X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;f=src%2Fcommon%2Felf.c;fp=src%2Fcommon%2Felf.c;h=b418176bcd7b901417c41a5ce23bedc0ef77d6ea;hb=4667b1924a9b01081722535013b8386c04700fe8;hp=0000000000000000000000000000000000000000;hpb=08c0c18ad4d5acf6e6f84c39935f359e6706ea8b;p=lttng-ust.git

diff --git a/src/common/elf.c b/src/common/elf.c
new file mode 100644
index 00000000..b418176b
--- /dev/null
+++ b/src/common/elf.c
@@ -0,0 +1,705 @@
+/*
+ * SPDX-License-Identifier: LGPL-2.1-or-later
+ *
+ * Copyright (C) 2015 Antoine Busque <abusque@efficios.com>
+ */
+
+#define _LGPL_SOURCE
+#include <fcntl.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <lttng/ust-utils.h>
+
+#include "common/elf.h"
+#include "common/logging.h"
+#include "common/macros.h"
+#include "common/ust-fd.h"
+#include "common/utils.h"
+
+#define BUF_LEN	4096
+
+#ifndef NT_GNU_BUILD_ID
+# define NT_GNU_BUILD_ID	3
+#endif
+
+/*
+ * Retrieve the nth (where n is the `index` argument) phdr (program
+ * header) from the given elf instance.
+ *
+ * A pointer to the phdr is returned on success, NULL on failure.
+ */
+static
+struct lttng_ust_elf_phdr *lttng_ust_elf_get_phdr(struct lttng_ust_elf *elf,
+						uint16_t index)
+{
+	struct lttng_ust_elf_phdr *phdr = NULL;
+	off_t offset;
+
+	if (!elf) {
+		goto error;
+	}
+
+	if (index >= elf->ehdr->e_phnum) {
+		goto error;
+	}
+
+	phdr = zmalloc(sizeof(struct lttng_ust_elf_phdr));
+	if (!phdr) {
+		goto error;
+	}
+
+	offset = (off_t) elf->ehdr->e_phoff
+			+ (off_t) index * elf->ehdr->e_phentsize;
+	if (lseek(elf->fd, offset, SEEK_SET) < 0) {
+		goto error;
+	}
+
+	if (is_elf_32_bit(elf)) {
+		Elf32_Phdr elf_phdr;
+
+		if (lttng_ust_read(elf->fd, &elf_phdr, sizeof(elf_phdr))
+				< sizeof(elf_phdr)) {
+			goto error;
+		}
+		if (!is_elf_native_endian(elf)) {
+			bswap_phdr(elf_phdr);
+		}
+		copy_phdr(elf_phdr, *phdr);
+	} else {
+		Elf64_Phdr elf_phdr;
+
+		if (lttng_ust_read(elf->fd, &elf_phdr, sizeof(elf_phdr))
+				< sizeof(elf_phdr)) {
+			goto error;
+		}
+		if (!is_elf_native_endian(elf)) {
+			bswap_phdr(elf_phdr);
+		}
+		copy_phdr(elf_phdr, *phdr);
+	}
+
+	return phdr;
+
+error:
+	free(phdr);
+	return NULL;
+}
+
+/*
+ * Retrieve the nth (where n is the `index` argument) shdr (section
+ * header) from the given elf instance.
+ *
+ * A pointer to the shdr is returned on success, NULL on failure.
+ */
+static
+struct lttng_ust_elf_shdr *lttng_ust_elf_get_shdr(struct lttng_ust_elf *elf,
+						uint16_t index)
+{
+	struct lttng_ust_elf_shdr *shdr = NULL;
+	off_t offset;
+
+	if (!elf) {
+		goto error;
+	}
+
+	if (index >= elf->ehdr->e_shnum) {
+		goto error;
+	}
+
+	shdr = zmalloc(sizeof(struct lttng_ust_elf_shdr));
+	if (!shdr) {
+		goto error;
+	}
+
+	offset = (off_t) elf->ehdr->e_shoff
+			+ (off_t) index * elf->ehdr->e_shentsize;
+	if (lseek(elf->fd, offset, SEEK_SET) < 0) {
+		goto error;
+	}
+
+	if (is_elf_32_bit(elf)) {
+		Elf32_Shdr elf_shdr;
+
+		if (lttng_ust_read(elf->fd, &elf_shdr, sizeof(elf_shdr))
+				< sizeof(elf_shdr)) {
+			goto error;
+		}
+		if (!is_elf_native_endian(elf)) {
+			bswap_shdr(elf_shdr);
+		}
+		copy_shdr(elf_shdr, *shdr);
+	} else {
+		Elf64_Shdr elf_shdr;
+
+		if (lttng_ust_read(elf->fd, &elf_shdr, sizeof(elf_shdr))
+				< sizeof(elf_shdr)) {
+			goto error;
+		}
+		if (!is_elf_native_endian(elf)) {
+			bswap_shdr(elf_shdr);
+		}
+		copy_shdr(elf_shdr, *shdr);
+	}
+
+	return shdr;
+
+error:
+	free(shdr);
+	return NULL;
+}
+
+/*
+ * Lookup a section's name from a given offset (usually from an shdr's
+ * sh_name value) in bytes relative to the beginning of the section
+ * names string table.
+ *
+ * If no name is found, NULL is returned.
+ */
+static
+char *lttng_ust_elf_get_section_name(struct lttng_ust_elf *elf, off_t offset)
+{
+	char *name = NULL;
+	size_t len = 0, to_read;	/* len does not include \0 */
+
+	if (!elf) {
+		goto error;
+	}
+
+	if (offset >= elf->section_names_size) {
+		goto error;
+	}
+
+	if (lseek(elf->fd, elf->section_names_offset + offset, SEEK_SET) < 0) {
+		goto error;
+	}
+
+	to_read = elf->section_names_size - offset;
+
+	/* Find first \0 after or at current location, remember len. */
+	for (;;) {
+		char buf[BUF_LEN];
+		ssize_t read_len;
+		size_t i;
+
+		if (!to_read) {
+			goto error;
+		}
+		read_len = lttng_ust_read(elf->fd, buf,
+			min_t(size_t, BUF_LEN, to_read));
+		if (read_len <= 0) {
+			goto error;
+		}
+		for (i = 0; i < read_len; i++) {
+			if (buf[i] == '\0') {
+				len += i;
+				goto end;
+			}
+		}
+		len += read_len;
+		to_read -= read_len;
+	}
+end:
+	name = zmalloc(sizeof(char) * (len + 1));	/* + 1 for \0 */
+	if (!name) {
+		goto error;
+	}
+	if (lseek(elf->fd, elf->section_names_offset + offset,
+		SEEK_SET) < 0) {
+		goto error;
+	}
+	if (lttng_ust_read(elf->fd, name, len + 1) < len + 1) {
+		goto error;
+	}
+
+	return name;
+
+error:
+	free(name);
+	return NULL;
+}
+
+/*
+ * Create an instance of lttng_ust_elf for the ELF file located at
+ * `path`.
+ *
+ * Return a pointer to the instance on success, NULL on failure.
+ */
+struct lttng_ust_elf *lttng_ust_elf_create(const char *path)
+{
+	uint8_t e_ident[EI_NIDENT];
+	struct lttng_ust_elf_shdr *section_names_shdr;
+	struct lttng_ust_elf *elf = NULL;
+	int ret, fd;
+
+	elf = zmalloc(sizeof(struct lttng_ust_elf));
+	if (!elf) {
+		goto error;
+	}
+
+	/* Initialize fd field to -1. 0 is a valid fd number */
+	elf->fd = -1;
+
+	elf->path = strdup(path);
+	if (!elf->path) {
+		goto error;
+	}
+
+	lttng_ust_lock_fd_tracker();
+	fd = open(elf->path, O_RDONLY | O_CLOEXEC);
+	if (fd < 0) {
+		lttng_ust_unlock_fd_tracker();
+		goto error;
+	}
+
+	ret = lttng_ust_add_fd_to_tracker(fd);
+	if (ret < 0) {
+		ret = close(fd);
+		if (ret) {
+			PERROR("close on elf->fd");
+		}
+		ret = -1;
+		lttng_ust_unlock_fd_tracker();
+		goto error;
+	}
+	elf->fd = ret;
+	lttng_ust_unlock_fd_tracker();
+
+	if (lttng_ust_read(elf->fd, e_ident, EI_NIDENT) < EI_NIDENT) {
+		goto error;
+	}
+	elf->bitness = e_ident[EI_CLASS];
+	elf->endianness = e_ident[EI_DATA];
+
+	if (lseek(elf->fd, 0, SEEK_SET) < 0) {
+		goto error;
+	}
+
+	elf->ehdr = zmalloc(sizeof(struct lttng_ust_elf_ehdr));
+	if (!elf->ehdr) {
+		goto error;
+	}
+
+	if (is_elf_32_bit(elf)) {
+		Elf32_Ehdr elf_ehdr;
+
+		if (lttng_ust_read(elf->fd, &elf_ehdr, sizeof(elf_ehdr))
+				< sizeof(elf_ehdr)) {
+			goto error;
+		}
+		if (!is_elf_native_endian(elf)) {
+			bswap_ehdr(elf_ehdr);
+		}
+		copy_ehdr(elf_ehdr, *(elf->ehdr));
+	} else {
+		Elf64_Ehdr elf_ehdr;
+
+		if (lttng_ust_read(elf->fd, &elf_ehdr, sizeof(elf_ehdr))
+				< sizeof(elf_ehdr)) {
+			goto error;
+		}
+		if (!is_elf_native_endian(elf)) {
+			bswap_ehdr(elf_ehdr);
+		}
+		copy_ehdr(elf_ehdr, *(elf->ehdr));
+	}
+
+	section_names_shdr = lttng_ust_elf_get_shdr(elf, elf->ehdr->e_shstrndx);
+	if (!section_names_shdr) {
+		goto error;
+	}
+
+	elf->section_names_offset = section_names_shdr->sh_offset;
+	elf->section_names_size = section_names_shdr->sh_size;
+
+	free(section_names_shdr);
+	return elf;
+
+error:
+	lttng_ust_elf_destroy(elf);
+	return NULL;
+}
+
+/*
+ * Test whether the ELF file is position independent code (PIC)
+ */
+uint8_t lttng_ust_elf_is_pic(struct lttng_ust_elf *elf)
+{
+	/*
+	 * PIC has and e_type value of ET_DYN, see ELF specification
+	 * version 1.1 p. 1-3.
+	 */
+	return elf->ehdr->e_type == ET_DYN;
+}
+
+/*
+ * Destroy the given lttng_ust_elf instance.
+ */
+void lttng_ust_elf_destroy(struct lttng_ust_elf *elf)
+{
+	int ret;
+
+	if (!elf) {
+		return;
+	}
+
+	if (elf->fd >= 0) {
+		lttng_ust_lock_fd_tracker();
+		ret = close(elf->fd);
+		if (!ret) {
+			lttng_ust_delete_fd_from_tracker(elf->fd);
+		} else {
+			PERROR("close");
+			abort();
+		}
+		lttng_ust_unlock_fd_tracker();
+	}
+
+	free(elf->ehdr);
+	free(elf->path);
+	free(elf);
+}
+
+/*
+ * Compute the total in-memory size of the ELF file, in bytes.
+ *
+ * Returns 0 if successful, -1 if not. On success, the memory size is
+ * returned through the out parameter `memsz`.
+ */
+int lttng_ust_elf_get_memsz(struct lttng_ust_elf *elf, uint64_t *memsz)
+{
+	uint16_t i;
+	uint64_t low_addr = UINT64_MAX, high_addr = 0;
+
+	if (!elf || !memsz) {
+		goto error;
+	}
+
+	for (i = 0; i < elf->ehdr->e_phnum; ++i) {
+		struct lttng_ust_elf_phdr *phdr;
+
+		phdr = lttng_ust_elf_get_phdr(elf, i);
+		if (!phdr) {
+			goto error;
+		}
+
+		/*
+		 * Only PT_LOAD segments contribute to memsz. Skip
+		 * other segments.
+		 */
+		if (phdr->p_type != PT_LOAD) {
+			goto next_loop;
+		}
+
+		low_addr = min_t(uint64_t, low_addr, phdr->p_vaddr);
+		high_addr = max_t(uint64_t, high_addr,
+				phdr->p_vaddr + phdr->p_memsz);
+	next_loop:
+		free(phdr);
+	}
+
+	if (high_addr < low_addr) {
+		/* No PT_LOAD segments or corrupted data. */
+		goto error;
+	}
+
+	*memsz = high_addr - low_addr;
+	return 0;
+error:
+	return -1;
+}
+
+/*
+ * Internal method used to try and get the build_id from a PT_NOTE
+ * segment ranging from `offset` to `segment_end`.
+ *
+ * If the function returns successfully, the out parameter `found`
+ * indicates whether the build id information was present in the
+ * segment or not. If `found` is not 0, the out parameters `build_id`
+ * and `length` will both have been set with the retrieved
+ * information.
+ *
+ * Returns 0 on success, -1 if an error occurred.
+ */
+static
+int lttng_ust_elf_get_build_id_from_segment(
+	struct lttng_ust_elf *elf, uint8_t **build_id, size_t *length,
+	off_t offset, off_t segment_end)
+{
+	uint8_t *_build_id = NULL;	/* Silence old gcc warning. */
+	size_t _length = 0;		/* Silence old gcc warning. */
+
+	while (offset < segment_end) {
+		struct lttng_ust_elf_nhdr nhdr;
+		size_t read_len;
+
+		/* Align start of note entry */
+		offset += lttng_ust_offset_align(offset, ELF_NOTE_ENTRY_ALIGN);
+		if (offset >= segment_end) {
+			break;
+		}
+		/*
+		 * We seek manually because if the note isn't the
+		 * build id the data following the header will not
+		 * have been read.
+		 */
+		if (lseek(elf->fd, offset, SEEK_SET) < 0) {
+			goto error;
+		}
+		if (lttng_ust_read(elf->fd, &nhdr, sizeof(nhdr))
+				< sizeof(nhdr)) {
+			goto error;
+		}
+
+		if (!is_elf_native_endian(elf)) {
+			nhdr.n_namesz = bswap_32(nhdr.n_namesz);
+			nhdr.n_descsz = bswap_32(nhdr.n_descsz);
+			nhdr.n_type = bswap_32(nhdr.n_type);
+		}
+
+		offset += sizeof(nhdr) + nhdr.n_namesz;
+		/* Align start of desc entry */
+		offset += lttng_ust_offset_align(offset, ELF_NOTE_DESC_ALIGN);
+
+		if (nhdr.n_type != NT_GNU_BUILD_ID) {
+			/*
+			 * Ignore non build id notes but still
+			 * increase the offset.
+			 */
+			offset += nhdr.n_descsz;
+			continue;
+		}
+
+		_length = nhdr.n_descsz;
+		_build_id = zmalloc(sizeof(uint8_t) * _length);
+		if (!_build_id) {
+			goto error;
+		}
+
+		if (lseek(elf->fd, offset, SEEK_SET) < 0) {
+			goto error;
+		}
+		read_len = sizeof(*_build_id) * _length;
+		if (lttng_ust_read(elf->fd, _build_id, read_len) < read_len) {
+			goto error;
+		}
+
+		break;
+	}
+
+	if (_build_id) {
+		*build_id = _build_id;
+		*length = _length;
+	}
+
+	return 0;
+error:
+	free(_build_id);
+	return -1;
+}
+
+/*
+ * Retrieve a build ID (an array of bytes) from the corresponding
+ * section in the ELF file. The length of the build ID can be either
+ * 16 or 20 bytes depending on the method used to generate it, hence
+ * the length out parameter.
+ *
+ * If the function returns successfully, the out parameter `found`
+ * indicates whether the build id information was present in the ELF
+ * file or not. If `found` is not 0, the out parameters `build_id` and
+ * `length` will both have been set with the retrieved information.
+ *
+ * Returns 0 on success, -1 if an error occurred.
+ */
+int lttng_ust_elf_get_build_id(struct lttng_ust_elf *elf, uint8_t **build_id,
+			size_t *length, int *found)
+{
+	uint16_t i;
+	uint8_t *_build_id = NULL;	/* Silence old gcc warning. */
+	size_t _length = 0;		/* Silence old gcc warning. */
+
+	if (!elf || !build_id || !length || !found) {
+		goto error;
+	}
+
+	for (i = 0; i < elf->ehdr->e_phnum; ++i) {
+		off_t offset, segment_end;
+		struct lttng_ust_elf_phdr *phdr;
+		int ret = 0;
+
+		phdr = lttng_ust_elf_get_phdr(elf, i);
+		if (!phdr) {
+			goto error;
+		}
+
+		/* Build ID will be contained in a PT_NOTE segment. */
+		if (phdr->p_type != PT_NOTE) {
+			goto next_loop;
+		}
+
+		offset = phdr->p_offset;
+		segment_end = offset + phdr->p_filesz;
+		ret = lttng_ust_elf_get_build_id_from_segment(
+			elf, &_build_id, &_length, offset, segment_end);
+	next_loop:
+		free(phdr);
+		if (ret) {
+			goto error;
+		}
+		if (_build_id) {
+			break;
+		}
+	}
+
+	if (_build_id) {
+		*build_id = _build_id;
+		*length = _length;
+		*found = 1;
+	} else {
+		*found = 0;
+	}
+
+	return 0;
+error:
+	free(_build_id);
+	return -1;
+}
+
+/*
+ * Try to retrieve filename and CRC from given ELF section `shdr`.
+ *
+ * If the function returns successfully, the out parameter `found`
+ * indicates whether the debug link information was present in the ELF
+ * section or not. If `found` is not 0, the out parameters `filename` and
+ * `crc` will both have been set with the retrieved information.
+ *
+ * Returns 0 on success, -1 if an error occurred.
+ */
+static
+int lttng_ust_elf_get_debug_link_from_section(struct lttng_ust_elf *elf,
+					char **filename, uint32_t *crc,
+					struct lttng_ust_elf_shdr *shdr)
+{
+	char *_filename = NULL;		/* Silence old gcc warning. */
+	size_t filename_len;
+	char *section_name = NULL;
+	uint32_t _crc = 0;		/* Silence old gcc warning. */
+
+	if (!elf || !filename || !crc || !shdr) {
+		goto error;
+	}
+
+	/*
+	 * The .gnu_debuglink section is of type SHT_PROGBITS,
+	 * skip the other sections.
+	 */
+	if (shdr->sh_type != SHT_PROGBITS) {
+		goto end;
+	}
+
+	section_name = lttng_ust_elf_get_section_name(elf,
+						shdr->sh_name);
+	if (!section_name) {
+		goto end;
+	}
+	if (strcmp(section_name, ".gnu_debuglink")) {
+		goto end;
+	}
+
+	/*
+	 * The length of the filename is the sh_size excluding the CRC
+	 * which comes after it in the section.
+	 */
+	_filename = zmalloc(sizeof(char) * (shdr->sh_size - ELF_CRC_SIZE));
+	if (!_filename) {
+		goto error;
+	}
+	if (lseek(elf->fd, shdr->sh_offset, SEEK_SET) < 0) {
+		goto error;
+	}
+	filename_len = sizeof(*_filename) * (shdr->sh_size - ELF_CRC_SIZE);
+	if (lttng_ust_read(elf->fd, _filename, filename_len) < filename_len) {
+		goto error;
+	}
+	if (lttng_ust_read(elf->fd, &_crc, sizeof(_crc)) < sizeof(_crc)) {
+		goto error;
+	}
+	if (!is_elf_native_endian(elf)) {
+		_crc = bswap_32(_crc);
+	}
+
+end:
+	free(section_name);
+	if (_filename) {
+		*filename = _filename;
+		*crc = _crc;
+	}
+
+	return 0;
+
+error:
+	free(_filename);
+	free(section_name);
+	return -1;
+}
+
+/*
+ * Retrieve filename and CRC from ELF's .gnu_debuglink section, if any.
+ *
+ * If the function returns successfully, the out parameter `found`
+ * indicates whether the debug link information was present in the ELF
+ * file or not. If `found` is not 0, the out parameters `filename` and
+ * `crc` will both have been set with the retrieved information.
+ *
+ * Returns 0 on success, -1 if an error occurred.
+ */
+int lttng_ust_elf_get_debug_link(struct lttng_ust_elf *elf, char **filename,
+				uint32_t *crc, int *found)
+{
+	int ret;
+	uint16_t i;
+	char *_filename = NULL;		/* Silence old gcc warning. */
+	uint32_t _crc = 0;		/* Silence old gcc warning. */
+
+	if (!elf || !filename || !crc || !found) {
+		goto error;
+	}
+
+	for (i = 0; i < elf->ehdr->e_shnum; ++i) {
+		struct lttng_ust_elf_shdr *shdr = NULL;
+
+		shdr = lttng_ust_elf_get_shdr(elf, i);
+		if (!shdr) {
+			goto error;
+		}
+
+		ret = lttng_ust_elf_get_debug_link_from_section(
+			elf, &_filename, &_crc, shdr);
+		free(shdr);
+
+		if (ret) {
+			goto error;
+		}
+		if (_filename) {
+			break;
+		}
+	}
+
+	if (_filename) {
+		*filename = _filename;
+		*crc = _crc;
+		*found = 1;
+	} else {
+		*found = 0;
+	}
+
+	return 0;
+
+error:
+	free(_filename);
+	return -1;
+}