From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AB6E8C10DCE for ; Thu, 12 Mar 2020 05:58:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 75F3720663 for ; Thu, 12 Mar 2020 05:58:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=sifive.com header.i=@sifive.com header.b="CIc/RH60" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387871AbgCLF6G (ORCPT ); Thu, 12 Mar 2020 01:58:06 -0400 Received: from mail-oi1-f196.google.com ([209.85.167.196]:33501 "EHLO mail-oi1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387810AbgCLF6F (ORCPT ); Thu, 12 Mar 2020 01:58:05 -0400 Received: by mail-oi1-f196.google.com with SMTP id r7so4390358oij.0 for ; Wed, 11 Mar 2020 22:58:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sifive.com; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=Bn1hg/+PtzTsKNpb+Ce5m6JSgVn+95BJXkA8A4DMiPc=; b=CIc/RH60Iz3c1UBDBhEfsp4G27ouwBp+0Cl2CZ6BOGGts7w71kjT3VN6Z3TrI6+nAs sS211Q6PMK+X2V6hTiWFSxHxCUbIs9+W/Wz24mbDm+lHzxwDB09LzBzMeGVnT83OLr1U aoCavsEXtMLKRL/LcM1XZ4rkpPCtB5Szuejz08zeY/QRRc8bcxn2SbdWZqJUJZEhcnq7 3St2nNDnEqBTs8+01QfsxmSEFd8Vgmb49D+p8pROKCy3xAA7z8tKEQEuQ6g9tB3tU0Z0 lLaMqNMIbJM3bsbBbcy+13iWkq7BQH7sd34wkbtXAuX/0ONvOBGKKz64hpnuPnO3O+uw RgQQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=Bn1hg/+PtzTsKNpb+Ce5m6JSgVn+95BJXkA8A4DMiPc=; b=HWlLIR4DeKl2qYTdFssvrA6n0/zVzajoPZ9RJo0maAd2PQYWxDsLEp3Vs7luNJ9Bh9 lNXjY7V2wlPkriXFZA0dqXFxlMUWimL0KzbbwHAJWtrRSYUhZm6tKOGD29xhF6f+ecMR ujX6bHz24T0cqoGr4IEEDU5qfeBEnvcDRCB7X0KsXvGcOQflbPXJpAF/sV/gAgBzjgrb oqOl+iihlOL0TaP+qj2WP6/ZWbnDIuSwQF2eowKG4q6xYgcn+p93ZGiKmEoKTl3lwdRg uUXPL9+1LiMeZJsTY9YBWuqHcCk/EBpFU+WLnkESGNot3kAopCRX3FbB6WzlnoROgdyf swfA== X-Gm-Message-State: ANhLgQ15Op+Ax9KaMacCd7z+2TPVQWxpbGzU0IxoT+Dsi9N1nEv3OCze Zk7YF003p/PN2xfuD+HPvPgdOx5vHymYABft2xWrHA== X-Google-Smtp-Source: ADFU+vsMvyofqBnJoHR6vy8xgHA39d+khqv33FK27ksvDLfAygtUQztZFg7E6bYyG+UOaF0XTGt8780bAIQyv4vwvIc= X-Received: by 2002:a05:6808:56:: with SMTP id v22mr1415109oic.116.1583992683910; Wed, 11 Mar 2020 22:58:03 -0700 (PDT) MIME-Version: 1.0 References: <20200303054437.650-1-alex@ghiti.fr> In-Reply-To: From: Zong Li Date: Thu, 12 Mar 2020 13:57:53 +0800 Message-ID: Subject: Re: [PATCH RESEND v2] riscv: Introduce CONFIG_RELOCATABLE To: Palmer Dabbelt Cc: Alexandre Ghiti , Paul Walmsley , Anup Patel , linux-riscv , "linux-kernel@vger.kernel.org List" Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Mar 7, 2020 at 1:58 AM Palmer Dabbelt wrote: > > On Mon, 02 Mar 2020 21:44:37 PST (-0800), alex@ghiti.fr wrote: > > 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 > > Tested-by: Zong Li > > --- > > Changes in v2: > > - Make RELOCATABLE depend on MMU as suggested by Anup > > - Rename kernel_load_addr into kernel_virt_addr as suggested by Anup > > - Use __pa_symbol instead of __pa, as suggested by Zong > > - Rebased on top of v5.6-rc3 > > - Tested with sv48 patchset > > - Add Reviewed/Tested-by from Zong and Anup > > > > arch/riscv/Kconfig | 12 +++++ > > arch/riscv/Makefile | 5 +- > > arch/riscv/boot/loader.lds.S | 2 +- > > arch/riscv/include/asm/page.h | 5 +- > > arch/riscv/kernel/head.S | 3 +- > > arch/riscv/kernel/vmlinux.lds.S | 10 ++-- > > arch/riscv/mm/Makefile | 4 ++ > > arch/riscv/mm/init.c | 92 ++++++++++++++++++++++++++++----- > > 8 files changed, 111 insertions(+), 22 deletions(-) > > > > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig > > index 73f029eae0cc..f5f3d474504d 100644 > > --- a/arch/riscv/Kconfig > > +++ b/arch/riscv/Kconfig > > @@ -163,6 +163,18 @@ 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 b9009a2fbaf5..5a115cf6a9c1 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/boot/loader.lds.S b/arch/riscv/boot/loader.lds.S > > index 47a5003c2e28..a9ed218171aa 100644 > > --- a/arch/riscv/boot/loader.lds.S > > +++ b/arch/riscv/boot/loader.lds.S > > @@ -7,7 +7,7 @@ ENTRY(_start) > > > > SECTIONS > > { > > - . = PAGE_OFFSET; > > + . = CONFIG_PAGE_OFFSET; > > > > .payload : { > > *(.payload) > > diff --git a/arch/riscv/include/asm/page.h b/arch/riscv/include/asm/page.h > > index 8ca1930caa44..af5810f9aebd 100644 > > --- a/arch/riscv/include/asm/page.h > > +++ b/arch/riscv/include/asm/page.h > > @@ -31,9 +31,9 @@ > > * When not using MMU this corresponds to the first free page in > > * physical memory (aligned on a page boundary). > > */ > > -#define PAGE_OFFSET _AC(CONFIG_PAGE_OFFSET, UL) > > +#define PAGE_OFFSET kernel_virt_addr > > I assume we want to keep PAGE_OFFSET a constant for the non-relocatable > systems. As it currently stands this is imposing a performance hit even when > I had almost done the KASLR implementation on top of this patch. Actually, PAGE_OFFSET change is unnecessary in KASLR , because we would move kernel image to a random physical address as well, so the $pc will go to the relevant random virtual address. We need kernel_virt_addr to record the new destination, but keep PAGE_OFFSET to be CONFIG_PAGE_OFFSET is enough. > > -#define KERN_VIRT_SIZE (-PAGE_OFFSET) > > +#define KERN_VIRT_SIZE (-_AC(CONFIG_PAGE_OFFSET, UL)) > > This seems like it would cause issues if the kernel is relocated to high enough > addresses that "kernel_virt_addr+KERN_VIRT_SIZE" overflows. > Based on the same reason, keep KERN_VIRT_SIZE to be -PAGE_OFFSET is good. > > #ifndef __ASSEMBLY__ > > > > @@ -97,6 +97,7 @@ extern unsigned long pfn_base; > > #define ARCH_PFN_OFFSET (PAGE_OFFSET >> PAGE_SHIFT) > > #endif /* CONFIG_MMU */ > > > > +extern unsigned long kernel_virt_addr; > > extern unsigned long max_low_pfn; > > extern unsigned long min_low_pfn; > > > > diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S > > index 271860fc2c3f..d792912c2da3 100644 > > --- a/arch/riscv/kernel/head.S > > +++ b/arch/riscv/kernel/head.S > > @@ -131,7 +131,8 @@ clear_bss_done: > > #ifdef CONFIG_MMU > > relocate: > > /* Relocate return address */ > > - li a1, PAGE_OFFSET > > + la a1, kernel_virt_addr > > + REG_L a1, 0(a1) > > la a2, _start > > sub a1, a1, a2 > > add ra, ra, a1 > > diff --git a/arch/riscv/kernel/vmlinux.lds.S b/arch/riscv/kernel/vmlinux.lds.S > > index 1e0193ded420..5bf69e9b91e6 100644 > > --- a/arch/riscv/kernel/vmlinux.lds.S > > +++ b/arch/riscv/kernel/vmlinux.lds.S > > @@ -4,7 +4,7 @@ > > * Copyright (C) 2017 SiFive > > */ > > > > -#define LOAD_OFFSET PAGE_OFFSET > > +#define LOAD_OFFSET CONFIG_PAGE_OFFSET > > #include > > #include > > #include > > @@ -71,9 +71,11 @@ SECTIONS > > > > EXCEPTION_TABLE(0x10) > > > > - .rel.dyn : { > > - *(.rel.dyn*) > > - } > > + .rela.dyn : ALIGN(8) { > > + __rela_dyn_start = .; > > + *(.rela .rela*) > > + __rela_dyn_end = .; > > + } > > It looks like the indentation is screwed up here: I see a mix of tabs/spaces > that doesn't match the rest of the file. > > > > > _end = .; > > > > diff --git a/arch/riscv/mm/Makefile b/arch/riscv/mm/Makefile > > index 50b7af58c566..27593d362248 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 965a8cf4829c..428aee2669aa 100644 > > --- a/arch/riscv/mm/init.c > > +++ b/arch/riscv/mm/init.c > > @@ -12,6 +12,9 @@ > > #include > > #include > > #include > > +#ifdef CONFIG_RELOCATABLE > > +#include > > +#endif > > > > #include > > #include > > @@ -28,6 +31,9 @@ EXPORT_SYMBOL(empty_zero_page); > > extern char _start[]; > > void *dtb_early_va; > > > > +unsigned long kernel_virt_addr = _AC(CONFIG_PAGE_OFFSET, UL); > > +EXPORT_SYMBOL(kernel_virt_addr); > > + > > static void __init zone_sizes_init(void) > > { > > unsigned long max_zone_pfns[MAX_NR_ZONES] = { 0, }; > > @@ -132,7 +138,8 @@ void __init setup_bootmem(void) > > phys_addr_t end = reg->base + reg->size; > > > > if (reg->base <= vmlinux_end && vmlinux_end <= end) { > > - mem_size = min(reg->size, (phys_addr_t)-PAGE_OFFSET); > > + mem_size = min(reg->size, > > + (phys_addr_t)-kernel_virt_addr); > > PAGE_OFFSET is kernel_virt_addr, so I don't see any reason to change these -- > they account for a significant fraction of the diff. > kernel_virt_addr would be assigned to a random destination by KASLR, but here still should be PAGE_OFFSET rather than kernel_virt_addr as mentioned above. > > /* > > * Remove memblock from the end of usable area to the > > @@ -269,7 +276,7 @@ static phys_addr_t __init alloc_pmd(uintptr_t va) > > if (mmu_enabled) > > return memblock_phys_alloc(PAGE_SIZE, PAGE_SIZE); > > > > - pmd_num = (va - PAGE_OFFSET) >> PGDIR_SHIFT; > > + pmd_num = (va - kernel_virt_addr) >> PGDIR_SHIFT; Here is the same, please use PAGE_OFFSET instead of kernel_virt_addr. > > BUG_ON(pmd_num >= NUM_EARLY_PMDS); > > return (uintptr_t)&early_pmd[pmd_num * PTRS_PER_PMD]; > > } > > @@ -370,6 +377,54 @@ 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; > > + uintptr_t link_addr = _AC(CONFIG_PAGE_OFFSET, UL); > > + /* > > + * This holds the offset between the linked virtual address and the > > + * relocated virtual address. > > + */ > > + uintptr_t reloc_offset = kernel_virt_addr - link_addr; > > + /* > > + * This holds the offset between linked virtual address and physical > > + * address whereas va_pa_offset holds the offset between relocated > > + * virtual address and physical address. > > + */ > > + uintptr_t va_link_pa_offset = link_addr - load_pa; > > + > > + for ( ; rela < (Elf_Rela *)&__rela_dyn_end; rela++) { > > + Elf_Addr addr = (rela->r_offset - va_link_pa_offset); > > + Elf_Addr relocated_addr = rela->r_addend; > > + > > + if (rela->r_info != R_RISCV_RELATIVE) > > + continue; > > This should at least provide a warning when it encounters an unresolvable > relocation. Is it currently stands this just ignores all other runtime > relocations, and while I can buy the argument there shouldn't be any (though > I'd expect R_RISCV_{32,64} to show up?) we certainly shouldn't just silently > skip them. > > > + > > + /* > > + * 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 >= link_addr) > > + relocated_addr += reloc_offset; > > + > > + *(Elf_Addr *)addr = relocated_addr; > > + } > > +} > > +#endif > > + > > asmlinkage void __init setup_vm(uintptr_t dtb_pa) > > { > > uintptr_t va, end_va; > > @@ -377,9 +432,20 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa) > > uintptr_t load_sz = (uintptr_t)(&_end) - load_pa; > > uintptr_t map_size = best_map_size(load_pa, MAX_EARLY_MAPPING_SIZE); > > > > - va_pa_offset = PAGE_OFFSET - load_pa; > > + va_pa_offset = kernel_virt_addr - load_pa; > > pfn_base = PFN_DOWN(load_pa); > > > > +#ifdef CONFIG_RELOCATABLE > > + /* > > + * Early page table uses only one PGDIR, which makes it possible > > + * to map 1GB aligned on 1GB: if the relocation offset makes the kernel > > + * cross over a 1G boundary, raise a bug since a part of the kernel > > + * would not get mapped. > > + */ > > + BUG_ON(SZ_1G - (kernel_virt_addr & (SZ_1G - 1)) < load_sz); > > + relocate_kernel(load_pa); > > +#endif > > + > > /* > > * Enforce boot alignment requirements of RV32 and > > * RV64 by only allowing PMD or PGD mappings. > > @@ -387,7 +453,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa) > > BUG_ON(map_size == PAGE_SIZE); > > > > /* Sanity check alignment and size */ > > - BUG_ON((PAGE_OFFSET % PGDIR_SIZE) != 0); > > + BUILD_BUG_ON((_AC(CONFIG_PAGE_OFFSET, UL) % PGDIR_SIZE) != 0); > > BUG_ON((load_pa % map_size) != 0); > > BUG_ON(load_sz > MAX_EARLY_MAPPING_SIZE); > > > > @@ -400,13 +466,13 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa) > > create_pmd_mapping(fixmap_pmd, FIXADDR_START, > > (uintptr_t)fixmap_pte, PMD_SIZE, PAGE_TABLE); > > /* Setup trampoline PGD and PMD */ > > - create_pgd_mapping(trampoline_pg_dir, PAGE_OFFSET, > > + create_pgd_mapping(trampoline_pg_dir, kernel_virt_addr, > > (uintptr_t)trampoline_pmd, PGDIR_SIZE, PAGE_TABLE); > > - create_pmd_mapping(trampoline_pmd, PAGE_OFFSET, > > + create_pmd_mapping(trampoline_pmd, kernel_virt_addr, > > load_pa, PMD_SIZE, PAGE_KERNEL_EXEC); > > #else > > /* Setup trampoline PGD */ > > - create_pgd_mapping(trampoline_pg_dir, PAGE_OFFSET, > > + create_pgd_mapping(trampoline_pg_dir, kernel_virt_addr, > > load_pa, PGDIR_SIZE, PAGE_KERNEL_EXEC); > > #endif > > > > @@ -415,10 +481,10 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa) > > * us to reach paging_init(). We map all memory banks later > > * in setup_vm_final() below. > > */ > > - end_va = PAGE_OFFSET + load_sz; > > - for (va = PAGE_OFFSET; va < end_va; va += map_size) > > + end_va = kernel_virt_addr + load_sz; > > + for (va = kernel_virt_addr; va < end_va; va += map_size) > > create_pgd_mapping(early_pg_dir, va, > > - load_pa + (va - PAGE_OFFSET), > > + load_pa + (va - kernel_virt_addr), > > map_size, PAGE_KERNEL_EXEC); > > > > /* Create fixed mapping for early FDT parsing */ > > @@ -457,9 +523,9 @@ static void __init setup_vm_final(void) > > break; > > if (memblock_is_nomap(reg)) > > continue; > > - if (start <= __pa(PAGE_OFFSET) && > > - __pa(PAGE_OFFSET) < end) > > - start = __pa(PAGE_OFFSET); > > + if (start <= __pa_symbol(kernel_virt_addr) && > > + __pa(kernel_virt_addr) < end) > > + start = __pa_symbol(kernel_virt_addr); Here is the same, please use PAGE_OFFSET instead of kernel_virt_addr. > > > > map_size = best_map_size(start, end - start); > > for (pa = start; pa < end; pa += map_size) {