bpf: btf: Change how section is supported in btf_header
There are currently unused section descriptions in the btf_header. Those sections are here to support future BTF use cases. For example, the func section (func_off) is to support function signature (e.g. the BPF prog function signature). Instead of spelling out all potential sections up-front in the btf_header. This patch makes changes to btf_header such that extending it (e.g. adding a section) is possible later. The unused ones can be removed for now and they can be added back later. This patch: 1. adds a hdr_len to the btf_header. It will allow adding sections (and other info like parent_label and parent_name) later. The check is similar to the existing bpf_attr. If a user passes in a longer hdr_len, the kernel ensures the extra tailing bytes are 0. 2. allows the section order in the BTF object to be different from its sec_off order in btf_header. 3. each sec_off is followed by a sec_len. It must not have gap or overlapping among sections. The string section is ensured to be at the end due to the 4 bytes alignment requirement of the type section. The above changes will allow enough flexibility to add new sections (and other info) to the btf_header later. This patch also removes an unnecessary !err check at the end of btf_parse(). Signed-off-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Martin KaFai Lau
Daniel Borkmann
parent
dcab51f19b
commit
f80442a4cd
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@ -12,15 +12,11 @@ struct btf_header {
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__u16 magic;
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__u8 version;
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__u8 flags;
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__u32 parent_label;
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__u32 parent_name;
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__u32 hdr_len;
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/* All offsets are in bytes relative to the end of this header */
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__u32 label_off; /* offset of label section */
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__u32 object_off; /* offset of data object section*/
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__u32 func_off; /* offset of function section */
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__u32 type_off; /* offset of type section */
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__u32 type_len; /* length of type section */
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__u32 str_off; /* offset of string section */
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__u32 str_len; /* length of string section */
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};
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209
kernel/bpf/btf.c
209
kernel/bpf/btf.c
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@ -12,6 +12,7 @@
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#include <linux/uaccess.h>
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#include <linux/kernel.h>
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#include <linux/idr.h>
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#include <linux/sort.h>
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#include <linux/bpf_verifier.h>
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#include <linux/btf.h>
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@ -184,15 +185,13 @@ static DEFINE_IDR(btf_idr);
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static DEFINE_SPINLOCK(btf_idr_lock);
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struct btf {
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union {
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struct btf_header *hdr;
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void *data;
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};
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void *data;
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struct btf_type **types;
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u32 *resolved_ids;
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u32 *resolved_sizes;
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const char *strings;
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void *nohdr_data;
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struct btf_header hdr;
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u32 nr_types;
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u32 types_size;
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u32 data_size;
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@ -228,6 +227,11 @@ enum resolve_mode {
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#define MAX_RESOLVE_DEPTH 32
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struct btf_sec_info {
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u32 off;
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u32 len;
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};
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struct btf_verifier_env {
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struct btf *btf;
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u8 *visit_states;
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@ -418,14 +422,14 @@ static const struct btf_kind_operations *btf_type_ops(const struct btf_type *t)
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static bool btf_name_offset_valid(const struct btf *btf, u32 offset)
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{
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return !BTF_STR_TBL_ELF_ID(offset) &&
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BTF_STR_OFFSET(offset) < btf->hdr->str_len;
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BTF_STR_OFFSET(offset) < btf->hdr.str_len;
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}
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static const char *btf_name_by_offset(const struct btf *btf, u32 offset)
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{
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if (!BTF_STR_OFFSET(offset))
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return "(anon)";
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else if (BTF_STR_OFFSET(offset) < btf->hdr->str_len)
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else if (BTF_STR_OFFSET(offset) < btf->hdr.str_len)
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return &btf->strings[BTF_STR_OFFSET(offset)];
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else
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return "(invalid-name-offset)";
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@ -536,7 +540,8 @@ static void btf_verifier_log_member(struct btf_verifier_env *env,
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__btf_verifier_log(log, "\n");
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}
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static void btf_verifier_log_hdr(struct btf_verifier_env *env)
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static void btf_verifier_log_hdr(struct btf_verifier_env *env,
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u32 btf_data_size)
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{
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struct bpf_verifier_log *log = &env->log;
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const struct btf *btf = env->btf;
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@ -545,19 +550,16 @@ static void btf_verifier_log_hdr(struct btf_verifier_env *env)
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if (!bpf_verifier_log_needed(log))
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return;
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hdr = btf->hdr;
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hdr = &btf->hdr;
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__btf_verifier_log(log, "magic: 0x%x\n", hdr->magic);
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__btf_verifier_log(log, "version: %u\n", hdr->version);
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__btf_verifier_log(log, "flags: 0x%x\n", hdr->flags);
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__btf_verifier_log(log, "parent_label: %u\n", hdr->parent_label);
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__btf_verifier_log(log, "parent_name: %u\n", hdr->parent_name);
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__btf_verifier_log(log, "label_off: %u\n", hdr->label_off);
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__btf_verifier_log(log, "object_off: %u\n", hdr->object_off);
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__btf_verifier_log(log, "func_off: %u\n", hdr->func_off);
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__btf_verifier_log(log, "hdr_len: %u\n", hdr->hdr_len);
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__btf_verifier_log(log, "type_off: %u\n", hdr->type_off);
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__btf_verifier_log(log, "type_len: %u\n", hdr->type_len);
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__btf_verifier_log(log, "str_off: %u\n", hdr->str_off);
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__btf_verifier_log(log, "str_len: %u\n", hdr->str_len);
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__btf_verifier_log(log, "btf_total_size: %u\n", btf->data_size);
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__btf_verifier_log(log, "btf_total_size: %u\n", btf_data_size);
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}
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static int btf_add_type(struct btf_verifier_env *env, struct btf_type *t)
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@ -1754,9 +1756,9 @@ static int btf_check_all_metas(struct btf_verifier_env *env)
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struct btf_header *hdr;
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void *cur, *end;
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hdr = btf->hdr;
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hdr = &btf->hdr;
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cur = btf->nohdr_data + hdr->type_off;
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end = btf->nohdr_data + hdr->str_off;
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end = btf->nohdr_data + hdr->type_len;
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env->log_type_id = 1;
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while (cur < end) {
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@ -1866,8 +1868,20 @@ static int btf_check_all_types(struct btf_verifier_env *env)
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static int btf_parse_type_sec(struct btf_verifier_env *env)
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{
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const struct btf_header *hdr = &env->btf->hdr;
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int err;
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/* Type section must align to 4 bytes */
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if (hdr->type_off & (sizeof(u32) - 1)) {
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btf_verifier_log(env, "Unaligned type_off");
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return -EINVAL;
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}
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if (!hdr->type_len) {
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btf_verifier_log(env, "No type found");
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return -EINVAL;
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}
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err = btf_check_all_metas(env);
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if (err)
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return err;
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@ -1881,10 +1895,15 @@ static int btf_parse_str_sec(struct btf_verifier_env *env)
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struct btf *btf = env->btf;
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const char *start, *end;
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hdr = btf->hdr;
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hdr = &btf->hdr;
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start = btf->nohdr_data + hdr->str_off;
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end = start + hdr->str_len;
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if (end != btf->data + btf->data_size) {
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btf_verifier_log(env, "String section is not at the end");
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return -EINVAL;
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}
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if (!hdr->str_len || hdr->str_len - 1 > BTF_MAX_NAME_OFFSET ||
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start[0] || end[-1]) {
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btf_verifier_log(env, "Invalid string section");
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@ -1896,20 +1915,122 @@ static int btf_parse_str_sec(struct btf_verifier_env *env)
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return 0;
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}
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static int btf_parse_hdr(struct btf_verifier_env *env)
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static const size_t btf_sec_info_offset[] = {
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offsetof(struct btf_header, type_off),
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offsetof(struct btf_header, str_off),
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};
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static int btf_sec_info_cmp(const void *a, const void *b)
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{
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const struct btf_sec_info *x = a;
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const struct btf_sec_info *y = b;
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return (int)(x->off - y->off) ? : (int)(x->len - y->len);
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}
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static int btf_check_sec_info(struct btf_verifier_env *env,
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u32 btf_data_size)
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{
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const unsigned int nr_secs = ARRAY_SIZE(btf_sec_info_offset);
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struct btf_sec_info secs[nr_secs];
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u32 total, expected_total, i;
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const struct btf_header *hdr;
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const struct btf *btf;
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btf = env->btf;
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hdr = &btf->hdr;
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/* Populate the secs from hdr */
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for (i = 0; i < nr_secs; i++)
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secs[i] = *(struct btf_sec_info *)((void *)hdr +
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btf_sec_info_offset[i]);
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sort(secs, nr_secs, sizeof(struct btf_sec_info),
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btf_sec_info_cmp, NULL);
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/* Check for gaps and overlap among sections */
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total = 0;
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expected_total = btf_data_size - hdr->hdr_len;
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for (i = 0; i < nr_secs; i++) {
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if (expected_total < secs[i].off) {
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btf_verifier_log(env, "Invalid section offset");
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return -EINVAL;
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}
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if (total < secs[i].off) {
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/* gap */
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btf_verifier_log(env, "Unsupported section found");
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return -EINVAL;
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}
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if (total > secs[i].off) {
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btf_verifier_log(env, "Section overlap found");
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return -EINVAL;
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}
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if (expected_total - total < secs[i].len) {
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btf_verifier_log(env,
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"Total section length too long");
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return -EINVAL;
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}
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total += secs[i].len;
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}
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/* There is data other than hdr and known sections */
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if (expected_total != total) {
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btf_verifier_log(env, "Unsupported section found");
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return -EINVAL;
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}
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return 0;
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}
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static int btf_parse_hdr(struct btf_verifier_env *env, void __user *btf_data,
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u32 btf_data_size)
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{
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const struct btf_header *hdr;
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struct btf *btf = env->btf;
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u32 meta_left;
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u32 hdr_len, hdr_copy;
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/*
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* Minimal part of the "struct btf_header" that
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* contains the hdr_len.
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*/
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struct btf_min_header {
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u16 magic;
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u8 version;
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u8 flags;
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u32 hdr_len;
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} __user *min_hdr;
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struct btf *btf;
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int err;
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if (btf->data_size < sizeof(*hdr)) {
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btf = env->btf;
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min_hdr = btf_data;
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if (btf_data_size < sizeof(*min_hdr)) {
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btf_verifier_log(env, "hdr_len not found");
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return -EINVAL;
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}
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if (get_user(hdr_len, &min_hdr->hdr_len))
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return -EFAULT;
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if (btf_data_size < hdr_len) {
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btf_verifier_log(env, "btf_header not found");
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return -EINVAL;
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}
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btf_verifier_log_hdr(env);
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err = bpf_check_uarg_tail_zero(btf_data, sizeof(btf->hdr), hdr_len);
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if (err) {
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if (err == -E2BIG)
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btf_verifier_log(env, "Unsupported btf_header");
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return err;
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}
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hdr_copy = min_t(u32, hdr_len, sizeof(btf->hdr));
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if (copy_from_user(&btf->hdr, btf_data, hdr_copy))
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return -EFAULT;
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hdr = &btf->hdr;
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btf_verifier_log_hdr(env, btf_data_size);
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hdr = btf->hdr;
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if (hdr->magic != BTF_MAGIC) {
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btf_verifier_log(env, "Invalid magic");
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return -EINVAL;
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@ -1925,26 +2046,14 @@ static int btf_parse_hdr(struct btf_verifier_env *env)
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return -ENOTSUPP;
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}
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meta_left = btf->data_size - sizeof(*hdr);
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if (!meta_left) {
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if (btf_data_size == hdr->hdr_len) {
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btf_verifier_log(env, "No data");
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return -EINVAL;
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}
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if (meta_left < hdr->type_off || hdr->str_off <= hdr->type_off ||
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/* Type section must align to 4 bytes */
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hdr->type_off & (sizeof(u32) - 1)) {
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btf_verifier_log(env, "Invalid type_off");
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return -EINVAL;
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}
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if (meta_left < hdr->str_off ||
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meta_left - hdr->str_off < hdr->str_len) {
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btf_verifier_log(env, "Invalid str_off or str_len");
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return -EINVAL;
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}
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btf->nohdr_data = btf->hdr + 1;
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err = btf_check_sec_info(env, btf_data_size);
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if (err)
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return err;
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return 0;
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}
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@ -1987,6 +2096,11 @@ static struct btf *btf_parse(void __user *btf_data, u32 btf_data_size,
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err = -ENOMEM;
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goto errout;
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}
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env->btf = btf;
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err = btf_parse_hdr(env, btf_data, btf_data_size);
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if (err)
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goto errout;
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data = kvmalloc(btf_data_size, GFP_KERNEL | __GFP_NOWARN);
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if (!data) {
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@ -1996,18 +2110,13 @@ static struct btf *btf_parse(void __user *btf_data, u32 btf_data_size,
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btf->data = data;
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btf->data_size = btf_data_size;
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btf->nohdr_data = btf->data + btf->hdr.hdr_len;
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if (copy_from_user(data, btf_data, btf_data_size)) {
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err = -EFAULT;
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goto errout;
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}
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env->btf = btf;
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err = btf_parse_hdr(env);
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if (err)
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goto errout;
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err = btf_parse_str_sec(env);
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if (err)
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goto errout;
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@ -2016,16 +2125,14 @@ static struct btf *btf_parse(void __user *btf_data, u32 btf_data_size,
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if (err)
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goto errout;
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if (!err && log->level && bpf_verifier_log_full(log)) {
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if (log->level && bpf_verifier_log_full(log)) {
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err = -ENOSPC;
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goto errout;
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}
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if (!err) {
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btf_verifier_env_free(env);
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refcount_set(&btf->refcnt, 1);
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return btf;
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}
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btf_verifier_env_free(env);
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refcount_set(&btf->refcnt, 1);
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return btf;
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errout:
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btf_verifier_env_free(env);
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