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75 lines
2.7 KiB
C
75 lines
2.7 KiB
C
#include <stdint.h>
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#include <string.h>
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#include "utils.h"
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#include "randomcache.h"
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#include "se.h"
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#include "arm.h"
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/* TrustZone maintains a cache of random for the kernel. */
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/* So that requests can still be serviced even when a */
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/* usermode SMC is in progress. */
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static uint8_t g_random_cache[0x400];
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static unsigned int g_random_cache_low = 0;
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static unsigned int g_random_cache_high = 0x3FF;
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void randomcache_refill_segment(unsigned int offset, unsigned int size) {
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if (offset + size >= 0x400) {
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size = 0x400 - offset;
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}
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flush_dcache_range(&g_random_cache[offset], &g_random_cache[offset + size]);
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se_generate_random(KEYSLOT_SWITCH_RNGKEY, &g_random_cache[offset], size);
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flush_dcache_range(&g_random_cache[offset], &g_random_cache[offset + size]);
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}
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void randomcache_init(void) {
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randomcache_refill_segment(0, 0x400);
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g_random_cache_low = 0;
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g_random_cache_high = 0x3FF;
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}
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void randomcache_refill(void) {
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unsigned int high_plus_one = (g_random_cache_high + 1) & 0x3FF;
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if (g_random_cache_low != high_plus_one) {
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/* Only refill if there's data to refill. */
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if (g_random_cache_low < high_plus_one) {
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/* NOTE: There is a bug in official code that causes this to not work properly. */
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/* In particular, official code checks whether high_plus_one == 0x400. */
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/* However, because high_plus_one is &= 0x3FF'd, this can never be the case. */
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/* We will implement according to Nintendo's intention, and not include their bug. */
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/* This should have no impact on actual observable results, anyway, since this data is random anyway... */
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if (g_random_cache_high != 0x3FF) { /* This is if (true) in Nintendo's code due to the above bug. */
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randomcache_refill_segment(high_plus_one, 0x400 - high_plus_one);
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g_random_cache_high = (g_random_cache_high + 0x400 - high_plus_one) & 0x3FF;
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}
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if (g_random_cache_low > 0) {
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randomcache_refill_segment(0, g_random_cache_low);
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g_random_cache_high = (g_random_cache_high + g_random_cache_low) & 0x3FF;
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}
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} else { /* g_random_cache_low > high_plus_one */
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randomcache_refill_segment(high_plus_one, g_random_cache_low - high_plus_one);
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g_random_cache_high = g_random_cache_low - 1;
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}
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}
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}
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void randomcache_getbytes(void *dst, size_t num_bytes) {
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unsigned int low = g_random_cache_low;
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if (num_bytes == 0) {
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return;
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}
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memcpy(dst, &g_random_cache[low], num_bytes);
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unsigned int new_low = low + num_bytes;
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if (new_low + 0x38 > 0x3FF) {
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new_low = 0;
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}
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g_random_cache_low = new_low;
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}
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