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From:   Diana Madalina Craciun <diana.craciun@nxp.com>
To:     Jason Yan <yanaijie@huawei.com>,
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        <kernel-hardening@lists.openwall.com>
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Subject: Re: [PATCH v3 06/10] powerpc/fsl_booke/32: implement KASLR
 infrastructure
Thread-Topic: [PATCH v3 06/10] powerpc/fsl_booke/32: implement KASLR
 infrastructure
Thread-Index: AQHVR4I0njkKhpe8o0mqCq4ImCeR9A==
Date:   Fri, 2 Aug 2019 08:41:45 +0000
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References: <20190731094318.26538-1-yanaijie@huawei.com>
 <20190731094318.26538-7-yanaijie@huawei.com>
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On 7/31/2019 12:27 PM, Jason Yan wrote:=0A=
> This patch add support to boot kernel from places other than KERNELBASE.=
=0A=
> Since CONFIG_RELOCATABLE has already supported, what we need to do is=0A=
> map or copy kernel to a proper place and relocate. Freescale Book-E=0A=
> parts expect lowmem to be mapped by fixed TLB entries(TLB1). The TLB1=0A=
> entries are not suitable to map the kernel directly in a randomized=0A=
> region, so we chose to copy the kernel to a proper place and restart to=
=0A=
> relocate.=0A=
>=0A=
> The offset of the kernel was not randomized yet(a fixed 64M is set). We=
=0A=
> will randomize it in the next patch.=0A=
>=0A=
> Signed-off-by: Jason Yan <yanaijie@huawei.com>=0A=
> Cc: Diana Craciun <diana.craciun@nxp.com>=0A=
> Cc: Michael Ellerman <mpe@ellerman.id.au>=0A=
> Cc: Christophe Leroy <christophe.leroy@c-s.fr>=0A=
> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>=0A=
> Cc: Paul Mackerras <paulus@samba.org>=0A=
> Cc: Nicholas Piggin <npiggin@gmail.com>=0A=
> Cc: Kees Cook <keescook@chromium.org>=0A=
> ---=0A=
>  arch/powerpc/Kconfig                          | 11 +++=0A=
>  arch/powerpc/kernel/Makefile                  |  1 +=0A=
>  arch/powerpc/kernel/early_32.c                |  2 +-=0A=
>  arch/powerpc/kernel/fsl_booke_entry_mapping.S | 13 ++-=0A=
>  arch/powerpc/kernel/head_fsl_booke.S          | 13 ++-=0A=
>  arch/powerpc/kernel/kaslr_booke.c             | 84 +++++++++++++++++++=
=0A=
>  arch/powerpc/mm/mmu_decl.h                    |  6 ++=0A=
>  arch/powerpc/mm/nohash/fsl_booke.c            |  7 +-=0A=
>  8 files changed, 124 insertions(+), 13 deletions(-)=0A=
>  create mode 100644 arch/powerpc/kernel/kaslr_booke.c=0A=
>=0A=
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig=0A=
> index 77f6ebf97113..755378887912 100644=0A=
> --- a/arch/powerpc/Kconfig=0A=
> +++ b/arch/powerpc/Kconfig=0A=
> @@ -548,6 +548,17 @@ config RELOCATABLE=0A=
>  	  setting can still be useful to bootwrappers that need to know the=0A=
>  	  load address of the kernel (eg. u-boot/mkimage).=0A=
>  =0A=
> +config RANDOMIZE_BASE=0A=
> +	bool "Randomize the address of the kernel image"=0A=
> +	depends on (FSL_BOOKE && FLATMEM && PPC32)=0A=
> +	select RELOCATABLE=0A=
> +	help=0A=
> +	  Randomizes the virtual address at which the kernel image is=0A=
> +	  loaded, as a security feature that deters exploit attempts=0A=
> +	  relying on knowledge of the location of kernel internals.=0A=
> +=0A=
> +	  If unsure, say N.=0A=
> +=0A=
>  config RELOCATABLE_TEST=0A=
>  	bool "Test relocatable kernel"=0A=
>  	depends on (PPC64 && RELOCATABLE)=0A=
> diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile=
=0A=
> index ea0c69236789..32f6c5b99307 100644=0A=
> --- a/arch/powerpc/kernel/Makefile=0A=
> +++ b/arch/powerpc/kernel/Makefile=0A=
> @@ -106,6 +106,7 @@ extra-$(CONFIG_PPC_8xx)		:=3D head_8xx.o=0A=
>  extra-y				+=3D vmlinux.lds=0A=
>  =0A=
>  obj-$(CONFIG_RELOCATABLE)	+=3D reloc_$(BITS).o=0A=
> +obj-$(CONFIG_RANDOMIZE_BASE)	+=3D kaslr_booke.o=0A=
>  =0A=
>  obj-$(CONFIG_PPC32)		+=3D entry_32.o setup_32.o early_32.o=0A=
>  obj-$(CONFIG_PPC64)		+=3D dma-iommu.o iommu.o=0A=
> diff --git a/arch/powerpc/kernel/early_32.c b/arch/powerpc/kernel/early_3=
2.c=0A=
> index 3482118ffe76..fe8347cdc07d 100644=0A=
> --- a/arch/powerpc/kernel/early_32.c=0A=
> +++ b/arch/powerpc/kernel/early_32.c=0A=
> @@ -32,5 +32,5 @@ notrace unsigned long __init early_init(unsigned long d=
t_ptr)=0A=
>  =0A=
>  	apply_feature_fixups();=0A=
>  =0A=
> -	return KERNELBASE + offset;=0A=
> +	return kimage_vaddr + offset;=0A=
>  }=0A=
> diff --git a/arch/powerpc/kernel/fsl_booke_entry_mapping.S b/arch/powerpc=
/kernel/fsl_booke_entry_mapping.S=0A=
> index de0980945510..6d2967673ac7 100644=0A=
> --- a/arch/powerpc/kernel/fsl_booke_entry_mapping.S=0A=
> +++ b/arch/powerpc/kernel/fsl_booke_entry_mapping.S=0A=
> @@ -161,17 +161,16 @@ skpinv:	addi	r6,r6,1				/* Increment */=0A=
>  	lis	r6,(MAS1_VALID|MAS1_IPROT)@h=0A=
>  	ori	r6,r6,(MAS1_TSIZE(BOOK3E_PAGESZ_64M))@l=0A=
>  	mtspr	SPRN_MAS1,r6=0A=
> -	lis	r6,MAS2_VAL(PAGE_OFFSET, BOOK3E_PAGESZ_64M, M_IF_NEEDED)@h=0A=
> -	ori	r6,r6,MAS2_VAL(PAGE_OFFSET, BOOK3E_PAGESZ_64M, M_IF_NEEDED)@l=0A=
> -	mtspr	SPRN_MAS2,r6=0A=
> +	lis     r6,MAS2_EPN_MASK(BOOK3E_PAGESZ_64M)@h=0A=
> +	ori     r6,r6,MAS2_EPN_MASK(BOOK3E_PAGESZ_64M)@l=0A=
> +	and     r6,r6,r20=0A=
> +	ori	r6,r6,M_IF_NEEDED@l=0A=
> +	mtspr   SPRN_MAS2,r6=0A=
>  	mtspr	SPRN_MAS3,r8=0A=
>  	tlbwe=0A=
>  =0A=
>  /* 7. Jump to KERNELBASE mapping */=0A=
=0A=
The code has changed, but the comment reflects the old code (it no=0A=
longer jumps to KERNELBASE, but to kimage_vaddr). This is true for step=0A=
6 as well.=0A=
=0A=
> -	lis	r6,(KERNELBASE & ~0xfff)@h=0A=
> -	ori	r6,r6,(KERNELBASE & ~0xfff)@l=0A=
> -	rlwinm	r7,r25,0,0x03ffffff=0A=
> -	add	r6,r7,r6=0A=
> +	mr	r6,r20=0A=
>  =0A=
>  #elif defined(ENTRY_MAPPING_KEXEC_SETUP)=0A=
>  /*=0A=
> diff --git a/arch/powerpc/kernel/head_fsl_booke.S b/arch/powerpc/kernel/h=
ead_fsl_booke.S=0A=
> index 2083382dd662..aa55832e7506 100644=0A=
> --- a/arch/powerpc/kernel/head_fsl_booke.S=0A=
> +++ b/arch/powerpc/kernel/head_fsl_booke.S=0A=
> @@ -155,6 +155,8 @@ _ENTRY(_start);=0A=
>   */=0A=
>  =0A=
>  _ENTRY(__early_start)=0A=
> +	LOAD_REG_ADDR_PIC(r20, kimage_vaddr)=0A=
> +	lwz     r20,0(r20)=0A=
>  =0A=
>  #define ENTRY_MAPPING_BOOT_SETUP=0A=
>  #include "fsl_booke_entry_mapping.S"=0A=
> @@ -277,8 +279,8 @@ set_ivor:=0A=
>  	ori	r6, r6, swapper_pg_dir@l=0A=
>  	lis	r5, abatron_pteptrs@h=0A=
>  	ori	r5, r5, abatron_pteptrs@l=0A=
> -	lis	r4, KERNELBASE@h=0A=
> -	ori	r4, r4, KERNELBASE@l=0A=
> +	lis     r3, kimage_vaddr@ha=0A=
> +	lwz     r4, kimage_vaddr@l(r3)=0A=
>  	stw	r5, 0(r4)	/* Save abatron_pteptrs at a fixed location */=0A=
>  	stw	r6, 0(r5)=0A=
>  =0A=
> @@ -1067,7 +1069,12 @@ __secondary_start:=0A=
>  	mr	r5,r25		/* phys kernel start */=0A=
>  	rlwinm	r5,r5,0,~0x3ffffff	/* aligned 64M */=0A=
>  	subf	r4,r5,r4	/* memstart_addr - phys kernel start */=0A=
> -	li	r5,0		/* no device tree */=0A=
> +	lis	r7,KERNELBASE@h=0A=
> +	ori	r7,r7,KERNELBASE@l=0A=
> +	cmpw	r20,r7		/* if kimage_vaddr !=3D KERNELBASE, randomized */=0A=
> +	beq	2f=0A=
> +	li	r4,0=0A=
> +2:	li	r5,0		/* no device tree */=0A=
>  	li	r6,0		/* not boot cpu */=0A=
>  	bl	restore_to_as0=0A=
>  =0A=
> diff --git a/arch/powerpc/kernel/kaslr_booke.c b/arch/powerpc/kernel/kasl=
r_booke.c=0A=
> new file mode 100644=0A=
> index 000000000000..30f84c0321b2=0A=
> --- /dev/null=0A=
> +++ b/arch/powerpc/kernel/kaslr_booke.c=0A=
> @@ -0,0 +1,84 @@=0A=
> +// SPDX-License-Identifier: GPL-2.0-only=0A=
> +/*=0A=
> + * Copyright (C) 2019 Jason Yan <yanaijie@huawei.com>=0A=
> + *=0A=
> + * This program is free software; you can redistribute it and/or modify=
=0A=
> + * it under the terms of the GNU General Public License version 2 as=0A=
> + * published by the Free Software Foundation.=0A=
> + */=0A=
> +=0A=
> +#include <linux/signal.h>=0A=
> +#include <linux/sched.h>=0A=
> +#include <linux/kernel.h>=0A=
> +#include <linux/errno.h>=0A=
> +#include <linux/string.h>=0A=
> +#include <linux/types.h>=0A=
> +#include <linux/ptrace.h>=0A=
> +#include <linux/mman.h>=0A=
> +#include <linux/mm.h>=0A=
> +#include <linux/swap.h>=0A=
> +#include <linux/stddef.h>=0A=
> +#include <linux/vmalloc.h>=0A=
> +#include <linux/init.h>=0A=
> +#include <linux/delay.h>=0A=
> +#include <linux/highmem.h>=0A=
> +#include <linux/memblock.h>=0A=
> +#include <asm/pgalloc.h>=0A=
> +#include <asm/prom.h>=0A=
> +#include <asm/io.h>=0A=
> +#include <asm/mmu_context.h>=0A=
> +#include <asm/pgtable.h>=0A=
> +#include <asm/mmu.h>=0A=
> +#include <linux/uaccess.h>=0A=
> +#include <asm/smp.h>=0A=
> +#include <asm/machdep.h>=0A=
> +#include <asm/setup.h>=0A=
> +#include <asm/paca.h>=0A=
> +#include <mm/mmu_decl.h>=0A=
> +=0A=
> +extern int is_second_reloc;=0A=
> +=0A=
> +static unsigned long __init kaslr_choose_location(void *dt_ptr, phys_add=
r_t size,=0A=
> +						  unsigned long kernel_sz)=0A=
> +{=0A=
> +	/* return a fixed offset of 64M for now */=0A=
> +	return SZ_64M;=0A=
> +}=0A=
> +=0A=
> +/*=0A=
> + * To see if we need to relocate the kernel to a random offset=0A=
> + * void *dt_ptr - address of the device tree=0A=
> + * phys_addr_t size - size of the first memory block=0A=
> + */=0A=
> +notrace void __init kaslr_early_init(void *dt_ptr, phys_addr_t size)=0A=
> +{=0A=
> +	unsigned long tlb_virt;=0A=
> +	phys_addr_t tlb_phys;=0A=
> +	unsigned long offset;=0A=
> +	unsigned long kernel_sz;=0A=
> +=0A=
> +	kernel_sz =3D (unsigned long)_end - KERNELBASE;=0A=
> +=0A=
> +	offset =3D kaslr_choose_location(dt_ptr, size, kernel_sz);=0A=
> +=0A=
> +	if (offset =3D=3D 0)=0A=
> +		return;=0A=
> +=0A=
> +	kimage_vaddr +=3D offset;=0A=
> +	kernstart_addr +=3D offset;=0A=
> +=0A=
> +	is_second_reloc =3D 1;=0A=
> +=0A=
> +	if (offset >=3D SZ_64M) {=0A=
> +		tlb_virt =3D round_down(kimage_vaddr, SZ_64M);=0A=
> +		tlb_phys =3D round_down(kernstart_addr, SZ_64M);=0A=
> +=0A=
> +		/* Create kernel map to relocate in */=0A=
> +		create_tlb_entry(tlb_phys, tlb_virt, 1);=0A=
> +	}=0A=
> +=0A=
> +	/* Copy the kernel to it's new location and run */=0A=
> +	memcpy((void *)kimage_vaddr, (void *)KERNELBASE, kernel_sz);=0A=
> +=0A=
> +	reloc_kernel_entry(dt_ptr, kimage_vaddr);=0A=
> +}=0A=
> diff --git a/arch/powerpc/mm/mmu_decl.h b/arch/powerpc/mm/mmu_decl.h=0A=
> index 804da298beb3..9332772c8a66 100644=0A=
> --- a/arch/powerpc/mm/mmu_decl.h=0A=
> +++ b/arch/powerpc/mm/mmu_decl.h=0A=
> @@ -148,6 +148,12 @@ void reloc_kernel_entry(void *fdt, int addr);=0A=
>  extern void loadcam_entry(unsigned int index);=0A=
>  extern void loadcam_multi(int first_idx, int num, int tmp_idx);=0A=
>  =0A=
> +#ifdef CONFIG_RANDOMIZE_BASE=0A=
> +void kaslr_early_init(void *dt_ptr, phys_addr_t size);=0A=
> +#else=0A=
> +static inline void kaslr_early_init(void *dt_ptr, phys_addr_t size) {}=
=0A=
> +#endif=0A=
> +=0A=
>  struct tlbcam {=0A=
>  	u32	MAS0;=0A=
>  	u32	MAS1;=0A=
> diff --git a/arch/powerpc/mm/nohash/fsl_booke.c b/arch/powerpc/mm/nohash/=
fsl_booke.c=0A=
> index 556e3cd52a35..8d25a8dc965f 100644=0A=
> --- a/arch/powerpc/mm/nohash/fsl_booke.c=0A=
> +++ b/arch/powerpc/mm/nohash/fsl_booke.c=0A=
> @@ -263,7 +263,8 @@ void setup_initial_memory_limit(phys_addr_t first_mem=
block_base,=0A=
>  int __initdata is_second_reloc;=0A=
>  notrace void __init relocate_init(u64 dt_ptr, phys_addr_t start)=0A=
>  {=0A=
> -	unsigned long base =3D KERNELBASE;=0A=
> +	unsigned long base =3D kimage_vaddr;=0A=
> +	phys_addr_t size;=0A=
>  =0A=
>  	kernstart_addr =3D start;=0A=
>  	if (is_second_reloc) {=0A=
> @@ -291,7 +292,7 @@ notrace void __init relocate_init(u64 dt_ptr, phys_ad=
dr_t start)=0A=
>  	start &=3D ~0x3ffffff;=0A=
>  	base &=3D ~0x3ffffff;=0A=
>  	virt_phys_offset =3D base - start;=0A=
> -	early_get_first_memblock_info(__va(dt_ptr), NULL);=0A=
> +	early_get_first_memblock_info(__va(dt_ptr), &size);=0A=
>  	/*=0A=
>  	 * We now get the memstart_addr, then we should check if this=0A=
>  	 * address is the same as what the PAGE_OFFSET map to now. If=0A=
> @@ -316,6 +317,8 @@ notrace void __init relocate_init(u64 dt_ptr, phys_ad=
dr_t start)=0A=
>  		/* We should never reach here */=0A=
>  		panic("Relocation error");=0A=
>  	}=0A=
> +=0A=
> +	kaslr_early_init(__va(dt_ptr), size);=0A=
>  }=0A=
>  #endif=0A=
>  #endif=0A=
=0A=