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Commit d9762e84 authored by Martin KaFai Lau's avatar Martin KaFai Lau Committed by Alexei Starovoitov
Browse files

bpf: verbose log bpf_line_info in verifier 



This patch adds bpf_line_info during the verifier's verbose.
It can give error context for debug purpose.

~~~~~~~~~~
Here is the verbose log for backedge:
	while (a) {
		a += bpf_get_smp_processor_id();
		bpf_trace_printk(fmt, sizeof(fmt), a);
	}

~> bpftool prog load ./test_loop.o /sys/fs/bpf/test_loop type tracepoint
13: while (a) {
3: a += bpf_get_smp_processor_id();
back-edge from insn 13 to 3

~~~~~~~~~~
Here is the verbose log for invalid pkt access:
Modification to test_xdp_noinline.c:

	data = (void *)(long)xdp->data;
	data_end = (void *)(long)xdp->data_end;
/*
	if (data + 4 > data_end)
		return XDP_DROP;
*/
	*(u32 *)data = dst->dst;

~> bpftool prog load ./test_xdp_noinline.o /sys/fs/bpf/test_xdp_noinline type xdp
; data = (void *)(long)xdp->data;
224: (79) r2 = *(u64 *)(r10 -112)
225: (61) r2 = *(u32 *)(r2 +0)
; *(u32 *)data = dst->dst;
226: (63) *(u32 *)(r2 +0) = r1
invalid access to packet, off=0 size=4, R2(id=0,off=0,r=0)
R2 offset is outside of the packet

Signed-off-by: default avatarMartin KaFai Lau <kafai@fb.com>
Acked-by: default avatarYonghong Song <yhs@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 23127b33

include/linux/bpf_verifier.h

+1 −0
Original line number Diff line number Diff line
@@ -224,6 +224,7 @@ struct bpf_verifier_env { 
	bool allow_ptr_leaks;

	bool seen_direct_write;

	struct bpf_insn_aux_data *insn_aux_data; /* array of per-insn state */

	const struct bpf_line_info *prev_linfo;

	struct bpf_verifier_log log;

	struct bpf_subprog_info subprog_info[BPF_MAX_SUBPROGS + 1];

	u32 subprog_cnt;

kernel/bpf/verifier.c

+69 −5
Original line number Diff line number Diff line
@@ -26,6 +26,7 @@ 
#include <linux/bsearch.h>

#include <linux/sort.h>

#include <linux/perf_event.h>

#include <linux/ctype.h>



#include "disasm.h"
@@ -216,6 +217,27 @@ struct bpf_call_arg_meta { 


static DEFINE_MUTEX(bpf_verifier_lock);



static const struct bpf_line_info *

find_linfo(const struct bpf_verifier_env *env, u32 insn_off)

{

	const struct bpf_line_info *linfo;

	const struct bpf_prog *prog;

	u32 i, nr_linfo;



	prog = env->prog;

	nr_linfo = prog->aux->nr_linfo;



	if (!nr_linfo || insn_off >= prog->len)

		return NULL;



	linfo = prog->aux->linfo;

	for (i = 1; i < nr_linfo; i++)

		if (insn_off < linfo[i].insn_off)

			break;



	return &linfo[i - 1];

}



void bpf_verifier_vlog(struct bpf_verifier_log *log, const char *fmt,

		       va_list args)

{
@@ -266,6 +288,42 @@ __printf(2, 3) static void verbose(void *private_data, const char *fmt, ...) 
	va_end(args);

}



static const char *ltrim(const char *s)

{

	while (isspace(*s))

		s++;



	return s;

}



__printf(3, 4) static void verbose_linfo(struct bpf_verifier_env *env,

					 u32 insn_off,

					 const char *prefix_fmt, ...)

{

	const struct bpf_line_info *linfo;



	if (!bpf_verifier_log_needed(&env->log))

		return;



	linfo = find_linfo(env, insn_off);

	if (!linfo || linfo == env->prev_linfo)

		return;



	if (prefix_fmt) {

		va_list args;



		va_start(args, prefix_fmt);

		bpf_verifier_vlog(&env->log, prefix_fmt, args);

		va_end(args);

	}



	verbose(env, "%s\n",

		ltrim(btf_name_by_offset(env->prog->aux->btf,

					 linfo->line_off)));



	env->prev_linfo = linfo;

}



static bool type_is_pkt_pointer(enum bpf_reg_type type)

{

	return type == PTR_TO_PACKET ||
@@ -4561,6 +4619,7 @@ static int push_insn(int t, int w, int e, struct bpf_verifier_env *env) 
		return 0;



	if (w < 0 || w >= env->prog->len) {

		verbose_linfo(env, t, "%d: ", t);

		verbose(env, "jump out of range from insn %d to %d\n", t, w);

		return -EINVAL;

	}
@@ -4578,6 +4637,8 @@ static int push_insn(int t, int w, int e, struct bpf_verifier_env *env) 
		insn_stack[cur_stack++] = w;

		return 1;

	} else if ((insn_state[w] & 0xF0) == DISCOVERED) {

		verbose_linfo(env, t, "%d: ", t);

		verbose_linfo(env, w, "%d: ", w);

		verbose(env, "back-edge from insn %d to %d\n", t, w);

		return -EINVAL;

	} else if (insn_state[w] == EXPLORED) {
@@ -4600,10 +4661,6 @@ static int check_cfg(struct bpf_verifier_env *env) 
	int ret = 0;

	int i, t;



	ret = check_subprogs(env);

	if (ret < 0)

		return ret;



	insn_state = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL);

	if (!insn_state)

		return -ENOMEM;
@@ -5448,6 +5505,8 @@ static int do_check(struct bpf_verifier_env *env) 
	int insn_processed = 0;

	bool do_print_state = false;



	env->prev_linfo = NULL;



	state = kzalloc(sizeof(struct bpf_verifier_state), GFP_KERNEL);

	if (!state)

		return -ENOMEM;
@@ -5521,6 +5580,7 @@ static int do_check(struct bpf_verifier_env *env) 
				.private_data	= env,

			};



			verbose_linfo(env, insn_idx, "; ");

			verbose(env, "%d: ", insn_idx);

			print_bpf_insn(&cbs, insn, env->allow_ptr_leaks);

		}
@@ -6755,7 +6815,7 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, 


	env->allow_ptr_leaks = capable(CAP_SYS_ADMIN);



	ret = check_cfg(env);

	ret = check_subprogs(env);

	if (ret < 0)

		goto skip_full_check;
@@ -6763,6 +6823,10 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, 
	if (ret < 0)

		goto skip_full_check;



	ret = check_cfg(env);

	if (ret < 0)

		goto skip_full_check;



	ret = do_check(env);

	if (env->cur_state) {

		free_verifier_state(env->cur_state, true);