// 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/tsc.h>
#include <asm/archrandom.h>
#include <asm/e820/api.h>
#include <asm/shared/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) cpu_feature_enabled(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_CMD_READBACK | I8254_SELECT_COUNTER0,
                     I8254_PORT_CONTROL);
                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;

        if (purpose) {
                debug_putstr(purpose);
                debug_putstr(" KASLR using");
        }

        if (has_cpuflag(X86_FEATURE_RDRAND)) {
                if (purpose)
                        debug_putstr(" RDRAND");
                if (rdrand_long(&raw)) {
                        random ^= raw;
                        use_i8254 = false;
                }
        }

        if (has_cpuflag(X86_FEATURE_TSC)) {
                if (purpose)
                        debug_putstr(" RDTSC");
                raw = rdtsc();

                random ^= raw;
                use_i8254 = false;
        }

        if (use_i8254) {
                if (purpose)
                        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;

        if (purpose)
                debug_putstr("...\n");

        return random;
}