Commit 9ed9e9ba authored by Alexei Starovoitov's avatar Alexei Starovoitov Committed by Daniel Borkmann
Browse files

bpf: Count the number of times recursion was prevented 



Add per-program counter for number of times recursion prevention mechanism
was triggered and expose it via show_fdinfo and bpf_prog_info.
Teach bpftool to print it.

Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210210033634.62081-7-alexei.starovoitov@gmail.com
parent 406c557e

include/linux/filter.h

+1 −0
Original line number Diff line number Diff line
@@ -543,6 +543,7 @@ struct bpf_binary_header { 
struct bpf_prog_stats {

	u64 cnt;

	u64 nsecs;

	u64 misses;

	struct u64_stats_sync syncp;

} __aligned(2 * sizeof(u64));

include/uapi/linux/bpf.h

+1 −0
Original line number Diff line number Diff line
@@ -4501,6 +4501,7 @@ struct bpf_prog_info { 
	__aligned_u64 prog_tags;

	__u64 run_time_ns;

	__u64 run_cnt;

	__u64 recursion_misses;

} __attribute__((aligned(8)));



struct bpf_map_info {

kernel/bpf/syscall.c

+10 −4
Original line number Diff line number Diff line
@@ -1731,25 +1731,28 @@ static int bpf_prog_release(struct inode *inode, struct file *filp) 
static void bpf_prog_get_stats(const struct bpf_prog *prog,

			       struct bpf_prog_stats *stats)

{

	u64 nsecs = 0, cnt = 0;

	u64 nsecs = 0, cnt = 0, misses = 0;

	int cpu;



	for_each_possible_cpu(cpu) {

		const struct bpf_prog_stats *st;

		unsigned int start;

		u64 tnsecs, tcnt;

		u64 tnsecs, tcnt, tmisses;



		st = per_cpu_ptr(prog->stats, cpu);

		do {

			start = u64_stats_fetch_begin_irq(&st->syncp);

			tnsecs = st->nsecs;

			tcnt = st->cnt;

			tmisses = st->misses;

		} while (u64_stats_fetch_retry_irq(&st->syncp, start));

		nsecs += tnsecs;

		cnt += tcnt;

		misses += tmisses;

	}

	stats->nsecs = nsecs;

	stats->cnt = cnt;

	stats->misses = misses;

}



#ifdef CONFIG_PROC_FS
@@ -1768,14 +1771,16 @@ static void bpf_prog_show_fdinfo(struct seq_file *m, struct file *filp) 
		   "memlock:\t%llu\n"

		   "prog_id:\t%u\n"

		   "run_time_ns:\t%llu\n"

		   "run_cnt:\t%llu\n",

		   "run_cnt:\t%llu\n"

		   "recursion_misses:\t%llu\n",

		   prog->type,

		   prog->jited,

		   prog_tag,

		   prog->pages * 1ULL << PAGE_SHIFT,

		   prog->aux->id,

		   stats.nsecs,

		   stats.cnt);

		   stats.cnt,

		   stats.misses);

}

#endif
@@ -3438,6 +3443,7 @@ static int bpf_prog_get_info_by_fd(struct file *file, 
	bpf_prog_get_stats(prog, &stats);

	info.run_time_ns = stats.nsecs;

	info.run_cnt = stats.cnt;

	info.recursion_misses = stats.misses;



	if (!bpf_capable()) {

		info.jited_prog_len = 0;

kernel/bpf/trampoline.c

+16 −2
Original line number Diff line number Diff line
@@ -394,6 +394,16 @@ static u64 notrace bpf_prog_start_time(void) 
	return start;

}



static void notrace inc_misses_counter(struct bpf_prog *prog)

{

	struct bpf_prog_stats *stats;



	stats = this_cpu_ptr(prog->stats);

	u64_stats_update_begin(&stats->syncp);

	stats->misses++;

	u64_stats_update_end(&stats->syncp);

}



/* The logic is similar to BPF_PROG_RUN, but with an explicit

 * rcu_read_lock() and migrate_disable() which are required

 * for the trampoline. The macro is split into
@@ -412,8 +422,10 @@ u64 notrace __bpf_prog_enter(struct bpf_prog *prog) 
{

	rcu_read_lock();

	migrate_disable();

	if (unlikely(__this_cpu_inc_return(*(prog->active)) != 1))

	if (unlikely(__this_cpu_inc_return(*(prog->active)) != 1)) {

		inc_misses_counter(prog);

		return 0;

	}

	return bpf_prog_start_time();

}
@@ -451,8 +463,10 @@ u64 notrace __bpf_prog_enter_sleepable(struct bpf_prog *prog) 
	rcu_read_lock_trace();

	migrate_disable();

	might_fault();

	if (unlikely(__this_cpu_inc_return(*(prog->active)) != 1))

	if (unlikely(__this_cpu_inc_return(*(prog->active)) != 1)) {

		inc_misses_counter(prog);

		return 0;

	}

	return bpf_prog_start_time();

}

tools/bpf/bpftool/prog.c

+4 −0
Original line number Diff line number Diff line
@@ -368,6 +368,8 @@ static void print_prog_header_json(struct bpf_prog_info *info) 
		jsonw_uint_field(json_wtr, "run_time_ns", info->run_time_ns);

		jsonw_uint_field(json_wtr, "run_cnt", info->run_cnt);

	}

	if (info->recursion_misses)

		jsonw_uint_field(json_wtr, "recursion_misses", info->recursion_misses);

}



static void print_prog_json(struct bpf_prog_info *info, int fd)
@@ -446,6 +448,8 @@ static void print_prog_header_plain(struct bpf_prog_info *info) 
	if (info->run_time_ns)

		printf(" run_time_ns %lld run_cnt %lld",

		       info->run_time_ns, info->run_cnt);

	if (info->recursion_misses)

		printf(" recursion_misses %lld", info->recursion_misses);

	printf("\n");

}