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