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