mirror of
https://github.com/limine-bootloader/limine
synced 2024-12-16 03:22:39 +03:00
87 lines
2.2 KiB
C
87 lines
2.2 KiB
C
#include <stdint.h>
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#include <stddef.h>
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#include <stdbool.h>
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#include <lib/blib.h>
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#include <lib/print.h>
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#include <lib/rand.h>
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#include <sys/cpu.h>
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#include <mm/pmm.h>
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// TODO: Find where this mersenne twister implementation is inspired from
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// and properly credit the original author(s).
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static bool rand_initialised = false;
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#define n ((int)624)
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#define m ((int)397)
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#define matrix_a ((uint32_t)0x9908b0df)
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#define msb ((uint32_t)0x80000000)
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#define lsbs ((uint32_t)0x7fffffff)
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static uint32_t *status;
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static int ctr;
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static void init_rand(void) {
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uint32_t seed = ((uint32_t)0xc597060c * (uint32_t)rdtsc())
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* ((uint32_t)0xce86d624)
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^ ((uint32_t)0xee0da130 * (uint32_t)rdtsc());
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uint32_t eax, ebx, ecx, edx;
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// Check for rdseed
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if (cpuid(0x07, 0, &eax, &ebx, &ecx, &edx) && (ebx & (1 << 18))) {
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seed *= (seed ^ rdseed(uint32_t));
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} else if (cpuid(0x01, 0, &eax, &ebx, &ecx, &edx) && (ecx & (1 << 30))) {
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seed *= (seed ^ rdrand(uint32_t));
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}
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status = ext_mem_alloc(n * sizeof(uint32_t));
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srand(seed);
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rand_initialised = true;
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}
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void srand(uint32_t s) {
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status[0] = s;
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for (ctr = 1; ctr < n; ctr++)
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status[ctr] = (1812433253 * (status[ctr - 1] ^ (status[ctr - 1] >> 30)) + ctr);
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}
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uint32_t rand32(void) {
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if (!rand_initialised)
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init_rand();
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const uint32_t mag01[2] = {0, matrix_a};
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if (ctr >= n) {
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for (int kk = 0; kk < n - m; kk++) {
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uint32_t y = (status[kk] & msb) | (status[kk + 1] & lsbs);
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status[kk] = status[kk + m] ^ (y >> 1) ^ mag01[y & 1];
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}
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for (int kk = n - m; kk < n - 1; kk++) {
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uint32_t y = (status[kk] & msb) | (status[kk + 1] & lsbs);
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status[kk] = status[kk + (m - n)] ^ (y >> 1) ^ mag01[y & 1];
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}
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uint32_t y = (status[n - 1] & msb) | (status[0] & lsbs);
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status[n - 1] = status[m - 1] ^ (y >> 1) ^ mag01[y & 1];
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ctr = 0;
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}
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uint32_t res = status[ctr++];
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res ^= (res >> 11);
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res ^= (res << 7) & 0x9d2c5680;
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res ^= (res << 15) & 0xefc60000;
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res ^= (res >> 18);
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return res;
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}
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uint64_t rand64(void) {
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return (((uint64_t)rand32()) << 32) | (uint64_t)rand32();
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}
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