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[23.128.96.18]) by mx.google.com with ESMTP id hp39si569453ejc.214.2021.01.05.22.38.11; Tue, 05 Jan 2021 22:38:35 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726324AbhAFGhS (ORCPT + 99 others); Wed, 6 Jan 2021 01:37:18 -0500 Received: from relay12.mail.gandi.net ([217.70.178.232]:38173 "EHLO relay12.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725905AbhAFGhS (ORCPT ); Wed, 6 Jan 2021 01:37:18 -0500 Received: from [192.168.1.100] (lfbn-gre-1-231-212.w90-112.abo.wanadoo.fr [90.112.190.212]) (Authenticated sender: alex@ghiti.fr) by relay12.mail.gandi.net (Postfix) with ESMTPSA id 26377200002; Wed, 6 Jan 2021 06:36:32 +0000 (UTC) Subject: Re: [RFC PATCH 01/12] riscv: Move kernel mapping outside of linear mapping To: Anup Patel Cc: Paul Walmsley , Palmer Dabbelt , Zong Li , Christoph Hellwig , Ard Biesheuvel , Arnd Bergmann , linux-efi , linux-arch@vger.kernel.org, linux-riscv , "linux-kernel@vger.kernel.org List" References: <20210104195840.1593-1-alex@ghiti.fr> <20210104195840.1593-2-alex@ghiti.fr> From: Alex Ghiti Message-ID: Date: Wed, 6 Jan 2021 01:36:32 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: fr Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Anup, Le 1/5/21 à 6:40 AM, Anup Patel a écrit : > On Tue, Jan 5, 2021 at 1:29 AM Alexandre Ghiti wrote: >> >> This is a preparatory patch for relocatable kernel and sv48 support. >> >> The kernel used to be linked at PAGE_OFFSET address therefore we could use >> the linear mapping for the kernel mapping. But the relocated kernel base >> address will be different from PAGE_OFFSET and since in the linear mapping, >> two different virtual addresses cannot point to the same physical address, >> the kernel mapping needs to lie outside the linear mapping so that we don't >> have to copy it at the same physical offset. >> >> The kernel mapping is moved to the last 2GB of the address space and then >> BPF and modules are also pushed to the same range since they have to lie >> close to the kernel inside a 2GB window. >> >> Note then that KASLR implementation will simply have to move the kernel in >> this 2GB range and modify BPF/modules regions accordingly. >> >> In addition, by moving the kernel to the end of the address space, both >> sv39 and sv48 kernels will be exactly the same without needing to be >> relocated at runtime. > > Awesome ! This is a good approach with no performance impact. > >> >> Suggested-by: Arnd Bergmann >> Signed-off-by: Alexandre Ghiti >> --- >> arch/riscv/boot/loader.lds.S | 3 +- >> arch/riscv/include/asm/page.h | 10 ++++- >> arch/riscv/include/asm/pgtable.h | 39 +++++++++++++------ >> arch/riscv/kernel/head.S | 3 +- >> arch/riscv/kernel/module.c | 4 +- >> arch/riscv/kernel/vmlinux.lds.S | 3 +- >> arch/riscv/mm/init.c | 65 ++++++++++++++++++++++++-------- >> arch/riscv/mm/physaddr.c | 2 +- >> 8 files changed, 94 insertions(+), 35 deletions(-) >> >> diff --git a/arch/riscv/boot/loader.lds.S b/arch/riscv/boot/loader.lds.S >> index 47a5003c2e28..62d94696a19c 100644 >> --- a/arch/riscv/boot/loader.lds.S >> +++ b/arch/riscv/boot/loader.lds.S >> @@ -1,13 +1,14 @@ >> /* SPDX-License-Identifier: GPL-2.0 */ >> >> #include >> +#include >> >> OUTPUT_ARCH(riscv) >> ENTRY(_start) >> >> SECTIONS >> { >> - . = PAGE_OFFSET; >> + . = KERNEL_LINK_ADDR; >> >> .payload : { >> *(.payload) >> diff --git a/arch/riscv/include/asm/page.h b/arch/riscv/include/asm/page.h >> index 2d50f76efe48..98188e315e8d 100644 >> --- a/arch/riscv/include/asm/page.h >> +++ b/arch/riscv/include/asm/page.h >> @@ -90,18 +90,26 @@ typedef struct page *pgtable_t; >> >> #ifdef CONFIG_MMU >> extern unsigned long va_pa_offset; >> +extern unsigned long va_kernel_pa_offset; >> extern unsigned long pfn_base; >> #define ARCH_PFN_OFFSET (pfn_base) >> #else >> #define va_pa_offset 0 >> +#define va_kernel_pa_offset 0 >> #define ARCH_PFN_OFFSET (PAGE_OFFSET >> PAGE_SHIFT) >> #endif /* CONFIG_MMU */ >> >> extern unsigned long max_low_pfn; >> extern unsigned long min_low_pfn; >> +extern unsigned long kernel_virt_addr; >> >> #define __pa_to_va_nodebug(x) ((void *)((unsigned long) (x) + va_pa_offset)) >> -#define __va_to_pa_nodebug(x) ((unsigned long)(x) - va_pa_offset) >> +#define linear_mapping_va_to_pa(x) ((unsigned long)(x) - va_pa_offset) >> +#define kernel_mapping_va_to_pa(x) \ >> + ((unsigned long)(x) - va_kernel_pa_offset) >> +#define __va_to_pa_nodebug(x) \ >> + (((x) < KERNEL_LINK_ADDR) ? \ >> + linear_mapping_va_to_pa(x) : kernel_mapping_va_to_pa(x)) >> >> #ifdef CONFIG_DEBUG_VIRTUAL >> extern phys_addr_t __virt_to_phys(unsigned long x); >> diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h >> index 183f1f4b2ae6..102b728ca146 100644 >> --- a/arch/riscv/include/asm/pgtable.h >> +++ b/arch/riscv/include/asm/pgtable.h >> @@ -11,23 +11,32 @@ >> >> #include >> >> -#ifndef __ASSEMBLY__ >> - >> -/* Page Upper Directory not used in RISC-V */ >> -#include >> -#include >> -#include >> -#include >> +#ifndef CONFIG_MMU >> +#define KERNEL_VIRT_ADDR PAGE_OFFSET >> +#define KERNEL_LINK_ADDR PAGE_OFFSET >> +#else >> >> -#ifdef CONFIG_MMU >> +#define ADDRESS_SPACE_END (UL(-1)) >> +/* >> + * Leave 2GB for kernel, modules and BPF at the end of the address space >> + */ >> +#define KERNEL_VIRT_ADDR (ADDRESS_SPACE_END - SZ_2G + 1) >> +#define KERNEL_LINK_ADDR KERNEL_VIRT_ADDR >> >> #define VMALLOC_SIZE (KERN_VIRT_SIZE >> 1) >> #define VMALLOC_END (PAGE_OFFSET - 1) >> #define VMALLOC_START (PAGE_OFFSET - VMALLOC_SIZE) >> >> +/* KASLR should leave at least 128MB for BPF after the kernel */ >> #define BPF_JIT_REGION_SIZE (SZ_128M) >> -#define BPF_JIT_REGION_START (PAGE_OFFSET - BPF_JIT_REGION_SIZE) >> -#define BPF_JIT_REGION_END (VMALLOC_END) >> +#define BPF_JIT_REGION_START PFN_ALIGN((unsigned long)&_end) >> +#define BPF_JIT_REGION_END (BPF_JIT_REGION_START + BPF_JIT_REGION_SIZE) >> + >> +/* Modules always live before the kernel */ >> +#ifdef CONFIG_64BIT >> +#define VMALLOC_MODULE_START (PFN_ALIGN((unsigned long)&_end) - SZ_2G) >> +#define VMALLOC_MODULE_END (PFN_ALIGN((unsigned long)&_start)) >> +#endif > > This does not look right or I am missing something. > > I think the VMALLOC_MODULE_START should be: > #define VMALLOC_MODULE_START (PFN_ALIGN((unsigned long)&_start) - SZ_2G) > I think the patch is correct: worst-case, we want the first address of the module area to be able to access the last address of the kernel, so we must use _end and not _start to guarantee that the difference between those 2 addresses is not greater than 2GB. >> >> /* >> * Roughly size the vmemmap space to be large enough to fit enough >> @@ -57,9 +66,16 @@ >> #define FIXADDR_SIZE PGDIR_SIZE >> #endif >> #define FIXADDR_START (FIXADDR_TOP - FIXADDR_SIZE) >> - >> #endif >> >> +#ifndef __ASSEMBLY__ >> + >> +/* Page Upper Directory not used in RISC-V */ >> +#include >> +#include >> +#include >> +#include >> + >> #ifdef CONFIG_64BIT >> #include >> #else >> @@ -467,6 +483,7 @@ static inline void __kernel_map_pages(struct page *page, int numpages, int enabl >> >> #define kern_addr_valid(addr) (1) /* FIXME */ >> >> +extern char _start[]; >> extern void *dtb_early_va; >> extern uintptr_t dtb_early_pa; >> void setup_bootmem(void); >> diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S >> index 7e849797c9c3..66f40c49bf68 100644 >> --- a/arch/riscv/kernel/head.S >> +++ b/arch/riscv/kernel/head.S >> @@ -69,7 +69,8 @@ pe_head_start: >> #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/module.c b/arch/riscv/kernel/module.c >> index 104fba889cf7..75a0b9541266 100644 >> --- a/arch/riscv/kernel/module.c >> +++ b/arch/riscv/kernel/module.c >> @@ -408,12 +408,10 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab, >> } >> >> #if defined(CONFIG_MMU) && defined(CONFIG_64BIT) >> -#define VMALLOC_MODULE_START \ >> - max(PFN_ALIGN((unsigned long)&_end - SZ_2G), VMALLOC_START) >> void *module_alloc(unsigned long size) >> { >> return __vmalloc_node_range(size, 1, VMALLOC_MODULE_START, >> - VMALLOC_END, GFP_KERNEL, >> + VMALLOC_MODULE_END, GFP_KERNEL, >> PAGE_KERNEL_EXEC, 0, NUMA_NO_NODE, >> __builtin_return_address(0)); >> } >> diff --git a/arch/riscv/kernel/vmlinux.lds.S b/arch/riscv/kernel/vmlinux.lds.S >> index 3ffbd6cbdb86..c21dc46f41be 100644 >> --- a/arch/riscv/kernel/vmlinux.lds.S >> +++ b/arch/riscv/kernel/vmlinux.lds.S >> @@ -4,7 +4,8 @@ >> * Copyright (C) 2017 SiFive >> */ >> >> -#define LOAD_OFFSET PAGE_OFFSET >> +#include >> +#define LOAD_OFFSET KERNEL_LINK_ADDR >> #include >> #include >> #include >> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c >> index 8e577f14f120..9d06ff0e015a 100644 >> --- a/arch/riscv/mm/init.c >> +++ b/arch/riscv/mm/init.c >> @@ -23,6 +23,9 @@ >> >> #include "../kernel/head.h" >> >> +unsigned long kernel_virt_addr = KERNEL_VIRT_ADDR; >> +EXPORT_SYMBOL(kernel_virt_addr); >> + >> unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)] >> __page_aligned_bss; >> EXPORT_SYMBOL(empty_zero_page); >> @@ -201,8 +204,12 @@ void __init setup_bootmem(void) >> #ifdef CONFIG_MMU >> static struct pt_alloc_ops pt_ops; >> >> +/* Offset between linear mapping virtual address and kernel load address */ >> unsigned long va_pa_offset; >> EXPORT_SYMBOL(va_pa_offset); >> +/* Offset between kernel mapping virtual address and kernel load address */ >> +unsigned long va_kernel_pa_offset; >> +EXPORT_SYMBOL(va_kernel_pa_offset); >> unsigned long pfn_base; >> EXPORT_SYMBOL(pfn_base); >> >> @@ -316,7 +323,7 @@ static phys_addr_t __init alloc_pmd_early(uintptr_t va) >> { >> uintptr_t pmd_num; >> >> - pmd_num = (va - PAGE_OFFSET) >> PGDIR_SHIFT; >> + pmd_num = (va - kernel_virt_addr) >> PGDIR_SHIFT; >> BUG_ON(pmd_num >= NUM_EARLY_PMDS); >> return (uintptr_t)&early_pmd[pmd_num * PTRS_PER_PMD]; >> } >> @@ -431,17 +438,34 @@ 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 >> >> +static uintptr_t load_pa, load_sz; >> + >> +static void __init create_kernel_page_table(pgd_t *pgdir, uintptr_t map_size) >> +{ >> + uintptr_t va, end_va; >> + >> + end_va = kernel_virt_addr + load_sz; >> + for (va = kernel_virt_addr; va < end_va; va += map_size) >> + create_pgd_mapping(pgdir, va, >> + load_pa + (va - kernel_virt_addr), >> + map_size, PAGE_KERNEL_EXEC); >> +} >> + >> asmlinkage void __init setup_vm(uintptr_t dtb_pa) >> { >> - uintptr_t va, pa, end_va; >> - uintptr_t load_pa = (uintptr_t)(&_start); >> - uintptr_t load_sz = (uintptr_t)(&_end) - load_pa; >> - uintptr_t map_size = best_map_size(load_pa, MAX_EARLY_MAPPING_SIZE); >> + uintptr_t pa; >> + uintptr_t map_size; >> #ifndef __PAGETABLE_PMD_FOLDED >> pmd_t fix_bmap_spmd, fix_bmap_epmd; >> #endif >> >> + load_pa = (uintptr_t)(&_start); >> + load_sz = (uintptr_t)(&_end) - load_pa; >> + map_size = best_map_size(load_pa, MAX_EARLY_MAPPING_SIZE); >> + >> va_pa_offset = PAGE_OFFSET - load_pa; >> + va_kernel_pa_offset = kernel_virt_addr - load_pa; >> + >> pfn_base = PFN_DOWN(load_pa); >> >> /* >> @@ -470,26 +494,22 @@ 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 >> >> /* >> - * Setup early PGD covering entire kernel which will allows >> + * Setup early PGD covering entire kernel which will allow >> * 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) >> - create_pgd_mapping(early_pg_dir, va, >> - load_pa + (va - PAGE_OFFSET), >> - map_size, PAGE_KERNEL_EXEC); >> + create_kernel_page_table(early_pg_dir, map_size); >> >> #ifndef __PAGETABLE_PMD_FOLDED >> /* Setup early PMD for DTB */ >> @@ -549,6 +569,7 @@ static void __init setup_vm_final(void) >> uintptr_t va, map_size; >> phys_addr_t pa, start, end; >> u64 i; >> + static struct vm_struct vm_kernel = { 0 }; >> >> /** >> * MMU is enabled at this point. But page table setup is not complete yet. >> @@ -565,7 +586,7 @@ static void __init setup_vm_final(void) >> __pa_symbol(fixmap_pgd_next), >> PGDIR_SIZE, PAGE_TABLE); >> >> - /* Map all memory banks */ >> + /* Map all memory banks in the linear mapping */ >> for_each_mem_range(i, &start, &end) { >> if (start >= end) >> break; >> @@ -577,10 +598,22 @@ static void __init setup_vm_final(void) >> for (pa = start; pa < end; pa += map_size) { >> va = (uintptr_t)__va(pa); >> create_pgd_mapping(swapper_pg_dir, va, pa, >> - map_size, PAGE_KERNEL_EXEC); >> + map_size, PAGE_KERNEL); >> } >> } >> >> + /* Map the kernel */ >> + create_kernel_page_table(swapper_pg_dir, PMD_SIZE); >> + >> + /* Reserve the vmalloc area occupied by the kernel */ >> + vm_kernel.addr = (void *)kernel_virt_addr; >> + vm_kernel.phys_addr = load_pa; >> + vm_kernel.size = (load_sz + PMD_SIZE - 1) & ~(PMD_SIZE - 1); >> + vm_kernel.flags = VM_MAP | VM_NO_GUARD; >> + vm_kernel.caller = __builtin_return_address(0); >> + >> + vm_area_add_early(&vm_kernel); >> + >> /* Clear fixmap PTE and PMD mappings */ >> clear_fixmap(FIX_PTE); >> clear_fixmap(FIX_PMD); >> diff --git a/arch/riscv/mm/physaddr.c b/arch/riscv/mm/physaddr.c >> index e8e4dcd39fed..35703d5ef5fd 100644 >> --- a/arch/riscv/mm/physaddr.c >> +++ b/arch/riscv/mm/physaddr.c >> @@ -23,7 +23,7 @@ EXPORT_SYMBOL(__virt_to_phys); >> >> phys_addr_t __phys_addr_symbol(unsigned long x) >> { >> - unsigned long kernel_start = (unsigned long)PAGE_OFFSET; >> + unsigned long kernel_start = (unsigned long)kernel_virt_addr; >> unsigned long kernel_end = (unsigned long)_end; >> >> /* >> -- >> 2.20.1 >> > > Apart from the minor comment above, this looks good to me. > > Reviewed-by: Anup Patel Thanks for your time Anup, > > Regards, > Anup > Alex