diff options
Diffstat (limited to 'MdePkg/Library/BaseRngLib/Riscv/Rng.c')
| -rw-r--r-- | MdePkg/Library/BaseRngLib/Riscv/Rng.c | 277 |
1 files changed, 277 insertions, 0 deletions
diff --git a/MdePkg/Library/BaseRngLib/Riscv/Rng.c b/MdePkg/Library/BaseRngLib/Riscv/Rng.c new file mode 100644 index 0000000000..305ab60b4d --- /dev/null +++ b/MdePkg/Library/BaseRngLib/Riscv/Rng.c @@ -0,0 +1,277 @@ +/** @file
+ Random number generator service that uses the SEED instruction
+ to provide pseudorandom numbers.
+
+ Copyright (c) 2024, Rivos, Inc.
+
+ SPDX-License-Identifier: BSD-2-Clause-Patent
+ **/
+
+#include <Uefi.h>
+#include <Library/BaseLib.h>
+#include <Library/DebugLib.h>
+#include <Library/RngLib.h>
+#include <Register/RiscV64/RiscVEncoding.h>
+
+#include "BaseRngLibInternals.h"
+#define RISCV_CPU_FEATURE_ZKR_BITMASK 0x8
+
+#define SEED_RETRY_LOOPS 100
+
+// 64-bit Mersenne Twister implementation
+// A widely used pseudo random number generator. It performs bit shifts etc to
+// achieve the random number. It's output is determined by SEED value generated
+// by RISC-V SEED CSR"
+
+#define STATE_SIZE 312
+#define MIDDLE 156
+#define INIT_SHIFT 62
+#define TWIST_MASK 0xb5026f5aa96619e9ULL
+#define INIT_FACT 6364136223846793005ULL
+#define SHIFT1 29
+#define MASK1 0x5555555555555555ULL
+#define SHIFT2 17
+#define MASK2 0x71d67fffeda60000ULL
+#define SHIFT3 37
+#define MASK3 0xfff7eee000000000ULL
+#define SHIFT4 43
+
+#define LOWER_MASK 0x7fffffff
+#define UPPER_MASK (~(UINT64)LOWER_MASK)
+
+static UINT64 mState[STATE_SIZE];
+static UINTN mIndex = STATE_SIZE + 1;
+
+/**
+ Initialize mState to defualt state.
+
+ @param[in] S Input seed value
+ **/
+STATIC
+VOID
+SeedRng (
+ IN UINT64 S
+ )
+{
+ UINTN I;
+
+ mIndex = STATE_SIZE;
+ mState[0] = S;
+
+ for (I = 1; I < STATE_SIZE; I++) {
+ mState[I] = (INIT_FACT * (mState[I - 1] ^ (mState[I - 1] >> INIT_SHIFT))) + I;
+ }
+}
+
+/**
+ Initializes mState with entropy values. The initialization is based on the
+ Seed value populated in mState[0] which then influences all the other values
+ in the mState array. Later values are retrieved from the same array instead
+ of calling trng instruction every time.
+
+ **/
+STATIC
+VOID
+TwistRng (
+ VOID
+ )
+{
+ UINTN I;
+ UINT64 X;
+
+ for (I = 0; I < STATE_SIZE; I++) {
+ X = (mState[I] & UPPER_MASK) | (mState[(I + 1) % STATE_SIZE] & LOWER_MASK);
+ X = (X >> 1) ^ (X & 1 ? TWIST_MASK : 0);
+ mState[I] = mState[(I + MIDDLE) % STATE_SIZE] ^ X;
+ }
+
+ mIndex = 0;
+}
+
+// Defined in Seed.S
+extern UINT64
+ReadSeed (
+ VOID
+ );
+
+/**
+ Gets seed value by executing trng instruction (CSR 0x15) amd returns
+ the see to the caller 64bit value.
+
+ @param[out] Out Buffer pointer to store the 64-bit random value.
+ @retval TRUE Random number generated successfully.
+ @retval FALSE Failed to generate the random number.
+ **/
+STATIC
+BOOLEAN
+Get64BitSeed (
+ OUT UINT64 *Out
+ )
+{
+ UINT64 Seed;
+ UINTN Retry;
+ UINTN ValidSeeds;
+ UINTN NeededSeeds;
+ UINT16 *Entropy;
+
+ Retry = SEED_RETRY_LOOPS;
+ Entropy = (UINT16 *)Out;
+ NeededSeeds = sizeof (UINT64) / sizeof (UINT16);
+ ValidSeeds = 0;
+
+ if (!ArchIsRngSupported ()) {
+ DEBUG ((DEBUG_ERROR, "Get64BitSeed: HW not supported!\n"));
+ return FALSE;
+ }
+
+ do {
+ Seed = ReadSeed ();
+
+ switch (Seed & SEED_OPST_MASK) {
+ case SEED_OPST_ES16:
+ Entropy[ValidSeeds++] = Seed & SEED_ENTROPY_MASK;
+ if (ValidSeeds == NeededSeeds) {
+ return TRUE;
+ }
+
+ break;
+
+ case SEED_OPST_DEAD:
+ DEBUG ((DEBUG_ERROR, "Get64BitSeed: Unrecoverable error!\n"));
+ return FALSE;
+
+ case SEED_OPST_BIST: // fallthrough
+ case SEED_OPST_WAIT: // fallthrough
+ default:
+ continue;
+ }
+ } while (--Retry);
+
+ return FALSE;
+}
+
+/**
+ Constructor library which initializes Seeds and mStatus array.
+
+ @retval EFI_SUCCESS Intialization was successful.
+ @retval EFI_UNSUPPORTED Feature not supported.
+
+ **/
+EFI_STATUS
+EFIAPI
+BaseRngLibConstructor (
+ VOID
+ )
+{
+ UINT64 Seed;
+
+ if (Get64BitSeed (&Seed)) {
+ SeedRng (Seed);
+ return EFI_SUCCESS;
+ } else {
+ return EFI_UNSUPPORTED;
+ }
+}
+
+/**
+ Generates a 16-bit random number.
+
+ @param[out] Rand Buffer pointer to store the 16-bit random value.
+
+ @retval TRUE Random number generated successfully.
+ @retval FALSE Failed to generate the random number.
+
+ **/
+BOOLEAN
+EFIAPI
+ArchGetRandomNumber16 (
+ OUT UINT16 *Rand
+ )
+{
+ UINT64 Rand64;
+
+ if (ArchGetRandomNumber64 (&Rand64)) {
+ *Rand = Rand64 & MAX_UINT16;
+ return TRUE;
+ }
+
+ return FALSE;
+}
+
+/**
+ Generates a 32-bit random number.
+
+ @param[out] Rand Buffer pointer to store the 32-bit random value.
+
+ @retval TRUE Random number generated successfully.
+ @retval FALSE Failed to generate the random number.
+
+ **/
+BOOLEAN
+EFIAPI
+ArchGetRandomNumber32 (
+ OUT UINT32 *Rand
+ )
+{
+ UINT64 Rand64;
+
+ if (ArchGetRandomNumber64 (&Rand64)) {
+ *Rand = Rand64 & MAX_UINT32;
+ return TRUE;
+ }
+
+ return FALSE;
+}
+
+/**
+ Generates a 64-bit random number.
+
+ @param[out] Rand Buffer pointer to store the 64-bit random value.
+
+ @retval TRUE Random number generated successfully.
+ @retval FALSE Failed to generate the random number.
+
+ **/
+BOOLEAN
+EFIAPI
+ArchGetRandomNumber64 (
+ OUT UINT64 *Rand
+ )
+{
+ UINT64 Y;
+
+ // Never initialized.
+ if (mIndex > STATE_SIZE) {
+ return FALSE;
+ }
+
+ // Mersenne Twister
+ if (mIndex == STATE_SIZE) {
+ TwistRng ();
+ }
+
+ Y = mState[mIndex];
+ Y ^= (Y >> SHIFT1) & MASK1;
+ Y ^= (Y << SHIFT2) & MASK2;
+ Y ^= (Y << SHIFT3) & MASK3;
+ Y ^= Y >> SHIFT4;
+
+ mIndex++;
+
+ *Rand = Y;
+ return TRUE;
+}
+
+/**
+ Checks whether SEED is supported.
+
+ @retval TRUE SEED is supported.
+ **/
+BOOLEAN
+EFIAPI
+ArchIsRngSupported (
+ VOID
+ )
+{
+ return ((PcdGet64 (PcdRiscVFeatureOverride) & RISCV_CPU_FEATURE_ZKR_BITMASK) != 0);
+}
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