[mirror_ubuntu-focal-kernel.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 "elf.h"
#include "warn.h"

#define MAX_NAME_LEN 128

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

	list_for_each_entry(sec, &elf->sections, list)
		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;

	list_for_each_entry(sec, &elf->sections, list)
		if (sec->idx == idx)
			return sec;

	return NULL;
}

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

	list_for_each_entry(sec, &elf->sections, list)
		hash_for_each_possible(sec->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 symbol *sym;

	list_for_each_entry(sym, &sec->symbol_list, list)
		if (sym->type != STT_SECTION &&
		    sym->offset == offset)
			return sym;

	return NULL;
}

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

	list_for_each_entry(sec, &elf->sections, list)
		list_for_each_entry(sym, &sec->symbol_list, list)
			if (!strcmp(sym->name, name))
				return sym;

	return NULL;
}

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

	list_for_each_entry(sym, &sec->symbol_list, list)
		if (sym->type != STT_SECTION &&
		    offset >= sym->offset && offset < sym->offset + sym->len)
			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);
}

struct symbol *find_containing_func(struct section *sec, unsigned long offset)
{
	struct symbol *func;

	list_for_each_entry(func, &sec->symbol_list, list)
		if (func->type == STT_FUNC && offset >= func->offset &&
		    offset < func->offset + func->len)
			return func;

	return NULL;
}

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);
		hash_init(sec->symbol_hash);

		list_add_tail(&sec->list, &elf->sections);

		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;
	}

	/* 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, *alias;
	struct list_head *entry, *tmp;
	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));
		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;

		/* sorted insert into a per-section list */
		entry = &sym->sec->symbol_list;
		list_for_each_prev(tmp, &sym->sec->symbol_list) {
			struct symbol *s;

			s = list_entry(tmp, struct symbol, list);

			if (sym->offset > s->offset) {
				entry = tmp;
				break;
			}

			if (sym->offset == s->offset) {
				if (sym->len == s->len && alias == sym)
					alias = s;

				if (sym->len >= s->len) {
					entry = tmp;
					break;
				}
			}
		}
		sym->alias = alias;
		list_add(&sym->list, entry);
		hash_add(sym->sec->symbol_hash, &sym->hash, sym->idx);
	}

	/* 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;

	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;

		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->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);

		}
	}

	return 0;
}

struct elf *elf_open(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));

	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;
	struct 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);
	hash_init(sec->symbol_hash);

	list_add_tail(&sec->list, &elf->sections);

	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;

	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>
442f04c3 JP	18
	19	#include "elf.h"
	20	#include "warn.h"
	21
22566c16 AS	22	#define MAX_NAME_LEN 128
22566c16 AS	23
442f04c3 JP	24	struct section find_section_by_name(struct elf elf, const char *name)
	25	{
	26	struct section *sec;
	27
	28	list_for_each_entry(sec, &elf->sections, list)
	29	if (!strcmp(sec->name, name))
	30	return sec;
	31
	32	return NULL;
	33	}
	34
	35	static struct section find_section_by_index(struct elf elf,
	36	unsigned int idx)
	37	{
	38	struct section *sec;
	39
	40	list_for_each_entry(sec, &elf->sections, list)
	41	if (sec->idx == idx)
	42	return sec;
	43
	44	return NULL;
	45	}
	46
	47	static struct symbol find_symbol_by_index(struct elf elf, unsigned int idx)
	48	{
	49	struct section *sec;
	50	struct symbol *sym;
	51
	52	list_for_each_entry(sec, &elf->sections, list)
042ba73f	53	hash_for_each_possible(sec->symbol_hash, sym, hash, idx)
442f04c3 JP	54	if (sym->idx == idx)
	55	return sym;
	56
	57	return NULL;
	58	}
	59
	60	struct symbol find_symbol_by_offset(struct section sec, unsigned long offset)
	61	{
	62	struct symbol *sym;
	63
a196e171	64	list_for_each_entry(sym, &sec->symbol_list, list)
442f04c3 JP	65	if (sym->type != STT_SECTION &&
	66	sym->offset == offset)
	67	return sym;
	68
	69	return NULL;
	70	}
	71
13810435 JP	72	struct symbol find_symbol_by_name(struct elf elf, const char *name)
	73	{
	74	struct section *sec;
	75	struct symbol *sym;
	76
	77	list_for_each_entry(sec, &elf->sections, list)
	78	list_for_each_entry(sym, &sec->symbol_list, list)
	79	if (!strcmp(sym->name, name))
	80	return sym;
	81
	82	return NULL;
	83	}
	84
5c51f4ae JP	85	struct symbol find_symbol_containing(struct section sec, unsigned long offset)
	86	{
	87	struct symbol *sym;
	88
	89	list_for_each_entry(sym, &sec->symbol_list, list)
	90	if (sym->type != STT_SECTION &&
	91	offset >= sym->offset && offset < sym->offset + sym->len)
	92	return sym;
	93
	94	return NULL;
	95	}
	96
442f04c3 JP	97	struct rela find_rela_by_dest_range(struct section sec, unsigned long offset,
	98	unsigned int len)
	99	{
	100	struct rela *rela;
042ba73f	101	unsigned long o;
442f04c3 JP	102
	103	if (!sec->rela)
	104	return NULL;
	105
042ba73f JP	106	for (o = offset; o < offset + len; o++)
	107	hash_for_each_possible(sec->rela->rela_hash, rela, hash, o)
	108	if (rela->offset == o)
	109	return rela;
442f04c3 JP	110
	111	return NULL;
	112	}
	113
	114	struct rela find_rela_by_dest(struct section sec, unsigned long offset)
	115	{
	116	return find_rela_by_dest_range(sec, offset, 1);
	117	}
	118
	119	struct symbol find_containing_func(struct section sec, unsigned long offset)
	120	{
	121	struct symbol *func;
	122
a196e171	123	list_for_each_entry(func, &sec->symbol_list, list)
442f04c3 JP	124	if (func->type == STT_FUNC && offset >= func->offset &&
	125	offset < func->offset + func->len)
	126	return func;
	127
	128	return NULL;
	129	}
	130
	131	static int read_sections(struct elf *elf)
	132	{
	133	Elf_Scn *s = NULL;
	134	struct section *sec;
	135	size_t shstrndx, sections_nr;
	136	int i;
	137
	138	if (elf_getshdrnum(elf->elf, &sections_nr)) {
baa41469	139	WARN_ELF("elf_getshdrnum");
442f04c3 JP	140	return -1;
	141	}
	142
	143	if (elf_getshdrstrndx(elf->elf, &shstrndx)) {
baa41469	144	WARN_ELF("elf_getshdrstrndx");
442f04c3 JP	145	return -1;
	146	}
	147
	148	for (i = 0; i < sections_nr; i++) {
	149	sec = malloc(sizeof(*sec));
	150	if (!sec) {
	151	perror("malloc");
	152	return -1;
	153	}
	154	memset(sec, 0, sizeof(*sec));
	155
a196e171 JP	156	INIT_LIST_HEAD(&sec->symbol_list);
a196e171 JP	157	INIT_LIST_HEAD(&sec->rela_list);
042ba73f JP	158	hash_init(sec->rela_hash);
042ba73f JP	159	hash_init(sec->symbol_hash);
442f04c3 JP	160
	161	list_add_tail(&sec->list, &elf->sections);
	162
	163	s = elf_getscn(elf->elf, i);
	164	if (!s) {
baa41469	165	WARN_ELF("elf_getscn");
442f04c3 JP	166	return -1;
	167	}
	168
	169	sec->idx = elf_ndxscn(s);
	170
	171	if (!gelf_getshdr(s, &sec->sh)) {
baa41469	172	WARN_ELF("gelf_getshdr");
442f04c3 JP	173	return -1;
	174	}
	175
	176	sec->name = elf_strptr(elf->elf, shstrndx, sec->sh.sh_name);
	177	if (!sec->name) {
baa41469	178	WARN_ELF("elf_strptr");
442f04c3 JP	179	return -1;
	180	}
	181
df968c93 PV	182	if (sec->sh.sh_size != 0) {
	183	sec->data = elf_getdata(s, NULL);
	184	if (!sec->data) {
	185	WARN_ELF("elf_getdata");
	186	return -1;
	187	}
	188	if (sec->data->d_off != 0 \|\|
	189	sec->data->d_size != sec->sh.sh_size) {
	190	WARN("unexpected data attributes for %s",
	191	sec->name);
	192	return -1;
	193	}
442f04c3	194	}
df968c93	195	sec->len = sec->sh.sh_size;
442f04c3 JP	196	}
	197
	198	/* sanity check, one more call to elf_nextscn() should return NULL */
	199	if (elf_nextscn(elf->elf, s)) {
	200	WARN("section entry mismatch");
	201	return -1;
	202	}
	203
	204	return 0;
	205	}
	206
	207	static int read_symbols(struct elf *elf)
	208	{
13810435	209	struct section symtab, sec;
09f30d83	210	struct symbol sym, pfunc, *alias;
442f04c3 JP	211	struct list_head entry, tmp;
442f04c3 JP	212	int symbols_nr, i;
13810435	213	char *coldstr;
442f04c3 JP	214
	215	symtab = find_section_by_name(elf, ".symtab");
	216	if (!symtab) {
	217	WARN("missing symbol table");
	218	return -1;
	219	}
	220
	221	symbols_nr = symtab->sh.sh_size / symtab->sh.sh_entsize;
	222
	223	for (i = 0; i < symbols_nr; i++) {
	224	sym = malloc(sizeof(*sym));
	225	if (!sym) {
	226	perror("malloc");
	227	return -1;
	228	}
	229	memset(sym, 0, sizeof(*sym));
09f30d83	230	alias = sym;
442f04c3 JP	231
	232	sym->idx = i;
	233
baa41469 JP	234	if (!gelf_getsym(symtab->data, i, &sym->sym)) {
baa41469 JP	235	WARN_ELF("gelf_getsym");
442f04c3 JP	236	goto err;
	237	}
	238
	239	sym->name = elf_strptr(elf->elf, symtab->sh.sh_link,
	240	sym->sym.st_name);
	241	if (!sym->name) {
baa41469	242	WARN_ELF("elf_strptr");
442f04c3 JP	243	goto err;
	244	}
	245
	246	sym->type = GELF_ST_TYPE(sym->sym.st_info);
	247	sym->bind = GELF_ST_BIND(sym->sym.st_info);
	248
	249	if (sym->sym.st_shndx > SHN_UNDEF &&
	250	sym->sym.st_shndx < SHN_LORESERVE) {
	251	sym->sec = find_section_by_index(elf,
	252	sym->sym.st_shndx);
	253	if (!sym->sec) {
	254	WARN("couldn't find section for symbol %s",
	255	sym->name);
	256	goto err;
	257	}
	258	if (sym->type == STT_SECTION) {
	259	sym->name = sym->sec->name;
	260	sym->sec->sym = sym;
	261	}
	262	} else
	263	sym->sec = find_section_by_index(elf, 0);
	264
	265	sym->offset = sym->sym.st_value;
	266	sym->len = sym->sym.st_size;
	267
	268	/* sorted insert into a per-section list */
a196e171 JP	269	entry = &sym->sec->symbol_list;
a196e171 JP	270	list_for_each_prev(tmp, &sym->sec->symbol_list) {
442f04c3 JP	271	struct symbol *s;
	272
	273	s = list_entry(tmp, struct symbol, list);
	274
	275	if (sym->offset > s->offset) {
	276	entry = tmp;
	277	break;
	278	}
	279
09f30d83 PZ	280	if (sym->offset == s->offset) {
	281	if (sym->len == s->len && alias == sym)
	282	alias = s;
	283
	284	if (sym->len >= s->len) {
	285	entry = tmp;
	286	break;
	287	}
442f04c3 JP	288	}
442f04c3 JP	289	}
09f30d83	290	sym->alias = alias;
442f04c3	291	list_add(&sym->list, entry);
042ba73f	292	hash_add(sym->sec->symbol_hash, &sym->hash, sym->idx);
442f04c3 JP	293	}
442f04c3 JP	294
13810435 JP	295	/* Create parent/child links for any cold subfunctions */
	296	list_for_each_entry(sec, &elf->sections, list) {
	297	list_for_each_entry(sym, &sec->symbol_list, list) {
22566c16 AS	298	char pname[MAX_NAME_LEN + 1];
22566c16 AS	299	size_t pnamelen;
13810435 JP	300	if (sym->type != STT_FUNC)
	301	continue;
	302	sym->pfunc = sym->cfunc = sym;
bcb6fb5d	303	coldstr = strstr(sym->name, ".cold");
08b393d0 JP	304	if (!coldstr)
	305	continue;
	306
22566c16 AS	307	pnamelen = coldstr - sym->name;
	308	if (pnamelen > MAX_NAME_LEN) {
	309	WARN("%s(): parent function name exceeds maximum length of %d characters",
	310	sym->name, MAX_NAME_LEN);
	311	return -1;
	312	}
	313
	314	strncpy(pname, sym->name, pnamelen);
	315	pname[pnamelen] = '\0';
	316	pfunc = find_symbol_by_name(elf, pname);
08b393d0 JP	317
	318	if (!pfunc) {
	319	WARN("%s(): can't find parent function",
	320	sym->name);
0b9301fb	321	return -1;
08b393d0 JP	322	}
	323
	324	sym->pfunc = pfunc;
	325	pfunc->cfunc = sym;
	326
	327	/*
	328	* Unfortunately, -fnoreorder-functions puts the child
	329	* inside the parent. Remove the overlap so we can
	330	* have sane assumptions.
	331	*
	332	* Note that pfunc->len now no longer matches
	333	* pfunc->sym.st_size.
	334	*/
	335	if (sym->sec == pfunc->sec &&
	336	sym->offset >= pfunc->offset &&
	337	sym->offset + sym->len == pfunc->offset + pfunc->len) {
	338	pfunc->len -= sym->len;
13810435 JP	339	}
	340	}
	341	}
	342
442f04c3 JP	343	return 0;
	344
	345	err:
	346	free(sym);
	347	return -1;
	348	}
	349
	350	static int read_relas(struct elf *elf)
	351	{
	352	struct section *sec;
	353	struct rela *rela;
	354	int i;
	355	unsigned int symndx;
	356
	357	list_for_each_entry(sec, &elf->sections, list) {
	358	if (sec->sh.sh_type != SHT_RELA)
	359	continue;
	360
	361	sec->base = find_section_by_name(elf, sec->name + 5);
	362	if (!sec->base) {
	363	WARN("can't find base section for rela section %s",
	364	sec->name);
	365	return -1;
	366	}
	367
	368	sec->base->rela = sec;
	369
	370	for (i = 0; i < sec->sh.sh_size / sec->sh.sh_entsize; i++) {
	371	rela = malloc(sizeof(*rela));
	372	if (!rela) {
	373	perror("malloc");
	374	return -1;
	375	}
	376	memset(rela, 0, sizeof(*rela));
	377
baa41469 JP	378	if (!gelf_getrela(sec->data, i, &rela->rela)) {
baa41469 JP	379	WARN_ELF("gelf_getrela");
442f04c3 JP	380	return -1;
	381	}
	382
	383	rela->type = GELF_R_TYPE(rela->rela.r_info);
	384	rela->addend = rela->rela.r_addend;
	385	rela->offset = rela->rela.r_offset;
	386	symndx = GELF_R_SYM(rela->rela.r_info);
	387	rela->sym = find_symbol_by_index(elf, symndx);
4a60aa05	388	rela->rela_sec = sec;
442f04c3 JP	389	if (!rela->sym) {
	390	WARN("can't find rela entry symbol %d for %s",
	391	symndx, sec->name);
	392	return -1;
	393	}
042ba73f JP	394
	395	list_add_tail(&rela->list, &sec->rela_list);
	396	hash_add(sec->rela_hash, &rela->hash, rela->offset);
	397
442f04c3 JP	398	}
	399	}
	400
	401	return 0;
	402	}
	403
627fce14	404	struct elf elf_open(const char name, int flags)
442f04c3 JP	405	{
442f04c3 JP	406	struct elf *elf;
627fce14	407	Elf_Cmd cmd;
442f04c3 JP	408
	409	elf_version(EV_CURRENT);
	410
	411	elf = malloc(sizeof(*elf));
	412	if (!elf) {
	413	perror("malloc");
	414	return NULL;
	415	}
	416	memset(elf, 0, sizeof(*elf));
	417
	418	INIT_LIST_HEAD(&elf->sections);
	419
627fce14	420	elf->fd = open(name, flags);
442f04c3	421	if (elf->fd == -1) {
385d11b1 JP	422	fprintf(stderr, "objtool: Can't open '%s': %s\n",
385d11b1 JP	423	name, strerror(errno));
442f04c3 JP	424	goto err;
	425	}
	426
627fce14 JP	427	if ((flags & O_ACCMODE) == O_RDONLY)
	428	cmd = ELF_C_READ_MMAP;
	429	else if ((flags & O_ACCMODE) == O_RDWR)
	430	cmd = ELF_C_RDWR;
	431	else /* O_WRONLY */
	432	cmd = ELF_C_WRITE;
	433
	434	elf->elf = elf_begin(elf->fd, cmd, NULL);
442f04c3	435	if (!elf->elf) {
baa41469	436	WARN_ELF("elf_begin");
442f04c3 JP	437	goto err;
	438	}
	439
	440	if (!gelf_getehdr(elf->elf, &elf->ehdr)) {
baa41469	441	WARN_ELF("gelf_getehdr");
442f04c3 JP	442	goto err;
	443	}
	444
	445	if (read_sections(elf))
	446	goto err;
	447
	448	if (read_symbols(elf))
	449	goto err;
	450
	451	if (read_relas(elf))
	452	goto err;
	453
	454	return elf;
	455
	456	err:
	457	elf_close(elf);
	458	return NULL;
	459	}
	460
627fce14 JP	461	struct section elf_create_section(struct elf elf, const char *name,
	462	size_t entsize, int nr)
	463	{
	464	struct section sec, shstrtab;
	465	size_t size = entsize * nr;
	466	struct Elf_Scn *s;
	467	Elf_Data *data;
	468
	469	sec = malloc(sizeof(*sec));
	470	if (!sec) {
	471	perror("malloc");
	472	return NULL;
	473	}
	474	memset(sec, 0, sizeof(*sec));
	475
	476	INIT_LIST_HEAD(&sec->symbol_list);
	477	INIT_LIST_HEAD(&sec->rela_list);
	478	hash_init(sec->rela_hash);
	479	hash_init(sec->symbol_hash);
	480
	481	list_add_tail(&sec->list, &elf->sections);
	482
	483	s = elf_newscn(elf->elf);
	484	if (!s) {
	485	WARN_ELF("elf_newscn");
	486	return NULL;
	487	}
	488
	489	sec->name = strdup(name);
	490	if (!sec->name) {
	491	perror("strdup");
	492	return NULL;
	493	}
	494
	495	sec->idx = elf_ndxscn(s);
	496	sec->len = size;
	497	sec->changed = true;
	498
	499	sec->data = elf_newdata(s);
	500	if (!sec->data) {
	501	WARN_ELF("elf_newdata");
	502	return NULL;
	503	}
	504
	505	sec->data->d_size = size;
	506	sec->data->d_align = 1;
	507
	508	if (size) {
	509	sec->data->d_buf = malloc(size);
	510	if (!sec->data->d_buf) {
	511	perror("malloc");
	512	return NULL;
	513	}
	514	memset(sec->data->d_buf, 0, size);
	515	}
	516
	517	if (!gelf_getshdr(s, &sec->sh)) {
	518	WARN_ELF("gelf_getshdr");
	519	return NULL;
	520	}
	521
	522	sec->sh.sh_size = size;
	523	sec->sh.sh_entsize = entsize;
	524	sec->sh.sh_type = SHT_PROGBITS;
525	sec->sh.sh_addralign = 1;
526	sec->sh.sh_flags = SHF_ALLOC;
527
528
6d77d3b4	529	/* Add section name to .shstrtab (or .strtab for Clang) */
627fce14	530	shstrtab = find_section_by_name(elf, ".shstrtab");
6d77d3b4 SS	531	if (!shstrtab)
6d77d3b4 SS	532	shstrtab = find_section_by_name(elf, ".strtab");
627fce14	533	if (!shstrtab) {
6d77d3b4	534	WARN("can't find .shstrtab or .strtab section");
627fce14 JP	535	return NULL;
	536	}
	537
	538	s = elf_getscn(elf->elf, shstrtab->idx);
	539	if (!s) {
	540	WARN_ELF("elf_getscn");
	541	return NULL;
	542	}
	543
	544	data = elf_newdata(s);
	545	if (!data) {
	546	WARN_ELF("elf_newdata");
	547	return NULL;
	548	}
	549
	550	data->d_buf = sec->name;
	551	data->d_size = strlen(name) + 1;
	552	data->d_align = 1;
	553
	554	sec->sh.sh_name = shstrtab->len;
	555
	556	shstrtab->len += strlen(name) + 1;
	557	shstrtab->changed = true;
	558
	559	return sec;
	560	}
	561
	562	struct section elf_create_rela_section(struct elf elf, struct section *base)
	563	{
	564	char *relaname;
	565	struct section *sec;
	566
	567	relaname = malloc(strlen(base->name) + strlen(".rela") + 1);
	568	if (!relaname) {
	569	perror("malloc");
	570	return NULL;
	571	}
	572	strcpy(relaname, ".rela");
	573	strcat(relaname, base->name);
	574
	575	sec = elf_create_section(elf, relaname, sizeof(GElf_Rela), 0);
0998b7a0	576	free(relaname);
627fce14 JP	577	if (!sec)
	578	return NULL;
	579
	580	base->rela = sec;
	581	sec->base = base;
	582
	583	sec->sh.sh_type = SHT_RELA;
	584	sec->sh.sh_addralign = 8;
	585	sec->sh.sh_link = find_section_by_name(elf, ".symtab")->idx;
	586	sec->sh.sh_info = base->idx;
	587	sec->sh.sh_flags = SHF_INFO_LINK;
	588
	589	return sec;
	590	}
	591
	592	int elf_rebuild_rela_section(struct section *sec)
	593	{
	594	struct rela *rela;
	595	int nr, idx = 0, size;
	596	GElf_Rela *relas;
	597
	598	nr = 0;
	599	list_for_each_entry(rela, &sec->rela_list, list)
	600	nr++;
	601
	602	size = nr * sizeof(*relas);
	603	relas = malloc(size);
	604	if (!relas) {
	605	perror("malloc");
	606	return -1;
	607	}
	608
	609	sec->data->d_buf = relas;
	610	sec->data->d_size = size;
	611
	612	sec->sh.sh_size = size;
	613
	614	idx = 0;
	615	list_for_each_entry(rela, &sec->rela_list, list) {
	616	relas[idx].r_offset = rela->offset;
	617	relas[idx].r_addend = rela->addend;
	618	relas[idx].r_info = GELF_R_INFO(rela->sym->idx, rela->type);
	619	idx++;
	620	}
	621
	622	return 0;
	623	}
	624
	625	int elf_write(struct elf *elf)
	626	{
	627	struct section *sec;
	628	Elf_Scn *s;
	629
97dab2ae	630	/* Update section headers for changed sections: */
627fce14 JP	631	list_for_each_entry(sec, &elf->sections, list) {
	632	if (sec->changed) {
	633	s = elf_getscn(elf->elf, sec->idx);
	634	if (!s) {
	635	WARN_ELF("elf_getscn");
	636	return -1;
	637	}
97dab2ae	638	if (!gelf_update_shdr(s, &sec->sh)) {
627fce14 JP	639	WARN_ELF("gelf_update_shdr");
	640	return -1;
	641	}
	642	}
	643	}
	644
97dab2ae JP	645	/* Make sure the new section header entries get updated properly. */
	646	elf_flagelf(elf->elf, ELF_C_SET, ELF_F_DIRTY);
	647
	648	/* Write all changes to the file. */
627fce14 JP	649	if (elf_update(elf->elf, ELF_C_WRITE) < 0) {
	650	WARN_ELF("elf_update");
	651	return -1;
	652	}
	653
	654	return 0;
	655	}
	656
442f04c3 JP	657	void elf_close(struct elf *elf)
	658	{
	659	struct section sec, tmpsec;
	660	struct symbol sym, tmpsym;
	661	struct rela rela, tmprela;
	662
baa41469 JP	663	if (elf->elf)
	664	elf_end(elf->elf);
	665
	666	if (elf->fd > 0)
	667	close(elf->fd);
	668
442f04c3	669	list_for_each_entry_safe(sec, tmpsec, &elf->sections, list) {
a196e171	670	list_for_each_entry_safe(sym, tmpsym, &sec->symbol_list, list) {
442f04c3	671	list_del(&sym->list);
042ba73f	672	hash_del(&sym->hash);
442f04c3 JP	673	free(sym);
442f04c3 JP	674	}
a196e171	675	list_for_each_entry_safe(rela, tmprela, &sec->rela_list, list) {
442f04c3	676	list_del(&rela->list);
042ba73f	677	hash_del(&rela->hash);
442f04c3 JP	678	free(rela);
	679	}
	680	list_del(&sec->list);
	681	free(sec);
	682	}
baa41469	683
442f04c3 JP	684	free(elf);
442f04c3 JP	685	}