From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:38992 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S967024AbdEWOtu (ORCPT ); Tue, 23 May 2017 10:49:50 -0400 Subject: Patch "ARM: 8662/1: module: split core and init PLT sections" has been added to the 4.9-stable tree To: ard.biesheuvel@linaro.org, angus@angusclark.org, gregkh@linuxfoundation.org, rmk+kernel@armlinux.org.uk Cc: , From: Date: Tue, 23 May 2017 16:47:49 +0200 Message-ID: <149555086912553@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled ARM: 8662/1: module: split core and init PLT sections to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: arm-8662-1-module-split-core-and-init-plt-sections.patch and it can be found in the queue-4.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From b7ede5a1f5905ac394cc8e61712a13e3c5cb7b8f Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Wed, 22 Feb 2017 19:40:12 +0100 Subject: ARM: 8662/1: module: split core and init PLT sections From: Ard Biesheuvel commit b7ede5a1f5905ac394cc8e61712a13e3c5cb7b8f upstream. Since commit 35fa91eed817 ("ARM: kernel: merge core and init PLTs"), the ARM module PLT code allocates all PLT entries in a single core section, since the overhead of having a separate init PLT section is not justified by the small number of PLT entries usually required for init code. However, the core and init module regions are allocated independently, and there is a corner case where the core region may be allocated from the VMALLOC region if the dedicated module region is exhausted, but the init region, being much smaller, can still be allocated from the module region. This puts the PLT entries out of reach of the relocated branch instructions, defeating the whole purpose of PLTs. So split the core and init PLT regions, and name the latter ".init.plt" so it gets allocated along with (and sufficiently close to) the .init sections that it serves. Also, given that init PLT entries may need to be emitted for branches that target the core module, modify the logic that disregards defined symbols to only disregard symbols that are defined in the same section. Fixes: 35fa91eed817 ("ARM: kernel: merge core and init PLTs") Reported-by: Angus Clark Tested-by: Angus Clark Signed-off-by: Ard Biesheuvel Signed-off-by: Russell King Signed-off-by: Greg Kroah-Hartman --- arch/arm/include/asm/module.h | 9 +++- arch/arm/kernel/module-plts.c | 85 +++++++++++++++++++++++++++++------------- arch/arm/kernel/module.lds | 1 3 files changed, 67 insertions(+), 28 deletions(-) --- a/arch/arm/include/asm/module.h +++ b/arch/arm/include/asm/module.h @@ -18,13 +18,18 @@ enum { }; #endif +struct mod_plt_sec { + struct elf32_shdr *plt; + int plt_count; +}; + struct mod_arch_specific { #ifdef CONFIG_ARM_UNWIND struct unwind_table *unwind[ARM_SEC_MAX]; #endif #ifdef CONFIG_ARM_MODULE_PLTS - struct elf32_shdr *plt; - int plt_count; + struct mod_plt_sec core; + struct mod_plt_sec init; #endif }; --- a/arch/arm/kernel/module-plts.c +++ b/arch/arm/kernel/module-plts.c @@ -1,5 +1,5 @@ /* - * Copyright (C) 2014 Linaro Ltd. + * Copyright (C) 2014-2017 Linaro Ltd. * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as @@ -31,9 +31,17 @@ struct plt_entries { u32 lit[PLT_ENT_COUNT]; }; +static bool in_init(const struct module *mod, unsigned long loc) +{ + return loc - (u32)mod->init_layout.base < mod->init_layout.size; +} + u32 get_module_plt(struct module *mod, unsigned long loc, Elf32_Addr val) { - struct plt_entries *plt = (struct plt_entries *)mod->arch.plt->sh_addr; + struct mod_plt_sec *pltsec = !in_init(mod, loc) ? &mod->arch.core : + &mod->arch.init; + + struct plt_entries *plt = (struct plt_entries *)pltsec->plt->sh_addr; int idx = 0; /* @@ -41,9 +49,9 @@ u32 get_module_plt(struct module *mod, u * relocations are sorted, this will be the last entry we allocated. * (if one exists). */ - if (mod->arch.plt_count > 0) { - plt += (mod->arch.plt_count - 1) / PLT_ENT_COUNT; - idx = (mod->arch.plt_count - 1) % PLT_ENT_COUNT; + if (pltsec->plt_count > 0) { + plt += (pltsec->plt_count - 1) / PLT_ENT_COUNT; + idx = (pltsec->plt_count - 1) % PLT_ENT_COUNT; if (plt->lit[idx] == val) return (u32)&plt->ldr[idx]; @@ -53,8 +61,8 @@ u32 get_module_plt(struct module *mod, u plt++; } - mod->arch.plt_count++; - BUG_ON(mod->arch.plt_count * PLT_ENT_SIZE > mod->arch.plt->sh_size); + pltsec->plt_count++; + BUG_ON(pltsec->plt_count * PLT_ENT_SIZE > pltsec->plt->sh_size); if (!idx) /* Populate a new set of entries */ @@ -129,7 +137,7 @@ static bool duplicate_rel(Elf32_Addr bas /* Count how many PLT entries we may need */ static unsigned int count_plts(const Elf32_Sym *syms, Elf32_Addr base, - const Elf32_Rel *rel, int num) + const Elf32_Rel *rel, int num, Elf32_Word dstidx) { unsigned int ret = 0; const Elf32_Sym *s; @@ -144,13 +152,17 @@ static unsigned int count_plts(const Elf case R_ARM_THM_JUMP24: /* * We only have to consider branch targets that resolve - * to undefined symbols. This is not simply a heuristic, - * it is a fundamental limitation, since the PLT itself - * is part of the module, and needs to be within range - * as well, so modules can never grow beyond that limit. + * to symbols that are defined in a different section. + * This is not simply a heuristic, it is a fundamental + * limitation, since there is no guaranteed way to emit + * PLT entries sufficiently close to the branch if the + * section size exceeds the range of a branch + * instruction. So ignore relocations against defined + * symbols if they live in the same section as the + * relocation target. */ s = syms + ELF32_R_SYM(rel[i].r_info); - if (s->st_shndx != SHN_UNDEF) + if (s->st_shndx == dstidx) break; /* @@ -161,7 +173,12 @@ static unsigned int count_plts(const Elf * So we need to support them, but there is no need to * take them into consideration when trying to optimize * this code. So let's only check for duplicates when - * the addend is zero. + * the addend is zero. (Note that calls into the core + * module via init PLT entries could involve section + * relative symbol references with non-zero addends, for + * which we may end up emitting duplicates, but the init + * PLT is released along with the rest of the .init + * region as soon as module loading completes.) */ if (!is_zero_addend_relocation(base, rel + i) || !duplicate_rel(base, rel, i)) @@ -174,7 +191,8 @@ static unsigned int count_plts(const Elf int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, char *secstrings, struct module *mod) { - unsigned long plts = 0; + unsigned long core_plts = 0; + unsigned long init_plts = 0; Elf32_Shdr *s, *sechdrs_end = sechdrs + ehdr->e_shnum; Elf32_Sym *syms = NULL; @@ -184,13 +202,15 @@ int module_frob_arch_sections(Elf_Ehdr * */ for (s = sechdrs; s < sechdrs_end; ++s) { if (strcmp(".plt", secstrings + s->sh_name) == 0) - mod->arch.plt = s; + mod->arch.core.plt = s; + else if (strcmp(".init.plt", secstrings + s->sh_name) == 0) + mod->arch.init.plt = s; else if (s->sh_type == SHT_SYMTAB) syms = (Elf32_Sym *)s->sh_addr; } - if (!mod->arch.plt) { - pr_err("%s: module PLT section missing\n", mod->name); + if (!mod->arch.core.plt || !mod->arch.init.plt) { + pr_err("%s: module PLT section(s) missing\n", mod->name); return -ENOEXEC; } if (!syms) { @@ -213,16 +233,29 @@ int module_frob_arch_sections(Elf_Ehdr * /* sort by type and symbol index */ sort(rels, numrels, sizeof(Elf32_Rel), cmp_rel, NULL); - plts += count_plts(syms, dstsec->sh_addr, rels, numrels); + if (strncmp(secstrings + dstsec->sh_name, ".init", 5) != 0) + core_plts += count_plts(syms, dstsec->sh_addr, rels, + numrels, s->sh_info); + else + init_plts += count_plts(syms, dstsec->sh_addr, rels, + numrels, s->sh_info); } - mod->arch.plt->sh_type = SHT_NOBITS; - mod->arch.plt->sh_flags = SHF_EXECINSTR | SHF_ALLOC; - mod->arch.plt->sh_addralign = L1_CACHE_BYTES; - mod->arch.plt->sh_size = round_up(plts * PLT_ENT_SIZE, - sizeof(struct plt_entries)); - mod->arch.plt_count = 0; + mod->arch.core.plt->sh_type = SHT_NOBITS; + mod->arch.core.plt->sh_flags = SHF_EXECINSTR | SHF_ALLOC; + mod->arch.core.plt->sh_addralign = L1_CACHE_BYTES; + mod->arch.core.plt->sh_size = round_up(core_plts * PLT_ENT_SIZE, + sizeof(struct plt_entries)); + mod->arch.core.plt_count = 0; + + mod->arch.init.plt->sh_type = SHT_NOBITS; + mod->arch.init.plt->sh_flags = SHF_EXECINSTR | SHF_ALLOC; + mod->arch.init.plt->sh_addralign = L1_CACHE_BYTES; + mod->arch.init.plt->sh_size = round_up(init_plts * PLT_ENT_SIZE, + sizeof(struct plt_entries)); + mod->arch.init.plt_count = 0; - pr_debug("%s: plt=%x\n", __func__, mod->arch.plt->sh_size); + pr_debug("%s: plt=%x, init.plt=%x\n", __func__, + mod->arch.core.plt->sh_size, mod->arch.init.plt->sh_size); return 0; } --- a/arch/arm/kernel/module.lds +++ b/arch/arm/kernel/module.lds @@ -1,3 +1,4 @@ SECTIONS { .plt : { BYTE(0) } + .init.plt : { BYTE(0) } } Patches currently in stable-queue which might be from ard.biesheuvel@linaro.org are queue-4.9/arm-8662-1-module-split-core-and-init-plt-sections.patch