1 files changed, 403 insertions, 0 deletions

diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
new file mode 100644
index 0000000..d547e3f
--- /dev/null
+++ b/tools/objtool/elf.c
@@ -0,0 +1,403 @@
+/*
+ * 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 "elf.h"
+#include "warn.h"
+
+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)
+		list_for_each_entry(sym, &sec->symbols, list)
+			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->symbols, list)
+		if (sym->type != STT_SECTION &&
+		    sym->offset == offset)
+			return sym;
+
+	return NULL;
+}
+
+struct rela *find_rela_by_dest_range(struct section *sec, unsigned long offset,
+				     unsigned int len)
+{
+	struct rela *rela;
+
+	if (!sec->rela)
+		return NULL;
+
+	list_for_each_entry(rela, &sec->rela->relas, list)
+		if (rela->offset >= offset && rela->offset < offset + len)
+			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->symbols, 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)) {
+		perror("elf_getshdrnum");
+		return -1;
+	}
+
+	if (elf_getshdrstrndx(elf->elf, &shstrndx)) {
+		perror("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->symbols);
+		INIT_LIST_HEAD(&sec->relas);
+
+		list_add_tail(&sec->list, &elf->sections);
+
+		s = elf_getscn(elf->elf, i);
+		if (!s) {
+			perror("elf_getscn");
+			return -1;
+		}
+
+		sec->idx = elf_ndxscn(s);
+
+		if (!gelf_getshdr(s, &sec->sh)) {
+			perror("gelf_getshdr");
+			return -1;
+		}
+
+		sec->name = elf_strptr(elf->elf, shstrndx, sec->sh.sh_name);
+		if (!sec->name) {
+			perror("elf_strptr");
+			return -1;
+		}
+
+		sec->elf_data = elf_getdata(s, NULL);
+		if (!sec->elf_data) {
+			perror("elf_getdata");
+			return -1;
+		}
+
+		if (sec->elf_data->d_off != 0 ||
+		    sec->elf_data->d_size != sec->sh.sh_size) {
+			WARN("unexpected data attributes for %s", sec->name);
+			return -1;
+		}
+
+		sec->data = (unsigned long)sec->elf_data->d_buf;
+		sec->len = sec->elf_data->d_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;
+	struct symbol *sym;
+	struct list_head *entry, *tmp;
+	int symbols_nr, i;
+
+	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->idx = i;
+
+		if (!gelf_getsym(symtab->elf_data, i, &sym->sym)) {
+			perror("gelf_getsym");
+			goto err;
+		}
+
+		sym->name = elf_strptr(elf->elf, symtab->sh.sh_link,
+				       sym->sym.st_name);
+		if (!sym->name) {
+			perror("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->symbols;
+		list_for_each_prev(tmp, &sym->sec->symbols) {
+			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);
+	}
+
+	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));
+
+			list_add_tail(&rela->list, &sec->relas);
+
+			if (!gelf_getrela(sec->elf_data, i, &rela->rela)) {
+				perror("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);
+			if (!rela->sym) {
+				WARN("can't find rela entry symbol %d for %s",
+				     symndx, sec->name);
+				return -1;
+			}
+		}
+	}
+
+	return 0;
+}
+
+struct elf *elf_open(const char *name)
+{
+	struct elf *elf;
+
+	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->name = strdup(name);
+	if (!elf->name) {
+		perror("strdup");
+		goto err;
+	}
+
+	elf->fd = open(name, O_RDONLY);
+	if (elf->fd == -1) {
+		perror("open");
+		goto err;
+	}
+
+	elf->elf = elf_begin(elf->fd, ELF_C_READ_MMAP, NULL);
+	if (!elf->elf) {
+		perror("elf_begin");
+		goto err;
+	}
+
+	if (!gelf_getehdr(elf->elf, &elf->ehdr)) {
+		perror("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;
+}
+
+void elf_close(struct elf *elf)
+{
+	struct section *sec, *tmpsec;
+	struct symbol *sym, *tmpsym;
+	struct rela *rela, *tmprela;
+
+	list_for_each_entry_safe(sec, tmpsec, &elf->sections, list) {
+		list_for_each_entry_safe(sym, tmpsym, &sec->symbols, list) {
+			list_del(&sym->list);
+			free(sym);
+		}
+		list_for_each_entry_safe(rela, tmprela, &sec->relas, list) {
+			list_del(&rela->list);
+			free(rela);
+		}
+		list_del(&sec->list);
+		free(sec);
+	}
+	if (elf->name)
+		free(elf->name);
+	if (elf->fd > 0)
+		close(elf->fd);
+	if (elf->elf)
+		elf_end(elf->elf);
+	free(elf);
+}