Commit 1f7c3363 authored by Mykyta Yatsenko's avatar Mykyta Yatsenko Committed by Andrii Nakryiko
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selftests/bpf: Increase verifier log limit in veristat 



The current default buffer size of 16MB allocated by veristat is no
longer sufficient to hold the verifier logs of some production BPF
programs. To address this issue, we need to increase the verifier log
limit.
Commit 7a9f5c65 ("bpf: increase verifier log limit") has already
increased the supported buffer size by the kernel, but veristat users
need to explicitly pass a log size argument to use the bigger log.

This patch adds a function to detect the maximum verifier log size
supported by the kernel and uses that by default in veristat.
This ensures that veristat can handle larger verifier logs without
requiring users to manually specify the log size.

Signed-off-by: default avatarMykyta Yatsenko <yatsenko@meta.com>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20241023155314.126255-1-mykyta.yatsenko5@gmail.com
parent efe79219

tools/testing/selftests/bpf/veristat.c

+31 −1
Original line number Diff line number Diff line
@@ -16,6 +16,7 @@ 
#include <sys/stat.h>

#include <bpf/libbpf.h>

#include <bpf/btf.h>

#include <bpf/bpf.h>

#include <libelf.h>

#include <gelf.h>

#include <float.h>
@@ -1109,6 +1110,35 @@ static void fixup_obj(struct bpf_object *obj, struct bpf_program *prog, const ch 
	return;

}



static int max_verifier_log_size(void)

{

	const int SMALL_LOG_SIZE = UINT_MAX >> 8;

	const int BIG_LOG_SIZE = UINT_MAX >> 2;

	struct bpf_insn insns[] = {

		{ .code = BPF_ALU | BPF_MOV | BPF_X, .dst_reg = BPF_REG_0, },

		{ .code  = BPF_JMP | BPF_EXIT, },

	};

	LIBBPF_OPTS(bpf_prog_load_opts, opts,

		    .log_size = BIG_LOG_SIZE,

		    .log_buf = (void *)-1,

		    .log_level = 4

	);

	int ret, insn_cnt = ARRAY_SIZE(insns);

	static int log_size;



	if (log_size != 0)

		return log_size;



	ret = bpf_prog_load(BPF_PROG_TYPE_TRACEPOINT, NULL, "GPL", insns, insn_cnt, &opts);



	if (ret == -EFAULT)

		log_size = BIG_LOG_SIZE;

	else /* ret == -EINVAL, big log size is not supported by the verifier */

		log_size = SMALL_LOG_SIZE;



	return log_size;

}



static int process_prog(const char *filename, struct bpf_object *obj, struct bpf_program *prog)

{

	const char *base_filename = basename(strdupa(filename));
@@ -1132,7 +1162,7 @@ static int process_prog(const char *filename, struct bpf_object *obj, struct bpf 
	memset(stats, 0, sizeof(*stats));



	if (env.verbose || env.top_src_lines > 0) {

		buf_sz = env.log_size ? env.log_size : 16 * 1024 * 1024;

		buf_sz = env.log_size ? env.log_size : max_verifier_log_size();

		buf = malloc(buf_sz);

		if (!buf)

			return -ENOMEM;