mirror of
https://github.com/torvalds/linux.git
synced 2024-12-11 21:52:04 +00:00
07ade45a76
module_kallsyms_lookup_name() has several exit conditions but can't return immediately due to preempt_disable(). Refactor module_kallsyms_lookup_name() to allow returning from anywhere, and reduce depth. Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
535 lines
14 KiB
C
535 lines
14 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
|
|
/*
|
|
* Module kallsyms support
|
|
*
|
|
* Copyright (C) 2010 Rusty Russell
|
|
*/
|
|
|
|
#include <linux/module.h>
|
|
#include <linux/kallsyms.h>
|
|
#include <linux/buildid.h>
|
|
#include <linux/bsearch.h>
|
|
#include "internal.h"
|
|
|
|
/* Lookup exported symbol in given range of kernel_symbols */
|
|
static const struct kernel_symbol *lookup_exported_symbol(const char *name,
|
|
const struct kernel_symbol *start,
|
|
const struct kernel_symbol *stop)
|
|
{
|
|
return bsearch(name, start, stop - start,
|
|
sizeof(struct kernel_symbol), cmp_name);
|
|
}
|
|
|
|
static int is_exported(const char *name, unsigned long value,
|
|
const struct module *mod)
|
|
{
|
|
const struct kernel_symbol *ks;
|
|
|
|
if (!mod)
|
|
ks = lookup_exported_symbol(name, __start___ksymtab, __stop___ksymtab);
|
|
else
|
|
ks = lookup_exported_symbol(name, mod->syms, mod->syms + mod->num_syms);
|
|
|
|
return ks && kernel_symbol_value(ks) == value;
|
|
}
|
|
|
|
/* As per nm */
|
|
static char elf_type(const Elf_Sym *sym, const struct load_info *info)
|
|
{
|
|
const Elf_Shdr *sechdrs = info->sechdrs;
|
|
|
|
if (ELF_ST_BIND(sym->st_info) == STB_WEAK) {
|
|
if (ELF_ST_TYPE(sym->st_info) == STT_OBJECT)
|
|
return 'v';
|
|
else
|
|
return 'w';
|
|
}
|
|
if (sym->st_shndx == SHN_UNDEF)
|
|
return 'U';
|
|
if (sym->st_shndx == SHN_ABS || sym->st_shndx == info->index.pcpu)
|
|
return 'a';
|
|
if (sym->st_shndx >= SHN_LORESERVE)
|
|
return '?';
|
|
if (sechdrs[sym->st_shndx].sh_flags & SHF_EXECINSTR)
|
|
return 't';
|
|
if (sechdrs[sym->st_shndx].sh_flags & SHF_ALLOC &&
|
|
sechdrs[sym->st_shndx].sh_type != SHT_NOBITS) {
|
|
if (!(sechdrs[sym->st_shndx].sh_flags & SHF_WRITE))
|
|
return 'r';
|
|
else if (sechdrs[sym->st_shndx].sh_flags & ARCH_SHF_SMALL)
|
|
return 'g';
|
|
else
|
|
return 'd';
|
|
}
|
|
if (sechdrs[sym->st_shndx].sh_type == SHT_NOBITS) {
|
|
if (sechdrs[sym->st_shndx].sh_flags & ARCH_SHF_SMALL)
|
|
return 's';
|
|
else
|
|
return 'b';
|
|
}
|
|
if (strstarts(info->secstrings + sechdrs[sym->st_shndx].sh_name,
|
|
".debug")) {
|
|
return 'n';
|
|
}
|
|
return '?';
|
|
}
|
|
|
|
static bool is_core_symbol(const Elf_Sym *src, const Elf_Shdr *sechdrs,
|
|
unsigned int shnum, unsigned int pcpundx)
|
|
{
|
|
const Elf_Shdr *sec;
|
|
|
|
if (src->st_shndx == SHN_UNDEF ||
|
|
src->st_shndx >= shnum ||
|
|
!src->st_name)
|
|
return false;
|
|
|
|
#ifdef CONFIG_KALLSYMS_ALL
|
|
if (src->st_shndx == pcpundx)
|
|
return true;
|
|
#endif
|
|
|
|
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;
|
|
}
|
|
|
|
/*
|
|
* We only allocate and copy the strings needed by the parts of symtab
|
|
* we keep. This is simple, but has the effect of making multiple
|
|
* copies of duplicates. We could be more sophisticated, see
|
|
* linux-kernel thread starting with
|
|
* <73defb5e4bca04a6431392cc341112b1@localhost>.
|
|
*/
|
|
void layout_symtab(struct module *mod, struct load_info *info)
|
|
{
|
|
Elf_Shdr *symsect = info->sechdrs + info->index.sym;
|
|
Elf_Shdr *strsect = info->sechdrs + info->index.str;
|
|
const Elf_Sym *src;
|
|
unsigned int i, nsrc, ndst, strtab_size = 0;
|
|
|
|
/* Put symbol section at end of init part of module. */
|
|
symsect->sh_flags |= SHF_ALLOC;
|
|
symsect->sh_entsize = module_get_offset(mod, &mod->init_layout.size, symsect,
|
|
info->index.sym) | INIT_OFFSET_MASK;
|
|
pr_debug("\t%s\n", info->secstrings + symsect->sh_name);
|
|
|
|
src = (void *)info->hdr + symsect->sh_offset;
|
|
nsrc = symsect->sh_size / sizeof(*src);
|
|
|
|
/* Compute total space required for the core symbols' strtab. */
|
|
for (ndst = i = 0; i < nsrc; i++) {
|
|
if (i == 0 || is_livepatch_module(mod) ||
|
|
is_core_symbol(src + i, info->sechdrs, info->hdr->e_shnum,
|
|
info->index.pcpu)) {
|
|
strtab_size += strlen(&info->strtab[src[i].st_name]) + 1;
|
|
ndst++;
|
|
}
|
|
}
|
|
|
|
/* Append room for core symbols at end of core part. */
|
|
info->symoffs = ALIGN(mod->data_layout.size, symsect->sh_addralign ?: 1);
|
|
info->stroffs = mod->data_layout.size = info->symoffs + ndst * sizeof(Elf_Sym);
|
|
mod->data_layout.size += strtab_size;
|
|
/* Note add_kallsyms() computes strtab_size as core_typeoffs - stroffs */
|
|
info->core_typeoffs = mod->data_layout.size;
|
|
mod->data_layout.size += ndst * sizeof(char);
|
|
mod->data_layout.size = strict_align(mod->data_layout.size);
|
|
|
|
/* Put string table section at end of init part of module. */
|
|
strsect->sh_flags |= SHF_ALLOC;
|
|
strsect->sh_entsize = module_get_offset(mod, &mod->init_layout.size, strsect,
|
|
info->index.str) | INIT_OFFSET_MASK;
|
|
pr_debug("\t%s\n", info->secstrings + strsect->sh_name);
|
|
|
|
/* We'll tack temporary mod_kallsyms on the end. */
|
|
mod->init_layout.size = ALIGN(mod->init_layout.size,
|
|
__alignof__(struct mod_kallsyms));
|
|
info->mod_kallsyms_init_off = mod->init_layout.size;
|
|
mod->init_layout.size += sizeof(struct mod_kallsyms);
|
|
info->init_typeoffs = mod->init_layout.size;
|
|
mod->init_layout.size += nsrc * sizeof(char);
|
|
mod->init_layout.size = strict_align(mod->init_layout.size);
|
|
}
|
|
|
|
/*
|
|
* We use the full symtab and strtab which layout_symtab arranged to
|
|
* be appended to the init section. Later we switch to the cut-down
|
|
* core-only ones.
|
|
*/
|
|
void add_kallsyms(struct module *mod, const struct load_info *info)
|
|
{
|
|
unsigned int i, ndst;
|
|
const Elf_Sym *src;
|
|
Elf_Sym *dst;
|
|
char *s;
|
|
Elf_Shdr *symsec = &info->sechdrs[info->index.sym];
|
|
unsigned long strtab_size;
|
|
|
|
/* Set up to point into init section. */
|
|
mod->kallsyms = (void __rcu *)mod->init_layout.base +
|
|
info->mod_kallsyms_init_off;
|
|
|
|
rcu_read_lock();
|
|
/* The following is safe since this pointer cannot change */
|
|
rcu_dereference(mod->kallsyms)->symtab = (void *)symsec->sh_addr;
|
|
rcu_dereference(mod->kallsyms)->num_symtab = symsec->sh_size / sizeof(Elf_Sym);
|
|
/* Make sure we get permanent strtab: don't use info->strtab. */
|
|
rcu_dereference(mod->kallsyms)->strtab =
|
|
(void *)info->sechdrs[info->index.str].sh_addr;
|
|
rcu_dereference(mod->kallsyms)->typetab = mod->init_layout.base + info->init_typeoffs;
|
|
|
|
/*
|
|
* Now populate the cut down core kallsyms for after init
|
|
* and set types up while we still have access to sections.
|
|
*/
|
|
mod->core_kallsyms.symtab = dst = mod->data_layout.base + info->symoffs;
|
|
mod->core_kallsyms.strtab = s = mod->data_layout.base + info->stroffs;
|
|
mod->core_kallsyms.typetab = mod->data_layout.base + info->core_typeoffs;
|
|
strtab_size = info->core_typeoffs - info->stroffs;
|
|
src = rcu_dereference(mod->kallsyms)->symtab;
|
|
for (ndst = i = 0; i < rcu_dereference(mod->kallsyms)->num_symtab; i++) {
|
|
rcu_dereference(mod->kallsyms)->typetab[i] = elf_type(src + i, info);
|
|
if (i == 0 || is_livepatch_module(mod) ||
|
|
is_core_symbol(src + i, info->sechdrs, info->hdr->e_shnum,
|
|
info->index.pcpu)) {
|
|
ssize_t ret;
|
|
|
|
mod->core_kallsyms.typetab[ndst] =
|
|
rcu_dereference(mod->kallsyms)->typetab[i];
|
|
dst[ndst] = src[i];
|
|
dst[ndst++].st_name = s - mod->core_kallsyms.strtab;
|
|
ret = strscpy(s,
|
|
&rcu_dereference(mod->kallsyms)->strtab[src[i].st_name],
|
|
strtab_size);
|
|
if (ret < 0)
|
|
break;
|
|
s += ret + 1;
|
|
strtab_size -= ret + 1;
|
|
}
|
|
}
|
|
rcu_read_unlock();
|
|
mod->core_kallsyms.num_symtab = ndst;
|
|
}
|
|
|
|
#if IS_ENABLED(CONFIG_STACKTRACE_BUILD_ID)
|
|
void init_build_id(struct module *mod, const struct load_info *info)
|
|
{
|
|
const Elf_Shdr *sechdr;
|
|
unsigned int i;
|
|
|
|
for (i = 0; i < info->hdr->e_shnum; i++) {
|
|
sechdr = &info->sechdrs[i];
|
|
if (!sect_empty(sechdr) && sechdr->sh_type == SHT_NOTE &&
|
|
!build_id_parse_buf((void *)sechdr->sh_addr, mod->build_id,
|
|
sechdr->sh_size))
|
|
break;
|
|
}
|
|
}
|
|
#else
|
|
void init_build_id(struct module *mod, const struct load_info *info)
|
|
{
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
* This ignores the intensely annoying "mapping symbols" found
|
|
* in ARM ELF files: $a, $t and $d.
|
|
*/
|
|
static inline int is_arm_mapping_symbol(const char *str)
|
|
{
|
|
if (str[0] == '.' && str[1] == 'L')
|
|
return true;
|
|
return str[0] == '$' && strchr("axtd", str[1]) &&
|
|
(str[2] == '\0' || str[2] == '.');
|
|
}
|
|
|
|
static const char *kallsyms_symbol_name(struct mod_kallsyms *kallsyms, unsigned int symnum)
|
|
{
|
|
return kallsyms->strtab + kallsyms->symtab[symnum].st_name;
|
|
}
|
|
|
|
/*
|
|
* Given a module and address, find the corresponding symbol and return its name
|
|
* while providing its size and offset if needed.
|
|
*/
|
|
static const char *find_kallsyms_symbol(struct module *mod,
|
|
unsigned long addr,
|
|
unsigned long *size,
|
|
unsigned long *offset)
|
|
{
|
|
unsigned int i, best = 0;
|
|
unsigned long nextval, bestval;
|
|
struct mod_kallsyms *kallsyms = rcu_dereference_sched(mod->kallsyms);
|
|
|
|
/* At worse, next value is at end of module */
|
|
if (within_module_init(addr, mod))
|
|
nextval = (unsigned long)mod->init_layout.base + mod->init_layout.text_size;
|
|
else
|
|
nextval = (unsigned long)mod->core_layout.base + mod->core_layout.text_size;
|
|
|
|
bestval = kallsyms_symbol_value(&kallsyms->symtab[best]);
|
|
|
|
/*
|
|
* Scan for closest preceding symbol, and next symbol. (ELF
|
|
* starts real symbols at 1).
|
|
*/
|
|
for (i = 1; i < kallsyms->num_symtab; i++) {
|
|
const Elf_Sym *sym = &kallsyms->symtab[i];
|
|
unsigned long thisval = kallsyms_symbol_value(sym);
|
|
|
|
if (sym->st_shndx == SHN_UNDEF)
|
|
continue;
|
|
|
|
/*
|
|
* We ignore unnamed symbols: they're uninformative
|
|
* and inserted at a whim.
|
|
*/
|
|
if (*kallsyms_symbol_name(kallsyms, i) == '\0' ||
|
|
is_arm_mapping_symbol(kallsyms_symbol_name(kallsyms, i)))
|
|
continue;
|
|
|
|
if (thisval <= addr && thisval > bestval) {
|
|
best = i;
|
|
bestval = thisval;
|
|
}
|
|
if (thisval > addr && thisval < nextval)
|
|
nextval = thisval;
|
|
}
|
|
|
|
if (!best)
|
|
return NULL;
|
|
|
|
if (size)
|
|
*size = nextval - bestval;
|
|
if (offset)
|
|
*offset = addr - bestval;
|
|
|
|
return kallsyms_symbol_name(kallsyms, best);
|
|
}
|
|
|
|
void * __weak dereference_module_function_descriptor(struct module *mod,
|
|
void *ptr)
|
|
{
|
|
return ptr;
|
|
}
|
|
|
|
/*
|
|
* For kallsyms to ask for address resolution. NULL means not found. Careful
|
|
* not to lock to avoid deadlock on oopses, simply disable preemption.
|
|
*/
|
|
const char *module_address_lookup(unsigned long addr,
|
|
unsigned long *size,
|
|
unsigned long *offset,
|
|
char **modname,
|
|
const unsigned char **modbuildid,
|
|
char *namebuf)
|
|
{
|
|
const char *ret = NULL;
|
|
struct module *mod;
|
|
|
|
preempt_disable();
|
|
mod = __module_address(addr);
|
|
if (mod) {
|
|
if (modname)
|
|
*modname = mod->name;
|
|
if (modbuildid) {
|
|
#if IS_ENABLED(CONFIG_STACKTRACE_BUILD_ID)
|
|
*modbuildid = mod->build_id;
|
|
#else
|
|
*modbuildid = NULL;
|
|
#endif
|
|
}
|
|
|
|
ret = find_kallsyms_symbol(mod, addr, size, offset);
|
|
}
|
|
/* Make a copy in here where it's safe */
|
|
if (ret) {
|
|
strncpy(namebuf, ret, KSYM_NAME_LEN - 1);
|
|
ret = namebuf;
|
|
}
|
|
preempt_enable();
|
|
|
|
return ret;
|
|
}
|
|
|
|
int lookup_module_symbol_name(unsigned long addr, char *symname)
|
|
{
|
|
struct module *mod;
|
|
|
|
preempt_disable();
|
|
list_for_each_entry_rcu(mod, &modules, list) {
|
|
if (mod->state == MODULE_STATE_UNFORMED)
|
|
continue;
|
|
if (within_module(addr, mod)) {
|
|
const char *sym;
|
|
|
|
sym = find_kallsyms_symbol(mod, addr, NULL, NULL);
|
|
if (!sym)
|
|
goto out;
|
|
|
|
strscpy(symname, sym, KSYM_NAME_LEN);
|
|
preempt_enable();
|
|
return 0;
|
|
}
|
|
}
|
|
out:
|
|
preempt_enable();
|
|
return -ERANGE;
|
|
}
|
|
|
|
int lookup_module_symbol_attrs(unsigned long addr, unsigned long *size,
|
|
unsigned long *offset, char *modname, char *name)
|
|
{
|
|
struct module *mod;
|
|
|
|
preempt_disable();
|
|
list_for_each_entry_rcu(mod, &modules, list) {
|
|
if (mod->state == MODULE_STATE_UNFORMED)
|
|
continue;
|
|
if (within_module(addr, mod)) {
|
|
const char *sym;
|
|
|
|
sym = find_kallsyms_symbol(mod, addr, size, offset);
|
|
if (!sym)
|
|
goto out;
|
|
if (modname)
|
|
strscpy(modname, mod->name, MODULE_NAME_LEN);
|
|
if (name)
|
|
strscpy(name, sym, KSYM_NAME_LEN);
|
|
preempt_enable();
|
|
return 0;
|
|
}
|
|
}
|
|
out:
|
|
preempt_enable();
|
|
return -ERANGE;
|
|
}
|
|
|
|
int module_get_kallsym(unsigned int symnum, unsigned long *value, char *type,
|
|
char *name, char *module_name, int *exported)
|
|
{
|
|
struct module *mod;
|
|
|
|
preempt_disable();
|
|
list_for_each_entry_rcu(mod, &modules, list) {
|
|
struct mod_kallsyms *kallsyms;
|
|
|
|
if (mod->state == MODULE_STATE_UNFORMED)
|
|
continue;
|
|
kallsyms = rcu_dereference_sched(mod->kallsyms);
|
|
if (symnum < kallsyms->num_symtab) {
|
|
const Elf_Sym *sym = &kallsyms->symtab[symnum];
|
|
|
|
*value = kallsyms_symbol_value(sym);
|
|
*type = kallsyms->typetab[symnum];
|
|
strscpy(name, kallsyms_symbol_name(kallsyms, symnum), KSYM_NAME_LEN);
|
|
strscpy(module_name, mod->name, MODULE_NAME_LEN);
|
|
*exported = is_exported(name, *value, mod);
|
|
preempt_enable();
|
|
return 0;
|
|
}
|
|
symnum -= kallsyms->num_symtab;
|
|
}
|
|
preempt_enable();
|
|
return -ERANGE;
|
|
}
|
|
|
|
/* Given a module and name of symbol, find and return the symbol's value */
|
|
unsigned long find_kallsyms_symbol_value(struct module *mod, const char *name)
|
|
{
|
|
unsigned int i;
|
|
struct mod_kallsyms *kallsyms = rcu_dereference_sched(mod->kallsyms);
|
|
|
|
for (i = 0; i < kallsyms->num_symtab; i++) {
|
|
const Elf_Sym *sym = &kallsyms->symtab[i];
|
|
|
|
if (strcmp(name, kallsyms_symbol_name(kallsyms, i)) == 0 &&
|
|
sym->st_shndx != SHN_UNDEF)
|
|
return kallsyms_symbol_value(sym);
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
static unsigned long __module_kallsyms_lookup_name(const char *name)
|
|
{
|
|
struct module *mod;
|
|
char *colon;
|
|
|
|
colon = strnchr(name, MODULE_NAME_LEN, ':');
|
|
if (colon) {
|
|
mod = find_module_all(name, colon - name, false);
|
|
if (mod)
|
|
return find_kallsyms_symbol_value(mod, colon + 1);
|
|
return 0;
|
|
}
|
|
|
|
list_for_each_entry_rcu(mod, &modules, list) {
|
|
unsigned long ret;
|
|
|
|
if (mod->state == MODULE_STATE_UNFORMED)
|
|
continue;
|
|
ret = find_kallsyms_symbol_value(mod, name);
|
|
if (ret)
|
|
return ret;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
/* Look for this name: can be of form module:name. */
|
|
unsigned long module_kallsyms_lookup_name(const char *name)
|
|
{
|
|
unsigned long ret;
|
|
|
|
/* Don't lock: we're in enough trouble already. */
|
|
preempt_disable();
|
|
ret = __module_kallsyms_lookup_name(name);
|
|
preempt_enable();
|
|
return ret;
|
|
}
|
|
|
|
#ifdef CONFIG_LIVEPATCH
|
|
int module_kallsyms_on_each_symbol(int (*fn)(void *, const char *,
|
|
struct module *, unsigned long),
|
|
void *data)
|
|
{
|
|
struct module *mod;
|
|
unsigned int i;
|
|
int ret = 0;
|
|
|
|
mutex_lock(&module_mutex);
|
|
list_for_each_entry(mod, &modules, list) {
|
|
struct mod_kallsyms *kallsyms;
|
|
|
|
if (mod->state == MODULE_STATE_UNFORMED)
|
|
continue;
|
|
|
|
/* Use rcu_dereference_sched() to remain compliant with the sparse tool */
|
|
preempt_disable();
|
|
kallsyms = rcu_dereference_sched(mod->kallsyms);
|
|
preempt_enable();
|
|
|
|
for (i = 0; i < kallsyms->num_symtab; i++) {
|
|
const Elf_Sym *sym = &kallsyms->symtab[i];
|
|
|
|
if (sym->st_shndx == SHN_UNDEF)
|
|
continue;
|
|
|
|
ret = fn(data, kallsyms_symbol_name(kallsyms, i),
|
|
mod, kallsyms_symbol_value(sym));
|
|
if (ret != 0)
|
|
goto out;
|
|
}
|
|
}
|
|
out:
|
|
mutex_unlock(&module_mutex);
|
|
return ret;
|
|
}
|
|
#endif /* CONFIG_LIVEPATCH */
|