diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c index 89fecfe5cb2b..fa1b147c63c6 100644 --- a/tools/lib/bpf/btf.c +++ b/tools/lib/bpf/btf.c @@ -90,6 +90,14 @@ struct btf { struct hashmap *strs_hash; /* whether strings are already deduplicated */ bool strs_deduped; + /* extra indirection layer to make strings hashmap work with stable + * string offsets and ability to transparently choose between + * btf->strs_data or btf_dedup->strs_data as a source of strings. + * This is used for BTF strings dedup to transfer deduplicated strings + * data back to struct btf without re-building strings index. + */ + void **strs_data_ptr; + /* BTF object FD, if loaded into kernel */ int fd; @@ -1363,17 +1371,19 @@ int btf__get_map_kv_tids(const struct btf *btf, const char *map_name, static size_t strs_hash_fn(const void *key, void *ctx) { - struct btf *btf = ctx; - const char *str = btf->strs_data + (long)key; + const struct btf *btf = ctx; + const char *strs = *btf->strs_data_ptr; + const char *str = strs + (long)key; return str_hash(str); } static bool strs_hash_equal_fn(const void *key1, const void *key2, void *ctx) { - struct btf *btf = ctx; - const char *str1 = btf->strs_data + (long)key1; - const char *str2 = btf->strs_data + (long)key2; + const struct btf *btf = ctx; + const char *strs = *btf->strs_data_ptr; + const char *str1 = strs + (long)key1; + const char *str2 = strs + (long)key2; return strcmp(str1, str2) == 0; } @@ -1418,6 +1428,9 @@ static int btf_ensure_modifiable(struct btf *btf) memcpy(types, btf->types_data, btf->hdr->type_len); memcpy(strs, btf->strs_data, btf->hdr->str_len); + /* make hashmap below use btf->strs_data as a source of strings */ + btf->strs_data_ptr = &btf->strs_data; + /* build lookup index for all strings */ hash = hashmap__new(strs_hash_fn, strs_hash_equal_fn, btf); if (IS_ERR(hash)) { @@ -2824,19 +2837,11 @@ struct btf_dedup { size_t hypot_cap; /* Various option modifying behavior of algorithm */ struct btf_dedup_opts opts; -}; - -struct btf_str_ptr { - const char *str; - __u32 new_off; - bool used; -}; - -struct btf_str_ptrs { - struct btf_str_ptr *ptrs; - const char *data; - __u32 cnt; - __u32 cap; + /* temporary strings deduplication state */ + void *strs_data; + size_t strs_cap; + size_t strs_len; + struct hashmap* strs_hash; }; static long hash_combine(long h, long value) @@ -3063,64 +3068,41 @@ static int btf_for_each_str_off(struct btf_dedup *d, str_off_fn_t fn, void *ctx) return 0; } -static int str_sort_by_content(const void *a1, const void *a2) +static int strs_dedup_remap_str_off(__u32 *str_off_ptr, void *ctx) { - const struct btf_str_ptr *p1 = a1; - const struct btf_str_ptr *p2 = a2; - - return strcmp(p1->str, p2->str); -} - -static int str_sort_by_offset(const void *a1, const void *a2) -{ - const struct btf_str_ptr *p1 = a1; - const struct btf_str_ptr *p2 = a2; - - if (p1->str != p2->str) - return p1->str < p2->str ? -1 : 1; - return 0; -} - -static int btf_dedup_str_ptr_cmp(const void *str_ptr, const void *pelem) -{ - const struct btf_str_ptr *p = pelem; - - if (str_ptr != p->str) - return (const char *)str_ptr < p->str ? -1 : 1; - return 0; -} - -static int btf_str_mark_as_used(__u32 *str_off_ptr, void *ctx) -{ - struct btf_str_ptrs *strs; - struct btf_str_ptr *s; + struct btf_dedup *d = ctx; + long old_off, new_off, len; + const char *s; + void *p; + int err; if (*str_off_ptr == 0) return 0; - strs = ctx; - s = bsearch(strs->data + *str_off_ptr, strs->ptrs, strs->cnt, - sizeof(struct btf_str_ptr), btf_dedup_str_ptr_cmp); - if (!s) - return -EINVAL; - s->used = true; - return 0; -} + s = btf__str_by_offset(d->btf, *str_off_ptr); + len = strlen(s) + 1; -static int btf_str_remap_offset(__u32 *str_off_ptr, void *ctx) -{ - struct btf_str_ptrs *strs; - struct btf_str_ptr *s; + new_off = d->strs_len; + p = btf_add_mem(&d->strs_data, &d->strs_cap, 1, new_off, BTF_MAX_STR_OFFSET, len); + if (!p) + return -ENOMEM; - if (*str_off_ptr == 0) - return 0; + memcpy(p, s, len); - strs = ctx; - s = bsearch(strs->data + *str_off_ptr, strs->ptrs, strs->cnt, - sizeof(struct btf_str_ptr), btf_dedup_str_ptr_cmp); - if (!s) - return -EINVAL; - *str_off_ptr = s->new_off; + /* Now attempt to add the string, but only if the string with the same + * contents doesn't exist already (HASHMAP_ADD strategy). If such + * string exists, we'll get its offset in old_off (that's old_key). + */ + err = hashmap__insert(d->strs_hash, (void *)new_off, (void *)new_off, + HASHMAP_ADD, (const void **)&old_off, NULL); + if (err == -EEXIST) { + *str_off_ptr = old_off; + } else if (err) { + return err; + } else { + *str_off_ptr = new_off; + d->strs_len += len; + } return 0; } @@ -3137,118 +3119,69 @@ static int btf_str_remap_offset(__u32 *str_off_ptr, void *ctx) */ static int btf_dedup_strings(struct btf_dedup *d) { - char *start = d->btf->strs_data; - char *end = start + d->btf->hdr->str_len; - char *p = start, *tmp_strs = NULL; - struct btf_str_ptrs strs = { - .cnt = 0, - .cap = 0, - .ptrs = NULL, - .data = start, - }; - int i, j, err = 0, grp_idx; - bool grp_used; + char *s; + int err; if (d->btf->strs_deduped) return 0; - /* build index of all strings */ - while (p < end) { - if (strs.cnt + 1 > strs.cap) { - struct btf_str_ptr *new_ptrs; + s = btf_add_mem(&d->strs_data, &d->strs_cap, 1, d->strs_len, BTF_MAX_STR_OFFSET, 1); + if (!s) + return -ENOMEM; + /* initial empty string */ + s[0] = 0; + d->strs_len = 1; - strs.cap += max(strs.cnt / 2, 16U); - new_ptrs = libbpf_reallocarray(strs.ptrs, strs.cap, sizeof(strs.ptrs[0])); - if (!new_ptrs) { - err = -ENOMEM; - goto done; - } - strs.ptrs = new_ptrs; - } - - strs.ptrs[strs.cnt].str = p; - strs.ptrs[strs.cnt].used = false; - - p += strlen(p) + 1; - strs.cnt++; - } - - /* temporary storage for deduplicated strings */ - tmp_strs = malloc(d->btf->hdr->str_len); - if (!tmp_strs) { - err = -ENOMEM; - goto done; - } - - /* mark all used strings */ - strs.ptrs[0].used = true; - err = btf_for_each_str_off(d, btf_str_mark_as_used, &strs); - if (err) - goto done; - - /* sort strings by context, so that we can identify duplicates */ - qsort(strs.ptrs, strs.cnt, sizeof(strs.ptrs[0]), str_sort_by_content); - - /* - * iterate groups of equal strings and if any instance in a group was - * referenced, emit single instance and remember new offset + /* temporarily switch to use btf_dedup's strs_data for strings for hash + * functions; later we'll just transfer hashmap to struct btf as is, + * along the strs_data */ - p = tmp_strs; - grp_idx = 0; - grp_used = strs.ptrs[0].used; - /* iterate past end to avoid code duplication after loop */ - for (i = 1; i <= strs.cnt; i++) { - /* - * when i == strs.cnt, we want to skip string comparison and go - * straight to handling last group of strings (otherwise we'd - * need to handle last group after the loop w/ duplicated code) - */ - if (i < strs.cnt && - !strcmp(strs.ptrs[i].str, strs.ptrs[grp_idx].str)) { - grp_used = grp_used || strs.ptrs[i].used; - continue; - } + d->btf->strs_data_ptr = &d->strs_data; - /* - * this check would have been required after the loop to handle - * last group of strings, but due to <= condition in a loop - * we avoid that duplication - */ - if (grp_used) { - int new_off = p - tmp_strs; - __u32 len = strlen(strs.ptrs[grp_idx].str); - - memmove(p, strs.ptrs[grp_idx].str, len + 1); - for (j = grp_idx; j < i; j++) - strs.ptrs[j].new_off = new_off; - p += len + 1; - } - - if (i < strs.cnt) { - grp_idx = i; - grp_used = strs.ptrs[i].used; - } + d->strs_hash = hashmap__new(strs_hash_fn, strs_hash_equal_fn, d->btf); + if (IS_ERR(d->strs_hash)) { + err = PTR_ERR(d->strs_hash); + d->strs_hash = NULL; + goto err_out; } - /* replace original strings with deduped ones */ - d->btf->hdr->str_len = p - tmp_strs; - memmove(start, tmp_strs, d->btf->hdr->str_len); - end = start + d->btf->hdr->str_len; - - /* restore original order for further binary search lookups */ - qsort(strs.ptrs, strs.cnt, sizeof(strs.ptrs[0]), str_sort_by_offset); + /* insert empty string; we won't be looking it up during strings + * dedup, but it's good to have it for generic BTF string lookups + */ + err = hashmap__insert(d->strs_hash, (void *)0, (void *)0, + HASHMAP_ADD, NULL, NULL); + if (err) + goto err_out; /* remap string offsets */ - err = btf_for_each_str_off(d, btf_str_remap_offset, &strs); + err = btf_for_each_str_off(d, strs_dedup_remap_str_off, d); if (err) - goto done; + goto err_out; - d->btf->hdr->str_len = end - start; + /* replace BTF string data and hash with deduped ones */ + free(d->btf->strs_data); + hashmap__free(d->btf->strs_hash); + d->btf->strs_data = d->strs_data; + d->btf->strs_data_cap = d->strs_cap; + d->btf->hdr->str_len = d->strs_len; + d->btf->strs_hash = d->strs_hash; + /* now point strs_data_ptr back to btf->strs_data */ + d->btf->strs_data_ptr = &d->btf->strs_data; + + d->strs_data = d->strs_hash = NULL; + d->strs_len = d->strs_cap = 0; d->btf->strs_deduped = true; + return 0; + +err_out: + free(d->strs_data); + hashmap__free(d->strs_hash); + d->strs_data = d->strs_hash = NULL; + d->strs_len = d->strs_cap = 0; + + /* restore strings pointer for existing d->btf->strs_hash back */ + d->btf->strs_data_ptr = &d->strs_data; -done: - free(tmp_strs); - free(strs.ptrs); return err; }