[PATCH bpf-next] libbpf: don't allocate 16M for log buffer by default
From: Stanislav Fomichev <hidden>
Date: 2020-03-24 23:31:52
Also in:
bpf
Subsystem:
bpf [general] (safe dynamic programs and tools), bpf [library] (libbpf), the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Linus Torvalds
For each prog/btf load we allocate and free 16 megs of verifier buffer. On production systems it doesn't really make sense because the programs/btf have gone through extensive testing and (mostly) guaranteed to successfully load. Let's switch to a much smaller buffer by default (128 bytes, sys_bpf doesn't accept smaller log buffer) and resize it if the kernel returns ENOSPC. On the first ENOSPC error we resize the buffer to BPF_LOG_BUF_SIZE and then, on each subsequent ENOSPC, we keep doubling the buffer. Signed-off-by: Stanislav Fomichev <redacted> --- tools/lib/bpf/btf.c | 10 +++++++++- tools/lib/bpf/libbpf.c | 10 ++++++++-- tools/lib/bpf/libbpf_internal.h | 2 ++ 3 files changed, 19 insertions(+), 3 deletions(-)
diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 3d1c25fc97ae..53c7efc3b347 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c@@ -657,13 +657,14 @@ int btf__finalize_data(struct bpf_object *obj, struct btf *btf) int btf__load(struct btf *btf) { - __u32 log_buf_size = BPF_LOG_BUF_SIZE; + __u32 log_buf_size = BPF_MIN_LOG_BUF_SIZE; char *log_buf = NULL; int err = 0; if (btf->fd >= 0) return -EEXIST; +retry_load: log_buf = malloc(log_buf_size); if (!log_buf) return -ENOMEM;
@@ -673,6 +674,13 @@ int btf__load(struct btf *btf) btf->fd = bpf_load_btf(btf->data, btf->data_size, log_buf, log_buf_size, false); if (btf->fd < 0) { + if (errno == ENOSPC) { + log_buf_size = max((__u32)BPF_LOG_BUF_SIZE, + log_buf_size << 1); + free(log_buf); + goto retry_load; + } + err = -errno; pr_warn("Error loading BTF: %s(%d)\n", strerror(errno), errno); if (*log_buf)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 085e41f9b68e..793c81b35ccc 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c@@ -4855,7 +4855,7 @@ load_program(struct bpf_program *prog, struct bpf_insn *insns, int insns_cnt, { struct bpf_load_program_attr load_attr; char *cp, errmsg[STRERR_BUFSIZE]; - int log_buf_size = BPF_LOG_BUF_SIZE; + size_t log_buf_size = BPF_MIN_LOG_BUF_SIZE; char *log_buf; int btf_fd, ret;
@@ -4911,7 +4911,13 @@ load_program(struct bpf_program *prog, struct bpf_insn *insns, int insns_cnt, } if (errno == ENOSPC) { - log_buf_size <<= 1; + if (errno == ENOSPC) { + log_buf_size = max((size_t)BPF_LOG_BUF_SIZE, + log_buf_size << 1); + free(log_buf); + goto retry_load; + } + free(log_buf); goto retry_load; }
diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index 8c3afbd97747..2720f3366798 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h@@ -23,6 +23,8 @@ #define BTF_PARAM_ENC(name, type) (name), (type) #define BTF_VAR_SECINFO_ENC(type, offset, size) (type), (offset), (size) +#define BPF_MIN_LOG_BUF_SIZE 128 + #ifndef min # define min(x, y) ((x) < (y) ? (x) : (y)) #endif
--
2.25.1.696.g5e7596f4ac-goog