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// SPDX-License-Identifier: GPL-2.0
/*
* Entropy functions used on early boot for KASLR base and memory
* randomization. The base randomization is done in the compressed
* kernel and memory randomization is done early when the regular
* kernel starts. This file is included in the compressed kernel and
* normally linked in the regular.
*/
#include <asm/asm.h>
#include <asm/kaslr.h>
#include <asm/msr.h>
#include <asm/archrandom.h>
#include <asm/e820/api.h>
#include <asm/io.h>
/*
* When built for the regular kernel, several functions need to be stubbed out
* or changed to their regular kernel equivalent.
*/
#ifndef KASLR_COMPRESSED_BOOT
#include <asm/cpufeature.h>
#include <asm/setup.h>
#define debug_putstr(v) early_printk("%s", v)
#define has_cpuflag(f) boot_cpu_has(f)
#define get_boot_seed() kaslr_offset()
#endif
#define I8254_PORT_CONTROL 0x43
#define I8254_PORT_COUNTER0 0x40
#define I8254_CMD_READBACK 0xC0
#define I8254_SELECT_COUNTER0 0x02
#define I8254_STATUS_NOTREADY 0x40
static inline u16 i8254(void)
{
u16 status, timer;
do {
outb(I8254_PORT_CONTROL,
I8254_CMD_READBACK | I8254_SELECT_COUNTER0);
status = inb(I8254_PORT_COUNTER0);
timer = inb(I8254_PORT_COUNTER0);
timer |= inb(I8254_PORT_COUNTER0) << 8;
} while (status & I8254_STATUS_NOTREADY);
return timer;
}
unsigned long kaslr_get_random_long(const char *purpose)
{
#ifdef CONFIG_X86_64
const unsigned long mix_const = 0x5d6008cbf3848dd3UL;
#else
const unsigned long mix_const = 0x3f39e593UL;
#endif
unsigned long raw, random = get_boot_seed();
bool use_i8254 = true;
debug_putstr(purpose);
debug_putstr(" KASLR using");
if (has_cpuflag(X86_FEATURE_RDRAND)) {
debug_putstr(" RDRAND");
if (rdrand_long(&raw)) {
random ^= raw;
use_i8254 = false;
}
}
if (has_cpuflag(X86_FEATURE_TSC)) {
debug_putstr(" RDTSC");
raw = rdtsc();
random ^= raw;
use_i8254 = false;
}
if (use_i8254) {
debug_putstr(" i8254");
random ^= i8254();
}
/* Circular multiply for better bit diffusion */
asm(_ASM_MUL "%3"
: "=a" (random), "=d" (raw)
: "a" (random), "rm" (mix_const));
random += raw;
debug_putstr("...\n");
return random;
}
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