On Mon, Oct 21, 2024 at 03:16:16PM +0100, Mykyta Yatsenko wrote:
> From: Mykyta Yatsenko <yatsenko@xxxxxxxx>
>
> 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 7a9f5c65abcc ("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: Mykyta Yatsenko <yatsenko@xxxxxxxx>
> ---
> tools/testing/selftests/bpf/veristat.c | 40 +++++++++++++++++++++++++-
> 1 file changed, 39 insertions(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/bpf/veristat.c b/tools/testing/selftests/bpf/veristat.c
> index c8efd44590d9..1d0708839f4b 100644
> --- a/tools/testing/selftests/bpf/veristat.c
> +++ b/tools/testing/selftests/bpf/veristat.c
> @@ -16,10 +16,12 @@
> #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>
> #include <math.h>
> +#include <linux/filter.h>
>
> #ifndef ARRAY_SIZE
> #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))
> @@ -1109,6 +1111,42 @@ static void fixup_obj(struct bpf_object *obj, struct bpf_program *prog, const ch
> return;
> }
>
> +static int max_verifier_log_size(void)
> +{
> + const int big_log_size = UINT_MAX >> 2;
> + const int small_log_size = UINT_MAX >> 8;
> + struct bpf_insn insns[] = {
> + BPF_MOV64_IMM(BPF_REG_0, 0),
> + BPF_EXIT_INSN(),
> + };
> + int ret, insn_cnt = ARRAY_SIZE(insns);
> + char *log_buf;
> + static int log_size;
> +
> + if (log_size != 0)
> + return log_size;
> +
> + log_size = small_log_size;
> + log_buf = malloc(big_log_size);
IIUC this would try to use 1GB by default? seems to agresive.. could we perhaps
do that gradually and double the size on each failed load attempt?
jirka
> +
> + if (!log_buf)
> + return log_size;
> +
> + LIBBPF_OPTS(bpf_prog_load_opts, opts,
> + .log_buf = log_buf,
> + .log_size = big_log_size,
> + .log_level = 2
> + );
> + ret = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, NULL, "GPL", insns, insn_cnt, &opts);
> + free(log_buf);
> +
> + if (ret > 0) {
> + log_size = big_log_size;
> + close(ret);
> + }
> + 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 +1170,7 @@ 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;
> --
> 2.47.0
>
>
