+
+/*
+ * Compute the offsets of SDT probes from the begining of the ELF binary.
+ *
+ * On success, returns 0 and the nb_probes parameter is set to the number of
+ * offsets found and the offsets parameter points to an array of offsets where
+ * the SDT probes are.
+ * On failure, returns -1.
+ */
+int lttng_elf_get_sdt_probe_offsets(int fd, const char *provider_name,
+ const char *probe_name, uint64_t **offsets, uint32_t *nb_probes)
+{
+ int ret = 0, nb_match = 0;
+ struct lttng_elf_shdr *stap_note_section_hdr = NULL;
+ struct lttng_elf *elf = NULL;
+ char *stap_note_section_data = NULL;
+ char *curr_note_section_begin, *curr_data_ptr, *curr_probe, *curr_provider;
+ char *next_note_ptr, *curr_desc_beg;
+ uint32_t name_size, desc_size, note_type;
+ uint64_t curr_probe_location, curr_probe_offset, curr_semaphore_location;
+ uint64_t *probe_locs = NULL, *new_probe_locs = NULL;
+
+ if (!provider_name || !probe_name || !nb_probes || !offsets) {
+ DBG("Invalid arguments.");
+ ret = LTTNG_ERR_ELF_PARSING;
+ goto error;
+ }
+
+ elf = lttng_elf_create(fd);
+ if (!elf) {
+ DBG("Error allocation ELF.");
+ ret = LTTNG_ERR_ELF_PARSING;
+ goto error;
+ }
+
+ /* Get the stap note section header. */
+ ret = lttng_elf_get_section_hdr_by_name(elf, NOTE_STAPSDT_SECTION_NAME,
+ &stap_note_section_hdr);
+ if (ret) {
+ DBG("Cannot get ELF stap note section.");
+ goto destroy_elf_error;
+ }
+
+ /* Get the data associated with the stap note section. */
+ stap_note_section_data = lttng_elf_get_section_data(elf, stap_note_section_hdr);
+ if (stap_note_section_data == NULL) {
+ DBG("Cannot get ELF stap note section data.");
+ ret = LTTNG_ERR_ELF_PARSING;
+ goto destroy_elf_error;
+ }
+
+ curr_data_ptr = stap_note_section_data;
+ next_note_ptr = stap_note_section_data;
+ curr_note_section_begin = stap_note_section_data;
+
+ *offsets = NULL;
+ while (1) {
+ curr_data_ptr = next_note_ptr;
+ /* Check if we have reached the end of the note section. */
+ if (curr_data_ptr >=
+ curr_note_section_begin + stap_note_section_hdr->sh_size) {
+ *nb_probes = nb_match;
+ *offsets = probe_locs;
+ ret = 0;
+ break;
+ }
+ /* Get name size field. */
+ name_size = next_4bytes_boundary(*(uint32_t*) curr_data_ptr);
+ curr_data_ptr += sizeof(uint32_t);
+
+ /* Sanity check; a zero name_size is reserved. */
+ if (name_size == 0) {
+ DBG("Invalid name size field in SDT probe descriptions"
+ "section.");
+ ret = -1;
+ goto realloc_error;
+ }
+
+ /* Get description size field. */
+ desc_size = next_4bytes_boundary(*(uint32_t*) curr_data_ptr);
+ curr_data_ptr += sizeof(uint32_t);
+
+ /* Get type field. */
+ note_type = *(uint32_t *) curr_data_ptr;
+ curr_data_ptr += sizeof(uint32_t);
+
+ /*
+ * Move the pointer to the next note to be ready for the next
+ * iteration. The current note is made of 3 unsigned 32bit
+ * integers (name size, descriptor size and note type), the
+ * name and the descriptor. To move to the next note, we move
+ * the pointer according to those values.
+ */
+ next_note_ptr = next_note_ptr +
+ (3 * sizeof(uint32_t)) + desc_size + name_size;
+
+ /*
+ * Move ptr to the end of the name string (we don't need it)
+ * and go to the next 4 byte alignement.
+ */
+ if (note_type != NOTE_STAPSDT_TYPE ||
+ strncmp(curr_data_ptr, NOTE_STAPSDT_NAME, name_size) != 0) {
+ continue;
+ }
+
+ curr_data_ptr += name_size;
+
+ /* Get description field. */
+ curr_desc_beg = curr_data_ptr;
+
+ /* Get probe location. */
+ curr_probe_location = *(uint64_t *) curr_data_ptr;
+ curr_data_ptr += sizeof(uint64_t);
+
+ /* Pass over the base. Not needed. */
+ curr_data_ptr += sizeof(uint64_t);
+
+ /* Get semaphore location. */
+ curr_semaphore_location = *(uint64_t *) curr_data_ptr;
+ curr_data_ptr += sizeof(uint64_t);
+ /* Get provider name. */
+ curr_provider = curr_data_ptr;
+ curr_data_ptr += strlen(curr_provider) + 1;
+
+ /* Get probe name. */
+ curr_probe = curr_data_ptr;
+ curr_data_ptr += strlen(curr_probe) + 1;
+
+ curr_data_ptr = curr_desc_beg + desc_size;
+
+ /* Check if the provider and probe name match */
+ if (strcmp(provider_name, curr_provider) == 0 &&
+ strcmp(probe_name, curr_probe) == 0) {
+ int new_size;
+
+ /*
+ * We currently don't support SDT probes with semaphores. Return
+ * success as we found a matching probe but it's guarded by a
+ * semaphore.
+ */
+ if (curr_semaphore_location != 0) {
+ ret = LTTNG_ERR_SDT_PROBE_SEMAPHORE;
+ goto end;
+ }
+
+ new_size = (++nb_match) * sizeof(uint64_t);
+
+ /*
+ * Found a match with not semaphore, we need to copy the
+ * probe_location to the output parameter.
+ */
+ new_probe_locs = realloc(probe_locs, new_size);
+ if (!new_probe_locs) {
+ /* Error allocating a larger buffer */
+ DBG("Allocation error in SDT.");
+ ret = LTTNG_ERR_NOMEM;
+ goto realloc_error;
+ }
+ probe_locs = new_probe_locs;
+ new_probe_locs = NULL;
+
+ /*
+ * Use the virtual address of the probe to compute the offset of
+ * this probe from the beginning of the executable file.
+ */
+ ret = lttng_elf_convert_addr_in_text_to_offset(elf,
+ curr_probe_location, &curr_probe_offset);
+ if (ret) {
+ DBG("Conversion error in SDT.");
+ goto realloc_error;
+ }
+
+ probe_locs[nb_match - 1] = curr_probe_offset;
+ }
+ }
+
+end:
+ free(stap_note_section_data);
+destroy_elf_error:
+ lttng_elf_destroy(elf);
+error:
+ return ret;
+realloc_error:
+ free(probe_locs);
+ goto end;
+}
projects / lttng-tools.git / commitdiff
