1/*
 2 * Entropy functions used on early boot for KASLR base and memory
 3 * randomization. The base randomization is done in the compressed
 4 * kernel and memory randomization is done early when the regular
 5 * kernel starts. This file is included in the compressed kernel and
 6 * normally linked in the regular.
 7 */
 8#include <asm/kaslr.h>
 9#include <asm/msr.h>
10#include <asm/archrandom.h>
11#include <asm/e820.h>
12#include <asm/io.h>
13
14/*
15 * When built for the regular kernel, several functions need to be stubbed out
16 * or changed to their regular kernel equivalent.
17 */
18#ifndef KASLR_COMPRESSED_BOOT
19#include <asm/cpufeature.h>
20#include <asm/setup.h>
21
22#define debug_putstr(v) early_printk("%s", v)
23#define has_cpuflag(f) boot_cpu_has(f)
24#define get_boot_seed() kaslr_offset()
25#endif
26
27#define I8254_PORT_CONTROL	0x43
28#define I8254_PORT_COUNTER0	0x40
29#define I8254_CMD_READBACK	0xC0
30#define I8254_SELECT_COUNTER0	0x02
31#define I8254_STATUS_NOTREADY	0x40
32static inline u16 i8254(void)
33{
34	u16 status, timer;
35
36	do {
37		outb(I8254_PORT_CONTROL,
38		     I8254_CMD_READBACK | I8254_SELECT_COUNTER0);
39		status = inb(I8254_PORT_COUNTER0);
40		timer  = inb(I8254_PORT_COUNTER0);
41		timer |= inb(I8254_PORT_COUNTER0) << 8;
42	} while (status & I8254_STATUS_NOTREADY);
43
44	return timer;
45}
46
47unsigned long kaslr_get_random_long(const char *purpose)
48{
49#ifdef CONFIG_X86_64
50	const unsigned long mix_const = 0x5d6008cbf3848dd3UL;
51#else
52	const unsigned long mix_const = 0x3f39e593UL;
53#endif
54	unsigned long raw, random = get_boot_seed();
55	bool use_i8254 = true;
56
57	debug_putstr(purpose);
58	debug_putstr(" KASLR using");
59
60	if (has_cpuflag(X86_FEATURE_RDRAND)) {
61		debug_putstr(" RDRAND");
62		if (rdrand_long(&raw)) {
63			random ^= raw;
64			use_i8254 = false;
65		}
66	}
67
68	if (has_cpuflag(X86_FEATURE_TSC)) {
69		debug_putstr(" RDTSC");
70		raw = rdtsc();
71
72		random ^= raw;
73		use_i8254 = false;
74	}
75
76	if (use_i8254) {
77		debug_putstr(" i8254");
78		random ^= i8254();
79	}
80
81	/* Circular multiply for better bit diffusion */
82	asm("mul %3"
83	    : "=a" (random), "=d" (raw)
84	    : "a" (random), "rm" (mix_const));
85	random += raw;
86
87	debug_putstr("...\n");
88
89	return random;
90}