Re: [PATCH v2 06/10] powerpc/fsl_booke/32: implement KASLR infrastructure

[Christophe Leroy <christophe.leroy@c-s.fr>]

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@huawei.com>
> Cc: Diana Craciun <diana.craciun@nxp.com>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: Christophe Leroy <christophe.leroy@c-s.fr>
> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Cc: Paul Mackerras <paulus@samba.org>
> Cc: Nicholas Piggin <npiggin@gmail.com>
> Cc: Kees Cook <keescook@chromium.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@huawei.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
>