Add a more proper rand implementation

src/lib/rand.c

@@ -0,0 +1,101 @@
+#include <stdint.h>
+#include <stddef.h>
+#include <stdbool.h>
+#include <lib/blib.h>
+#include <lib/print.h>
+#include <lib/rand.h>
+
+// TODO: Find where this mersenne twister implementation is inspired from
+//       and properly credit the original author(s).
+
+#define rdrand(type) ({ \
+    type ret; \
+    asm volatile ( \
+        "1: " \
+        "rdrand %0;" \
+        "jnc 1b;" \
+        : "=r" (ret) \
+    ); \
+    ret; \
+})
+
+#define rdtsc(type) ({ \
+    type ret; \
+    asm volatile ( \
+        "rdtsc;" \
+        : "=A" (ret) \
+    ); \
+    ret; \
+})
+
+static bool rdrand_available = false;
+
+void init_rand(void) {
+    {
+        uint32_t eax, ebx, ecx, edx;
+        int ret = cpuid(1, 0, &eax, &ebx, &ecx, &edx);
+
+        if (!ret && (ecx & (1 << 30)))
+            rdrand_available = true;
+    }
+
+    uint32_t seed = ((uint32_t)0xc597060c * rdtsc(uint32_t))
+                  * ((uint32_t)0xce86d624)
+                  ^ ((uint32_t)0xee0da130 * rdtsc(uint32_t));
+
+    if (!rdrand_available) {
+        srand(seed);
+    } else {
+        seed *= (seed ^ rdrand(uint32_t));
+        srand(seed);
+    }
+}
+
+#define n ((int)624)
+#define m ((int)397)
+#define matrix_a ((uint32_t)0x9908b0df)
+#define msb ((uint32_t)0x80000000)
+#define lsbs ((uint32_t)0x7fffffff)
+
+static uint32_t status[n];
+static int ctr;
+
+void srand(uint32_t s) {
+    status[0] = s;
+    for (ctr = 1; ctr < n; ctr++)
+        status[ctr] = (1812433253 * (status[ctr - 1] ^ (status[ctr - 1] >> 30)) + ctr);
+}
+
+uint32_t rand32(void) {
+    const uint32_t mag01[2] = {0, matrix_a};
+
+    if (ctr >= n) {
+        for (int kk = 0; kk < n - m; kk++) {
+            uint32_t y = (status[kk] & msb) | (status[kk + 1] & lsbs);
+            status[kk] = status[kk + m] ^ (y >> 1) ^ mag01[y & 1];
+        }
+
+        for (int kk = n - m; kk < n - 1; kk++) {
+            uint32_t y = (status[kk] & msb) | (status[kk + 1] & lsbs);
+            status[kk] = status[kk + (m - n)] ^ (y >> 1) ^ mag01[y & 1];
+        }
+
+        uint32_t y = (status[n - 1] & msb) | (status[0] & lsbs);
+        status[n - 1] = status[m - 1] ^ (y >> 1) ^ mag01[y & 1];
+
+        ctr = 0;
+    }
+
+    uint32_t res = status[ctr++];
+
+    res ^= (res >> 11);
+    res ^= (res << 7) & 0x9d2c5680;
+    res ^= (res << 15) & 0xefc60000;
+    res ^= (res >> 18);
+
+    return res;
+}
+
+uint64_t rand64(void) {
+    return (((uint64_t)rand32()) << 32) | (uint64_t)rand32();
+}

src/lib/rand.h

@@ -0,0 +1,13 @@
+#ifndef __LIB__RAND_H__
+#define __LIB__RAND_H__
+
+#include <stdint.h>
+
+void init_rand(void);
+
+void srand(uint32_t s);
+
+uint32_t rand32(void);
+uint64_t rand64(void);
+
+#endif

src/lib/random.c

@@ -1,48 +0,0 @@
-#include <lib/blib.h>
-
-int rdrand_available = 0;
-
-static void check_rdrand(void) {
-    uint32_t eax, ebx, ecx, edx;
-    int ret = cpuid(1, 0, &eax, &ebx, &ecx, &edx);
-    if (ret)
-        return;
-
-    if (ecx & (1 << 30))
-        rdrand_available = 1;
-}
-
-static void init_simple_rand(void) {
-    // TODO: Some fallback randomness init
-}
-
-void init_random(void) {
-    check_rdrand();
-    if (!rdrand_available) {
-        init_simple_rand();
-    }
-}
-
-static uint32_t rdrand(void) {
-    uint32_t val;
-
-    asm (
-        "1:rdrand %0\n\t"
-        "jnc 1b\n\t"
-        :"=r"(val)
-    );
-
-    return val;
-}
-
-static uint32_t simple_rand(void) {
-    // TODO: Some fallback randomness
-    return 0xFEEDFACE;
-}
-
-uint32_t get_random(void) {
-    if (rdrand_available)
-        return rdrand();
-    else
-        return simple_rand();
-}

src/lib/random.h

@@ -1,10 +0,0 @@
-#ifndef __LIB__RANDOM_H__
-#define __LIB__RANDOM_H__
-
-#include <stdint.h>
-
-void init_random(void);
-
-uint32_t get_random(void);
-
-#endif

src/main.c

@@ -22,7 +22,7 @@ asm (
 #include <lib/config.h>
 #include <lib/e820.h>
 #include <lib/print.h>
-#include <lib/random.h>
+#include <lib/rand.h>
 #include <fs/file.h>
 #include <lib/elf.h>
 #include <protos/stivale.h>
@@ -99,7 +99,7 @@ refresh:
 void main(int boot_drive) {
     // Initial prompt.
     init_vga_textmode();
-    init_random();
+    init_rand();
 
     print("qloader2\n\n");
 

src/protos/stivale.c

@@ -9,7 +9,7 @@
 #include <lib/config.h>
 #include <lib/time.h>
 #include <lib/print.h>
-#include <lib/random.h>
+#include <lib/rand.h>
 #include <lib/real.h>
 #include <drivers/vbe.h>
 #include <drivers/vga_textmode.h>
@@ -110,7 +110,7 @@ void stivale_load(char *cmdline, int boot_drive) {
 
             if (!ret && ((stivale_hdr.flags >> 2) & 1)) {
                 // KASLR is enabled, set the slide
-                slide = get_random() & KASLR_SLIDE_BITMASK;
+                slide = rand64() & KASLR_SLIDE_BITMASK;
 
                 // Re-read the .stivalehdr with slid relocations
                 ret = elf64_load_section(fd, &stivale_hdr, ".stivalehdr", sizeof(struct stivale_header), slide);