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Date: Thu, 20 Feb 2020 14:48:23 +0100
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, oss@...error.net
Cc: linux-kernel@...r.kernel.org, zhaohongjiang@...wei.com
Subject: Re: [PATCH v3 3/6] powerpc/fsl_booke/64: implement KASLR for
fsl_booke64
Le 06/02/2020 à 03:58, Jason Yan a écrit :
> The implementation for Freescale BookE64 is similar as BookE32. One
> difference is that Freescale BookE64 set up a TLB mapping of 1G during
> booting. Another difference is that ppc64 needs the kernel to be
> 64K-aligned. So we can randomize the kernel in this 1G mapping and make
> it 64K-aligned. This can save some code to creat another TLB map at
> early boot. The disadvantage is that we only have about 1G/64K = 16384
> slots to put the kernel in.
>
> To support secondary cpu boot up, a variable __kaslr_offset was added in
> first_256B section. This can help secondary cpu get the kaslr offset
> before the 1:1 mapping has been setup.
>
> Signed-off-by: Jason Yan <yanaijie@...wei.com>
> Cc: Scott Wood <oss@...error.net>
> 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 | 2 +-
> arch/powerpc/kernel/exceptions-64e.S | 10 +++++++++
> arch/powerpc/kernel/head_64.S | 7 ++++++
> arch/powerpc/kernel/setup_64.c | 4 +++-
> arch/powerpc/mm/mmu_decl.h | 16 +++++++-------
> arch/powerpc/mm/nohash/kaslr_booke.c | 33 +++++++++++++++++++++++++---
> 6 files changed, 59 insertions(+), 13 deletions(-)
>
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index c150a9d49343..754aeb96bb1c 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -568,7 +568,7 @@ config RELOCATABLE
>
> config RANDOMIZE_BASE
> bool "Randomize the address of the kernel image"
> - depends on (FSL_BOOKE && FLATMEM && PPC32)
> + depends on (PPC_FSL_BOOK3E && FLATMEM)
> depends on RELOCATABLE
> help
> Randomizes the virtual address at which the kernel image is
> diff --git a/arch/powerpc/kernel/exceptions-64e.S b/arch/powerpc/kernel/exceptions-64e.S
> index 1b9b174bee86..c1c05b8684ca 100644
> --- a/arch/powerpc/kernel/exceptions-64e.S
> +++ b/arch/powerpc/kernel/exceptions-64e.S
> @@ -1378,6 +1378,7 @@ skpinv: addi r6,r6,1 /* Increment */
> 1: mflr r6
> addi r6,r6,(2f - 1b)
> tovirt(r6,r6)
> + add r6,r6,r19
> lis r7,MSR_KERNEL@h
> ori r7,r7,MSR_KERNEL@l
> mtspr SPRN_SRR0,r6
> @@ -1400,6 +1401,7 @@ skpinv: addi r6,r6,1 /* Increment */
>
> /* We translate LR and return */
> tovirt(r8,r8)
> + add r8,r8,r19
> mtlr r8
> blr
>
> @@ -1528,6 +1530,7 @@ a2_tlbinit_code_end:
> */
> _GLOBAL(start_initialization_book3e)
> mflr r28
> + li r19, 0
>
> /* First, we need to setup some initial TLBs to map the kernel
> * text, data and bss at PAGE_OFFSET. We don't have a real mode
> @@ -1570,6 +1573,12 @@ _GLOBAL(book3e_secondary_core_init)
> cmplwi r4,0
> bne 2f
>
> + li r19, 0
> +#ifdef CONFIG_RANDOMIZE_BASE
> + LOAD_REG_ADDR_PIC(r19, __kaslr_offset)
> + lwz r19,0(r19)
> + rlwinm r19,r19,0,0,5
> +#endif
> /* Setup TLB for this core */
> bl initial_tlb_book3e
>
> @@ -1602,6 +1611,7 @@ _GLOBAL(book3e_secondary_core_init)
> lis r3,PAGE_OFFSET@...hest
> sldi r3,r3,32
> or r28,r28,r3
> + add r28,r28,r19
> 1: mtlr r28
> blr
>
> diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
> index ad79fddb974d..744624140fb8 100644
> --- a/arch/powerpc/kernel/head_64.S
> +++ b/arch/powerpc/kernel/head_64.S
> @@ -104,6 +104,13 @@ __secondary_hold_acknowledge:
> .8byte 0x0
>
> #ifdef CONFIG_RELOCATABLE
> +#ifdef CONFIG_RANDOMIZE_BASE
> + . = 0x58
> + .globl __kaslr_offset
> +__kaslr_offset:
> +DEFINE_FIXED_SYMBOL(__kaslr_offset)
> + .long 0
> +#endif
> /* This flag is set to 1 by a loader if the kernel should run
> * at the loaded address instead of the linked address. This
> * is used by kexec-tools to keep the the kdump kernel in the
> diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
> index 6104917a282d..a16b970a8d1a 100644
> --- a/arch/powerpc/kernel/setup_64.c
> +++ b/arch/powerpc/kernel/setup_64.c
> @@ -66,7 +66,7 @@
> #include <asm/feature-fixups.h>
> #include <asm/kup.h>
> #include <asm/early_ioremap.h>
> -
Why remove this new line which clearly separates things in asm/ and
things in local dir ?
> +#include <mm/mmu_decl.h>
> #include "setup.h"
>
> int spinning_secondaries;
> @@ -300,6 +300,8 @@ void __init early_setup(unsigned long dt_ptr)
> /* Enable early debugging if any specified (see udbg.h) */
> udbg_early_init();
>
> + kaslr_early_init(__va(dt_ptr), 0);
> +
> udbg_printf(" -> %s(), dt_ptr: 0x%lx\n", __func__, dt_ptr);
>
> /*
> diff --git a/arch/powerpc/mm/mmu_decl.h b/arch/powerpc/mm/mmu_decl.h
> index 3e1c85c7d10b..bbd721d1e3d7 100644
> --- a/arch/powerpc/mm/mmu_decl.h
> +++ b/arch/powerpc/mm/mmu_decl.h
> @@ -147,14 +147,6 @@ void reloc_kernel_entry(void *fdt, long 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);
> -void kaslr_late_init(void);
> -#else
> -static inline void kaslr_early_init(void *dt_ptr, phys_addr_t size) {}
> -static inline void kaslr_late_init(void) {}
> -#endif
> -
> struct tlbcam {
> u32 MAS0;
> u32 MAS1;
> @@ -164,6 +156,14 @@ struct tlbcam {
> };
> #endif
>
> +#ifdef CONFIG_RANDOMIZE_BASE
> +void kaslr_early_init(void *dt_ptr, phys_addr_t size);
> +void kaslr_late_init(void);
> +#else
> +static inline void kaslr_early_init(void *dt_ptr, phys_addr_t size) {}
> +static inline void kaslr_late_init(void) {}
> +#endif
> +
> #if defined(CONFIG_PPC_BOOK3S_32) || defined(CONFIG_FSL_BOOKE) || defined(CONFIG_PPC_8xx)
> /* 6xx have BATS */
> /* FSL_BOOKE have TLBCAM */
> diff --git a/arch/powerpc/mm/nohash/kaslr_booke.c b/arch/powerpc/mm/nohash/kaslr_booke.c
> index 07b036e98353..c6f5c1db1394 100644
> --- a/arch/powerpc/mm/nohash/kaslr_booke.c
> +++ b/arch/powerpc/mm/nohash/kaslr_booke.c
> @@ -231,7 +231,7 @@ static __init unsigned long get_usable_address(const void *fdt,
> unsigned long pa;
> unsigned long pa_end;
>
> - for (pa = offset; (long)pa > (long)start; pa -= SZ_16K) {
> + for (pa = offset; (long)pa > (long)start; pa -= SZ_64K) {
Doesn't this modify the behaviour for PPC32 too ?
> pa_end = pa + regions.kernel_size;
> if (overlaps_region(fdt, pa, pa_end))
> continue;
> @@ -265,14 +265,14 @@ static unsigned long __init kaslr_legal_offset(void *dt_ptr, unsigned long rando
> {
> unsigned long koffset = 0;
> unsigned long start;
> - unsigned long index;
> unsigned long offset;
>
> +#ifdef CONFIG_PPC32
Can we use
if (IS_ENABLED(CONFIG_PPC32)) {
/* 32 bits stuff */
} else {
/* 64 bits stuff */
}
> /*
> * Decide which 64M we want to start
> * Only use the low 8 bits of the random seed
> */
> - index = random & 0xFF;
> + unsigned long index = random & 0xFF;
That's not good in terms of readability, index declaration should remain
at the top of the function, should be possible if using IS_ENABLED() instead
> index %= regions.linear_sz / SZ_64M;
>
> /* Decide offset inside 64M */
> @@ -287,6 +287,15 @@ static unsigned long __init kaslr_legal_offset(void *dt_ptr, unsigned long rando
> break;
> index--;
> }
> +#else
> + /* Decide kernel offset inside 1G */
> + offset = random % (SZ_1G - regions.kernel_size);
> + offset = round_down(offset, SZ_64K);
> +
> + start = memstart_addr;
> + offset = memstart_addr + offset;
> + koffset = get_usable_address(dt_ptr, start, offset);
> +#endif
>
> if (koffset != 0)
> koffset -= memstart_addr;
> @@ -325,6 +334,7 @@ static unsigned long __init kaslr_choose_location(void *dt_ptr, phys_addr_t size
> else
> pr_warn("KASLR: No safe seed for randomizing the kernel base.\n");
>
> +#ifdef CONFIG_PPC32
> ram = min_t(phys_addr_t, __max_low_memory, size);
> ram = map_mem_in_cams(ram, CONFIG_LOWMEM_CAM_NUM, true);
> linear_sz = min_t(unsigned long, ram, SZ_512M);
> @@ -332,6 +342,7 @@ static unsigned long __init kaslr_choose_location(void *dt_ptr, phys_addr_t size
> /* If the linear size is smaller than 64M, do not randmize */
> if (linear_sz < SZ_64M)
> return 0;
> +#endif
>
> /* check for a reserved-memory node and record its cell sizes */
> regions.reserved_mem = fdt_path_offset(dt_ptr, "/reserved-memory");
> @@ -363,6 +374,17 @@ notrace void __init kaslr_early_init(void *dt_ptr, phys_addr_t size)
> unsigned long offset;
> unsigned long kernel_sz;
>
> +#ifdef CONFIG_PPC64
Same, can we use a standard C if/else sequence with
IS_ENABLED(CONFIG_PPC64) ?
> + unsigned int *__kaslr_offset = (unsigned int *)(KERNELBASE + 0x58);
> + unsigned int *__run_at_load = (unsigned int *)(KERNELBASE + 0x5c);
> +
> + if (*__run_at_load == 1)
> + return;
> +
> + /* Setup flat device-tree pointer */
> + initial_boot_params = dt_ptr;
> +#endif
> +
> kernel_sz = (unsigned long)_end - (unsigned long)_stext;
>
> offset = kaslr_choose_location(dt_ptr, size, kernel_sz);
> @@ -372,6 +394,7 @@ notrace void __init kaslr_early_init(void *dt_ptr, phys_addr_t size)
> kernstart_virt_addr += offset;
> kernstart_addr += offset;
>
> +#ifdef CONFIG_PPC32
> is_second_reloc = 1;
>
> if (offset >= SZ_64M) {
> @@ -381,6 +404,10 @@ notrace void __init kaslr_early_init(void *dt_ptr, phys_addr_t size)
> /* Create kernel map to relocate in */
> create_kaslr_tlb_entry(1, tlb_virt, tlb_phys);
> }
> +#else
> + *__kaslr_offset = kernstart_virt_addr - KERNELBASE;
> + *__run_at_load = 1;
> +#endif
>
> /* Copy the kernel to it's new location and run */
> memcpy((void *)kernstart_virt_addr, (void *)_stext, kernel_sz);
>
Christophe
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