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libbpf: Extract internal set-of-strings datastructure APIs
Extract BTF logic for maintaining a set of strings data structure, used for BTF strings section construction in writable mode, into separate re-usable API. This data structure is going to be used by bpf_linker to maintains ELF STRTAB section, which has the same layout as BTF strings section. Suggested-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20210318194036.3521577-5-andrii@kernel.org
This commit is contained in:
Andrii Nakryiko
Alexei Starovoitov
parent
3b029e06f6
commit
90d76d3ece
4 changed files with 259 additions and 195 deletions
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@ -1,3 +1,3 @@
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libbpf-y := libbpf.o bpf.o nlattr.o btf.o libbpf_errno.o str_error.o \
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netlink.o bpf_prog_linfo.o libbpf_probes.o xsk.o hashmap.o \
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btf_dump.o ringbuf.o
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btf_dump.o ringbuf.o strset.o
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@ -21,6 +21,7 @@
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#include "libbpf.h"
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#include "libbpf_internal.h"
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#include "hashmap.h"
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#include "strset.h"
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#define BTF_MAX_NR_TYPES 0x7fffffffU
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#define BTF_MAX_STR_OFFSET 0x7fffffffU
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@ -67,7 +68,7 @@ struct btf {
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* | | |
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* hdr | |
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* types_data----+ |
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* strs_data------------------+
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* strset__data(strs_set)-----+
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*
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* +----------+---------+-----------+
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* | Header | Types | Strings |
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@ -105,20 +106,15 @@ struct btf {
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*/
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int start_str_off;
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/* only one of strs_data or strs_set can be non-NULL, depending on
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* whether BTF is in a modifiable state (strs_set is used) or not
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* (strs_data points inside raw_data)
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*/
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void *strs_data;
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size_t strs_data_cap; /* used size stored in hdr->str_len */
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/* lookup index for each unique string in strings section */
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struct hashmap *strs_hash;
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/* a set of unique strings */
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struct strset *strs_set;
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/* whether strings are already deduplicated */
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bool strs_deduped;
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/* extra indirection layer to make strings hashmap work with stable
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* string offsets and ability to transparently choose between
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* btf->strs_data or btf_dedup->strs_data as a source of strings.
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* This is used for BTF strings dedup to transfer deduplicated strings
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* data back to struct btf without re-building strings index.
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*/
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void **strs_data_ptr;
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/* BTF object FD, if loaded into kernel */
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int fd;
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@ -738,7 +734,7 @@ void btf__free(struct btf *btf)
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*/
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free(btf->hdr);
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free(btf->types_data);
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free(btf->strs_data);
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strset__free(btf->strs_set);
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}
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free(btf->raw_data);
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free(btf->raw_data_swapped);
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@ -1246,6 +1242,11 @@ void btf__set_fd(struct btf *btf, int fd)
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btf->fd = fd;
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}
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static const void *btf_strs_data(const struct btf *btf)
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{
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return btf->strs_data ? btf->strs_data : strset__data(btf->strs_set);
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}
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static void *btf_get_raw_data(const struct btf *btf, __u32 *size, bool swap_endian)
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{
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struct btf_header *hdr = btf->hdr;
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@ -1286,7 +1287,7 @@ static void *btf_get_raw_data(const struct btf *btf, __u32 *size, bool swap_endi
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}
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p += hdr->type_len;
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memcpy(p, btf->strs_data, hdr->str_len);
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memcpy(p, btf_strs_data(btf), hdr->str_len);
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p += hdr->str_len;
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*size = data_sz;
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@ -1320,7 +1321,7 @@ const char *btf__str_by_offset(const struct btf *btf, __u32 offset)
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if (offset < btf->start_str_off)
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return btf__str_by_offset(btf->base_btf, offset);
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else if (offset - btf->start_str_off < btf->hdr->str_len)
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return btf->strs_data + (offset - btf->start_str_off);
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return btf_strs_data(btf) + (offset - btf->start_str_off);
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else
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return NULL;
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}
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@ -1474,25 +1475,6 @@ int btf__get_map_kv_tids(const struct btf *btf, const char *map_name,
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return 0;
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}
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static size_t strs_hash_fn(const void *key, void *ctx)
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{
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const struct btf *btf = ctx;
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const char *strs = *btf->strs_data_ptr;
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const char *str = strs + (long)key;
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return str_hash(str);
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}
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static bool strs_hash_equal_fn(const void *key1, const void *key2, void *ctx)
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{
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const struct btf *btf = ctx;
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const char *strs = *btf->strs_data_ptr;
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const char *str1 = strs + (long)key1;
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const char *str2 = strs + (long)key2;
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return strcmp(str1, str2) == 0;
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}
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static void btf_invalidate_raw_data(struct btf *btf)
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{
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if (btf->raw_data) {
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@ -1511,10 +1493,9 @@ static void btf_invalidate_raw_data(struct btf *btf)
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*/
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static int btf_ensure_modifiable(struct btf *btf)
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{
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void *hdr, *types, *strs, *strs_end, *s;
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struct hashmap *hash = NULL;
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long off;
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int err;
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void *hdr, *types;
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struct strset *set = NULL;
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int err = -ENOMEM;
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if (btf_is_modifiable(btf)) {
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/* any BTF modification invalidates raw_data */
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@ -1525,44 +1506,25 @@ static int btf_ensure_modifiable(struct btf *btf)
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/* split raw data into three memory regions */
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hdr = malloc(btf->hdr->hdr_len);
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types = malloc(btf->hdr->type_len);
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strs = malloc(btf->hdr->str_len);
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if (!hdr || !types || !strs)
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if (!hdr || !types)
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goto err_out;
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memcpy(hdr, btf->hdr, btf->hdr->hdr_len);
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memcpy(types, btf->types_data, btf->hdr->type_len);
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memcpy(strs, btf->strs_data, btf->hdr->str_len);
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/* make hashmap below use btf->strs_data as a source of strings */
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btf->strs_data_ptr = &btf->strs_data;
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/* build lookup index for all strings */
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hash = hashmap__new(strs_hash_fn, strs_hash_equal_fn, btf);
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if (IS_ERR(hash)) {
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err = PTR_ERR(hash);
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hash = NULL;
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set = strset__new(BTF_MAX_STR_OFFSET, btf->strs_data, btf->hdr->str_len);
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if (IS_ERR(set)) {
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err = PTR_ERR(set);
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goto err_out;
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}
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strs_end = strs + btf->hdr->str_len;
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for (off = 0, s = strs; s < strs_end; off += strlen(s) + 1, s = strs + off) {
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/* hashmap__add() returns EEXIST if string with the same
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* content already is in the hash map
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*/
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err = hashmap__add(hash, (void *)off, (void *)off);
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if (err == -EEXIST)
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continue; /* duplicate */
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if (err)
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goto err_out;
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}
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/* only when everything was successful, update internal state */
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btf->hdr = hdr;
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btf->types_data = types;
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btf->types_data_cap = btf->hdr->type_len;
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btf->strs_data = strs;
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btf->strs_data_cap = btf->hdr->str_len;
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btf->strs_hash = hash;
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btf->strs_data = NULL;
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btf->strs_set = set;
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/* if BTF was created from scratch, all strings are guaranteed to be
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* unique and deduplicated
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*/
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@ -1577,17 +1539,10 @@ static int btf_ensure_modifiable(struct btf *btf)
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return 0;
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err_out:
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hashmap__free(hash);
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strset__free(set);
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free(hdr);
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free(types);
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free(strs);
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return -ENOMEM;
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}
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static void *btf_add_str_mem(struct btf *btf, size_t add_sz)
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{
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return libbpf_add_mem(&btf->strs_data, &btf->strs_data_cap, 1,
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btf->hdr->str_len, BTF_MAX_STR_OFFSET, add_sz);
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return err;
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}
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/* Find an offset in BTF string section that corresponds to a given string *s*.
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@ -1598,34 +1553,23 @@ static void *btf_add_str_mem(struct btf *btf, size_t add_sz)
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*/
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int btf__find_str(struct btf *btf, const char *s)
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{
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long old_off, new_off, len;
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void *p;
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int off;
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if (btf->base_btf) {
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int ret;
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ret = btf__find_str(btf->base_btf, s);
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if (ret != -ENOENT)
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return ret;
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off = btf__find_str(btf->base_btf, s);
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if (off != -ENOENT)
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return off;
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}
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/* BTF needs to be in a modifiable state to build string lookup index */
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if (btf_ensure_modifiable(btf))
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return -ENOMEM;
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/* see btf__add_str() for why we do this */
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len = strlen(s) + 1;
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p = btf_add_str_mem(btf, len);
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if (!p)
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return -ENOMEM;
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off = strset__find_str(btf->strs_set, s);
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if (off < 0)
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return off;
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new_off = btf->hdr->str_len;
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memcpy(p, s, len);
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if (hashmap__find(btf->strs_hash, (void *)new_off, (void **)&old_off))
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return btf->start_str_off + old_off;
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return -ENOENT;
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return btf->start_str_off + off;
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}
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/* Add a string s to the BTF string section.
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@ -1635,50 +1579,24 @@ int btf__find_str(struct btf *btf, const char *s)
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*/
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int btf__add_str(struct btf *btf, const char *s)
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{
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long old_off, new_off, len;
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void *p;
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int err;
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int off;
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if (btf->base_btf) {
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int ret;
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ret = btf__find_str(btf->base_btf, s);
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if (ret != -ENOENT)
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return ret;
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off = btf__find_str(btf->base_btf, s);
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if (off != -ENOENT)
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return off;
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}
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if (btf_ensure_modifiable(btf))
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return -ENOMEM;
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/* Hashmap keys are always offsets within btf->strs_data, so to even
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* look up some string from the "outside", we need to first append it
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* at the end, so that it can be addressed with an offset. Luckily,
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* until btf->hdr->str_len is incremented, that string is just a piece
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* of garbage for the rest of BTF code, so no harm, no foul. On the
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* other hand, if the string is unique, it's already appended and
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* ready to be used, only a simple btf->hdr->str_len increment away.
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*/
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len = strlen(s) + 1;
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p = btf_add_str_mem(btf, len);
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if (!p)
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return -ENOMEM;
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off = strset__add_str(btf->strs_set, s);
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if (off < 0)
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return off;
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new_off = btf->hdr->str_len;
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memcpy(p, s, len);
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btf->hdr->str_len = strset__data_size(btf->strs_set);
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/* Now attempt to add the string, but only if the string with the same
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* contents doesn't exist already (HASHMAP_ADD strategy). If such
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* string exists, we'll get its offset in old_off (that's old_key).
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*/
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err = hashmap__insert(btf->strs_hash, (void *)new_off, (void *)new_off,
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HASHMAP_ADD, (const void **)&old_off, NULL);
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if (err == -EEXIST)
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return btf->start_str_off + old_off; /* duplicated string, return existing offset */
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if (err)
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return err;
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btf->hdr->str_len += len; /* new unique string, adjust data length */
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return btf->start_str_off + new_off;
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return btf->start_str_off + off;
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}
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static void *btf_add_type_mem(struct btf *btf, size_t add_sz)
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@ -3016,10 +2934,7 @@ struct btf_dedup {
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/* Various option modifying behavior of algorithm */
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struct btf_dedup_opts opts;
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/* temporary strings deduplication state */
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void *strs_data;
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size_t strs_cap;
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size_t strs_len;
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struct hashmap* strs_hash;
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struct strset *strs_set;
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};
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static long hash_combine(long h, long value)
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@ -3185,10 +3100,8 @@ static int strs_dedup_remap_str_off(__u32 *str_off_ptr, void *ctx)
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{
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struct btf_dedup *d = ctx;
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__u32 str_off = *str_off_ptr;
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long old_off, new_off, len;
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const char *s;
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void *p;
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int err;
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int off, err;
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/* don't touch empty string or string in main BTF */
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if (str_off == 0 || str_off < d->btf->start_str_off)
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@ -3205,29 +3118,11 @@ static int strs_dedup_remap_str_off(__u32 *str_off_ptr, void *ctx)
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return err;
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}
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len = strlen(s) + 1;
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off = strset__add_str(d->strs_set, s);
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if (off < 0)
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return off;
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new_off = d->strs_len;
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p = libbpf_add_mem(&d->strs_data, &d->strs_cap, 1, new_off, BTF_MAX_STR_OFFSET, len);
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if (!p)
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return -ENOMEM;
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memcpy(p, s, len);
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/* Now attempt to add the string, but only if the string with the same
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* contents doesn't exist already (HASHMAP_ADD strategy). If such
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* string exists, we'll get its offset in old_off (that's old_key).
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*/
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err = hashmap__insert(d->strs_hash, (void *)new_off, (void *)new_off,
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HASHMAP_ADD, (const void **)&old_off, NULL);
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if (err == -EEXIST) {
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*str_off_ptr = d->btf->start_str_off + old_off;
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} else if (err) {
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return err;
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} else {
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*str_off_ptr = d->btf->start_str_off + new_off;
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d->strs_len += len;
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}
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*str_off_ptr = d->btf->start_str_off + off;
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return 0;
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}
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@ -3244,39 +3139,23 @@ static int strs_dedup_remap_str_off(__u32 *str_off_ptr, void *ctx)
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*/
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static int btf_dedup_strings(struct btf_dedup *d)
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{
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char *s;
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int err;
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if (d->btf->strs_deduped)
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return 0;
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/* temporarily switch to use btf_dedup's strs_data for strings for hash
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* functions; later we'll just transfer hashmap to struct btf as is,
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* along the strs_data
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*/
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d->btf->strs_data_ptr = &d->strs_data;
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d->strs_hash = hashmap__new(strs_hash_fn, strs_hash_equal_fn, d->btf);
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if (IS_ERR(d->strs_hash)) {
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err = PTR_ERR(d->strs_hash);
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d->strs_hash = NULL;
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d->strs_set = strset__new(BTF_MAX_STR_OFFSET, NULL, 0);
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if (IS_ERR(d->strs_set)) {
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err = PTR_ERR(d->strs_set);
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goto err_out;
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}
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if (!d->btf->base_btf) {
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s = libbpf_add_mem(&d->strs_data, &d->strs_cap, 1, d->strs_len, BTF_MAX_STR_OFFSET, 1);
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if (!s)
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return -ENOMEM;
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/* initial empty string */
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s[0] = 0;
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d->strs_len = 1;
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/* insert empty string; we won't be looking it up during strings
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* dedup, but it's good to have it for generic BTF string lookups
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*/
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err = hashmap__insert(d->strs_hash, (void *)0, (void *)0,
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HASHMAP_ADD, NULL, NULL);
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if (err)
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err = strset__add_str(d->strs_set, "");
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if (err < 0)
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goto err_out;
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}
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@ -3286,28 +3165,16 @@ static int btf_dedup_strings(struct btf_dedup *d)
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goto err_out;
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/* replace BTF string data and hash with deduped ones */
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free(d->btf->strs_data);
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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;
|
||||
strset__free(d->btf->strs_set);
|
||||
d->btf->hdr->str_len = strset__data_size(d->strs_set);
|
||||
d->btf->strs_set = d->strs_set;
|
||||
d->strs_set = NULL;
|
||||
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;
|
||||
strset__free(d->strs_set);
|
||||
d->strs_set = NULL;
|
||||
|
||||
return err;
|
||||
}
|
||||
|
|
|
|||
176
tools/lib/bpf/strset.c
Normal file
176
tools/lib/bpf/strset.c
Normal file
|
|
@ -0,0 +1,176 @@
|
|||
// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
|
||||
/* Copyright (c) 2021 Facebook */
|
||||
#include <stdint.h>
|
||||
#include <stdlib.h>
|
||||
#include <stdio.h>
|
||||
#include <errno.h>
|
||||
#include <linux/err.h>
|
||||
#include "hashmap.h"
|
||||
#include "libbpf_internal.h"
|
||||
#include "strset.h"
|
||||
|
||||
struct strset {
|
||||
void *strs_data;
|
||||
size_t strs_data_len;
|
||||
size_t strs_data_cap;
|
||||
size_t strs_data_max_len;
|
||||
|
||||
/* lookup index for each unique string in strings set */
|
||||
struct hashmap *strs_hash;
|
||||
};
|
||||
|
||||
static size_t strset_hash_fn(const void *key, void *ctx)
|
||||
{
|
||||
const struct strset *s = ctx;
|
||||
const char *str = s->strs_data + (long)key;
|
||||
|
||||
return str_hash(str);
|
||||
}
|
||||
|
||||
static bool strset_equal_fn(const void *key1, const void *key2, void *ctx)
|
||||
{
|
||||
const struct strset *s = ctx;
|
||||
const char *str1 = s->strs_data + (long)key1;
|
||||
const char *str2 = s->strs_data + (long)key2;
|
||||
|
||||
return strcmp(str1, str2) == 0;
|
||||
}
|
||||
|
||||
struct strset *strset__new(size_t max_data_sz, const char *init_data, size_t init_data_sz)
|
||||
{
|
||||
struct strset *set = calloc(1, sizeof(*set));
|
||||
struct hashmap *hash;
|
||||
int err = -ENOMEM;
|
||||
|
||||
if (!set)
|
||||
return ERR_PTR(-ENOMEM);
|
||||
|
||||
hash = hashmap__new(strset_hash_fn, strset_equal_fn, set);
|
||||
if (IS_ERR(hash))
|
||||
goto err_out;
|
||||
|
||||
set->strs_data_max_len = max_data_sz;
|
||||
set->strs_hash = hash;
|
||||
|
||||
if (init_data) {
|
||||
long off;
|
||||
|
||||
set->strs_data = malloc(init_data_sz);
|
||||
if (!set->strs_data)
|
||||
goto err_out;
|
||||
|
||||
memcpy(set->strs_data, init_data, init_data_sz);
|
||||
set->strs_data_len = init_data_sz;
|
||||
set->strs_data_cap = init_data_sz;
|
||||
|
||||
for (off = 0; off < set->strs_data_len; off += strlen(set->strs_data + off) + 1) {
|
||||
/* hashmap__add() returns EEXIST if string with the same
|
||||
* content already is in the hash map
|
||||
*/
|
||||
err = hashmap__add(hash, (void *)off, (void *)off);
|
||||
if (err == -EEXIST)
|
||||
continue; /* duplicate */
|
||||
if (err)
|
||||
goto err_out;
|
||||
}
|
||||
}
|
||||
|
||||
return set;
|
||||
err_out:
|
||||
strset__free(set);
|
||||
return ERR_PTR(err);
|
||||
}
|
||||
|
||||
void strset__free(struct strset *set)
|
||||
{
|
||||
if (IS_ERR_OR_NULL(set))
|
||||
return;
|
||||
|
||||
hashmap__free(set->strs_hash);
|
||||
free(set->strs_data);
|
||||
}
|
||||
|
||||
size_t strset__data_size(const struct strset *set)
|
||||
{
|
||||
return set->strs_data_len;
|
||||
}
|
||||
|
||||
const char *strset__data(const struct strset *set)
|
||||
{
|
||||
return set->strs_data;
|
||||
}
|
||||
|
||||
static void *strset_add_str_mem(struct strset *set, size_t add_sz)
|
||||
{
|
||||
return libbpf_add_mem(&set->strs_data, &set->strs_data_cap, 1,
|
||||
set->strs_data_len, set->strs_data_max_len, add_sz);
|
||||
}
|
||||
|
||||
/* Find string offset that corresponds to a given string *s*.
|
||||
* Returns:
|
||||
* - >0 offset into string data, if string is found;
|
||||
* - -ENOENT, if string is not in the string data;
|
||||
* - <0, on any other error.
|
||||
*/
|
||||
int strset__find_str(struct strset *set, const char *s)
|
||||
{
|
||||
long old_off, new_off, len;
|
||||
void *p;
|
||||
|
||||
/* see strset__add_str() for why we do this */
|
||||
len = strlen(s) + 1;
|
||||
p = strset_add_str_mem(set, len);
|
||||
if (!p)
|
||||
return -ENOMEM;
|
||||
|
||||
new_off = set->strs_data_len;
|
||||
memcpy(p, s, len);
|
||||
|
||||
if (hashmap__find(set->strs_hash, (void *)new_off, (void **)&old_off))
|
||||
return old_off;
|
||||
|
||||
return -ENOENT;
|
||||
}
|
||||
|
||||
/* Add a string s to the string data. If the string already exists, return its
|
||||
* offset within string data.
|
||||
* Returns:
|
||||
* - > 0 offset into string data, on success;
|
||||
* - < 0, on error.
|
||||
*/
|
||||
int strset__add_str(struct strset *set, const char *s)
|
||||
{
|
||||
long old_off, new_off, len;
|
||||
void *p;
|
||||
int err;
|
||||
|
||||
/* Hashmap keys are always offsets within set->strs_data, so to even
|
||||
* look up some string from the "outside", we need to first append it
|
||||
* at the end, so that it can be addressed with an offset. Luckily,
|
||||
* until set->strs_data_len is incremented, that string is just a piece
|
||||
* of garbage for the rest of the code, so no harm, no foul. On the
|
||||
* other hand, if the string is unique, it's already appended and
|
||||
* ready to be used, only a simple set->strs_data_len increment away.
|
||||
*/
|
||||
len = strlen(s) + 1;
|
||||
p = strset_add_str_mem(set, len);
|
||||
if (!p)
|
||||
return -ENOMEM;
|
||||
|
||||
new_off = set->strs_data_len;
|
||||
memcpy(p, s, len);
|
||||
|
||||
/* 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(set->strs_hash, (void *)new_off, (void *)new_off,
|
||||
HASHMAP_ADD, (const void **)&old_off, NULL);
|
||||
if (err == -EEXIST)
|
||||
return old_off; /* duplicated string, return existing offset */
|
||||
if (err)
|
||||
return err;
|
||||
|
||||
set->strs_data_len += len; /* new unique string, adjust data length */
|
||||
return new_off;
|
||||
}
|
||||
21
tools/lib/bpf/strset.h
Normal file
21
tools/lib/bpf/strset.h
Normal file
|
|
@ -0,0 +1,21 @@
|
|||
/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
|
||||
|
||||
/* Copyright (c) 2021 Facebook */
|
||||
#ifndef __LIBBPF_STRSET_H
|
||||
#define __LIBBPF_STRSET_H
|
||||
|
||||
#include <stdbool.h>
|
||||
#include <stddef.h>
|
||||
|
||||
struct strset;
|
||||
|
||||
struct strset *strset__new(size_t max_data_sz, const char *init_data, size_t init_data_sz);
|
||||
void strset__free(struct strset *set);
|
||||
|
||||
const char *strset__data(const struct strset *set);
|
||||
size_t strset__data_size(const struct strset *set);
|
||||
|
||||
int strset__find_str(struct strset *set, const char *s);
|
||||
int strset__add_str(struct strset *set, const char *s);
|
||||
|
||||
#endif /* __LIBBPF_STRSET_H */
|
||||
Loading…
Reference in a new issue