu printk buffers
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*/
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trace_printk_init_buffers();
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return &bpf_trace_printk_proto;
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}
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static u64 bpf_perf_event_read(u64 r1, u64 index, u64 r3, u64 r4, u64 r5)
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{
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struct bpf_map *map = (struct bpf_map *) (unsigned long) r1;
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struct bpf_array *array = container_of(map, struct bpf_array, map);
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struct perf_event *event;
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if (unlikely(index >= array->map.max_entries))
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return -E2BIG;
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event = (struct perf_event *)array->ptrs[index];
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if (!event)
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return -ENOENT;
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/*
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* we don't know if the function is run successfully by the
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* return value. It can be judged in other places, such as
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* eBPF programs.
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*/
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return perf_event_read_local(event);
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}
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const struct bpf_func_proto bpf_perf_event_read_proto = {
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.func = bpf_perf_event_read,
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.gpl_only = false,
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.ret_type = RET_INTEGER,
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.arg1_type = ARG_CONST_MAP_PTR,
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.arg2_type = ARG_ANYTHING,
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};
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static const struct bpf_func_proto *kprobe_prog_func_proto(enum bpf_func_id func_id)
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{
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switch (func_id) {
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case BPF_FUNC_map_lookup_elem:
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return &bpf_map_lookup_elem_proto;
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case BPF_FUNC_map_update_elem:
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return &bpf_map_update_elem_proto;
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case BPF_FUNC_map_delete_elem:
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return &bpf_map_delete_elem_proto;
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case BPF_FUNC_probe_read:
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return &bpf_probe_read_proto;
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case BPF_FUNC_ktime_get_ns:
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return &bpf_ktime_get_ns_proto;
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case BPF_FUNC_tail_call:
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return &bpf_tail_call_proto;
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case BPF_FUNC_get_current_pid_tgid:
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return &bpf_get_current_pid_tgid_proto;
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case BPF_FUNC_get_current_uid_gid:
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return &bpf_get_current_uid_gid_proto;
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case BPF_FUNC_get_current_comm:
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return &bpf_get_current_comm_proto;
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case BPF_FUNC_trace_printk:
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return bpf_get_trace_printk_proto();
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case BPF_FUNC_get_smp_processor_id:
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return &bpf_get_smp_processor_id_proto;
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case BPF_FUNC_perf_event_read:
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return &bpf_perf_event_read_proto;
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default:
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return NULL;
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}
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}
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/* bpf+kprobe programs can access fields of 'struct pt_regs' */
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static bool kprobe_prog_is_valid_access(int off, int size, enum bpf_access_type type)
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{
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/* check bounds */
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if (off < 0 || off >= sizeof(struct pt_regs))
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return false;
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/* only read is allowed */
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if (type != BPF_READ)
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return false;
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/* disallow misaligned access */
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if (off % size != 0)
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return false;
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return true;
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}
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static struct bpf_verifier_ops kprobe_prog_ops = {
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.get_func_proto = kprobe_prog_func_proto,
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.is_valid_access = kprobe_prog_is_valid_access,
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};
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static struct bpf_prog_type_list kprobe_tl = {
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.ops = &kprobe_prog_ops,
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.type = BPF_PROG_TYPE_KPROBE,
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};
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static int __init register_kprobe_prog_ops(void)
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{
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bpf_register_prog_type(&kprobe_tl);
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return 0;
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}
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late_initcall(register_kprobe_prog_ops);
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