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Message-ID: <6c0b0720-6998-f43a-a2b6-0632d4df1126@c-s.fr>
Date: Thu, 20 Feb 2020 14:40:31 +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 1/6] powerpc/fsl_booke/kaslr: refactor
kaslr_legal_offset() and kaslr_early_init()
Le 06/02/2020 à 03:58, Jason Yan a écrit :
> Some code refactor in kaslr_legal_offset() and kaslr_early_init(). No
> functional change. This is a preparation for KASLR fsl_booke64.
>
> 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/mm/nohash/kaslr_booke.c | 40 ++++++++++++++--------------
> 1 file changed, 20 insertions(+), 20 deletions(-)
>
> diff --git a/arch/powerpc/mm/nohash/kaslr_booke.c b/arch/powerpc/mm/nohash/kaslr_booke.c
> index 4a75f2d9bf0e..07b036e98353 100644
> --- a/arch/powerpc/mm/nohash/kaslr_booke.c
> +++ b/arch/powerpc/mm/nohash/kaslr_booke.c
> @@ -25,6 +25,7 @@ struct regions {
> unsigned long pa_start;
> unsigned long pa_end;
> unsigned long kernel_size;
> + unsigned long linear_sz;
> unsigned long dtb_start;
> unsigned long dtb_end;
> unsigned long initrd_start;
> @@ -260,11 +261,23 @@ static __init void get_cell_sizes(const void *fdt, int node, int *addr_cells,
> *size_cells = fdt32_to_cpu(*prop);
> }
>
> -static unsigned long __init kaslr_legal_offset(void *dt_ptr, unsigned long index,
> - unsigned long offset)
> +static unsigned long __init kaslr_legal_offset(void *dt_ptr, unsigned long random)
> {
> unsigned long koffset = 0;
> unsigned long start;
> + unsigned long index;
> + unsigned long offset;
> +
> + /*
> + * Decide which 64M we want to start
> + * Only use the low 8 bits of the random seed
> + */
> + index = random & 0xFF;
> + index %= regions.linear_sz / SZ_64M;
> +
> + /* Decide offset inside 64M */
> + offset = random % (SZ_64M - regions.kernel_size);
> + offset = round_down(offset, SZ_16K);
>
> while ((long)index >= 0) {
> offset = memstart_addr + index * SZ_64M + offset;
> @@ -289,10 +302,9 @@ static inline __init bool kaslr_disabled(void)
> static unsigned long __init kaslr_choose_location(void *dt_ptr, phys_addr_t size,
> unsigned long kernel_sz)
> {
> - unsigned long offset, random;
> + unsigned long random;
> unsigned long ram, linear_sz;
> u64 seed;
> - unsigned long index;
>
> kaslr_get_cmdline(dt_ptr);
> if (kaslr_disabled())
> @@ -333,22 +345,12 @@ static unsigned long __init kaslr_choose_location(void *dt_ptr, phys_addr_t size
> regions.dtb_start = __pa(dt_ptr);
> regions.dtb_end = __pa(dt_ptr) + fdt_totalsize(dt_ptr);
> regions.kernel_size = kernel_sz;
> + regions.linear_sz = linear_sz;
>
> get_initrd_range(dt_ptr);
> get_crash_kernel(dt_ptr, ram);
>
> - /*
> - * Decide which 64M we want to start
> - * Only use the low 8 bits of the random seed
> - */
> - index = random & 0xFF;
> - index %= linear_sz / SZ_64M;
> -
> - /* Decide offset inside 64M */
> - offset = random % (SZ_64M - kernel_sz);
> - offset = round_down(offset, SZ_16K);
> -
> - return kaslr_legal_offset(dt_ptr, index, offset);
> + return kaslr_legal_offset(dt_ptr, random);
> }
>
> /*
> @@ -358,8 +360,6 @@ static unsigned long __init kaslr_choose_location(void *dt_ptr, phys_addr_t size
> */
> 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;
>
> @@ -375,8 +375,8 @@ notrace void __init kaslr_early_init(void *dt_ptr, phys_addr_t size)
> is_second_reloc = 1;
>
> if (offset >= SZ_64M) {
> - tlb_virt = round_down(kernstart_virt_addr, SZ_64M);
> - tlb_phys = round_down(kernstart_addr, SZ_64M);
> + unsigned long tlb_virt = round_down(kernstart_virt_addr, SZ_64M);
> + phys_addr_t tlb_phys = round_down(kernstart_addr, SZ_64M);
That looks like cleanup unrelated to the patch itself.
>
> /* Create kernel map to relocate in */
> create_kaslr_tlb_entry(1, tlb_virt, tlb_phys);
>
Christophe
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