Commit 192f5a1f authored by Andrii Nakryiko's avatar Andrii Nakryiko Committed by Alexei Starovoitov

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.
Signed-off-by: default avatarAndrii Nakryiko <andriin@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarJohn Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20200926011357.2366158-4-andriin@fb.com
parent b8604247
......@@ -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;
......
......@@ -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)
......
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