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 Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 5A018C433EF for ; Mon, 10 Jan 2022 08:05:52 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4JXRGQ58kkz3bck for ; Mon, 10 Jan 2022 19:05:50 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=none (no SPF record) smtp.mailfrom=ghiti.fr (client-ip=217.70.183.195; helo=relay3-d.mail.gandi.net; envelope-from=alex@ghiti.fr; receiver=) Received: from relay3-d.mail.gandi.net (relay3-d.mail.gandi.net [217.70.183.195]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4JXRFv1W5Hz2xrm for ; Mon, 10 Jan 2022 19:05:22 +1100 (AEDT) Received: (Authenticated sender: alex@ghiti.fr) by relay3-d.mail.gandi.net (Postfix) with ESMTPSA id 4688960005; Mon, 10 Jan 2022 08:05:02 +0000 (UTC) Message-ID: Date: Mon, 10 Jan 2022 09:05:02 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.3.1 Subject: Re: [PATCH v7 1/3] riscv: Introduce CONFIG_RELOCATABLE Content-Language: en-US From: Alexandre ghiti To: Palmer Dabbelt References: <5846825d-cd7e-5085-569e-17cfaf36630f@ghiti.fr> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: aou@eecs.berkeley.edu, linux-kernel@vger.kernel.org, paulus@samba.org, Paul Walmsley , linux-riscv@lists.infradead.org, alexandre.ghiti@canonical.com, linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Hi Palmer, Do you think this could go in for-next? Thanks, Alex On 12/6/21 10:44, Alexandre ghiti wrote: > @Palmer, can I do anything for that to be pulled in 5.17? > > Thanks, > > Alex > > On 10/27/21 07:04, Alexandre ghiti wrote: >> Hi Palmer, >> >> On 10/26/21 11:29 PM, Palmer Dabbelt wrote: >>> On Sat, 09 Oct 2021 10:20:20 PDT (-0700), alex@ghiti.fr wrote: >>>> Arf, I have sent this patchset with the wrong email address. @Palmer >>>> tell me if you want me to resend it correctly. >>> Sorry for being kind of slow here. It's fine: there's a "From:" in >>> the patch, and git picks those up so it'll match the signed-off-by >>> line. I send pretty much all my patches that way, as I never managed >>> to get my Google address working correctly. >>> >>>> Thanks, >>>> >>>> Alex >>>> >>>> On 10/9/21 7:12 PM, Alexandre Ghiti wrote: >>>>> From: Alexandre Ghiti >>>>> >>>>> This config allows to compile 64b kernel as PIE and to relocate it at >>>>> any virtual address at runtime: this paves the way to KASLR. >>>>> Runtime relocation is possible since relocation metadata are >>>>> embedded into >>>>> the kernel. >>> IMO this should really be user selectable, at a bare minimum so it's >>> testable. >>> I just sent along a patch to do that (my power's off at home, so email >>> is a bit >>> wacky right now). >>> >>> I haven't put this on for-next yet as I'm not sure if you had a fix >>> for the >>> kasan issue (which IIUC would conflict with this). >> >> The kasan issue only revealed that I need to move the kasan shadow >> memory around with sv48 support, that's not related to the relocatable >> kernel. >> >> Thanks, >> >> Alex >> >> >>>>> 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 | 12 ++++++++ >>>>> arch/riscv/Makefile | 7 +++-- >>>>> arch/riscv/kernel/vmlinux.lds.S | 6 ++++ >>>>> arch/riscv/mm/Makefile | 4 +++ >>>>> arch/riscv/mm/init.c | 54 >>>>> ++++++++++++++++++++++++++++++++- >>>>> 5 files changed, 80 insertions(+), 3 deletions(-) >>>>> >>>>> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig >>>>> index ea16fa2dd768..043ba92559fa 100644 >>>>> --- a/arch/riscv/Kconfig >>>>> +++ b/arch/riscv/Kconfig >>>>> @@ -213,6 +213,18 @@ config PGTABLE_LEVELS >>>>> config LOCKDEP_SUPPORT >>>>> def_bool y >>>>> >>>>> +config RELOCATABLE >>>>> + bool >>>>> + depends on MMU && 64BIT && !XIP_KERNEL >>>>> + 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" >>>>> source "arch/riscv/Kconfig.erratas" >>>>> >>>>> diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile >>>>> index 0eb4568fbd29..2f509915f246 100644 >>>>> --- a/arch/riscv/Makefile >>>>> +++ b/arch/riscv/Makefile >>>>> @@ -9,9 +9,12 @@ >>>>> # >>>>> >>>>> 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 >>>>> + LDFLAGS_vmlinux += --no-relax >>>>> KBUILD_CPPFLAGS += -DCC_USING_PATCHABLE_FUNCTION_ENTRY >>>>> CC_FLAGS_FTRACE := -fpatchable-function-entry=8 >>>>> endif >>>>> diff --git a/arch/riscv/kernel/vmlinux.lds.S >>>>> b/arch/riscv/kernel/vmlinux.lds.S >>>>> index 5104f3a871e3..862a8c09723c 100644 >>>>> --- a/arch/riscv/kernel/vmlinux.lds.S >>>>> +++ b/arch/riscv/kernel/vmlinux.lds.S >>>>> @@ -133,6 +133,12 @@ SECTIONS >>>>> >>>>> BSS_SECTION(PAGE_SIZE, PAGE_SIZE, 0) >>>>> >>>>> + .rela.dyn : ALIGN(8) { >>>>> + __rela_dyn_start = .; >>>>> + *(.rela .rela*) >>>>> + __rela_dyn_end = .; >>>>> + } >>>>> + >>>>> #ifdef CONFIG_EFI >>>>> . = ALIGN(PECOFF_SECTION_ALIGNMENT); >>>>> __pecoff_data_virt_size = ABSOLUTE(. - __pecoff_text_end); >>>>> diff --git a/arch/riscv/mm/Makefile b/arch/riscv/mm/Makefile >>>>> index 7ebaef10ea1b..2d33ec574bbb 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 = $(CC_FLAGS_FTRACE) >>>>> CFLAGS_REMOVE_cacheflush.o = $(CC_FLAGS_FTRACE) >>>>> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c >>>>> index c0cddf0fc22d..42041c12d496 100644 >>>>> --- a/arch/riscv/mm/init.c >>>>> +++ b/arch/riscv/mm/init.c >>>>> @@ -20,6 +20,9 @@ >>>>> #include >>>>> #include >>>>> #include >>>>> +#ifdef CONFIG_RELOCATABLE >>>>> +#include >>>>> +#endif >>>>> >>>>> #include >>>>> #include >>>>> @@ -103,7 +106,7 @@ static void __init print_vm_layout(void) >>>>> print_mlm("lowmem", (unsigned long)PAGE_OFFSET, >>>>> (unsigned long)high_memory); >>>>> #ifdef CONFIG_64BIT >>>>> - print_mlm("kernel", (unsigned long)KERNEL_LINK_ADDR, >>>>> + print_mlm("kernel", (unsigned long)kernel_map.virt_addr, >>>>> (unsigned long)ADDRESS_SPACE_END); >>>>> #endif >>>>> } >>>>> @@ -518,6 +521,44 @@ static __init pgprot_t pgprot_from_va(uintptr_t >>>>> va) >>>>> #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; >>>>> + >>>>> +static void __init relocate_kernel(void) >>>>> +{ >>>>> + Elf64_Rela *rela = (Elf64_Rela *)&__rela_dyn_start; >>>>> + /* >>>>> + * This holds the offset between the linked virtual address and >>>>> the >>>>> + * relocated virtual address. >>>>> + */ >>>>> + uintptr_t reloc_offset = kernel_map.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 - >>>>> kernel_map.phys_addr; >>>>> + >>>>> + for ( ; rela < (Elf64_Rela *)&__rela_dyn_end; rela++) { >>>>> + Elf64_Addr addr = (rela->r_offset - >>>>> va_kernel_link_pa_offset); >>>>> + Elf64_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; >>>>> + >>>>> + *(Elf64_Addr *)addr = relocated_addr; >>>>> + } >>>>> +} >>>>> +#endif /* CONFIG_RELOCATABLE */ >>>>> + >>>>> #ifdef CONFIG_XIP_KERNEL >>>>> static void __init create_kernel_page_table(pgd_t *pgdir, >>>>> __always_unused bool early) >>>>> @@ -625,6 +666,17 @@ asmlinkage void __init setup_vm(uintptr_t >>>>> dtb_pa) >>>>> BUG_ON((kernel_map.virt_addr + kernel_map.size) > >>>>> ADDRESS_SPACE_END - SZ_4K); >>>>> #endif >>>>> >>>>> +#ifdef CONFIG_RELOCATABLE >>>>> + /* >>>>> + * 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. >>>>> + */ >>>>> + BUG_ON(PGDIR_SIZE - (kernel_map.virt_addr & (PGDIR_SIZE - 1)) < >>>>> kernel_map.size); >>>>> + relocate_kernel(); >>>>> +#endif >>>>> + >>>>> pt_ops.alloc_pte = alloc_pte_early; >>>>> pt_ops.get_pte_virt = get_pte_virt_early; >>>>> #ifndef __PAGETABLE_PMD_FOLDED > > _______________________________________________ > linux-riscv mailing list > linux-riscv@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-riscv