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module: Move kallsyms support into a separate file

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No functional change.

This patch migrates kallsyms code out of core module
code kernel/module/kallsyms.c

Signed-off-by: Aaron Tomlin <atomlin@redhat.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
This commit is contained in:
Aaron Tomlin 2022-03-22 14:03:39 +00:00 committed by Luis Chamberlain
parent 473c84d185
commit 91fb02f315
4 changed files with 538 additions and 525 deletions
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1
kernel/module/Makefile
View File

@ -14,3 +14,4 @@ obj-$(CONFIG_LIVEPATCH) += livepatch.o
obj-$(CONFIG_MODULES_TREE_LOOKUP) += tree_lookup.o
obj-$(CONFIG_STRICT_MODULE_RWX) += strict_rwx.o
obj-$(CONFIG_DEBUG_KMEMLEAK) += debug_kmemleak.o
obj-$(CONFIG_KALLSYMS) += kallsyms.o

29
kernel/module/internal.h
View File

@ -68,6 +68,19 @@ struct load_info {
};
int mod_verify_sig(const void *mod, struct load_info *info);
struct module *find_module_all(const char *name, size_t len, bool even_unformed);
int cmp_name(const void *name, const void *sym);
long module_get_offset(struct module *mod, unsigned int *size, Elf_Shdr *sechdr,
unsigned int section);
static inline unsigned long kernel_symbol_value(const struct kernel_symbol *sym)
{
#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
return (unsigned long)offset_to_ptr(&sym->value_offset);
#else
return sym->value;
#endif
}
#ifdef CONFIG_LIVEPATCH
int copy_module_elf(struct module *mod, struct load_info *info);
@ -174,3 +187,19 @@ void kmemleak_load_module(const struct module *mod, const struct load_info *info
static inline void kmemleak_load_module(const struct module *mod,
const struct load_info *info) { }
#endif /* CONFIG_DEBUG_KMEMLEAK */
#ifdef CONFIG_KALLSYMS
void init_build_id(struct module *mod, const struct load_info *info);
void layout_symtab(struct module *mod, struct load_info *info);
void add_kallsyms(struct module *mod, const struct load_info *info);
unsigned long find_kallsyms_symbol_value(struct module *mod, const char *name);
static inline bool sect_empty(const Elf_Shdr *sect)
{
return !(sect->sh_flags & SHF_ALLOC) || sect->sh_size == 0;
}
#else /* !CONFIG_KALLSYMS */
static inline void init_build_id(struct module *mod, const struct load_info *info) { }
static inline void layout_symtab(struct module *mod, struct load_info *info) { }
static inline void add_kallsyms(struct module *mod, const struct load_info *info) { }
#endif /* CONFIG_KALLSYMS */

502
kernel/module/kallsyms.c Normal file
View File

@ -0,0 +1,502 @@
// 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->core_layout.size, symsect->sh_addralign ?: 1);
info->stroffs = mod->core_layout.size = info->symoffs + ndst * sizeof(Elf_Sym);
mod->core_layout.size += strtab_size;
info->core_typeoffs = mod->core_layout.size;
mod->core_layout.size += ndst * sizeof(char);
mod->core_layout.size = debug_align(mod->core_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 = debug_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];
/* Set up to point into init section. */
mod->kallsyms = mod->init_layout.base + info->mod_kallsyms_init_off;
/* The following is safe since this pointer cannot change */
mod->kallsyms->symtab = (void *)symsec->sh_addr;
mod->kallsyms->num_symtab = symsec->sh_size / sizeof(Elf_Sym);
/* Make sure we get permanent strtab: don't use info->strtab. */
mod->kallsyms->strtab = (void *)info->sechdrs[info->index.str].sh_addr;
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->core_layout.base + info->symoffs;
mod->core_kallsyms.strtab = s = mod->core_layout.base + info->stroffs;
mod->core_kallsyms.typetab = mod->core_layout.base + info->core_typeoffs;
src = mod->kallsyms->symtab;
for (ndst = i = 0; i < mod->kallsyms->num_symtab; i++) {
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)) {
mod->core_kallsyms.typetab[ndst] =
mod->kallsyms->typetab[i];
dst[ndst] = src[i];
dst[ndst++].st_name = s - mod->core_kallsyms.strtab;
s += strscpy(s, &mod->kallsyms->strtab[src[i].st_name],
KSYM_NAME_LEN) + 1;
}
}
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;
}
/* Look for this name: can be of form module:name. */
unsigned long module_kallsyms_lookup_name(const char *name)
{
struct module *mod;
char *colon;
unsigned long ret = 0;
/* Don't lock: we're in enough trouble already. */
preempt_disable();
if ((colon = strnchr(name, MODULE_NAME_LEN, ':')) != NULL) {
if ((mod = find_module_all(name, colon - name, false)) != NULL)
ret = find_kallsyms_symbol_value(mod, colon + 1);
} else {
list_for_each_entry_rcu(mod, &modules, list) {
if (mod->state == MODULE_STATE_UNFORMED)
continue;
if ((ret = find_kallsyms_symbol_value(mod, name)) != 0)
break;
}
}
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) {
/* We hold module_mutex: no need for rcu_dereference_sched */
struct mod_kallsyms *kallsyms = mod->kallsyms;
if (mod->state == MODULE_STATE_UNFORMED)
continue;
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 */

531
kernel/module/main.c
View File

@ -288,15 +288,6 @@ static bool check_exported_symbol(const struct symsearch *syms,
return true;
}
static unsigned long kernel_symbol_value(const struct kernel_symbol *sym)
{
#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
return (unsigned long)offset_to_ptr(&sym->value_offset);
#else
return sym->value;
#endif
}
static const char *kernel_symbol_name(const struct kernel_symbol *sym)
{
#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
@ -317,7 +308,7 @@ static const char *kernel_symbol_namespace(const struct kernel_symbol *sym)
#endif
}
static int cmp_name(const void *name, const void *sym)
int cmp_name(const void *name, const void *sym)
{
return strcmp(name, kernel_symbol_name(sym));
}
@ -387,8 +378,8 @@ static bool find_symbol(struct find_symbol_arg *fsa)
* Search for module by name: must hold module_mutex (or preempt disabled
* for read-only access).
*/
static struct module *find_module_all(const char *name, size_t len,
bool even_unformed)
struct module *find_module_all(const char *name, size_t len,
bool even_unformed)
{
struct module *mod;
@ -1294,13 +1285,6 @@ resolve_symbol_wait(struct module *mod,
return ksym;
}
#ifdef CONFIG_KALLSYMS
static inline bool sect_empty(const Elf_Shdr *sect)
{
return !(sect->sh_flags & SHF_ALLOC) || sect->sh_size == 0;
}
#endif
/*
* /sys/module/foo/sections stuff
* J. Corbet <corbet@lwn.net>
@ -2065,7 +2049,7 @@ unsigned int __weak arch_mod_section_prepend(struct module *mod,
}
/* Update size with this section: return offset. */
static long get_offset(struct module *mod, unsigned int *size,
long module_get_offset(struct module *mod, unsigned int *size,
Elf_Shdr *sechdr, unsigned int section)
{
long ret;
@ -2121,7 +2105,7 @@ static void layout_sections(struct module *mod, struct load_info *info)
|| s->sh_entsize != ~0UL
|| module_init_layout_section(sname))
continue;
s->sh_entsize = get_offset(mod, &mod->core_layout.size, s, i);
s->sh_entsize = module_get_offset(mod, &mod->core_layout.size, s, i);
pr_debug("\t%s\n", sname);
}
switch (m) {
@ -2154,7 +2138,7 @@ static void layout_sections(struct module *mod, struct load_info *info)
|| s->sh_entsize != ~0UL
|| !module_init_layout_section(sname))
continue;
s->sh_entsize = (get_offset(mod, &mod->init_layout.size, s, i)
s->sh_entsize = (module_get_offset(mod, &mod->init_layout.size, s, i)
| INIT_OFFSET_MASK);
pr_debug("\t%s\n", sname);
}
@ -2267,228 +2251,6 @@ static void free_modinfo(struct module *mod)
}
}
#ifdef CONFIG_KALLSYMS
/* 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 != NULL && 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>.
*/
static 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 = 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->core_layout.size, symsect->sh_addralign ?: 1);
info->stroffs = mod->core_layout.size = info->symoffs + ndst * sizeof(Elf_Sym);
mod->core_layout.size += strtab_size;
info->core_typeoffs = mod->core_layout.size;
mod->core_layout.size += ndst * sizeof(char);
mod->core_layout.size = debug_align(mod->core_layout.size);
/* Put string table section at end of init part of module. */
strsect->sh_flags |= SHF_ALLOC;
strsect->sh_entsize = 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 = debug_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.
*/
static 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];
/* Set up to point into init section. */
mod->kallsyms = mod->init_layout.base + info->mod_kallsyms_init_off;
mod->kallsyms->symtab = (void *)symsec->sh_addr;
mod->kallsyms->num_symtab = symsec->sh_size / sizeof(Elf_Sym);
/* Make sure we get permanent strtab: don't use info->strtab. */
mod->kallsyms->strtab = (void *)info->sechdrs[info->index.str].sh_addr;
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->core_layout.base + info->symoffs;
mod->core_kallsyms.strtab = s = mod->core_layout.base + info->stroffs;
mod->core_kallsyms.typetab = mod->core_layout.base + info->core_typeoffs;
src = mod->kallsyms->symtab;
for (ndst = i = 0; i < mod->kallsyms->num_symtab; i++) {
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)) {
mod->core_kallsyms.typetab[ndst] =
mod->kallsyms->typetab[i];
dst[ndst] = src[i];
dst[ndst++].st_name = s - mod->core_kallsyms.strtab;
s += strlcpy(s, &mod->kallsyms->strtab[src[i].st_name],
KSYM_NAME_LEN) + 1;
}
}
mod->core_kallsyms.num_symtab = ndst;
}
#else
static inline void layout_symtab(struct module *mod, struct load_info *info)
{
}
static void add_kallsyms(struct module *mod, const struct load_info *info)
{
}
#endif /* CONFIG_KALLSYMS */
#if IS_ENABLED(CONFIG_KALLSYMS) && IS_ENABLED(CONFIG_STACKTRACE_BUILD_ID)
static 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
static void init_build_id(struct module *mod, const struct load_info *info)
{
}
#endif
static void dynamic_debug_setup(struct module *mod, struct _ddebug *debug, unsigned int num)
{
if (!debug)
@ -3799,287 +3561,6 @@ static inline int within(unsigned long addr, void *start, unsigned long size)
return ((void *)addr >= start && (void *)addr < start + size);
}
#ifdef CONFIG_KALLSYMS
/*
* 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;
strlcpy(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)
strlcpy(modname, mod->name, MODULE_NAME_LEN);
if (name)
strlcpy(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];
strlcpy(name, kallsyms_symbol_name(kallsyms, symnum), KSYM_NAME_LEN);
strlcpy(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 */
static 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;
}
/* Look for this name: can be of form module:name. */
unsigned long module_kallsyms_lookup_name(const char *name)
{
struct module *mod;
char *colon;
unsigned long ret = 0;
/* Don't lock: we're in enough trouble already. */
preempt_disable();
if ((colon = strnchr(name, MODULE_NAME_LEN, ':')) != NULL) {
if ((mod = find_module_all(name, colon - name, false)) != NULL)
ret = find_kallsyms_symbol_value(mod, colon+1);
} else {
list_for_each_entry_rcu(mod, &modules, list) {
if (mod->state == MODULE_STATE_UNFORMED)
continue;
if ((ret = find_kallsyms_symbol_value(mod, name)) != 0)
break;
}
}
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) {
/* We hold module_mutex: no need for rcu_dereference_sched */
struct mod_kallsyms *kallsyms = mod->kallsyms;
if (mod->state == MODULE_STATE_UNFORMED)
continue;
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;
cond_resched();
}
}
out:
mutex_unlock(&module_mutex);
return ret;
}
#endif /* CONFIG_LIVEPATCH */
#endif /* CONFIG_KALLSYMS */
static void cfi_init(struct module *mod)
{
#ifdef CONFIG_CFI_CLANG