1 files changed, 693 insertions, 0 deletions

diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
new file mode 100644
index 000000000..264d49fea
--- /dev/null
+++ b/tools/objtool/elf.c
@@ -0,0 +1,693 @@
+/*
+ * 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>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#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;
+	struct list_head *entry, *tmp;
+	int symbols_nr, i;
+	char *coldstr;
+
+	symtab = find_section_by_name(elf, ".symtab");
+	if (!symtab) {
+		/*
+		 * A missing symbol table is actually possible if it's an empty
+		 * .o file.  This can happen for thunk_64.o.
+		 */
+		return 0;
+	}
+
+	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->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 && sym->len >= s->len) {
+				entry = tmp;
+				break;
+			}
+		}
+		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);
+}