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[83.153.85.71]) by smtp.gmail.com with ESMTPSA id i63sm22556235wmf.24.2015.12.28.03.21.08 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Mon, 28 Dec 2015 03:21:09 -0800 (PST) From: Ard Biesheuvel To: linux-arm-kernel@lists.infradead.org, kernel-hardening@lists.openwall.com, will.deacon@arm.com, catalin.marinas@arm.com, mark.rutland@arm.com, leif.lindholm@linaro.org, keescook@chromium.org, lkml@vger.kernel.org Subject: [RFC PATCH 05/10] arm64: add support for module PLTs Date: Mon, 28 Dec 2015 12:20:49 +0100 Message-Id: <1451301654-32019-6-git-send-email-ard.biesheuvel@linaro.org> X-Mailer: git-send-email 2.5.0 In-Reply-To: <1451301654-32019-1-git-send-email-ard.biesheuvel@linaro.org> References: <1451301654-32019-1-git-send-email-ard.biesheuvel@linaro.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20151228_032132_262070_AE1E58F4 X-CRM114-Status: GOOD ( 23.40 ) X-Spam-Score: -2.7 (--) X-Spam-Report: SpamAssassin version 3.4.0 on bombadil.infradead.org summary: Content analysis details: (-2.7 points) pts rule name description ---- ---------------------- -------------------------------------------------- -0.7 RCVD_IN_DNSWL_LOW RBL: Sender listed at http://www.dnswl.org/, low trust [2a00:1450:400c:c09:0:0:0:22e listed in] [list.dnswl.org] -0.0 SPF_PASS SPF: sender matches SPF record -1.9 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: bhupesh.sharma@freescale.com, stuart.yoder@freescale.com, Ard Biesheuvel MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patch=linaro.org@lists.infradead.org This adds support for emitting PLTs at module load time for relative branches that are out of range. This is a prerequisite for KASLR, which may place the kernel and the modules anywhere in the vmalloc area, making it likely that branch target offsets exceed the maximum range of +/- 128 MB. Signed-off-by: Ard Biesheuvel --- arch/arm64/Kconfig | 4 + arch/arm64/Makefile | 4 + arch/arm64/include/asm/module.h | 11 ++ arch/arm64/kernel/Makefile | 1 + arch/arm64/kernel/module-plts.c | 137 ++++++++++++++++++++ arch/arm64/kernel/module.c | 7 + arch/arm64/kernel/module.lds | 4 + 7 files changed, 168 insertions(+) -- 2.5.0 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 871f21783866..827e78f33944 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -704,6 +704,10 @@ config ARM64_LSE_ATOMICS endmenu +config ARM64_MODULE_PLTS + bool + select HAVE_MOD_ARCH_SPECIFIC + endmenu menu "Boot options" diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile index cd822d8454c0..d4654830e536 100644 --- a/arch/arm64/Makefile +++ b/arch/arm64/Makefile @@ -45,6 +45,10 @@ ifeq ($(CONFIG_ARM64_ERRATUM_843419), y) KBUILD_CFLAGS_MODULE += -mcmodel=large endif +ifeq ($(CONFIG_ARM64_MODULE_PLTS),y) +KBUILD_LDFLAGS_MODULE += -T $(srctree)/arch/arm64/kernel/module.lds +endif + # Default value head-y := arch/arm64/kernel/head.o diff --git a/arch/arm64/include/asm/module.h b/arch/arm64/include/asm/module.h index e80e232b730e..7b8cd3dc9d8e 100644 --- a/arch/arm64/include/asm/module.h +++ b/arch/arm64/include/asm/module.h @@ -20,4 +20,15 @@ #define MODULE_ARCH_VERMAGIC "aarch64" +#ifdef CONFIG_ARM64_MODULE_PLTS +struct mod_arch_specific { + struct elf64_shdr *core_plt; + struct elf64_shdr *init_plt; + int core_plt_count; + int init_plt_count; +}; +#endif + +u64 get_module_plt(struct module *mod, void *loc, u64 val); + #endif /* __ASM_MODULE_H */ diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile index 474691f8b13a..f42b0fff607f 100644 --- a/arch/arm64/kernel/Makefile +++ b/arch/arm64/kernel/Makefile @@ -30,6 +30,7 @@ arm64-obj-$(CONFIG_COMPAT) += sys32.o kuser32.o signal32.o \ ../../arm/kernel/opcodes.o arm64-obj-$(CONFIG_FUNCTION_TRACER) += ftrace.o entry-ftrace.o arm64-obj-$(CONFIG_MODULES) += arm64ksyms.o module.o +arm64-obj-$(CONFIG_ARM64_MODULE_PLTS) += module-plts.o arm64-obj-$(CONFIG_PERF_EVENTS) += perf_regs.o perf_callchain.o arm64-obj-$(CONFIG_HW_PERF_EVENTS) += perf_event.o arm64-obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o diff --git a/arch/arm64/kernel/module-plts.c b/arch/arm64/kernel/module-plts.c new file mode 100644 index 000000000000..b4199f2b4e69 --- /dev/null +++ b/arch/arm64/kernel/module-plts.c @@ -0,0 +1,137 @@ +/* + * Copyright (C) 2014-2015 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 + * published by the Free Software Foundation. + */ + +#include +#include +#include + +struct plt_entry { + u32 mov0; /* movn x16, #0x...., lsl #32 */ + u32 mov1; /* movk x16, #0x...., lsl #16 */ + u32 mov2; /* movk x16, #0x.... */ + u32 br; /* br x16 */ +}; + +static bool in_init(const struct module *mod, void *addr) +{ + return (u64)addr - (u64)mod->module_init < mod->init_size; +} + +u64 get_module_plt(struct module *mod, void *loc, u64 val) +{ + struct plt_entry entry, *plt; + int i, *count; + + entry.mov0 = 0x92c00010 | ((~val & 0xffff00000000) >> (32 - 5)); + entry.mov1 = 0xf2a00010 | (( val & 0xffff0000) >> (16 - 5)); + entry.mov2 = 0xf2800010 | (( val & 0xffff) << 5); + entry.br = 0xd61f0200; + + if (in_init(mod, loc)) { + plt = (struct plt_entry *)mod->arch.init_plt->sh_addr; + count = &mod->arch.init_plt_count; + } else { + plt = (struct plt_entry *)mod->arch.core_plt->sh_addr; + count = &mod->arch.core_plt_count; + } + + /* Look for an existing entry pointing to 'val' */ + for (i = 0; i < *count; i++) + if (plt[i].mov2 == entry.mov2 && + plt[i].mov1 == entry.mov1 && + plt[i].mov0 == entry.mov0) + return (u64)&plt[i]; + + i = (*count)++; + plt[i] = entry; + return (u64)&plt[i]; +} + +static int duplicate_rel(Elf64_Addr base, const Elf64_Rela *rela, int num) +{ + int i; + + for (i = 0; i < num; i++) { + if (rela[i].r_info == rela[num].r_info && + rela[i].r_addend == rela[num].r_addend) + return 1; + } + return 0; +} + +/* Count how many PLT entries we may need */ +static unsigned int count_plts(Elf64_Addr base, const Elf64_Rela *rela, int num) +{ + unsigned int ret = 0; + int i; + + /* + * Sure, this is order(n^2), but it's usually short, and not + * time critical + */ + for (i = 0; i < num; i++) + switch (ELF64_R_TYPE(rela[i].r_info)) { + case R_AARCH64_JUMP26: + case R_AARCH64_CALL26: + if (!duplicate_rel(base, rela, i)) + ret++; + break; + } + return ret; +} + +int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, + char *secstrings, struct module *mod) +{ + unsigned long core_plts = 0, init_plts = 0; + Elf64_Shdr *s, *sechdrs_end = sechdrs + ehdr->e_shnum; + + /* + * To store the PLTs, we expand the .text section for core module code + * and the .init.text section for initialization code. + */ + for (s = sechdrs; s < sechdrs_end; ++s) + if (strcmp(".core.plt", secstrings + s->sh_name) == 0) + mod->arch.core_plt = s; + else if (strcmp(".init.plt", secstrings + s->sh_name) == 0) + mod->arch.init_plt = s; + + if (!mod->arch.core_plt || !mod->arch.init_plt) { + pr_err("%s: sections missing\n", mod->name); + return -ENOEXEC; + } + + for (s = sechdrs + 1; s < sechdrs_end; ++s) { + const Elf64_Rela *rels = (void *)ehdr + s->sh_offset; + int numrels = s->sh_size / sizeof(Elf64_Rela); + Elf64_Shdr *dstsec = sechdrs + s->sh_info; + + if (s->sh_type != SHT_RELA) + continue; + + if (strstr(secstrings + s->sh_name, ".init")) + init_plts += count_plts(dstsec->sh_addr, rels, numrels); + else + core_plts += count_plts(dstsec->sh_addr, rels, numrels); + } + + 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 = core_plts * sizeof(struct plt_entry); + 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 = init_plts * sizeof(struct plt_entry); + mod->arch.init_plt_count = 0; + pr_debug("%s: core.plt=%lld, init.plt=%lld\n", __func__, + mod->arch.core_plt->sh_size, mod->arch.init_plt->sh_size); + return 0; +} diff --git a/arch/arm64/kernel/module.c b/arch/arm64/kernel/module.c index f4bc779e62e8..14880d77ec6f 100644 --- a/arch/arm64/kernel/module.c +++ b/arch/arm64/kernel/module.c @@ -388,6 +388,13 @@ int apply_relocate_add(Elf64_Shdr *sechdrs, case R_AARCH64_CALL26: ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 2, 26, AARCH64_INSN_IMM_26); + + if (IS_ENABLED(CONFIG_ARM64_MODULE_PLTS) && + ovf == -ERANGE) { + val = get_module_plt(me, loc, val); + ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 2, + 26, AARCH64_INSN_IMM_26); + } break; default: diff --git a/arch/arm64/kernel/module.lds b/arch/arm64/kernel/module.lds new file mode 100644 index 000000000000..3682fa107918 --- /dev/null +++ b/arch/arm64/kernel/module.lds @@ -0,0 +1,4 @@ +SECTIONS { + .core.plt : { BYTE(0) } + .init.plt : { BYTE(0) } +}