![Alexei Starovoitov](/assets/img/avatar_default.png)
%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
|
|
*
|
|
* 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 <linux/kernel.h>
|
|
#include <linux/types.h>
|
|
#include <linux/slab.h>
|
|
#include <linux/bpf.h>
|
|
#include <linux/filter.h>
|
|
#include <linux/uaccess.h>
|
|
#include <linux/ctype.h>
|
|
#include "trace.h"
|
|
|
|
static DEFINE_PER_CPU(int, bpf_prog_active);
|
|
|
|
/**
|
|
* trace_call_bpf - invoke BPF program
|
|
* @prog: BPF program
|
|
* @ctx: opaque context pointer
|
|
*
|
|
* kprobe handlers execute BPF programs via this helper.
|
|
* Can be used from static tracepoints in the future.
|
|
*
|
|
* Return: BPF programs always return an integer which is interpreted by
|
|
* kprobe handler as:
|
|
* 0 - return from kprobe (event is filtered out)
|
|
* 1 - store kprobe event into ring buffer
|
|
* Other values are reserved and currently alias to 1
|
|
*/
|
|
unsigned int trace_call_bpf(struct bpf_prog *prog, void *ctx)
|
|
{
|
|
unsigned int ret;
|
|
|
|
if (in_nmi()) /* not supported yet */
|
|
return 1;
|
|
|
|
preempt_disable();
|
|
|
|
if (unlikely(__this_cpu_inc_return(bpf_prog_active) != 1)) {
|
|
/*
|
|
* since some bpf program is already running on this cpu,
|
|
* don't call into another bpf program (same or different)
|
|
* and don't send kprobe event into ring-buffer,
|
|
* so return zero here
|
|
*/
|
|
ret = 0;
|
|
goto out;
|
|
}
|
|
|
|
rcu_read_lock();
|
|
ret = BPF_PROG_RUN(prog, ctx);
|
|
rcu_read_unlock();
|
|
|
|
out:
|
|
__this_cpu_dec(bpf_prog_active);
|
|
preempt_enable();
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(trace_call_bpf);
|
|
|
|
static u64 bpf_probe_read(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
|
|
{
|
|
void *dst = (void *) (long) r1;
|
|
int size = (int) r2;
|
|
void *unsafe_ptr = (void *) (long) r3;
|
|
|
|
return probe_kernel_read(dst, unsafe_ptr, size);
|
|
}
|
|
|
|
static const struct bpf_func_proto bpf_probe_read_proto = {
|
|
.func = bpf_probe_read,
|
|
.gpl_only = true,
|
|
.ret_type = RET_INTEGER,
|
|
.arg1_type = ARG_PTR_TO_STACK,
|
|
.arg2_type = ARG_CONST_STACK_SIZE,
|
|
.arg3_type = ARG_ANYTHING,
|
|
};
|
|
|
|
/*
|
|
* limited trace_printk()
|
|
* only %d %u %x %ld %lu %lx %lld %llu %llx %p %s conversion specifiers allowed
|
|
*/
|
|
static u64 bpf_trace_printk(u64 r1, u64 fmt_size, u64 r3, u64 r4, u64 r5)
|
|
{
|
|
char *fmt = (char *) (long) r1;
|
|
bool str_seen = false;
|
|
int mod[3] = {};
|
|
int fmt_cnt = 0;
|
|
u64 unsafe_addr;
|
|
char buf[64];
|
|
int i;
|
|
|
|
/*
|
|
* bpf_check()->check_func_arg()->check_stack_boundary()
|
|
* guarantees that fmt points to bpf program stack,
|
|
* fmt_size bytes of it were initialized and fmt_size > 0
|
|
*/
|
|
if (fmt[--fmt_size] != 0)
|
|
return -EINVAL;
|
|
|
|
/* check format string for allowed specifiers */
|
|
for (i = 0; i < fmt_size; i++) {
|
|
if ((!isprint(fmt[i]) && !isspace(fmt[i])) || !isascii(fmt[i]))
|
|
return -EINVAL;
|
|
|
|
if (fmt[i] != '%')
|
|
continue;
|
|
|
|
if (fmt_cnt >= 3)
|
|
return -EINVAL;
|
|
|
|
/* fmt[i] != 0 && fmt[last] == 0, so we can access fmt[i + 1] */
|
|
i++;
|
|
if (fmt[i] == 'l') {
|
|
mod[fmt_cnt]++;
|
|
i++;
|
|
} else if (fmt[i] == 'p' || fmt[i] == 's') {
|
|
mod[fmt_cnt]++;
|
|
i++;
|
|
if (!isspace(fmt[i]) && !ispunct(fmt[i]) && fmt[i] != 0)
|
|
return -EINVAL;
|
|
fmt_cnt++;
|
|
if (fmt[i - 1] == 's') {
|
|
if (str_seen)
|
|
/* allow only one '%s' per fmt string */
|
|
return -EINVAL;
|
|
str_seen = true;
|
|
|
|
switch (fmt_cnt) {
|
|
case 1:
|
|
unsafe_addr = r3;
|
|
r3 = (long) buf;
|
|
break;
|
|
case 2:
|
|
unsafe_addr = r4;
|
|
r4 = (long) buf;
|
|
break;
|
|
case 3:
|
|
unsafe_addr = r5;
|
|
r5 = (long) buf;
|
|
break;
|
|
}
|
|
buf[0] = 0;
|
|
strncpy_from_unsafe(buf,
|
|
(void *) (long) unsafe_addr,
|
|
sizeof(buf));
|
|
}
|
|
continue;
|
|
}
|
|
|
|
if (fmt[i] == 'l') {
|
|
mod[fmt_cnt]++;
|
|
i++;
|
|
}
|
|
|
|
if (fmt[i] != 'd' && fmt[i] != 'u' && fmt[i] != 'x')
|
|
return -EINVAL;
|
|
fmt_cnt++;
|
|
}
|
|
|
|
return __trace_printk(1/* fake ip will not be printed */, fmt,
|
|
mod[0] == 2 ? r3 : mod[0] == 1 ? (long) r3 : (u32) r3,
|
|
mod[1] == 2 ? r4 : mod[1] == 1 ? (long) r4 : (u32) r4,
|
|
mod[2] == 2 ? r5 : mod[2] == 1 ? (long) r5 : (u32) r5);
|
|
}
|
|
|
|
static const struct bpf_func_proto bpf_trace_printk_proto = {
|
|
.func = bpf_trace_printk,
|
|
.gpl_only = true,
|
|
.ret_type = RET_INTEGER,
|
|
.arg1_type = ARG_PTR_TO_STACK,
|
|
.arg2_type = ARG_CONST_STACK_SIZE,
|
|
};
|
|
|
|
const struct bpf_func_proto *bpf_get_trace_printk_proto(void)
|
|
{
|
|
/*
|
|
* this program might be calling bpf_trace_printk,
|
|
* so allocate per-cpu printk buffers
|
|
*/
|
|
trace_printk_init_buffers();
|
|
|
|
return &bpf_trace_printk_proto;
|
|
}
|
|
|
|
static u64 bpf_perf_event_read(u64 r1, u64 index, u64 r3, u64 r4, u64 r5)
|
|
{
|
|
struct bpf_map *map = (struct bpf_map *) (unsigned long) r1;
|
|
struct bpf_array *array = container_of(map, struct bpf_array, map);
|
|
struct perf_event *event;
|
|
|
|
if (unlikely(index >= array->map.max_entries))
|
|
return -E2BIG;
|
|
|
|
event = (struct perf_event *)array->ptrs[index];
|
|
if (!event)
|
|
return -ENOENT;
|
|
|
|
/*
|
|
* we don't know if the function is run successfully by the
|
|
* return value. It can be judged in other places, such as
|
|
* eBPF programs.
|
|
*/
|
|
return perf_event_read_local(event);
|
|
}
|
|
|
|
const struct bpf_func_proto bpf_perf_event_read_proto = {
|
|
.func = bpf_perf_event_read,
|
|
.gpl_only = false,
|
|
.ret_type = RET_INTEGER,
|
|
.arg1_type = ARG_CONST_MAP_PTR,
|
|
.arg2_type = ARG_ANYTHING,
|
|
};
|
|
|
|
static const struct bpf_func_proto *kprobe_prog_func_proto(enum bpf_func_id func_id)
|
|
{
|
|
switch (func_id) {
|
|
case BPF_FUNC_map_lookup_elem:
|
|
return &bpf_map_lookup_elem_proto;
|
|
case BPF_FUNC_map_update_elem:
|
|
return &bpf_map_update_elem_proto;
|
|
case BPF_FUNC_map_delete_elem:
|
|
return &bpf_map_delete_elem_proto;
|
|
case BPF_FUNC_probe_read:
|
|
return &bpf_probe_read_proto;
|
|
case BPF_FUNC_ktime_get_ns:
|
|
return &bpf_ktime_get_ns_proto;
|
|
case BPF_FUNC_tail_call:
|
|
return &bpf_tail_call_proto;
|
|
case BPF_FUNC_get_current_pid_tgid:
|
|
return &bpf_get_current_pid_tgid_proto;
|
|
case BPF_FUNC_get_current_uid_gid:
|
|
return &bpf_get_current_uid_gid_proto;
|
|
case BPF_FUNC_get_current_comm:
|
|
return &bpf_get_current_comm_proto;
|
|
case BPF_FUNC_trace_printk:
|
|
return bpf_get_trace_printk_proto();
|
|
case BPF_FUNC_get_smp_processor_id:
|
|
return &bpf_get_smp_processor_id_proto;
|
|
case BPF_FUNC_perf_event_read:
|
|
return &bpf_perf_event_read_proto;
|
|
default:
|
|
return NULL;
|
|
}
|
|
}
|
|
|
|
/* bpf+kprobe programs can access fields of 'struct pt_regs' */
|
|
static bool kprobe_prog_is_valid_access(int off, int size, enum bpf_access_type type)
|
|
{
|
|
/* check bounds */
|
|
if (off < 0 || off >= sizeof(struct pt_regs))
|
|
return false;
|
|
|
|
/* only read is allowed */
|
|
if (type != BPF_READ)
|
|
return false;
|
|
|
|
/* disallow misaligned access */
|
|
if (off % size != 0)
|
|
return false;
|
|
|
|
return true;
|
|
}
|
|
|
|
static struct bpf_verifier_ops kprobe_prog_ops = {
|
|
.get_func_proto = kprobe_prog_func_proto,
|
|
.is_valid_access = kprobe_prog_is_valid_access,
|
|
};
|
|
|
|
static struct bpf_prog_type_list kprobe_tl = {
|
|
.ops = &kprobe_prog_ops,
|
|
.type = BPF_PROG_TYPE_KPROBE,
|
|
};
|
|
|
|
static int __init register_kprobe_prog_ops(void)
|
|
{
|
|
bpf_register_prog_type(&kprobe_tl);
|
|
return 0;
|
|
}
|
|
late_initcall(register_kprobe_prog_ops);
|