grub/grub-core/kern/dl.c
2010-08-25 21:19:45 +02:00

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/* 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);
}
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);
if (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 = 0;
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;
if (! grub_dl_unref (dep->mod))
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;
}
}