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Date: Tue, 30 Jul 2019 11:34:25 +0200
From: Christophe Leroy <christophe.leroy@....fr>
To: Jason Yan <yanaijie@...wei.com>, mpe@...erman.id.au,
linuxppc-dev@...ts.ozlabs.org, diana.craciun@....com,
benh@...nel.crashing.org, paulus@...ba.org, npiggin@...il.com,
keescook@...omium.org, kernel-hardening@...ts.openwall.com
Cc: linux-kernel@...r.kernel.org, wangkefeng.wang@...wei.com,
yebin10@...wei.com, thunder.leizhen@...wei.com, jingxiangfeng@...wei.com,
fanchengyang@...wei.com, zhaohongjiang@...wei.com
Subject: Re: [PATCH v2 06/10] powerpc/fsl_booke/32: implement KASLR
infrastructure
Le 30/07/2019 à 09:42, Jason Yan a écrit :
> This patch add support to boot kernel from places other than KERNELBASE.
> Since CONFIG_RELOCATABLE has already supported, what we need to do is
> map or copy kernel to a proper place and relocate. Freescale Book-E
> parts expect lowmem to be mapped by fixed TLB entries(TLB1). The TLB1
> entries are not suitable to map the kernel directly in a randomized
> region, so we chose to copy the kernel to a proper place and restart to
> relocate.
>
> The offset of the kernel was not randomized yet(a fixed 64M is set). We
> will randomize it in the next patch.
>
> Signed-off-by: Jason Yan <yanaijie@...wei.com>
> Cc: Diana Craciun <diana.craciun@....com>
> Cc: Michael Ellerman <mpe@...erman.id.au>
> Cc: Christophe Leroy <christophe.leroy@....fr>
> Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> Cc: Paul Mackerras <paulus@...ba.org>
> Cc: Nicholas Piggin <npiggin@...il.com>
> Cc: Kees Cook <keescook@...omium.org>
> ---
> arch/powerpc/Kconfig | 11 +++
> arch/powerpc/kernel/Makefile | 1 +
> arch/powerpc/kernel/early_32.c | 2 +-
> arch/powerpc/kernel/fsl_booke_entry_mapping.S | 13 ++-
> arch/powerpc/kernel/head_fsl_booke.S | 15 +++-
> arch/powerpc/kernel/kaslr_booke.c | 84 +++++++++++++++++++
> arch/powerpc/mm/mmu_decl.h | 6 ++
> arch/powerpc/mm/nohash/fsl_booke.c | 7 +-
> 8 files changed, 126 insertions(+), 13 deletions(-)
> create mode 100644 arch/powerpc/kernel/kaslr_booke.c
>
[...]
> diff --git a/arch/powerpc/kernel/head_fsl_booke.S b/arch/powerpc/kernel/head_fsl_booke.S
> index 2083382dd662..a466c0f0d028 100644
> --- a/arch/powerpc/kernel/head_fsl_booke.S
> +++ b/arch/powerpc/kernel/head_fsl_booke.S
> @@ -155,6 +155,8 @@ _ENTRY(_start);
> */
>
> _ENTRY(__early_start)
> + LOAD_REG_ADDR_PIC(r20, kimage_vaddr)
> + lwz r20,0(r20)
>
> #define ENTRY_MAPPING_BOOT_SETUP
> #include "fsl_booke_entry_mapping.S"
> @@ -277,8 +279,8 @@ set_ivor:
> ori r6, r6, swapper_pg_dir@l
> lis r5, abatron_pteptrs@h
> ori r5, r5, abatron_pteptrs@l
> - lis r4, KERNELBASE@h
> - ori r4, r4, KERNELBASE@l
> + lis r3, kimage_vaddr@ha
> + lwz r4, kimage_vaddr@l(r3)
> stw r5, 0(r4) /* Save abatron_pteptrs at a fixed location */
> stw r6, 0(r5)
>
> @@ -1067,7 +1069,14 @@ __secondary_start:
> mr r5,r25 /* phys kernel start */
> rlwinm r5,r5,0,~0x3ffffff /* aligned 64M */
> subf r4,r5,r4 /* memstart_addr - phys kernel start */
> - li r5,0 /* no device tree */
> +#ifdef CONFIG_RANDOMIZE_BASE
Is that #ifdef really necessary ? Wouldn't it also work as expected when
CONFIG_RANDOMIZE_BASE is not selected ?
> + lis r7,KERNELBASE@h
> + ori r7,r7,KERNELBASE@l
> + cmpw r20,r7 /* if kimage_vaddr != KERNELBASE, randomized */
> + beq 2f
> + li r4,0
> +#endif
> +2: li r5,0 /* no device tree */
> li r6,0 /* not boot cpu */
> bl restore_to_as0
>
> diff --git a/arch/powerpc/kernel/kaslr_booke.c b/arch/powerpc/kernel/kaslr_booke.c
> new file mode 100644
> index 000000000000..960bce4aa8b9
> --- /dev/null
> +++ b/arch/powerpc/kernel/kaslr_booke.c
> @@ -0,0 +1,84 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2019 Jason Yan <yanaijie@...wei.com>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +
> +#include <linux/signal.h>
> +#include <linux/sched.h>
> +#include <linux/kernel.h>
> +#include <linux/errno.h>
> +#include <linux/string.h>
> +#include <linux/types.h>
> +#include <linux/ptrace.h>
> +#include <linux/mman.h>
> +#include <linux/mm.h>
> +#include <linux/swap.h>
> +#include <linux/stddef.h>
> +#include <linux/vmalloc.h>
> +#include <linux/init.h>
> +#include <linux/delay.h>
> +#include <linux/highmem.h>
> +#include <linux/memblock.h>
> +#include <asm/pgalloc.h>
> +#include <asm/prom.h>
> +#include <asm/io.h>
> +#include <asm/mmu_context.h>
> +#include <asm/pgtable.h>
> +#include <asm/mmu.h>
> +#include <linux/uaccess.h>
> +#include <asm/smp.h>
> +#include <asm/machdep.h>
> +#include <asm/setup.h>
> +#include <asm/paca.h>
> +#include <mm/mmu_decl.h>
> +
> +extern int is_second_reloc;
Couldn't the above be a bool ?
> +
> +static unsigned long __init kaslr_choose_location(void *dt_ptr, phys_addr_t size,
> + unsigned long kernel_sz)
> +{
> + /* return a fixed offset of 64M for now */
> + return 0x4000000;
64 << 20 would maybe be more explicit than 0x4000000.
Or return SZ_64M ?
Christophe
> +}
> +
> +/*
> + * To see if we need to relocate the kernel to a random offset
> + * void *dt_ptr - address of the device tree
> + * phys_addr_t size - size of the first memory block
> + */
> +notrace void __init kaslr_early_init(void *dt_ptr, phys_addr_t size)
> +{
> + unsigned long tlb_virt;
> + phys_addr_t tlb_phys;
> + unsigned long offset;
> + unsigned long kernel_sz;
> +
> + kernel_sz = (unsigned long)_end - KERNELBASE;
> +
> + offset = kaslr_choose_location(dt_ptr, size, kernel_sz);
> +
> + if (offset == 0)
> + return;
> +
> + kimage_vaddr += offset;
> + kernstart_addr += offset;
> +
> + is_second_reloc = 1;
> +
> + if (offset >= SZ_64M) {
> + tlb_virt = round_down(kimage_vaddr, SZ_64M);
> + tlb_phys = round_down(kernstart_addr, SZ_64M);
> +
> + /* Create kernel map to relocate in */
> + create_tlb_entry(tlb_phys, tlb_virt, 1);
> + }
> +
> + /* Copy the kernel to it's new location and run */
> + memcpy((void *)kimage_vaddr, (void *)KERNELBASE, kernel_sz);
> +
> + reloc_kernel_entry(dt_ptr, kimage_vaddr);
> +}
> diff --git a/arch/powerpc/mm/mmu_decl.h b/arch/powerpc/mm/mmu_decl.h
> index 804da298beb3..9332772c8a66 100644
> --- a/arch/powerpc/mm/mmu_decl.h
> +++ b/arch/powerpc/mm/mmu_decl.h
> @@ -148,6 +148,12 @@ void reloc_kernel_entry(void *fdt, int addr);
> extern void loadcam_entry(unsigned int index);
> extern void loadcam_multi(int first_idx, int num, int tmp_idx);
>
> +#ifdef CONFIG_RANDOMIZE_BASE
> +void kaslr_early_init(void *dt_ptr, phys_addr_t size);
> +#else
> +static inline void kaslr_early_init(void *dt_ptr, phys_addr_t size) {}
> +#endif
> +
> struct tlbcam {
> u32 MAS0;
> u32 MAS1;
> diff --git a/arch/powerpc/mm/nohash/fsl_booke.c b/arch/powerpc/mm/nohash/fsl_booke.c
> index 556e3cd52a35..8d25a8dc965f 100644
> --- a/arch/powerpc/mm/nohash/fsl_booke.c
> +++ b/arch/powerpc/mm/nohash/fsl_booke.c
> @@ -263,7 +263,8 @@ void setup_initial_memory_limit(phys_addr_t first_memblock_base,
> int __initdata is_second_reloc;
> notrace void __init relocate_init(u64 dt_ptr, phys_addr_t start)
> {
> - unsigned long base = KERNELBASE;
> + unsigned long base = kimage_vaddr;
> + phys_addr_t size;
>
> kernstart_addr = start;
> if (is_second_reloc) {
> @@ -291,7 +292,7 @@ notrace void __init relocate_init(u64 dt_ptr, phys_addr_t start)
> start &= ~0x3ffffff;
> base &= ~0x3ffffff;
> virt_phys_offset = base - start;
> - early_get_first_memblock_info(__va(dt_ptr), NULL);
> + early_get_first_memblock_info(__va(dt_ptr), &size);
> /*
> * We now get the memstart_addr, then we should check if this
> * address is the same as what the PAGE_OFFSET map to now. If
> @@ -316,6 +317,8 @@ notrace void __init relocate_init(u64 dt_ptr, phys_addr_t start)
> /* We should never reach here */
> panic("Relocation error");
> }
> +
> + kaslr_early_init(__va(dt_ptr), size);
> }
> #endif
> #endif
>
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