67 lines
1.5 KiB
C
67 lines
1.5 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
|
|
// Copyright 2022 Google LLC
|
|
// Author: Ard Biesheuvel <ardb@google.com>
|
|
|
|
// NOTE: code in this file runs *very* early, and is not permitted to use
|
|
// global variables or anything that relies on absolute addressing.
|
|
|
|
#include <linux/libfdt.h>
|
|
#include <linux/init.h>
|
|
#include <linux/linkage.h>
|
|
#include <linux/types.h>
|
|
#include <linux/sizes.h>
|
|
#include <linux/string.h>
|
|
|
|
#include <asm/archrandom.h>
|
|
#include <asm/memory.h>
|
|
#include <asm/pgtable.h>
|
|
|
|
#include "pi.h"
|
|
|
|
extern u16 memstart_offset_seed;
|
|
|
|
static u64 __init get_kaslr_seed(void *fdt, int node)
|
|
{
|
|
static char const seed_str[] __initconst = "kaslr-seed";
|
|
fdt64_t *prop;
|
|
u64 ret;
|
|
int len;
|
|
|
|
if (node < 0)
|
|
return 0;
|
|
|
|
prop = fdt_getprop_w(fdt, node, seed_str, &len);
|
|
if (!prop || len != sizeof(u64))
|
|
return 0;
|
|
|
|
ret = fdt64_to_cpu(*prop);
|
|
*prop = 0;
|
|
return ret;
|
|
}
|
|
|
|
u64 __init kaslr_early_init(void *fdt, int chosen)
|
|
{
|
|
u64 seed, range;
|
|
|
|
if (kaslr_disabled_cmdline())
|
|
return 0;
|
|
|
|
seed = get_kaslr_seed(fdt, chosen);
|
|
if (!seed) {
|
|
if (!__early_cpu_has_rndr() ||
|
|
!__arm64_rndr((unsigned long *)&seed))
|
|
return 0;
|
|
}
|
|
|
|
memstart_offset_seed = seed & U16_MAX;
|
|
|
|
/*
|
|
* OK, so we are proceeding with KASLR enabled. Calculate a suitable
|
|
* kernel image offset from the seed. Let's place the kernel in the
|
|
* 'middle' half of the VMALLOC area, and stay clear of the lower and
|
|
* upper quarters to avoid colliding with other allocations.
|
|
*/
|
|
range = (VMALLOC_END - KIMAGE_VADDR) / 2;
|
|
return range / 2 + (((__uint128_t)range * seed) >> 64);
|
|
}
|