+/*
+ * Find symbols before or equal addr and after addr - in the section sec.
+ * If we find two symbols with equal offset prefer one with a valid name.
+ * The ELF format may have a better way to detect what type of symbol
+ * it is, but this works for now.
+ **/
+static void find_symbols_between(struct elf_info *elf, Elf_Addr addr,
+ const char *sec,
+ Elf_Sym **before, Elf_Sym **after)
+{
+ Elf_Sym *sym;
+ Elf_Ehdr *hdr = elf->hdr;
+ Elf_Addr beforediff = ~0;
+ Elf_Addr afterdiff = ~0;
+ const char *secstrings = (void *)hdr +
+ elf->sechdrs[hdr->e_shstrndx].sh_offset;
+
+ *before = NULL;
+ *after = NULL;
+
+ for (sym = elf->symtab_start; sym < elf->symtab_stop; sym++) {
+ const char *symsec;
+
+ if (sym->st_shndx >= SHN_LORESERVE)
+ continue;
+ symsec = secstrings + elf->sechdrs[sym->st_shndx].sh_name;
+ if (strcmp(symsec, sec) != 0)
+ continue;
+ if (sym->st_value <= addr) {
+ if ((addr - sym->st_value) < beforediff) {
+ beforediff = addr - sym->st_value;
+ *before = sym;
+ }
+ else if ((addr - sym->st_value) == beforediff) {
+ /* equal offset, valid name? */
+ const char *name = elf->strtab + sym->st_name;
+ if (name && strlen(name))
+ *before = sym;
+ }
+ }
+ else
+ {
+ if ((sym->st_value - addr) < afterdiff) {
+ afterdiff = sym->st_value - addr;
+ *after = sym;
+ }
+ else if ((sym->st_value - addr) == afterdiff) {
+ /* equal offset, valid name? */
+ const char *name = elf->strtab + sym->st_name;
+ if (name && strlen(name))
+ *after = sym;
+ }
+ }
+ }
+}
+
+/**
+ * Print a warning about a section mismatch.
+ * Try to find symbols near it so user can find it.
+ * Check whitelist before warning - it may be a false positive.
+ **/
+static void warn_sec_mismatch(const char *modname, const char *fromsec,
+ struct elf_info *elf, Elf_Sym *sym, Elf_Rela r)
+{
+ const char *refsymname = "";
+ Elf_Sym *before, *after;
+ Elf_Sym *refsym;
+ Elf_Ehdr *hdr = elf->hdr;
+ Elf_Shdr *sechdrs = elf->sechdrs;
+ const char *secstrings = (void *)hdr +
+ sechdrs[hdr->e_shstrndx].sh_offset;
+ const char *secname = secstrings + sechdrs[sym->st_shndx].sh_name;
+
+ find_symbols_between(elf, r.r_offset, fromsec, &before, &after);
+
+ refsym = find_elf_symbol(elf, r.r_addend, sym);
+ if (refsym && strlen(elf->strtab + refsym->st_name))
+ refsymname = elf->strtab + refsym->st_name;
+
+ /* check whitelist - we may ignore it */
+ if (before &&
+ secref_whitelist(secname, fromsec, elf->strtab + before->st_name))
+ return;
+
+ if (before && after) {
+ warn("%s - Section mismatch: reference to %s:%s from %s "
+ "between '%s' (at offset 0x%llx) and '%s'\n",
+ modname, secname, refsymname, fromsec,
+ elf->strtab + before->st_name,
+ (long long)r.r_offset,
+ elf->strtab + after->st_name);
+ } else if (before) {
+ warn("%s - Section mismatch: reference to %s:%s from %s "
+ "after '%s' (at offset 0x%llx)\n",
+ modname, secname, refsymname, fromsec,
+ elf->strtab + before->st_name,
+ (long long)r.r_offset);
+ } else if (after) {
+ warn("%s - Section mismatch: reference to %s:%s from %s "
+ "before '%s' (at offset -0x%llx)\n",
+ modname, secname, refsymname, fromsec,
+ elf->strtab + after->st_name,
+ (long long)r.r_offset);
+ } else {
+ warn("%s - Section mismatch: reference to %s:%s from %s "
+ "(offset 0x%llx)\n",
+ modname, secname, fromsec, refsymname,
+ (long long)r.r_offset);
+ }
+}
+
+/**
+ * A module includes a number of sections that are discarded
+ * either when loaded or when used as built-in.
+ * For loaded modules all functions marked __init and all data
+ * marked __initdata will be discarded when the module has been intialized.
+ * Likewise for modules used built-in the sections marked __exit
+ * are discarded because __exit marked function are supposed to be called
+ * only when a moduel is unloaded which never happes for built-in modules.
+ * The check_sec_ref() function traverses all relocation records
+ * to find all references to a section that reference a section that will
+ * be discarded and warns about it.
+ **/
+static void check_sec_ref(struct module *mod, const char *modname,
+ struct elf_info *elf,
+ int section(const char*),
+ int section_ref_ok(const char *))
+{
+ int i;
+ Elf_Sym *sym;
+ Elf_Ehdr *hdr = elf->hdr;
+ Elf_Shdr *sechdrs = elf->sechdrs;
+ const char *secstrings = (void *)hdr +
+ sechdrs[hdr->e_shstrndx].sh_offset;
+
+ /* Walk through all sections */
+ for (i = 0; i < hdr->e_shnum; i++) {
+ const char *name = secstrings + sechdrs[i].sh_name;
+ const char *secname;
+ Elf_Rela r;
+ unsigned int r_sym;
+ /* We want to process only relocation sections and not .init */
+ if (sechdrs[i].sh_type == SHT_RELA) {
+ Elf_Rela *rela;
+ Elf_Rela *start = (void *)hdr + sechdrs[i].sh_offset;
+ Elf_Rela *stop = (void*)start + sechdrs[i].sh_size;
+ name += strlen(".rela");
+ if (section_ref_ok(name))
+ continue;
+
+ for (rela = start; rela < stop; rela++) {
+ r.r_offset = TO_NATIVE(rela->r_offset);
+#if KERNEL_ELFCLASS == ELFCLASS64
+ if (hdr->e_machine == EM_MIPS) {
+ r_sym = ELF64_MIPS_R_SYM(rela->r_info);
+ r_sym = TO_NATIVE(r_sym);
+ } else {
+ r.r_info = TO_NATIVE(rela->r_info);
+ r_sym = ELF_R_SYM(r.r_info);
+ }
+#else
+ r.r_info = TO_NATIVE(rela->r_info);
+ r_sym = ELF_R_SYM(r.r_info);
+#endif
+ r.r_addend = TO_NATIVE(rela->r_addend);
+ sym = elf->symtab_start + r_sym;
+ /* Skip special sections */
+ if (sym->st_shndx >= SHN_LORESERVE)
+ continue;
+
+ secname = secstrings +
+ sechdrs[sym->st_shndx].sh_name;
+ if (section(secname))
+ warn_sec_mismatch(modname, name,
+ elf, sym, r);
+ }
+ } else if (sechdrs[i].sh_type == SHT_REL) {
+ Elf_Rel *rel;
+ Elf_Rel *start = (void *)hdr + sechdrs[i].sh_offset;
+ Elf_Rel *stop = (void*)start + sechdrs[i].sh_size;
+ name += strlen(".rel");
+ if (section_ref_ok(name))
+ continue;
+
+ for (rel = start; rel < stop; rel++) {
+ r.r_offset = TO_NATIVE(rel->r_offset);
+#if KERNEL_ELFCLASS == ELFCLASS64
+ if (hdr->e_machine == EM_MIPS) {
+ r_sym = ELF64_MIPS_R_SYM(rel->r_info);
+ r_sym = TO_NATIVE(r_sym);
+ } else {
+ r.r_info = TO_NATIVE(rel->r_info);
+ r_sym = ELF_R_SYM(r.r_info);
+ }
+#else
+ r.r_info = TO_NATIVE(rel->r_info);
+ r_sym = ELF_R_SYM(r.r_info);
+#endif
+ r.r_addend = 0;
+ sym = elf->symtab_start + r_sym;
+ /* Skip special sections */
+ if (sym->st_shndx >= SHN_LORESERVE)
+ continue;
+
+ secname = secstrings +
+ sechdrs[sym->st_shndx].sh_name;
+ if (section(secname))
+ warn_sec_mismatch(modname, name,
+ elf, sym, r);
+ }
+ }
+ }
+}
+
+/**
+ * Functions used only during module init is marked __init and is stored in
+ * a .init.text section. Likewise data is marked __initdata and stored in
+ * a .init.data section.
+ * If this section is one of these sections return 1
+ * See include/linux/init.h for the details
+ **/
+static int init_section(const char *name)
+{
+ if (strcmp(name, ".init") == 0)
+ return 1;
+ if (strncmp(name, ".init.", strlen(".init.")) == 0)
+ return 1;
+ return 0;
+}
+
+/**
+ * Identify sections from which references to a .init section is OK.
+ *
+ * Unfortunately references to read only data that referenced .init
+ * sections had to be excluded. Almost all of these are false
+ * positives, they are created by gcc. The downside of excluding rodata
+ * is that there really are some user references from rodata to
+ * init code, e.g. drivers/video/vgacon.c:
+ *
+ * const struct consw vga_con = {
+ * con_startup: vgacon_startup,
+ *
+ * where vgacon_startup is __init. If you want to wade through the false
+ * positives, take out the check for rodata.
+ **/
+static int init_section_ref_ok(const char *name)
+{
+ const char **s;
+ /* Absolute section names */
+ const char *namelist1[] = {
+ ".init",
+ ".opd", /* see comment [OPD] at exit_section_ref_ok() */
+ ".toc1", /* used by ppc64 */
+ ".stab",
+ ".rodata",
+ ".text.lock",
+ "__bug_table", /* used by powerpc for BUG() */
+ ".pci_fixup_header",
+ ".pci_fixup_final",
+ ".pdr",
+ "__param",
+ NULL
+ };
+ /* Start of section names */
+ const char *namelist2[] = {
+ ".init.",
+ ".altinstructions",
+ ".eh_frame",
+ ".debug",
+ NULL
+ };
+ /* part of section name */
+ const char *namelist3 [] = {
+ ".unwind", /* sample: IA_64.unwind.init.text */
+ NULL
+ };
+
+ for (s = namelist1; *s; s++)
+ if (strcmp(*s, name) == 0)
+ return 1;
+ for (s = namelist2; *s; s++)
+ if (strncmp(*s, name, strlen(*s)) == 0)
+ return 1;
+ for (s = namelist3; *s; s++)
+ if (strstr(name, *s) != NULL)
+ return 1;
+ return 0;
+}
+
+/*
+ * Functions used only during module exit is marked __exit and is stored in
+ * a .exit.text section. Likewise data is marked __exitdata and stored in
+ * a .exit.data section.
+ * If this section is one of these sections return 1
+ * See include/linux/init.h for the details
+ **/
+static int exit_section(const char *name)
+{
+ if (strcmp(name, ".exit.text") == 0)
+ return 1;
+ if (strcmp(name, ".exit.data") == 0)
+ return 1;
+ return 0;
+
+}
+
+/*
+ * Identify sections from which references to a .exit section is OK.
+ *
+ * [OPD] Keith Ownes <kaos@sgi.com> commented:
+ * For our future {in}sanity, add a comment that this is the ppc .opd
+ * section, not the ia64 .opd section.
+ * ia64 .opd should not point to discarded sections.
+ * [.rodata] like for .init.text we ignore .rodata references -same reason
+ **/
+static int exit_section_ref_ok(const char *name)
+{
+ const char **s;
+ /* Absolute section names */
+ const char *namelist1[] = {
+ ".exit.text",
+ ".exit.data",
+ ".init.text",
+ ".rodata",
+ ".opd", /* See comment [OPD] */
+ ".toc1", /* used by ppc64 */
+ ".altinstructions",
+ ".pdr",
+ "__bug_table", /* used by powerpc for BUG() */
+ ".exitcall.exit",
+ ".eh_frame",
+ ".stab",
+ NULL
+ };
+ /* Start of section names */
+ const char *namelist2[] = {
+ ".debug",
+ NULL
+ };
+ /* part of section name */
+ const char *namelist3 [] = {
+ ".unwind", /* Sample: IA_64.unwind.exit.text */
+ NULL
+ };
+
+ for (s = namelist1; *s; s++)
+ if (strcmp(*s, name) == 0)
+ return 1;
+ for (s = namelist2; *s; s++)
+ if (strncmp(*s, name, strlen(*s)) == 0)
+ return 1;
+ for (s = namelist3; *s; s++)
+ if (strstr(name, *s) != NULL)
+ return 1;
+ return 0;
+}
+
+static void read_symbols(char *modname)