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92 lines
2.1 KiB
92 lines
2.1 KiB
// 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_CMD_READBACK | I8254_SELECT_COUNTER0, |
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I8254_PORT_CONTROL); |
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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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