[linux-block.git] / tools / objtool / elf.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * elf.c - ELF access library
 *
 * Adapted from kpatch (https://github.com/dynup/kpatch):
 * Copyright (C) 2013-2015 Josh Poimboeuf <jpoimboe@redhat.com>
 * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
 */

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include "builtin.h"

#include "elf.h"
#include "warn.h"

#define MAX_NAME_LEN 128

static inline u32 str_hash(const char *str)
{
	return jhash(str, strlen(str), 0);
}

static void rb_add(struct rb_root *tree, struct rb_node *node,
		   int (*cmp)(struct rb_node *, const struct rb_node *))
{
	struct rb_node **link = &tree->rb_node;
	struct rb_node *parent = NULL;

	while (*link) {
		parent = *link;
		if (cmp(node, parent) < 0)
			link = &parent->rb_left;
		else
			link = &parent->rb_right;
	}

	rb_link_node(node, parent, link);
	rb_insert_color(node, tree);
}

static struct rb_node *rb_find_first(struct rb_root *tree, const void *key,
			       int (*cmp)(const void *key, const struct rb_node *))
{
	struct rb_node *node = tree->rb_node;
	struct rb_node *match = NULL;

	while (node) {
		int c = cmp(key, node);
		if (c <= 0) {
			if (!c)
				match = node;
			node = node->rb_left;
		} else if (c > 0) {
			node = node->rb_right;
		}
	}

	return match;
}

static struct rb_node *rb_next_match(struct rb_node *node, const void *key,
				    int (*cmp)(const void *key, const struct rb_node *))
{
	node = rb_next(node);
	if (node && cmp(key, node))
		node = NULL;
	return node;
}

#define rb_for_each(tree, node, key, cmp) \
	for ((node) = rb_find_first((tree), (key), (cmp)); \
	     (node); (node) = rb_next_match((node), (key), (cmp)))

static int symbol_to_offset(struct rb_node *a, const struct rb_node *b)
{
	struct symbol *sa = rb_entry(a, struct symbol, node);
	struct symbol *sb = rb_entry(b, struct symbol, node);

	if (sa->offset < sb->offset)
		return -1;
	if (sa->offset > sb->offset)
		return 1;

	if (sa->len < sb->len)
		return -1;
	if (sa->len > sb->len)
		return 1;

	sa->alias = sb;

	return 0;
}

static int symbol_by_offset(const void *key, const struct rb_node *node)
{
	const struct symbol *s = rb_entry(node, struct symbol, node);
	const unsigned long *o = key;

	if (*o < s->offset)
		return -1;
	if (*o > s->offset + s->len)
		return 1;

	return 0;
}

struct section *find_section_by_name(struct elf *elf, const char *name)
{
	struct section *sec;

	hash_for_each_possible(elf->section_name_hash, sec, name_hash, str_hash(name))
		if (!strcmp(sec->name, name))
			return sec;

	return NULL;
}

static struct section *find_section_by_index(struct elf *elf,
					     unsigned int idx)
{
	struct section *sec;

	hash_for_each_possible(elf->section_hash, sec, hash, idx)
		if (sec->idx == idx)
			return sec;

	return NULL;
}

static struct symbol *find_symbol_by_index(struct elf *elf, unsigned int idx)
{
	struct symbol *sym;

	hash_for_each_possible(elf->symbol_hash, sym, hash, idx)
		if (sym->idx == idx)
			return sym;

	return NULL;
}

struct symbol *find_symbol_by_offset(struct section *sec, unsigned long offset)
{
	struct rb_node *node;

	rb_for_each(&sec->symbol_tree, node, &offset, symbol_by_offset) {
		struct symbol *s = rb_entry(node, struct symbol, node);

		if (s->offset == offset && s->type != STT_SECTION)
			return s;
	}

	return NULL;
}

struct symbol *find_func_by_offset(struct section *sec, unsigned long offset)
{
	struct rb_node *node;

	rb_for_each(&sec->symbol_tree, node, &offset, symbol_by_offset) {
		struct symbol *s = rb_entry(node, struct symbol, node);

		if (s->offset == offset && s->type == STT_FUNC)
			return s;
	}

	return NULL;
}

struct symbol *find_symbol_containing(struct section *sec, unsigned long offset)
{
	struct rb_node *node;

	rb_for_each(&sec->symbol_tree, node, &offset, symbol_by_offset) {
		struct symbol *s = rb_entry(node, struct symbol, node);

		if (s->type != STT_SECTION)
			return s;
	}

	return NULL;
}

struct symbol *find_func_containing(struct section *sec, unsigned long offset)
{
	struct rb_node *node;

	rb_for_each(&sec->symbol_tree, node, &offset, symbol_by_offset) {
		struct symbol *s = rb_entry(node, struct symbol, node);

		if (s->type == STT_FUNC)
			return s;
	}

	return NULL;
}

struct symbol *find_symbol_by_name(struct elf *elf, const char *name)
{
	struct symbol *sym;

	hash_for_each_possible(elf->symbol_name_hash, sym, name_hash, str_hash(name))
		if (!strcmp(sym->name, name))
			return sym;

	return NULL;
}

struct rela *find_rela_by_dest_range(struct section *sec, unsigned long offset,
				     unsigned int len)
{
	struct rela *rela;
	unsigned long o;

	if (!sec->rela)
		return NULL;

	for (o = offset; o < offset + len; o++)
		hash_for_each_possible(sec->rela->rela_hash, rela, hash, o)
			if (rela->offset == o)
				return rela;

	return NULL;
}

struct rela *find_rela_by_dest(struct section *sec, unsigned long offset)
{
	return find_rela_by_dest_range(sec, offset, 1);
}

static int read_sections(struct elf *elf)
{
	Elf_Scn *s = NULL;
	struct section *sec;
	size_t shstrndx, sections_nr;
	int i;

	if (elf_getshdrnum(elf->elf, &sections_nr)) {
		WARN_ELF("elf_getshdrnum");
		return -1;
	}

	if (elf_getshdrstrndx(elf->elf, &shstrndx)) {
		WARN_ELF("elf_getshdrstrndx");
		return -1;
	}

	for (i = 0; i < sections_nr; i++) {
		sec = malloc(sizeof(*sec));
		if (!sec) {
			perror("malloc");
			return -1;
		}
		memset(sec, 0, sizeof(*sec));

		INIT_LIST_HEAD(&sec->symbol_list);
		INIT_LIST_HEAD(&sec->rela_list);
		hash_init(sec->rela_hash);

		s = elf_getscn(elf->elf, i);
		if (!s) {
			WARN_ELF("elf_getscn");
			return -1;
		}

		sec->idx = elf_ndxscn(s);

		if (!gelf_getshdr(s, &sec->sh)) {
			WARN_ELF("gelf_getshdr");
			return -1;
		}

		sec->name = elf_strptr(elf->elf, shstrndx, sec->sh.sh_name);
		if (!sec->name) {
			WARN_ELF("elf_strptr");
			return -1;
		}

		if (sec->sh.sh_size != 0) {
			sec->data = elf_getdata(s, NULL);
			if (!sec->data) {
				WARN_ELF("elf_getdata");
				return -1;
			}
			if (sec->data->d_off != 0 ||
			    sec->data->d_size != sec->sh.sh_size) {
				WARN("unexpected data attributes for %s",
				     sec->name);
				return -1;
			}
		}
		sec->len = sec->sh.sh_size;

		list_add_tail(&sec->list, &elf->sections);
		hash_add(elf->section_hash, &sec->hash, sec->idx);
		hash_add(elf->section_name_hash, &sec->name_hash, str_hash(sec->name));
	}

	if (stats)
		printf("nr_sections: %lu\n", (unsigned long)sections_nr);

	/* sanity check, one more call to elf_nextscn() should return NULL */
	if (elf_nextscn(elf->elf, s)) {
		WARN("section entry mismatch");
		return -1;
	}

	return 0;
}

static int read_symbols(struct elf *elf)
{
	struct section *symtab, *sec;
	struct symbol *sym, *pfunc;
	struct list_head *entry;
	struct rb_node *pnode;
	int symbols_nr, i;
	char *coldstr;

	symtab = find_section_by_name(elf, ".symtab");
	if (!symtab) {
		WARN("missing symbol table");
		return -1;
	}

	symbols_nr = symtab->sh.sh_size / symtab->sh.sh_entsize;

	for (i = 0; i < symbols_nr; i++) {
		sym = malloc(sizeof(*sym));
		if (!sym) {
			perror("malloc");
			return -1;
		}
		memset(sym, 0, sizeof(*sym));
		sym->alias = sym;

		sym->idx = i;

		if (!gelf_getsym(symtab->data, i, &sym->sym)) {
			WARN_ELF("gelf_getsym");
			goto err;
		}

		sym->name = elf_strptr(elf->elf, symtab->sh.sh_link,
				       sym->sym.st_name);
		if (!sym->name) {
			WARN_ELF("elf_strptr");
			goto err;
		}

		sym->type = GELF_ST_TYPE(sym->sym.st_info);
		sym->bind = GELF_ST_BIND(sym->sym.st_info);

		if (sym->sym.st_shndx > SHN_UNDEF &&
		    sym->sym.st_shndx < SHN_LORESERVE) {
			sym->sec = find_section_by_index(elf,
							 sym->sym.st_shndx);
			if (!sym->sec) {
				WARN("couldn't find section for symbol %s",
				     sym->name);
				goto err;
			}
			if (sym->type == STT_SECTION) {
				sym->name = sym->sec->name;
				sym->sec->sym = sym;
			}
		} else
			sym->sec = find_section_by_index(elf, 0);

		sym->offset = sym->sym.st_value;
		sym->len = sym->sym.st_size;

		rb_add(&sym->sec->symbol_tree, &sym->node, symbol_to_offset);
		pnode = rb_prev(&sym->node);
		if (pnode)
			entry = &rb_entry(pnode, struct symbol, node)->list;
		else
			entry = &sym->sec->symbol_list;
		list_add(&sym->list, entry);
		hash_add(elf->symbol_hash, &sym->hash, sym->idx);
		hash_add(elf->symbol_name_hash, &sym->name_hash, str_hash(sym->name));
	}

	if (stats)
		printf("nr_symbols: %lu\n", (unsigned long)symbols_nr);

	/* Create parent/child links for any cold subfunctions */
	list_for_each_entry(sec, &elf->sections, list) {
		list_for_each_entry(sym, &sec->symbol_list, list) {
			char pname[MAX_NAME_LEN + 1];
			size_t pnamelen;
			if (sym->type != STT_FUNC)
				continue;
			sym->pfunc = sym->cfunc = sym;
			coldstr = strstr(sym->name, ".cold");
			if (!coldstr)
				continue;

			pnamelen = coldstr - sym->name;
			if (pnamelen > MAX_NAME_LEN) {
				WARN("%s(): parent function name exceeds maximum length of %d characters",
				     sym->name, MAX_NAME_LEN);
				return -1;
			}

			strncpy(pname, sym->name, pnamelen);
			pname[pnamelen] = '\0';
			pfunc = find_symbol_by_name(elf, pname);

			if (!pfunc) {
				WARN("%s(): can't find parent function",
				     sym->name);
				return -1;
			}

			sym->pfunc = pfunc;
			pfunc->cfunc = sym;

			/*
			 * Unfortunately, -fnoreorder-functions puts the child
			 * inside the parent.  Remove the overlap so we can
			 * have sane assumptions.
			 *
			 * Note that pfunc->len now no longer matches
			 * pfunc->sym.st_size.
			 */
			if (sym->sec == pfunc->sec &&
			    sym->offset >= pfunc->offset &&
			    sym->offset + sym->len == pfunc->offset + pfunc->len) {
				pfunc->len -= sym->len;
			}
		}
	}

	return 0;

err:
	free(sym);
	return -1;
}

static int read_relas(struct elf *elf)
{
	struct section *sec;
	struct rela *rela;
	int i;
	unsigned int symndx;
	unsigned long nr_rela, max_rela = 0, tot_rela = 0;

	list_for_each_entry(sec, &elf->sections, list) {
		if (sec->sh.sh_type != SHT_RELA)
			continue;

		sec->base = find_section_by_name(elf, sec->name + 5);
		if (!sec->base) {
			WARN("can't find base section for rela section %s",
			     sec->name);
			return -1;
		}

		sec->base->rela = sec;

		nr_rela = 0;
		for (i = 0; i < sec->sh.sh_size / sec->sh.sh_entsize; i++) {
			rela = malloc(sizeof(*rela));
			if (!rela) {
				perror("malloc");
				return -1;
			}
			memset(rela, 0, sizeof(*rela));

			if (!gelf_getrela(sec->data, i, &rela->rela)) {
				WARN_ELF("gelf_getrela");
				return -1;
			}

			rela->type = GELF_R_TYPE(rela->rela.r_info);
			rela->addend = rela->rela.r_addend;
			rela->offset = rela->rela.r_offset;
			symndx = GELF_R_SYM(rela->rela.r_info);
			rela->sym = find_symbol_by_index(elf, symndx);
			rela->sec = sec;
			if (!rela->sym) {
				WARN("can't find rela entry symbol %d for %s",
				     symndx, sec->name);
				return -1;
			}

			list_add_tail(&rela->list, &sec->rela_list);
			hash_add(sec->rela_hash, &rela->hash, rela->offset);
			nr_rela++;
		}
		max_rela = max(max_rela, nr_rela);
		tot_rela += nr_rela;
	}

	if (stats) {
		printf("max_rela: %lu\n", max_rela);
		printf("tot_rela: %lu\n", tot_rela);
	}

	return 0;
}

struct elf *elf_read(const char *name, int flags)
{
	struct elf *elf;
	Elf_Cmd cmd;

	elf_version(EV_CURRENT);

	elf = malloc(sizeof(*elf));
	if (!elf) {
		perror("malloc");
		return NULL;
	}
	memset(elf, 0, sizeof(*elf));

	hash_init(elf->symbol_hash);
	hash_init(elf->symbol_name_hash);
	hash_init(elf->section_hash);
	hash_init(elf->section_name_hash);
	INIT_LIST_HEAD(&elf->sections);

	elf->fd = open(name, flags);
	if (elf->fd == -1) {
		fprintf(stderr, "objtool: Can't open '%s': %s\n",
			name, strerror(errno));
		goto err;
	}

	if ((flags & O_ACCMODE) == O_RDONLY)
		cmd = ELF_C_READ_MMAP;
	else if ((flags & O_ACCMODE) == O_RDWR)
		cmd = ELF_C_RDWR;
	else /* O_WRONLY */
		cmd = ELF_C_WRITE;

	elf->elf = elf_begin(elf->fd, cmd, NULL);
	if (!elf->elf) {
		WARN_ELF("elf_begin");
		goto err;
	}

	if (!gelf_getehdr(elf->elf, &elf->ehdr)) {
		WARN_ELF("gelf_getehdr");
		goto err;
	}

	if (read_sections(elf))
		goto err;

	if (read_symbols(elf))
		goto err;

	if (read_relas(elf))
		goto err;

	return elf;

err:
	elf_close(elf);
	return NULL;
}

struct section *elf_create_section(struct elf *elf, const char *name,
				   size_t entsize, int nr)
{
	struct section *sec, *shstrtab;
	size_t size = entsize * nr;
	Elf_Scn *s;
	Elf_Data *data;

	sec = malloc(sizeof(*sec));
	if (!sec) {
		perror("malloc");
		return NULL;
	}
	memset(sec, 0, sizeof(*sec));

	INIT_LIST_HEAD(&sec->symbol_list);
	INIT_LIST_HEAD(&sec->rela_list);
	hash_init(sec->rela_hash);

	s = elf_newscn(elf->elf);
	if (!s) {
		WARN_ELF("elf_newscn");
		return NULL;
	}

	sec->name = strdup(name);
	if (!sec->name) {
		perror("strdup");
		return NULL;
	}

	sec->idx = elf_ndxscn(s);
	sec->len = size;
	sec->changed = true;

	sec->data = elf_newdata(s);
	if (!sec->data) {
		WARN_ELF("elf_newdata");
		return NULL;
	}

	sec->data->d_size = size;
	sec->data->d_align = 1;

	if (size) {
		sec->data->d_buf = malloc(size);
		if (!sec->data->d_buf) {
			perror("malloc");
			return NULL;
		}
		memset(sec->data->d_buf, 0, size);
	}

	if (!gelf_getshdr(s, &sec->sh)) {
		WARN_ELF("gelf_getshdr");
		return NULL;
	}

	sec->sh.sh_size = size;
	sec->sh.sh_entsize = entsize;
	sec->sh.sh_type = SHT_PROGBITS;
	sec->sh.sh_addralign = 1;
	sec->sh.sh_flags = SHF_ALLOC;


	/* Add section name to .shstrtab (or .strtab for Clang) */
	shstrtab = find_section_by_name(elf, ".shstrtab");
	if (!shstrtab)
		shstrtab = find_section_by_name(elf, ".strtab");
	if (!shstrtab) {
		WARN("can't find .shstrtab or .strtab section");
		return NULL;
	}

	s = elf_getscn(elf->elf, shstrtab->idx);
	if (!s) {
		WARN_ELF("elf_getscn");
		return NULL;
	}

	data = elf_newdata(s);
	if (!data) {
		WARN_ELF("elf_newdata");
		return NULL;
	}

	data->d_buf = sec->name;
	data->d_size = strlen(name) + 1;
	data->d_align = 1;

	sec->sh.sh_name = shstrtab->len;

	shstrtab->len += strlen(name) + 1;
	shstrtab->changed = true;

	list_add_tail(&sec->list, &elf->sections);
	hash_add(elf->section_hash, &sec->hash, sec->idx);
	hash_add(elf->section_name_hash, &sec->name_hash, str_hash(sec->name));

	return sec;
}

struct section *elf_create_rela_section(struct elf *elf, struct section *base)
{
	char *relaname;
	struct section *sec;

	relaname = malloc(strlen(base->name) + strlen(".rela") + 1);
	if (!relaname) {
		perror("malloc");
		return NULL;
	}
	strcpy(relaname, ".rela");
	strcat(relaname, base->name);

	sec = elf_create_section(elf, relaname, sizeof(GElf_Rela), 0);
	free(relaname);
	if (!sec)
		return NULL;

	base->rela = sec;
	sec->base = base;

	sec->sh.sh_type = SHT_RELA;
	sec->sh.sh_addralign = 8;
	sec->sh.sh_link = find_section_by_name(elf, ".symtab")->idx;
	sec->sh.sh_info = base->idx;
	sec->sh.sh_flags = SHF_INFO_LINK;

	return sec;
}

int elf_rebuild_rela_section(struct section *sec)
{
	struct rela *rela;
	int nr, idx = 0, size;
	GElf_Rela *relas;

	nr = 0;
	list_for_each_entry(rela, &sec->rela_list, list)
		nr++;

	size = nr * sizeof(*relas);
	relas = malloc(size);
	if (!relas) {
		perror("malloc");
		return -1;
	}

	sec->data->d_buf = relas;
	sec->data->d_size = size;

	sec->sh.sh_size = size;

	idx = 0;
	list_for_each_entry(rela, &sec->rela_list, list) {
		relas[idx].r_offset = rela->offset;
		relas[idx].r_addend = rela->addend;
		relas[idx].r_info = GELF_R_INFO(rela->sym->idx, rela->type);
		idx++;
	}

	return 0;
}

int elf_write(struct elf *elf)
{
	struct section *sec;
	Elf_Scn *s;

	/* Update section headers for changed sections: */
	list_for_each_entry(sec, &elf->sections, list) {
		if (sec->changed) {
			s = elf_getscn(elf->elf, sec->idx);
			if (!s) {
				WARN_ELF("elf_getscn");
				return -1;
			}
			if (!gelf_update_shdr(s, &sec->sh)) {
				WARN_ELF("gelf_update_shdr");
				return -1;
			}
		}
	}

	/* Make sure the new section header entries get updated properly. */
	elf_flagelf(elf->elf, ELF_C_SET, ELF_F_DIRTY);

	/* Write all changes to the file. */
	if (elf_update(elf->elf, ELF_C_WRITE) < 0) {
		WARN_ELF("elf_update");
		return -1;
	}

	return 0;
}

void elf_close(struct elf *elf)
{
	struct section *sec, *tmpsec;
	struct symbol *sym, *tmpsym;
	struct rela *rela, *tmprela;

	if (elf->elf)
		elf_end(elf->elf);

	if (elf->fd > 0)
		close(elf->fd);

	list_for_each_entry_safe(sec, tmpsec, &elf->sections, list) {
		list_for_each_entry_safe(sym, tmpsym, &sec->symbol_list, list) {
			list_del(&sym->list);
			hash_del(&sym->hash);
			free(sym);
		}
		list_for_each_entry_safe(rela, tmprela, &sec->rela_list, list) {
			list_del(&rela->list);
			hash_del(&rela->hash);
			free(rela);
		}
		list_del(&sec->list);
		free(sec);
	}

	free(elf);
}
Commit	Line	Data
1ccea77e	1	// SPDX-License-Identifier: GPL-2.0-or-later
442f04c3 JP	2	/*
	3	* elf.c - ELF access library
	4	*
	5	* Adapted from kpatch (https://github.com/dynup/kpatch):
	6	* Copyright (C) 2013-2015 Josh Poimboeuf <jpoimboe@redhat.com>
	7	* Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
442f04c3 JP	8	*/
	9
	10	#include <sys/types.h>
	11	#include <sys/stat.h>
	12	#include <fcntl.h>
	13	#include <stdio.h>
	14	#include <stdlib.h>
	15	#include <string.h>
	16	#include <unistd.h>
385d11b1	17	#include <errno.h>
1e11f3fd	18	#include "builtin.h"
442f04c3 JP	19
	20	#include "elf.h"
	21	#include "warn.h"
	22
22566c16 AS	23	#define MAX_NAME_LEN 128
22566c16 AS	24
ae358196 PZ	25	static inline u32 str_hash(const char *str)
	26	{
	27	return jhash(str, strlen(str), 0);
	28	}
	29
2a362ecc PZ	30	static void rb_add(struct rb_root tree, struct rb_node node,
	31	int (cmp)(struct rb_node , const struct rb_node *))
	32	{
	33	struct rb_node **link = &tree->rb_node;
	34	struct rb_node *parent = NULL;
	35
	36	while (*link) {
	37	parent = *link;
	38	if (cmp(node, parent) < 0)
	39	link = &parent->rb_left;
	40	else
	41	link = &parent->rb_right;
	42	}
	43
	44	rb_link_node(node, parent, link);
	45	rb_insert_color(node, tree);
	46	}
	47
	48	static struct rb_node rb_find_first(struct rb_root tree, const void *key,
	49	int (cmp)(const void key, const struct rb_node *))
	50	{
	51	struct rb_node *node = tree->rb_node;
	52	struct rb_node *match = NULL;
	53
	54	while (node) {
	55	int c = cmp(key, node);
	56	if (c <= 0) {
	57	if (!c)
	58	match = node;
	59	node = node->rb_left;
	60	} else if (c > 0) {
	61	node = node->rb_right;
	62	}
	63	}
	64
	65	return match;
	66	}
	67
	68	static struct rb_node rb_next_match(struct rb_node node, const void *key,
	69	int (cmp)(const void key, const struct rb_node *))
	70	{
	71	node = rb_next(node);
	72	if (node && cmp(key, node))
	73	node = NULL;
	74	return node;
	75	}
	76
	77	#define rb_for_each(tree, node, key, cmp) \
	78	for ((node) = rb_find_first((tree), (key), (cmp)); \
	79	(node); (node) = rb_next_match((node), (key), (cmp)))
	80
	81	static int symbol_to_offset(struct rb_node a, const struct rb_node b)
	82	{
	83	struct symbol *sa = rb_entry(a, struct symbol, node);
	84	struct symbol *sb = rb_entry(b, struct symbol, node);
	85
	86	if (sa->offset < sb->offset)
	87	return -1;
	88	if (sa->offset > sb->offset)
	89	return 1;
	90
	91	if (sa->len < sb->len)
	92	return -1;
	93	if (sa->len > sb->len)
94	return 1;
95
96	sa->alias = sb;
97
98	return 0;
99	}
100
101	static int symbol_by_offset(const void key, const struct rb_node node)
102	{
103	const struct symbol *s = rb_entry(node, struct symbol, node);
104	const unsigned long *o = key;
105
106	if (*o < s->offset)
107	return -1;
108	if (*o > s->offset + s->len)
109	return 1;
110
111	return 0;
112	}
113
442f04c3 JP	114	struct section find_section_by_name(struct elf elf, const char *name)
	115	{
	116	struct section *sec;
	117
ae358196	118	hash_for_each_possible(elf->section_name_hash, sec, name_hash, str_hash(name))
442f04c3 JP	119	if (!strcmp(sec->name, name))
	120	return sec;
	121
	122	return NULL;
	123	}
	124
	125	static struct section find_section_by_index(struct elf elf,
	126	unsigned int idx)
	127	{
	128	struct section *sec;
	129
53038996	130	hash_for_each_possible(elf->section_hash, sec, hash, idx)
442f04c3 JP	131	if (sec->idx == idx)
	132	return sec;
	133
	134	return NULL;
	135	}
	136
	137	static struct symbol find_symbol_by_index(struct elf elf, unsigned int idx)
	138	{
442f04c3 JP	139	struct symbol *sym;
442f04c3 JP	140
65fb11a7 PZ	141	hash_for_each_possible(elf->symbol_hash, sym, hash, idx)
	142	if (sym->idx == idx)
	143	return sym;
442f04c3 JP	144
	145	return NULL;
	146	}
	147
	148	struct symbol find_symbol_by_offset(struct section sec, unsigned long offset)
	149	{
2a362ecc	150	struct rb_node *node;
442f04c3	151
2a362ecc PZ	152	rb_for_each(&sec->symbol_tree, node, &offset, symbol_by_offset) {
	153	struct symbol *s = rb_entry(node, struct symbol, node);
	154
	155	if (s->offset == offset && s->type != STT_SECTION)
	156	return s;
	157	}
7acfe531 JP	158
	159	return NULL;
	160	}
	161
	162	struct symbol find_func_by_offset(struct section sec, unsigned long offset)
	163	{
2a362ecc	164	struct rb_node *node;
7acfe531	165
2a362ecc PZ	166	rb_for_each(&sec->symbol_tree, node, &offset, symbol_by_offset) {
	167	struct symbol *s = rb_entry(node, struct symbol, node);
	168
	169	if (s->offset == offset && s->type == STT_FUNC)
	170	return s;
	171	}
442f04c3 JP	172
	173	return NULL;
	174	}
	175
2a362ecc	176	struct symbol find_symbol_containing(struct section sec, unsigned long offset)
13810435	177	{
2a362ecc	178	struct rb_node *node;
13810435	179
2a362ecc PZ	180	rb_for_each(&sec->symbol_tree, node, &offset, symbol_by_offset) {
	181	struct symbol *s = rb_entry(node, struct symbol, node);
	182
	183	if (s->type != STT_SECTION)
	184	return s;
	185	}
13810435 JP	186
	187	return NULL;
	188	}
	189
53d20720	190	struct symbol find_func_containing(struct section sec, unsigned long offset)
2a362ecc PZ	191	{
	192	struct rb_node *node;
	193
	194	rb_for_each(&sec->symbol_tree, node, &offset, symbol_by_offset) {
	195	struct symbol *s = rb_entry(node, struct symbol, node);
	196
	197	if (s->type == STT_FUNC)
	198	return s;
	199	}
	200
	201	return NULL;
	202	}
	203
	204	struct symbol find_symbol_by_name(struct elf elf, const char *name)
5c51f4ae JP	205	{
	206	struct symbol *sym;
	207
cdb3d057 PZ	208	hash_for_each_possible(elf->symbol_name_hash, sym, name_hash, str_hash(name))
	209	if (!strcmp(sym->name, name))
	210	return sym;
5c51f4ae JP	211
	212	return NULL;
	213	}
	214
442f04c3 JP	215	struct rela find_rela_by_dest_range(struct section sec, unsigned long offset,
	216	unsigned int len)
	217	{
	218	struct rela *rela;
042ba73f	219	unsigned long o;
442f04c3 JP	220
	221	if (!sec->rela)
	222	return NULL;
	223
042ba73f JP	224	for (o = offset; o < offset + len; o++)
	225	hash_for_each_possible(sec->rela->rela_hash, rela, hash, o)
	226	if (rela->offset == o)
	227	return rela;
442f04c3 JP	228
	229	return NULL;
	230	}
	231
	232	struct rela find_rela_by_dest(struct section sec, unsigned long offset)
	233	{
	234	return find_rela_by_dest_range(sec, offset, 1);
	235	}
	236
442f04c3 JP	237	static int read_sections(struct elf *elf)
	238	{
	239	Elf_Scn *s = NULL;
	240	struct section *sec;
	241	size_t shstrndx, sections_nr;
	242	int i;
	243
	244	if (elf_getshdrnum(elf->elf, &sections_nr)) {
baa41469	245	WARN_ELF("elf_getshdrnum");
442f04c3 JP	246	return -1;
	247	}
	248
	249	if (elf_getshdrstrndx(elf->elf, &shstrndx)) {
baa41469	250	WARN_ELF("elf_getshdrstrndx");
442f04c3 JP	251	return -1;
	252	}
	253
	254	for (i = 0; i < sections_nr; i++) {
	255	sec = malloc(sizeof(*sec));
	256	if (!sec) {
	257	perror("malloc");
	258	return -1;
	259	}
	260	memset(sec, 0, sizeof(*sec));
	261
a196e171 JP	262	INIT_LIST_HEAD(&sec->symbol_list);
a196e171 JP	263	INIT_LIST_HEAD(&sec->rela_list);
042ba73f	264	hash_init(sec->rela_hash);
442f04c3	265
442f04c3 JP	266	s = elf_getscn(elf->elf, i);
442f04c3 JP	267	if (!s) {
baa41469	268	WARN_ELF("elf_getscn");
442f04c3 JP	269	return -1;
	270	}
	271
	272	sec->idx = elf_ndxscn(s);
	273
	274	if (!gelf_getshdr(s, &sec->sh)) {
baa41469	275	WARN_ELF("gelf_getshdr");
442f04c3 JP	276	return -1;
	277	}
	278
	279	sec->name = elf_strptr(elf->elf, shstrndx, sec->sh.sh_name);
	280	if (!sec->name) {
baa41469	281	WARN_ELF("elf_strptr");
442f04c3 JP	282	return -1;
	283	}
	284
df968c93 PV	285	if (sec->sh.sh_size != 0) {
	286	sec->data = elf_getdata(s, NULL);
	287	if (!sec->data) {
	288	WARN_ELF("elf_getdata");
	289	return -1;
	290	}
	291	if (sec->data->d_off != 0 \|\|
	292	sec->data->d_size != sec->sh.sh_size) {
	293	WARN("unexpected data attributes for %s",
	294	sec->name);
	295	return -1;
	296	}
442f04c3	297	}
df968c93	298	sec->len = sec->sh.sh_size;
53038996 PZ	299
	300	list_add_tail(&sec->list, &elf->sections);
	301	hash_add(elf->section_hash, &sec->hash, sec->idx);
ae358196	302	hash_add(elf->section_name_hash, &sec->name_hash, str_hash(sec->name));
442f04c3 JP	303	}
442f04c3 JP	304
1e11f3fd PZ	305	if (stats)
	306	printf("nr_sections: %lu\n", (unsigned long)sections_nr);
	307
442f04c3 JP	308	/* sanity check, one more call to elf_nextscn() should return NULL */
	309	if (elf_nextscn(elf->elf, s)) {
	310	WARN("section entry mismatch");
	311	return -1;
	312	}
	313
	314	return 0;
	315	}
	316
	317	static int read_symbols(struct elf *elf)
	318	{
13810435	319	struct section symtab, sec;
2a362ecc PZ	320	struct symbol sym, pfunc;
	321	struct list_head *entry;
	322	struct rb_node *pnode;
442f04c3	323	int symbols_nr, i;
13810435	324	char *coldstr;
442f04c3 JP	325
	326	symtab = find_section_by_name(elf, ".symtab");
	327	if (!symtab) {
	328	WARN("missing symbol table");
	329	return -1;
	330	}
	331
	332	symbols_nr = symtab->sh.sh_size / symtab->sh.sh_entsize;
	333
	334	for (i = 0; i < symbols_nr; i++) {
	335	sym = malloc(sizeof(*sym));
	336	if (!sym) {
	337	perror("malloc");
	338	return -1;
	339	}
	340	memset(sym, 0, sizeof(*sym));
2a362ecc	341	sym->alias = sym;
442f04c3 JP	342
	343	sym->idx = i;
	344
baa41469 JP	345	if (!gelf_getsym(symtab->data, i, &sym->sym)) {
baa41469 JP	346	WARN_ELF("gelf_getsym");
442f04c3 JP	347	goto err;
	348	}
	349
	350	sym->name = elf_strptr(elf->elf, symtab->sh.sh_link,
	351	sym->sym.st_name);
	352	if (!sym->name) {
baa41469	353	WARN_ELF("elf_strptr");
442f04c3 JP	354	goto err;
	355	}
	356
	357	sym->type = GELF_ST_TYPE(sym->sym.st_info);
	358	sym->bind = GELF_ST_BIND(sym->sym.st_info);
	359
	360	if (sym->sym.st_shndx > SHN_UNDEF &&
	361	sym->sym.st_shndx < SHN_LORESERVE) {
	362	sym->sec = find_section_by_index(elf,
	363	sym->sym.st_shndx);
	364	if (!sym->sec) {
	365	WARN("couldn't find section for symbol %s",
	366	sym->name);
	367	goto err;
	368	}
	369	if (sym->type == STT_SECTION) {
	370	sym->name = sym->sec->name;
	371	sym->sec->sym = sym;
	372	}
	373	} else
	374	sym->sec = find_section_by_index(elf, 0);
	375
	376	sym->offset = sym->sym.st_value;
	377	sym->len = sym->sym.st_size;
	378
2a362ecc PZ	379	rb_add(&sym->sec->symbol_tree, &sym->node, symbol_to_offset);
	380	pnode = rb_prev(&sym->node);
	381	if (pnode)
	382	entry = &rb_entry(pnode, struct symbol, node)->list;
	383	else
	384	entry = &sym->sec->symbol_list;
442f04c3	385	list_add(&sym->list, entry);
65fb11a7	386	hash_add(elf->symbol_hash, &sym->hash, sym->idx);
cdb3d057	387	hash_add(elf->symbol_name_hash, &sym->name_hash, str_hash(sym->name));
442f04c3 JP	388	}
442f04c3 JP	389
1e11f3fd PZ	390	if (stats)
	391	printf("nr_symbols: %lu\n", (unsigned long)symbols_nr);
	392
13810435 JP	393	/* Create parent/child links for any cold subfunctions */
	394	list_for_each_entry(sec, &elf->sections, list) {
	395	list_for_each_entry(sym, &sec->symbol_list, list) {
22566c16 AS	396	char pname[MAX_NAME_LEN + 1];
22566c16 AS	397	size_t pnamelen;
13810435 JP	398	if (sym->type != STT_FUNC)
	399	continue;
	400	sym->pfunc = sym->cfunc = sym;
bcb6fb5d	401	coldstr = strstr(sym->name, ".cold");
08b393d0 JP	402	if (!coldstr)
	403	continue;
	404
22566c16 AS	405	pnamelen = coldstr - sym->name;
	406	if (pnamelen > MAX_NAME_LEN) {
	407	WARN("%s(): parent function name exceeds maximum length of %d characters",
	408	sym->name, MAX_NAME_LEN);
	409	return -1;
	410	}
	411
	412	strncpy(pname, sym->name, pnamelen);
	413	pname[pnamelen] = '\0';
	414	pfunc = find_symbol_by_name(elf, pname);
08b393d0 JP	415
	416	if (!pfunc) {
	417	WARN("%s(): can't find parent function",
	418	sym->name);
0b9301fb	419	return -1;
08b393d0 JP	420	}
	421
	422	sym->pfunc = pfunc;
	423	pfunc->cfunc = sym;
	424
	425	/*
	426	* Unfortunately, -fnoreorder-functions puts the child
	427	* inside the parent. Remove the overlap so we can
	428	* have sane assumptions.
	429	*
	430	* Note that pfunc->len now no longer matches
	431	* pfunc->sym.st_size.
	432	*/
	433	if (sym->sec == pfunc->sec &&
	434	sym->offset >= pfunc->offset &&
	435	sym->offset + sym->len == pfunc->offset + pfunc->len) {
	436	pfunc->len -= sym->len;
13810435 JP	437	}
	438	}
	439	}
	440
442f04c3 JP	441	return 0;
	442
	443	err:
	444	free(sym);
	445	return -1;
	446	}
	447
	448	static int read_relas(struct elf *elf)
	449	{
	450	struct section *sec;
	451	struct rela *rela;
	452	int i;
	453	unsigned int symndx;
1e11f3fd	454	unsigned long nr_rela, max_rela = 0, tot_rela = 0;
442f04c3 JP	455
	456	list_for_each_entry(sec, &elf->sections, list) {
	457	if (sec->sh.sh_type != SHT_RELA)
	458	continue;
	459
	460	sec->base = find_section_by_name(elf, sec->name + 5);
	461	if (!sec->base) {
	462	WARN("can't find base section for rela section %s",
	463	sec->name);
	464	return -1;
	465	}
	466
	467	sec->base->rela = sec;
	468
1e11f3fd	469	nr_rela = 0;
442f04c3 JP	470	for (i = 0; i < sec->sh.sh_size / sec->sh.sh_entsize; i++) {
	471	rela = malloc(sizeof(*rela));
	472	if (!rela) {
	473	perror("malloc");
	474	return -1;
	475	}
	476	memset(rela, 0, sizeof(*rela));
	477
baa41469 JP	478	if (!gelf_getrela(sec->data, i, &rela->rela)) {
baa41469 JP	479	WARN_ELF("gelf_getrela");
442f04c3 JP	480	return -1;
	481	}
	482
	483	rela->type = GELF_R_TYPE(rela->rela.r_info);
	484	rela->addend = rela->rela.r_addend;
	485	rela->offset = rela->rela.r_offset;
	486	symndx = GELF_R_SYM(rela->rela.r_info);
	487	rela->sym = find_symbol_by_index(elf, symndx);
e7c2bc37	488	rela->sec = sec;
442f04c3 JP	489	if (!rela->sym) {
	490	WARN("can't find rela entry symbol %d for %s",
	491	symndx, sec->name);
	492	return -1;
	493	}
042ba73f JP	494
	495	list_add_tail(&rela->list, &sec->rela_list);
	496	hash_add(sec->rela_hash, &rela->hash, rela->offset);
1e11f3fd	497	nr_rela++;
442f04c3	498	}
1e11f3fd PZ	499	max_rela = max(max_rela, nr_rela);
	500	tot_rela += nr_rela;
	501	}
	502
	503	if (stats) {
	504	printf("max_rela: %lu\n", max_rela);
	505	printf("tot_rela: %lu\n", tot_rela);
442f04c3 JP	506	}
	507
	508	return 0;
	509	}
	510
8e144797	511	struct elf elf_read(const char name, int flags)
442f04c3 JP	512	{
442f04c3 JP	513	struct elf *elf;
627fce14	514	Elf_Cmd cmd;
442f04c3 JP	515
	516	elf_version(EV_CURRENT);
	517
	518	elf = malloc(sizeof(*elf));
	519	if (!elf) {
	520	perror("malloc");
	521	return NULL;
	522	}
	523	memset(elf, 0, sizeof(*elf));
	524
65fb11a7	525	hash_init(elf->symbol_hash);
cdb3d057	526	hash_init(elf->symbol_name_hash);
53038996	527	hash_init(elf->section_hash);
ae358196	528	hash_init(elf->section_name_hash);
442f04c3 JP	529	INIT_LIST_HEAD(&elf->sections);
442f04c3 JP	530
627fce14	531	elf->fd = open(name, flags);
442f04c3	532	if (elf->fd == -1) {
385d11b1 JP	533	fprintf(stderr, "objtool: Can't open '%s': %s\n",
385d11b1 JP	534	name, strerror(errno));
442f04c3 JP	535	goto err;
	536	}
	537
627fce14 JP	538	if ((flags & O_ACCMODE) == O_RDONLY)
	539	cmd = ELF_C_READ_MMAP;
	540	else if ((flags & O_ACCMODE) == O_RDWR)
	541	cmd = ELF_C_RDWR;
	542	else /* O_WRONLY */
	543	cmd = ELF_C_WRITE;
	544
	545	elf->elf = elf_begin(elf->fd, cmd, NULL);
442f04c3	546	if (!elf->elf) {
baa41469	547	WARN_ELF("elf_begin");
442f04c3 JP	548	goto err;
	549	}
	550
	551	if (!gelf_getehdr(elf->elf, &elf->ehdr)) {
baa41469	552	WARN_ELF("gelf_getehdr");
442f04c3 JP	553	goto err;
	554	}
	555
	556	if (read_sections(elf))
	557	goto err;
	558
	559	if (read_symbols(elf))
	560	goto err;
	561
	562	if (read_relas(elf))
	563	goto err;
	564
	565	return elf;
	566
	567	err:
	568	elf_close(elf);
	569	return NULL;
	570	}
	571
627fce14 JP	572	struct section elf_create_section(struct elf elf, const char *name,
	573	size_t entsize, int nr)
	574	{
	575	struct section sec, shstrtab;
	576	size_t size = entsize * nr;
3c3ea503	577	Elf_Scn *s;
627fce14 JP	578	Elf_Data *data;
	579
	580	sec = malloc(sizeof(*sec));
	581	if (!sec) {
	582	perror("malloc");
	583	return NULL;
	584	}
	585	memset(sec, 0, sizeof(*sec));
	586
	587	INIT_LIST_HEAD(&sec->symbol_list);
	588	INIT_LIST_HEAD(&sec->rela_list);
	589	hash_init(sec->rela_hash);
627fce14	590
627fce14 JP	591	s = elf_newscn(elf->elf);
	592	if (!s) {
	593	WARN_ELF("elf_newscn");
	594	return NULL;
	595	}
	596
	597	sec->name = strdup(name);
	598	if (!sec->name) {
	599	perror("strdup");
	600	return NULL;
	601	}
	602
	603	sec->idx = elf_ndxscn(s);
	604	sec->len = size;
	605	sec->changed = true;
	606
	607	sec->data = elf_newdata(s);
	608	if (!sec->data) {
	609	WARN_ELF("elf_newdata");
	610	return NULL;
	611	}
	612
	613	sec->data->d_size = size;
	614	sec->data->d_align = 1;
	615
	616	if (size) {
	617	sec->data->d_buf = malloc(size);
	618	if (!sec->data->d_buf) {
	619	perror("malloc");
	620	return NULL;
	621	}
	622	memset(sec->data->d_buf, 0, size);
	623	}
	624
	625	if (!gelf_getshdr(s, &sec->sh)) {
	626	WARN_ELF("gelf_getshdr");
	627	return NULL;
	628	}
	629
	630	sec->sh.sh_size = size;
	631	sec->sh.sh_entsize = entsize;
	632	sec->sh.sh_type = SHT_PROGBITS;
	633	sec->sh.sh_addralign = 1;
	634	sec->sh.sh_flags = SHF_ALLOC;
	635
	636
6d77d3b4	637	/* Add section name to .shstrtab (or .strtab for Clang) */
627fce14	638	shstrtab = find_section_by_name(elf, ".shstrtab");
6d77d3b4 SS	639	if (!shstrtab)
6d77d3b4 SS	640	shstrtab = find_section_by_name(elf, ".strtab");
627fce14	641	if (!shstrtab) {
6d77d3b4	642	WARN("can't find .shstrtab or .strtab section");
627fce14 JP	643	return NULL;
	644	}
	645
	646	s = elf_getscn(elf->elf, shstrtab->idx);
	647	if (!s) {
	648	WARN_ELF("elf_getscn");
	649	return NULL;
	650	}
	651
	652	data = elf_newdata(s);
	653	if (!data) {
	654	WARN_ELF("elf_newdata");
	655	return NULL;
	656	}
	657
	658	data->d_buf = sec->name;
	659	data->d_size = strlen(name) + 1;
	660	data->d_align = 1;
	661
	662	sec->sh.sh_name = shstrtab->len;
	663
	664	shstrtab->len += strlen(name) + 1;
	665	shstrtab->changed = true;
	666
53038996 PZ	667	list_add_tail(&sec->list, &elf->sections);
53038996 PZ	668	hash_add(elf->section_hash, &sec->hash, sec->idx);
ae358196	669	hash_add(elf->section_name_hash, &sec->name_hash, str_hash(sec->name));
53038996	670
627fce14 JP	671	return sec;
	672	}
	673
	674	struct section elf_create_rela_section(struct elf elf, struct section *base)
	675	{
	676	char *relaname;
	677	struct section *sec;
	678
	679	relaname = malloc(strlen(base->name) + strlen(".rela") + 1);
	680	if (!relaname) {
	681	perror("malloc");
	682	return NULL;
	683	}
	684	strcpy(relaname, ".rela");
	685	strcat(relaname, base->name);
	686
	687	sec = elf_create_section(elf, relaname, sizeof(GElf_Rela), 0);
0998b7a0	688	free(relaname);
627fce14 JP	689	if (!sec)
	690	return NULL;
	691
	692	base->rela = sec;
	693	sec->base = base;
	694
	695	sec->sh.sh_type = SHT_RELA;
	696	sec->sh.sh_addralign = 8;
	697	sec->sh.sh_link = find_section_by_name(elf, ".symtab")->idx;
	698	sec->sh.sh_info = base->idx;
	699	sec->sh.sh_flags = SHF_INFO_LINK;
	700
	701	return sec;
	702	}
	703
	704	int elf_rebuild_rela_section(struct section *sec)
	705	{
	706	struct rela *rela;
	707	int nr, idx = 0, size;
	708	GElf_Rela *relas;
	709
	710	nr = 0;
	711	list_for_each_entry(rela, &sec->rela_list, list)
	712	nr++;
	713
	714	size = nr * sizeof(*relas);
	715	relas = malloc(size);
	716	if (!relas) {
	717	perror("malloc");
	718	return -1;
	719	}
	720
	721	sec->data->d_buf = relas;
	722	sec->data->d_size = size;
	723
	724	sec->sh.sh_size = size;
	725
	726	idx = 0;
	727	list_for_each_entry(rela, &sec->rela_list, list) {
	728	relas[idx].r_offset = rela->offset;
	729	relas[idx].r_addend = rela->addend;
	730	relas[idx].r_info = GELF_R_INFO(rela->sym->idx, rela->type);
	731	idx++;
	732	}
	733
	734	return 0;
	735	}
	736
	737	int elf_write(struct elf *elf)
	738	{
	739	struct section *sec;
	740	Elf_Scn *s;
	741
97dab2ae	742	/* Update section headers for changed sections: */
627fce14 JP	743	list_for_each_entry(sec, &elf->sections, list) {
	744	if (sec->changed) {
	745	s = elf_getscn(elf->elf, sec->idx);
	746	if (!s) {
	747	WARN_ELF("elf_getscn");
	748	return -1;
	749	}
97dab2ae	750	if (!gelf_update_shdr(s, &sec->sh)) {
627fce14 JP	751	WARN_ELF("gelf_update_shdr");
	752	return -1;
	753	}
	754	}
	755	}
	756
97dab2ae JP	757	/* Make sure the new section header entries get updated properly. */
	758	elf_flagelf(elf->elf, ELF_C_SET, ELF_F_DIRTY);
	759
	760	/* Write all changes to the file. */
627fce14 JP	761	if (elf_update(elf->elf, ELF_C_WRITE) < 0) {
	762	WARN_ELF("elf_update");
	763	return -1;
	764	}
	765
	766	return 0;
	767	}
	768
442f04c3 JP	769	void elf_close(struct elf *elf)
	770	{
	771	struct section sec, tmpsec;
	772	struct symbol sym, tmpsym;
	773	struct rela rela, tmprela;
	774
baa41469 JP	775	if (elf->elf)
	776	elf_end(elf->elf);
	777
	778	if (elf->fd > 0)
	779	close(elf->fd);
	780
442f04c3	781	list_for_each_entry_safe(sec, tmpsec, &elf->sections, list) {
a196e171	782	list_for_each_entry_safe(sym, tmpsym, &sec->symbol_list, list) {
442f04c3	783	list_del(&sym->list);
042ba73f	784	hash_del(&sym->hash);
442f04c3 JP	785	free(sym);
442f04c3 JP	786	}
a196e171	787	list_for_each_entry_safe(rela, tmprela, &sec->rela_list, list) {
442f04c3	788	list_del(&rela->list);
042ba73f	789	hash_del(&rela->hash);
442f04c3 JP	790	free(rela);
	791	}
	792	list_del(&sec->list);
	793	free(sec);
	794	}
baa41469	795
442f04c3 JP	796	free(elf);
442f04c3 JP	797	}