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module: reduce symbol table for loaded modules (v2)

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Discard all symbols not interesting for kallsyms use: absolute,
section, and in the common case (!KALLSYMS_ALL) data ones.

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Jan Beulich 2009-07-06 14:50:42 +01:00 committed by Rusty Russell
parent 94a8d5caba
commit 4a4962263f
2 changed files with 94 additions and 7 deletions
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10
include/linux/module.h
View file

@ -308,9 +308,13 @@ struct module
#endif
#ifdef CONFIG_KALLSYMS
/* We keep the symbol and string tables for kallsyms. */
Elf_Sym *symtab;
unsigned int num_symtab;
/*
* We keep the symbol and string tables for kallsyms.
* The core_* fields below are temporary, loader-only (they
* could really be discarded after module init).
*/
Elf_Sym *symtab, *core_symtab;
unsigned int num_symtab, core_num_syms;
char *strtab;
/* Section attributes */

97
kernel/module.c
View file

@ -1862,13 +1862,68 @@ static char elf_type(const Elf_Sym *sym,
return '?';
}
static void add_kallsyms(struct module *mod,
static bool is_core_symbol(const Elf_Sym *src, const Elf_Shdr *sechdrs,
unsigned int shnum)
{
const Elf_Shdr *sec;
if (src->st_shndx == SHN_UNDEF
|| src->st_shndx >= shnum
|| !src->st_name)
return false;
sec = sechdrs + src->st_shndx;
if (!(sec->sh_flags & SHF_ALLOC)
#ifndef CONFIG_KALLSYMS_ALL
|| !(sec->sh_flags & SHF_EXECINSTR)
#endif
|| (sec->sh_entsize & INIT_OFFSET_MASK))
return false;
return true;
}
static unsigned long layout_symtab(struct module *mod,
Elf_Shdr *sechdrs,
unsigned int symindex,
unsigned int strindex,
const Elf_Ehdr *hdr,
const char *secstrings)
{
unsigned int i;
unsigned long symoffs;
Elf_Shdr *symsect = sechdrs + symindex;
const Elf_Sym *src;
unsigned int i, nsrc, ndst;
/* Put symbol section at end of init part of module. */
symsect->sh_flags |= SHF_ALLOC;
symsect->sh_entsize = get_offset(mod, &mod->init_size, symsect,
symindex) | INIT_OFFSET_MASK;
DEBUGP("\t%s\n", secstrings + symsect->sh_name);
src = (void *)hdr + symsect->sh_offset;
nsrc = symsect->sh_size / sizeof(*src);
for (ndst = i = 1; i < nsrc; ++i, ++src)
if (is_core_symbol(src, sechdrs, hdr->e_shnum))
++ndst;
/* Append room for core symbols at end of core part. */
symoffs = ALIGN(mod->core_size, symsect->sh_addralign ?: 1);
mod->core_size = symoffs + ndst * sizeof(Elf_Sym);
return symoffs;
}
static void add_kallsyms(struct module *mod,
Elf_Shdr *sechdrs,
unsigned int shnum,
unsigned int symindex,
unsigned int strindex,
unsigned long symoffs,
const char *secstrings)
{
unsigned int i, ndst;
const Elf_Sym *src;
Elf_Sym *dst;
mod->symtab = (void *)sechdrs[symindex].sh_addr;
mod->num_symtab = sechdrs[symindex].sh_size / sizeof(Elf_Sym);
@ -1878,12 +1933,32 @@ static void add_kallsyms(struct module *mod,
for (i = 0; i < mod->num_symtab; i++)
mod->symtab[i].st_info
= elf_type(&mod->symtab[i], sechdrs, secstrings, mod);
mod->core_symtab = dst = mod->module_core + symoffs;
src = mod->symtab;
*dst = *src;
for (ndst = i = 1; i < mod->num_symtab; ++i, ++src) {
if (!is_core_symbol(src, sechdrs, shnum))
continue;
dst[ndst] = *src;
++ndst;
}
mod->core_num_syms = ndst;
}
#else
static inline void add_kallsyms(struct module *mod,
static inline unsigned long layout_symtab(struct module *mod,
Elf_Shdr *sechdrs,
unsigned int symindex,
const Elf_Hdr *hdr,
const char *secstrings)
{
}
static inline void add_kallsyms(struct module *mod,
Elf_Shdr *sechdrs,
unsigned int shnum,
unsigned int symindex,
unsigned int strindex,
unsigned long symoffs,
const char *secstrings)
{
}
@ -1959,6 +2034,9 @@ static noinline struct module *load_module(void __user *umod,
struct module *mod;
long err = 0;
void *percpu = NULL, *ptr = NULL; /* Stops spurious gcc warning */
#ifdef CONFIG_KALLSYMS
unsigned long symoffs;
#endif
mm_segment_t old_fs;
DEBUGP("load_module: umod=%p, len=%lu, uargs=%p\n",
@ -2041,8 +2119,7 @@ static noinline struct module *load_module(void __user *umod,
sechdrs[infoindex].sh_flags &= ~(unsigned long)SHF_ALLOC;
sechdrs[versindex].sh_flags &= ~(unsigned long)SHF_ALLOC;
#ifdef CONFIG_KALLSYMS
/* Keep symbol and string tables for decoding later. */
sechdrs[symindex].sh_flags |= SHF_ALLOC;
/* Keep string table for decoding later. */
sechdrs[strindex].sh_flags |= SHF_ALLOC;
#endif
@ -2109,6 +2186,7 @@ static noinline struct module *load_module(void __user *umod,
this is done generically; there doesn't appear to be any
special cases for the architectures. */
layout_sections(mod, hdr, sechdrs, secstrings);
symoffs = layout_symtab(mod, sechdrs, symindex, hdr, secstrings);
/* Do the allocs. */
ptr = module_alloc_update_bounds(mod->core_size);
@ -2313,7 +2391,8 @@ static noinline struct module *load_module(void __user *umod,
percpu_modcopy(mod->percpu, (void *)sechdrs[pcpuindex].sh_addr,
sechdrs[pcpuindex].sh_size);
add_kallsyms(mod, sechdrs, symindex, strindex, secstrings);
add_kallsyms(mod, sechdrs, hdr->e_shnum, symindex, strindex,
symoffs, secstrings);
if (!mod->taints) {
struct _ddebug *debug;
@ -2491,6 +2570,10 @@ SYSCALL_DEFINE3(init_module, void __user *, umod,
/* Drop initial reference. */
module_put(mod);
trim_init_extable(mod);
#ifdef CONFIG_KALLSYMS
mod->num_symtab = mod->core_num_syms;
mod->symtab = mod->core_symtab;
#endif
module_free(mod, mod->module_init);
mod->module_init = NULL;
mod->init_size = 0;