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Message-ID: <20200926011357.2366158-4-andriin@fb.com>
Date: Fri, 25 Sep 2020 18:13:51 -0700
From: Andrii Nakryiko <andriin@...com>
To: <bpf@...r.kernel.org>, <netdev@...r.kernel.org>, <ast@...com>,
<daniel@...earbox.net>
CC: <andrii.nakryiko@...il.com>, <kernel-team@...com>,
Andrii Nakryiko <andriin@...com>,
Arnaldo Carvalho de Melo <acme@...hat.com>,
John Fastabend <john.fastabend@...il.com>
Subject: [PATCH v2 bpf-next 3/9] libbpf: generalize common logic for managing dynamically-sized arrays
Managing dynamically-sized array is a common, but not trivial functionality,
which significant amount of logic and code to implement properly. So instead
of re-implementing it all the time, extract it into a helper function ans
reuse.
Acked-by: John Fastabend <john.fastabend@...il.com>
Signed-off-by: Andrii Nakryiko <andriin@...com>
---
tools/lib/bpf/btf.c | 77 ++++++++++++++++++++++++---------
tools/lib/bpf/libbpf_internal.h | 3 ++
2 files changed, 59 insertions(+), 21 deletions(-)
diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index d180a677a3fb..f5255e2bd222 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -51,7 +51,7 @@ struct btf {
/* type ID to `struct btf_type *` lookup index */
__u32 *type_offs;
- __u32 type_offs_cap;
+ size_t type_offs_cap;
__u32 nr_types;
/* BTF object FD, if loaded into kernel */
@@ -66,31 +66,60 @@ static inline __u64 ptr_to_u64(const void *ptr)
return (__u64) (unsigned long) ptr;
}
-static int btf_add_type_idx_entry(struct btf *btf, __u32 type_off)
+/* Ensure given dynamically allocated memory region pointed to by *data* with
+ * capacity of *cap_cnt* elements each taking *elem_sz* bytes has enough
+ * memory to accomodate *add_cnt* new elements, assuming *cur_cnt* elements
+ * are already used. At most *max_cnt* elements can be ever allocated.
+ * If necessary, memory is reallocated and all existing data is copied over,
+ * new pointer to the memory region is stored at *data, new memory region
+ * capacity (in number of elements) is stored in *cap.
+ * On success, memory pointer to the beginning of unused memory is returned.
+ * On error, NULL is returned.
+ */
+void *btf_add_mem(void **data, size_t *cap_cnt, size_t elem_sz,
+ size_t cur_cnt, size_t max_cnt, size_t add_cnt)
{
- /* nr_types is 1-based, so N types means we need N+1-sized array */
- if (btf->nr_types + 2 > btf->type_offs_cap) {
- __u32 *new_offs;
- __u32 expand_by, new_size;
+ size_t new_cnt;
+ void *new_data;
- if (btf->type_offs_cap == BTF_MAX_NR_TYPES)
- return -E2BIG;
+ if (cur_cnt + add_cnt <= *cap_cnt)
+ return *data + cur_cnt * elem_sz;
- expand_by = max(btf->type_offs_cap / 4, 16U);
- new_size = min(BTF_MAX_NR_TYPES, btf->type_offs_cap + expand_by);
+ /* requested more than the set limit */
+ if (cur_cnt + add_cnt > max_cnt)
+ return NULL;
- new_offs = libbpf_reallocarray(btf->type_offs, new_size, sizeof(*new_offs));
- if (!new_offs)
- return -ENOMEM;
+ new_cnt = *cap_cnt;
+ new_cnt += new_cnt / 4; /* expand by 25% */
+ if (new_cnt < 16) /* but at least 16 elements */
+ new_cnt = 16;
+ if (new_cnt > max_cnt) /* but not exceeding a set limit */
+ new_cnt = max_cnt;
+ if (new_cnt < cur_cnt + add_cnt) /* also ensure we have enough memory */
+ new_cnt = cur_cnt + add_cnt;
+
+ new_data = libbpf_reallocarray(*data, new_cnt, elem_sz);
+ if (!new_data)
+ return NULL;
- new_offs[0] = UINT_MAX; /* VOID is specially handled */
+ /* zero out newly allocated portion of memory */
+ memset(new_data + (*cap_cnt) * elem_sz, 0, (new_cnt - *cap_cnt) * elem_sz);
- btf->type_offs = new_offs;
- btf->type_offs_cap = new_size;
- }
+ *data = new_data;
+ *cap_cnt = new_cnt;
+ return new_data + cur_cnt * elem_sz;
+}
- btf->type_offs[btf->nr_types + 1] = type_off;
+static int btf_add_type_idx_entry(struct btf *btf, __u32 type_off)
+{
+ __u32 *p;
+
+ p = btf_add_mem((void **)&btf->type_offs, &btf->type_offs_cap, sizeof(__u32),
+ btf->nr_types + 1, BTF_MAX_NR_TYPES, 1);
+ if (!p)
+ return -ENOMEM;
+ *p = type_off;
return 0;
}
@@ -203,11 +232,17 @@ static int btf_parse_type_sec(struct btf *btf)
struct btf_header *hdr = btf->hdr;
void *next_type = btf->types_data;
void *end_type = next_type + hdr->type_len;
+ int err, type_size;
- while (next_type < end_type) {
- int type_size;
- int err;
+ /* VOID (type_id == 0) is specially handled by btf__get_type_by_id(),
+ * so ensure we can never properly use its offset from index by
+ * setting it to a large value
+ */
+ err = btf_add_type_idx_entry(btf, UINT_MAX);
+ if (err)
+ return err;
+ while (next_type < end_type) {
err = btf_add_type_idx_entry(btf, next_type - btf->types_data);
if (err)
return err;
diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index 4d1c366fca2c..d43ce00e0022 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -105,6 +105,9 @@ static inline void *libbpf_reallocarray(void *ptr, size_t nmemb, size_t size)
return realloc(ptr, total);
}
+void *btf_add_mem(void **data, size_t *cap_cnt, size_t elem_sz,
+ size_t cur_cnt, size_t max_cnt, size_t add_cnt);
+
static inline bool libbpf_validate_opts(const char *opts,
size_t opts_sz, size_t user_sz,
const char *type_name)
--
2.24.1
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