From patchwork Wed Jun 3 08:00:08 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexandre Ghiti X-Patchwork-Id: 11585197 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 15CBE739 for ; Wed, 3 Jun 2020 08:02:44 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id E8636206C3 for ; Wed, 3 Jun 2020 08:02:43 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="K5FG8jrO" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E8636206C3 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ghiti.fr Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-riscv-bounces+patchwork-linux-riscv=patchwork.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender:Cc:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id: Content-Transfer-Encoding:MIME-Version:References:In-Reply-To:Message-Id:Date :Subject:To:From:Reply-To:Content-Type:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=29+8z/xa7h9hmzayif50gTtiY4Uf3e6o2dXUVmzQCUg=; b=K5FG8jrOBcZBzt DZ4RMcoMaMlklJAvxhAHJ2On4f8FfvblublbP6yOB59Wzdfz5g4PVXVca0HSk2wgaqBjtO6KUMOuO U13++NlHHj2q8d3deHwdI9ZK1AM9m1J+tjcui5JlWbUxRs0G7zskZqoSRN9orHy5wzlpS1dmCCVEm iJQjNK8GPDrt3OPJnz/tmoFYHrL6QhQa1Y5ZaqV5SvVkigvFTtsEI/9CAxE5UK/1ABbGHE+7hL9aO Sjh5YO8/adub0SubpwmxDv9mJxlElf+KqUOnshYn9aaXjr4fuFdDagJ8XkpbMzgcWcOT1wl74zx0O EyQQOa3rBT20A/dds3Bw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jgOMD-0008QR-UH; Wed, 03 Jun 2020 08:02:41 +0000 Received: from relay12.mail.gandi.net ([217.70.178.232]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jgOMA-0008Pt-ON for linux-riscv@lists.infradead.org; Wed, 03 Jun 2020 08:02:40 +0000 Received: from debian.home (lfbn-gre-1-325-105.w90-112.abo.wanadoo.fr [90.112.45.105]) (Authenticated sender: alex@ghiti.fr) by relay12.mail.gandi.net (Postfix) with ESMTPSA id 05B7E20000E; Wed, 3 Jun 2020 08:02:28 +0000 (UTC) From: Alexandre Ghiti To: Michael Ellerman , Benjamin Herrenschmidt , Paul Mackerras , Paul Walmsley , Palmer Dabbelt , Albert Ou , Anup Patel , Atish Patra , Zong Li , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org Subject: [PATCH v4 2/4] riscv: Introduce CONFIG_RELOCATABLE Date: Wed, 3 Jun 2020 04:00:08 -0400 Message-Id: <20200603080010.13366-3-alex@ghiti.fr> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200603080010.13366-1-alex@ghiti.fr> References: <20200603080010.13366-1-alex@ghiti.fr> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200603_010239_068222_61A21261 X-CRM114-Status: GOOD ( 16.81 ) X-Spam-Score: -0.7 (/) X-Spam-Report: SpamAssassin version 3.4.4 on bombadil.infradead.org summary: Content analysis details: (-0.7 points) pts rule name description ---- ---------------------- -------------------------------------------------- -0.7 RCVD_IN_DNSWL_LOW RBL: Sender listed at https://www.dnswl.org/, low trust [217.70.178.232 listed in list.dnswl.org] -0.0 RCVD_IN_MSPIKE_H2 RBL: Average reputation (+2) [217.70.178.232 listed in wl.mailspike.net] 0.0 SPF_NONE SPF: sender does not publish an SPF Record 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Anup Patel , Alexandre Ghiti Sender: "linux-riscv" Errors-To: linux-riscv-bounces+patchwork-linux-riscv=patchwork.kernel.org@lists.infradead.org This config allows to compile the kernel as PIE and to relocate it at any virtual address at runtime: this paves the way to KASLR and to 4-level page table folding at runtime. Runtime relocation is possible since relocation metadata are embedded into the kernel. Note that relocating at runtime introduces an overhead even if the kernel is loaded at the same address it was linked at and that the compiler options are those used in arm64 which uses the same RELA relocation format. Signed-off-by: Alexandre Ghiti Reviewed-by: Zong Li Reviewed-by: Anup Patel --- arch/riscv/Kconfig | 12 +++++++ arch/riscv/Makefile | 5 ++- arch/riscv/kernel/vmlinux.lds.S | 6 ++-- arch/riscv/mm/Makefile | 4 +++ arch/riscv/mm/init.c | 63 +++++++++++++++++++++++++++++++++ 5 files changed, 87 insertions(+), 3 deletions(-) diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index a31e1a41913a..93127d5913fe 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -170,6 +170,18 @@ config PGTABLE_LEVELS default 3 if 64BIT default 2 +config RELOCATABLE + bool + depends on MMU + help + This builds a kernel as a Position Independent Executable (PIE), + which retains all relocation metadata required to relocate the + kernel binary at runtime to a different virtual address than the + address it was linked at. + Since RISCV uses the RELA relocation format, this requires a + relocation pass at runtime even if the kernel is loaded at the + same address it was linked at. + source "arch/riscv/Kconfig.socs" menu "Platform type" diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile index fb6e37db836d..1406416ea743 100644 --- a/arch/riscv/Makefile +++ b/arch/riscv/Makefile @@ -9,7 +9,10 @@ # OBJCOPYFLAGS := -O binary -LDFLAGS_vmlinux := +ifeq ($(CONFIG_RELOCATABLE),y) +LDFLAGS_vmlinux := -shared -Bsymbolic -z notext -z norelro +KBUILD_CFLAGS += -fPIE +endif ifeq ($(CONFIG_DYNAMIC_FTRACE),y) LDFLAGS_vmlinux := --no-relax endif diff --git a/arch/riscv/kernel/vmlinux.lds.S b/arch/riscv/kernel/vmlinux.lds.S index a9abde62909f..e8ffba8c2044 100644 --- a/arch/riscv/kernel/vmlinux.lds.S +++ b/arch/riscv/kernel/vmlinux.lds.S @@ -85,8 +85,10 @@ SECTIONS BSS_SECTION(PAGE_SIZE, PAGE_SIZE, 0) - .rel.dyn : { - *(.rel.dyn*) + .rela.dyn : ALIGN(8) { + __rela_dyn_start = .; + *(.rela .rela*) + __rela_dyn_end = .; } _end = .; diff --git a/arch/riscv/mm/Makefile b/arch/riscv/mm/Makefile index 363ef01c30b1..dc5cdaa80bc1 100644 --- a/arch/riscv/mm/Makefile +++ b/arch/riscv/mm/Makefile @@ -1,6 +1,10 @@ # SPDX-License-Identifier: GPL-2.0-only CFLAGS_init.o := -mcmodel=medany +ifdef CONFIG_RELOCATABLE +CFLAGS_init.o += -fno-pie +endif + ifdef CONFIG_FTRACE CFLAGS_REMOVE_init.o = -pg endif diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c index 37be2eb45e58..e63ea5b6b6cf 100644 --- a/arch/riscv/mm/init.c +++ b/arch/riscv/mm/init.c @@ -13,6 +13,9 @@ #include #include #include +#ifdef CONFIG_RELOCATABLE +#include +#endif #include #include @@ -379,6 +382,53 @@ static uintptr_t __init best_map_size(phys_addr_t base, phys_addr_t size) #error "setup_vm() is called from head.S before relocate so it should not use absolute addressing." #endif +#ifdef CONFIG_RELOCATABLE +extern unsigned long __rela_dyn_start, __rela_dyn_end; + +#ifdef CONFIG_64BIT +#define Elf_Rela Elf64_Rela +#define Elf_Addr Elf64_Addr +#else +#define Elf_Rela Elf32_Rela +#define Elf_Addr Elf32_Addr +#endif + +void __init relocate_kernel(uintptr_t load_pa) +{ + Elf_Rela *rela = (Elf_Rela *)&__rela_dyn_start; + /* + * This holds the offset between the linked virtual address and the + * relocated virtual address. + */ + uintptr_t reloc_offset = kernel_virt_addr - KERNEL_LINK_ADDR; + /* + * This holds the offset between kernel linked virtual address and + * physical address. + */ + uintptr_t va_kernel_link_pa_offset = KERNEL_LINK_ADDR - load_pa; + + for ( ; rela < (Elf_Rela *)&__rela_dyn_end; rela++) { + Elf_Addr addr = (rela->r_offset - va_kernel_link_pa_offset); + Elf_Addr relocated_addr = rela->r_addend; + + if (rela->r_info != R_RISCV_RELATIVE) + continue; + + /* + * Make sure to not relocate vdso symbols like rt_sigreturn + * which are linked from the address 0 in vmlinux since + * vdso symbol addresses are actually used as an offset from + * mm->context.vdso in VDSO_OFFSET macro. + */ + if (relocated_addr >= KERNEL_LINK_ADDR) + relocated_addr += reloc_offset; + + *(Elf_Addr *)addr = relocated_addr; + } +} + +#endif + static uintptr_t load_pa, load_sz; void create_kernel_page_table(pgd_t *pgdir, uintptr_t map_size) @@ -405,6 +455,19 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa) pfn_base = PFN_DOWN(load_pa); +#ifdef CONFIG_RELOCATABLE +#ifdef CONFIG_64BIT + /* + * Early page table uses only one PGDIR, which makes it possible + * to map PGDIR_SIZE aligned on PGDIR_SIZE: if the relocation offset + * makes the kernel cross over a PGDIR_SIZE boundary, raise a bug + * since a part of the kernel would not get mapped. + * This cannot happen on rv32 as we use the entire page directory level. + */ + BUG_ON(PGDIR_SIZE - (kernel_virt_addr & (PGDIR_SIZE - 1)) < load_sz); +#endif + relocate_kernel(load_pa); +#endif /* * Enforce boot alignment requirements of RV32 and * RV64 by only allowing PMD or PGD mappings.