diff options
Diffstat (limited to 'grub-core/kern/dl.c')
| -rw-r--r-- | grub-core/kern/dl.c | 724 |
1 files changed, 724 insertions, 0 deletions
diff --git a/grub-core/kern/dl.c b/grub-core/kern/dl.c new file mode 100644 index 0000000..623e0cb --- /dev/null +++ b/grub-core/kern/dl.c @@ -0,0 +1,724 @@ +/* dl.c - loadable module support */ +/* + * GRUB -- GRand Unified Bootloader + * Copyright (C) 2002,2003,2004,2005,2007,2008,2009 Free Software Foundation, Inc. + * + * GRUB 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 3 of the License, or + * (at your option) any later version. + * + * GRUB 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 GRUB. If not, see <http://www.gnu.org/licenses/>. + */ + +/* Force native word size */ +#define GRUB_TARGET_WORDSIZE (8 * GRUB_CPU_SIZEOF_VOID_P) + +#include <config.h> +#include <grub/elf.h> +#include <grub/dl.h> +#include <grub/misc.h> +#include <grub/mm.h> +#include <grub/err.h> +#include <grub/types.h> +#include <grub/symbol.h> +#include <grub/file.h> +#include <grub/env.h> +#include <grub/cache.h> + +/* Platforms where modules are in a readonly area of memory. */ +#if defined(GRUB_MACHINE_QEMU) +#define GRUB_MODULES_MACHINE_READONLY +#endif + + + +grub_dl_t grub_dl_head = 0; + +static grub_err_t +grub_dl_add (grub_dl_t mod) +{ + if (grub_dl_get (mod->name)) + return grub_error (GRUB_ERR_BAD_MODULE, + "`%s' is already loaded", mod->name); + + mod->next = grub_dl_head; + grub_dl_head = mod; + + return GRUB_ERR_NONE; +} + +static void +grub_dl_remove (grub_dl_t mod) +{ + grub_dl_t *p, q; + + for (p = &grub_dl_head, q = *p; q; p = &q->next, q = *p) + if (q == mod) + { + *p = q->next; + return; + } +} + +grub_dl_t +grub_dl_get (const char *name) +{ + grub_dl_t l; + + for (l = grub_dl_head; l; l = l->next) + if (grub_strcmp (name, l->name) == 0) + return l; + + return 0; +} + + + +struct grub_symbol +{ + struct grub_symbol *next; + const char *name; + void *addr; + grub_dl_t mod; /* The module to which this symbol belongs. */ +}; +typedef struct grub_symbol *grub_symbol_t; + +/* The size of the symbol table. */ +#define GRUB_SYMTAB_SIZE 509 + +/* The symbol table (using an open-hash). */ +static struct grub_symbol *grub_symtab[GRUB_SYMTAB_SIZE]; + +/* Simple hash function. */ +static unsigned +grub_symbol_hash (const char *s) +{ + unsigned key = 0; + + while (*s) + key = key * 65599 + *s++; + + return (key + (key >> 5)) % GRUB_SYMTAB_SIZE; +} + +/* Resolve the symbol name NAME and return the address. + Return NULL, if not found. */ +static void * +grub_dl_resolve_symbol (const char *name) +{ + grub_symbol_t sym; + + for (sym = grub_symtab[grub_symbol_hash (name)]; sym; sym = sym->next) + if (grub_strcmp (sym->name, name) == 0) + return sym->addr; + + return 0; +} + +/* Register a symbol with the name NAME and the address ADDR. */ +grub_err_t +grub_dl_register_symbol (const char *name, void *addr, grub_dl_t mod) +{ + grub_symbol_t sym; + unsigned k; + + sym = (grub_symbol_t) grub_malloc (sizeof (*sym)); + if (! sym) + return grub_errno; + + if (mod) + { + sym->name = grub_strdup (name); + if (! sym->name) + { + grub_free (sym); + return grub_errno; + } + } + else + sym->name = name; + + sym->addr = addr; + sym->mod = mod; + + k = grub_symbol_hash (name); + sym->next = grub_symtab[k]; + grub_symtab[k] = sym; + + return GRUB_ERR_NONE; +} + +/* Unregister all the symbols defined in the module MOD. */ +static void +grub_dl_unregister_symbols (grub_dl_t mod) +{ + unsigned i; + + if (! mod) + grub_fatal ("core symbols cannot be unregistered"); + + for (i = 0; i < GRUB_SYMTAB_SIZE; i++) + { + grub_symbol_t sym, *p, q; + + for (p = &grub_symtab[i], sym = *p; sym; sym = q) + { + q = sym->next; + if (sym->mod == mod) + { + *p = q; + grub_free ((void *) sym->name); + grub_free (sym); + } + else + p = &sym->next; + } + } +} + +/* Return the address of a section whose index is N. */ +static void * +grub_dl_get_section_addr (grub_dl_t mod, unsigned n) +{ + grub_dl_segment_t seg; + + for (seg = mod->segment; seg; seg = seg->next) + if (seg->section == n) + return seg->addr; + + return 0; +} + +/* Check if EHDR is a valid ELF header. */ +static grub_err_t +grub_dl_check_header (void *ehdr, grub_size_t size) +{ + Elf_Ehdr *e = ehdr; + + /* Check the header size. */ + if (size < sizeof (Elf_Ehdr)) + return grub_error (GRUB_ERR_BAD_OS, "ELF header smaller than expected"); + + /* Check the magic numbers. */ + if (grub_arch_dl_check_header (ehdr) + || e->e_ident[EI_MAG0] != ELFMAG0 + || e->e_ident[EI_MAG1] != ELFMAG1 + || e->e_ident[EI_MAG2] != ELFMAG2 + || e->e_ident[EI_MAG3] != ELFMAG3 + || e->e_ident[EI_VERSION] != EV_CURRENT + || e->e_version != EV_CURRENT) + return grub_error (GRUB_ERR_BAD_OS, "invalid arch independent ELF magic"); + + return GRUB_ERR_NONE; +} + +/* Load all segments from memory specified by E. */ +static grub_err_t +grub_dl_load_segments (grub_dl_t mod, const Elf_Ehdr *e) +{ + unsigned i; + Elf_Shdr *s; + + for (i = 0, s = (Elf_Shdr *)((char *) e + e->e_shoff); + i < e->e_shnum; + i++, s = (Elf_Shdr *)((char *) s + e->e_shentsize)) + { + if (s->sh_flags & SHF_ALLOC) + { + grub_dl_segment_t seg; + + seg = (grub_dl_segment_t) grub_malloc (sizeof (*seg)); + if (! seg) + return grub_errno; + + if (s->sh_size) + { + void *addr; + + addr = grub_memalign (s->sh_addralign, s->sh_size); + if (! addr) + { + grub_free (seg); + return grub_errno; + } + + switch (s->sh_type) + { + case SHT_PROGBITS: + grub_memcpy (addr, (char *) e + s->sh_offset, s->sh_size); + break; + case SHT_NOBITS: + grub_memset (addr, 0, s->sh_size); + break; + } + + seg->addr = addr; + } + else + seg->addr = 0; + + seg->size = s->sh_size; + seg->section = i; + seg->next = mod->segment; + mod->segment = seg; + } + } + + return GRUB_ERR_NONE; +} + +static grub_err_t +grub_dl_resolve_symbols (grub_dl_t mod, Elf_Ehdr *e) +{ + unsigned i; + Elf_Shdr *s; + Elf_Sym *sym; + const char *str; + Elf_Word size, entsize; + + for (i = 0, s = (Elf_Shdr *) ((char *) e + e->e_shoff); + i < e->e_shnum; + i++, s = (Elf_Shdr *) ((char *) s + e->e_shentsize)) + if (s->sh_type == SHT_SYMTAB) + break; + + if (i == e->e_shnum) + return grub_error (GRUB_ERR_BAD_MODULE, "no symbol table"); + +#ifdef GRUB_MODULES_MACHINE_READONLY + mod->symtab = grub_malloc (s->sh_size); + memcpy (mod->symtab, (char *) e + s->sh_offset, s->sh_size); +#else + mod->symtab = (Elf_Sym *) ((char *) e + s->sh_offset); +#endif + sym = mod->symtab; + size = s->sh_size; + entsize = s->sh_entsize; + + s = (Elf_Shdr *) ((char *) e + e->e_shoff + e->e_shentsize * s->sh_link); + str = (char *) e + s->sh_offset; + + for (i = 0; + i < size / entsize; + i++, sym = (Elf_Sym *) ((char *) sym + entsize)) + { + unsigned char type = ELF_ST_TYPE (sym->st_info); + unsigned char bind = ELF_ST_BIND (sym->st_info); + const char *name = str + sym->st_name; + + switch (type) + { + case STT_NOTYPE: + case STT_OBJECT: + /* Resolve a global symbol. */ + if (sym->st_name != 0 && sym->st_shndx == 0) + { + sym->st_value = (Elf_Addr) grub_dl_resolve_symbol (name); + if (! sym->st_value) + return grub_error (GRUB_ERR_BAD_MODULE, + "symbol not found: `%s'", name); + } + else + { + sym->st_value += (Elf_Addr) grub_dl_get_section_addr (mod, + sym->st_shndx); + if (bind != STB_LOCAL) + if (grub_dl_register_symbol (name, (void *) sym->st_value, mod)) + return grub_errno; + } + break; + + case STT_FUNC: + sym->st_value += (Elf_Addr) grub_dl_get_section_addr (mod, + sym->st_shndx); + if (bind != STB_LOCAL) + if (grub_dl_register_symbol (name, (void *) sym->st_value, mod)) + return grub_errno; + + if (grub_strcmp (name, "grub_mod_init") == 0) + mod->init = (void (*) (grub_dl_t)) sym->st_value; + else if (grub_strcmp (name, "grub_mod_fini") == 0) + mod->fini = (void (*) (void)) sym->st_value; + break; + + case STT_SECTION: + sym->st_value = (Elf_Addr) grub_dl_get_section_addr (mod, + sym->st_shndx); + break; + + case STT_FILE: + sym->st_value = 0; + break; + + default: + return grub_error (GRUB_ERR_BAD_MODULE, + "unknown symbol type `%d'", (int) type); + } + } + + return GRUB_ERR_NONE; +} + +static void +grub_dl_call_init (grub_dl_t mod) +{ + if (mod->init) + (mod->init) (mod); +} + +/* Me, Vladimir Serbinenko, hereby I add this module check as per new + GNU module policy. Note that this license check is informative only. + Modules have to be licensed under GPLv3 or GPLv3+ (optionally + multi-licensed under other licences as well) independently of the + presence of this check and solely by linking (module loading in GRUB + constitutes linking) and GRUB core being licensed under GPLv3+. + Be sure to understand your license obligations. +*/ +static grub_err_t +grub_dl_check_license (Elf_Ehdr *e) +{ + Elf_Shdr *s; + const char *str; + unsigned i; + + s = (Elf_Shdr *) ((char *) e + e->e_shoff + e->e_shstrndx * e->e_shentsize); + str = (char *) e + s->sh_offset; + + for (i = 0, s = (Elf_Shdr *) ((char *) e + e->e_shoff); + i < e->e_shnum; + i++, s = (Elf_Shdr *) ((char *) s + e->e_shentsize)) + if (grub_strcmp (str + s->sh_name, ".module_license") == 0) + { + if (grub_strcmp ((char *) e + s->sh_offset, "LICENSE=GPLv3") == 0 + || grub_strcmp ((char *) e + s->sh_offset, "LICENSE=GPLv3+") == 0 + || grub_strcmp ((char *) e + s->sh_offset, "LICENSE=GPLv2+") == 0) + return GRUB_ERR_NONE; + } + + return grub_error (GRUB_ERR_BAD_MODULE, "incompatible license"); +} + +static grub_err_t +grub_dl_resolve_name (grub_dl_t mod, Elf_Ehdr *e) +{ + Elf_Shdr *s; + const char *str; + unsigned i; + + s = (Elf_Shdr *) ((char *) e + e->e_shoff + e->e_shstrndx * e->e_shentsize); + str = (char *) e + s->sh_offset; + + for (i = 0, s = (Elf_Shdr *) ((char *) e + e->e_shoff); + i < e->e_shnum; + i++, s = (Elf_Shdr *) ((char *) s + e->e_shentsize)) + if (grub_strcmp (str + s->sh_name, ".modname") == 0) + { + mod->name = grub_strdup ((char *) e + s->sh_offset); + if (! mod->name) + return grub_errno; + break; + } + + if (i == e->e_shnum) + return grub_error (GRUB_ERR_BAD_MODULE, "no module name found"); + + return GRUB_ERR_NONE; +} + +static grub_err_t +grub_dl_resolve_dependencies (grub_dl_t mod, Elf_Ehdr *e) +{ + Elf_Shdr *s; + const char *str; + unsigned i; + + s = (Elf_Shdr *) ((char *) e + e->e_shoff + e->e_shstrndx * e->e_shentsize); + str = (char *) e + s->sh_offset; + + for (i = 0, s = (Elf_Shdr *) ((char *) e + e->e_shoff); + i < e->e_shnum; + i++, s = (Elf_Shdr *) ((char *) s + e->e_shentsize)) + if (grub_strcmp (str + s->sh_name, ".moddeps") == 0) + { + const char *name = (char *) e + s->sh_offset; + const char *max = name + s->sh_size; + + while ((name < max) && (*name)) + { + grub_dl_t m; + grub_dl_dep_t dep; + + m = grub_dl_load (name); + if (! m) + return grub_errno; + + grub_dl_ref (m); + + dep = (grub_dl_dep_t) grub_malloc (sizeof (*dep)); + if (! dep) + return grub_errno; + + dep->mod = m; + dep->next = mod->dep; + mod->dep = dep; + + name += grub_strlen (name) + 1; + } + } + + return GRUB_ERR_NONE; +} + +int +grub_dl_ref (grub_dl_t mod) +{ + grub_dl_dep_t dep; + + if (!mod) + return 0; + + for (dep = mod->dep; dep; dep = dep->next) + grub_dl_ref (dep->mod); + + return ++mod->ref_count; +} + +int +grub_dl_unref (grub_dl_t mod) +{ + grub_dl_dep_t dep; + + if (!mod) + return 0; + + for (dep = mod->dep; dep; dep = dep->next) + grub_dl_unref (dep->mod); + + return --mod->ref_count; +} + +static void +grub_dl_flush_cache (grub_dl_t mod) +{ + grub_dl_segment_t seg; + + for (seg = mod->segment; seg; seg = seg->next) { + if (seg->size) { + grub_dprintf ("modules", "flushing 0x%lx bytes at %p\n", + (unsigned long) seg->size, seg->addr); + grub_arch_sync_caches (seg->addr, seg->size); + } + } +} + +/* Load a module from core memory. */ +grub_dl_t +grub_dl_load_core (void *addr, grub_size_t size) +{ + Elf_Ehdr *e; + grub_dl_t mod; + + grub_dprintf ("modules", "module at %p, size 0x%lx\n", addr, + (unsigned long) size); + e = addr; + if (grub_dl_check_header (e, size)) + return 0; + + if (e->e_type != ET_REL) + { + grub_error (GRUB_ERR_BAD_MODULE, "invalid ELF file type"); + return 0; + } + + /* Make sure that every section is within the core. */ + if (size < e->e_shoff + e->e_shentsize * e->e_shnum) + { + grub_error (GRUB_ERR_BAD_OS, "ELF sections outside core"); + return 0; + } + + mod = (grub_dl_t) grub_zalloc (sizeof (*mod)); + if (! mod) + return 0; + + mod->ref_count = 1; + + grub_dprintf ("modules", "relocating to %p\n", mod); + /* Me, Vladimir Serbinenko, hereby I add this module check as per new + GNU module policy. Note that this license check is informative only. + Modules have to be licensed under GPLv3 or GPLv3+ (optionally + multi-licensed under other licences as well) independently of the + presence of this check and solely by linking (module loading in GRUB + constitutes linking) and GRUB core being licensed under GPLv3+. + Be sure to understand your license obligations. + */ + if (grub_dl_check_license (e) + || grub_dl_resolve_name (mod, e) + || grub_dl_resolve_dependencies (mod, e) + || grub_dl_load_segments (mod, e) + || grub_dl_resolve_symbols (mod, e) + || grub_arch_dl_relocate_symbols (mod, e)) + { + mod->fini = 0; + grub_dl_unload (mod); + return 0; + } + + grub_dl_flush_cache (mod); + + grub_dprintf ("modules", "module name: %s\n", mod->name); + grub_dprintf ("modules", "init function: %p\n", mod->init); + grub_dl_call_init (mod); + + if (grub_dl_add (mod)) + { + grub_dl_unload (mod); + return 0; + } + + return mod; +} + +/* Load a module from the file FILENAME. */ +grub_dl_t +grub_dl_load_file (const char *filename) +{ + grub_file_t file = NULL; + grub_ssize_t size; + void *core = 0; + grub_dl_t mod = 0; + + file = grub_file_open (filename); + if (! file) + return 0; + + size = grub_file_size (file); + core = grub_malloc (size); + if (! core) + { + grub_file_close (file); + return 0; + } + + if (grub_file_read (file, core, size) != (int) size) + { + grub_file_close (file); + grub_free (core); + return 0; + } + + /* We must close this before we try to process dependencies. + Some disk backends do not handle gracefully multiple concurrent + opens of the same device. */ + grub_file_close (file); + + mod = grub_dl_load_core (core, size); + if (! mod) + { + grub_free (core); + return 0; + } + + mod->ref_count--; + return mod; +} + +/* Load a module using a symbolic name. */ +grub_dl_t +grub_dl_load (const char *name) +{ + char *filename; + grub_dl_t mod; + char *grub_dl_dir = grub_env_get ("prefix"); + + mod = grub_dl_get (name); + if (mod) + return mod; + + if (! grub_dl_dir) { + grub_error (GRUB_ERR_FILE_NOT_FOUND, "\"prefix\" is not set"); + return 0; + } + + filename = grub_xasprintf ("%s/%s.mod", grub_dl_dir, name); + if (! filename) + return 0; + + mod = grub_dl_load_file (filename); + grub_free (filename); + + if (! mod) + return 0; + + if (grub_strcmp (mod->name, name) != 0) + grub_error (GRUB_ERR_BAD_MODULE, "mismatched names"); + + return mod; +} + +/* Unload the module MOD. */ +int +grub_dl_unload (grub_dl_t mod) +{ + grub_dl_dep_t dep, depn; + grub_dl_segment_t seg, segn; + + if (mod->ref_count > 0) + return 0; + + if (mod->fini) + (mod->fini) (); + + grub_dl_remove (mod); + grub_dl_unregister_symbols (mod); + + for (dep = mod->dep; dep; dep = depn) + { + depn = dep->next; + + grub_dl_unload (dep->mod); + + grub_free (dep); + } + + for (seg = mod->segment; seg; seg = segn) + { + segn = seg->next; + grub_free (seg->addr); + grub_free (seg); + } + + grub_free (mod->name); +#ifdef GRUB_MODULES_MACHINE_READONLY + grub_free (mod->symtab); +#endif + grub_free (mod); + return 1; +} + +/* Unload unneeded modules. */ +void +grub_dl_unload_unneeded (void) +{ + /* Because grub_dl_remove modifies the list of modules, this + implementation is tricky. */ + grub_dl_t p = grub_dl_head; + + while (p) + { + if (grub_dl_unload (p)) + { + p = grub_dl_head; + continue; + } + + p = p->next; + } +} |