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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=Zg2vKQrCJvc4xP5ymxAbeODlg+/OAdHgAqTwJVSZIKE=; b=NeCiotTEi50nVKUhkHE+AiEjBPfoHK0u8kdMEdDTyEvm0+xpftBRURbdKyhukYhdYt Cdi7hcK18OAqNgG7c8hmoWuze/lphi+fuBA4gJ6ZxDpWny7WcR6bcfzru3Yr70vs5rXe RlhK2fxQ5LxjDrC3Unvom7ej3rXXHkQzcoqvNrzZnKie94TM1YhSVu7bh4E17nGH5gNj cRlUDJbtZKvB73A58OU/DNsA2SKWc5S4o3XlBayYDb2E6/2ikOJvIukrK1KXnZGUMFD4 xTMnOYNh0ArKqsISVfUFzUT/5z2K9Wg92Q1ecTqIMoNK/3JjApIuFOsaOi5BD1A6fFxq dnFw== X-Gm-Message-State: APjAAAVoDfkcnDQZJLSiaD08ws/p4jZiYiFdY17AoIRQQYGKTjVUEWbU 7JcPm/ulheqPLzgiCEPzijZAJJcXlFI5EOAbY6K41Q== X-Google-Smtp-Source: APXvYqxWC2ROqkjJE5ZTZE2vqBV9CTNcTOGWLXAMLPSffrX9qAg6uJA3K/cdtJ8joNJIvo5WX62dWcmFAjpU2DsMBPM= X-Received: by 2002:aca:2210:: with SMTP id b16mr3063337oic.32.1580815761621; Tue, 04 Feb 2020 03:29:21 -0800 (PST) MIME-Version: 1.0 References: <20200123201414.8933-1-alex@ghiti.fr> <39ffe627-d358-e1bd-dff2-653baca1fe37@ghiti.fr> In-Reply-To: <39ffe627-d358-e1bd-dff2-653baca1fe37@ghiti.fr> From: Zong Li Date: Tue, 4 Feb 2020 19:29:11 +0800 Message-ID: Subject: Re: [PATCH] riscv: Introduce CONFIG_RELOCATABLE To: Alex Ghiti Content-Type: text/plain; charset="UTF-8" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200204_032922_973288_62D93F6B X-CRM114-Status: GOOD ( 25.48 ) 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 , linux-riscv , Palmer Dabbelt , "linux-kernel@vger.kernel.org List" , Paul Walmsley Sender: "linux-riscv" Errors-To: linux-riscv-bounces+infradead-linux-riscv=archiver.kernel.org@lists.infradead.org On Fri, Jan 31, 2020 at 4:02 AM Alex Ghiti wrote: > > Hi Zong, > > On 1/29/20 11:13 PM, Zong Li wrote: > > On Fri, Jan 24, 2020 at 4:14 AM Alexandre Ghiti 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 > >> --- > >> arch/riscv/Kconfig | 11 ++++ > >> 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, 110 insertions(+), 22 deletions(-) > >> > >> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig > >> index fa7dc03459e7..c652b4b850ce 100644 > >> --- a/arch/riscv/Kconfig > >> +++ b/arch/riscv/Kconfig > >> @@ -163,6 +163,17 @@ config PGTABLE_LEVELS > >> default 3 if 64BIT > >> default 2 > >> > >> +config RELOCATABLE > >> + bool > >> + 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 ac699246ae7e..27c95da68ecb 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_load_addr > >> > >> -#define KERN_VIRT_SIZE (-PAGE_OFFSET) > >> +#define KERN_VIRT_SIZE (-_AC(CONFIG_PAGE_OFFSET, UL)) > >> > >> #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_load_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 2227db63f895..5042b2b48a06 100644 > >> --- a/arch/riscv/kernel/head.S > >> +++ b/arch/riscv/kernel/head.S > >> @@ -126,7 +126,8 @@ clear_bss_done: > >> #ifdef CONFIG_MMU > >> relocate: > >> /* Relocate return address */ > >> - li a1, PAGE_OFFSET > >> + la a1, kernel_load_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 12f42f96d46e..5095aee7c37e 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 > >> @@ -70,9 +70,11 @@ SECTIONS > >> > >> EXCEPTION_TABLE(0x10) > >> > >> - .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 a1bd95c8047a..dcd3d806243f 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..ac9a9f69abc0 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_load_addr = _AC(CONFIG_PAGE_OFFSET, UL); > >> +EXPORT_SYMBOL(kernel_load_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_load_addr); > >> > >> /* > >> * 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_load_addr) >> PGDIR_SHIFT; > >> 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_load_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; > >> + > >> + /* > >> + * 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_load_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_load_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_load_addr, > >> (uintptr_t)trampoline_pmd, PGDIR_SIZE, PAGE_TABLE); > >> - create_pmd_mapping(trampoline_pmd, PAGE_OFFSET, > >> + create_pmd_mapping(trampoline_pmd, kernel_load_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_load_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_load_addr + load_sz; > >> + for (va = kernel_load_addr; va < end_va; va += map_size) > >> create_pgd_mapping(early_pg_dir, va, > >> - load_pa + (va - PAGE_OFFSET), > >> + load_pa + (va - kernel_load_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(kernel_load_addr) && > >> + __pa(kernel_load_addr) < end) > >> + start = __pa(kernel_load_addr); > > Here should use __pa_symbol() instead of __pa() for kernel symbols. > > > I'll add it to the v2 too, thanks. > > > > I'm working on KASLR on top of this patch, it's work to me. > > > If I can help, don't hesitate, even if it is simply for testing :) > > > > > > Reviewed-by: Zong Li > > Tested-by: Zong Li > > > Thanks for that, > > Alex > > > > > >> map_size = best_map_size(start, end - start); > >> for (pa = start; pa < end; pa += map_size) { > >> -- > >> 2.20.1 > >> Hi all, I find that there is a risk when building kernel as PIE. The problem is that hart_lottery will be put in .bss section rather than .sdata section, so the value of hart_lottery will be cleared by main hart. I post a patch to mark hart_lottery as sdata section by using gcc attribution. Please refer to https://patchwork.kernel.org/patch/11364457/. Feel free to give any feedbacks and comments. Thanks.