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Merge bitcoin/bitcoin#31863: random: Initialize variables in hardware RNG functions

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99755e04ff random: Initialize variables in hardware RNG functions (Eval EXEC)

Pull request description:

  See: https://github.com/bitcoin/bitcoin/pull/31826#discussion_r1955045279 , So this PR want to prevent potential uninitialized value issues and improve code clarity.

ACKs for top commit:
  sipa:
    utACK 99755e04ff
  achow101:
    ACK 99755e04ff

Tree-SHA512: 4cf9c214617769cf051b4f36453275b407e37d96315b6a206102d17019375b3834ba07e2ccb28c7650c90ff8e1f1034522fccafaa33e136dfe63cc68396a1f6e
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Ava Chow 2025-02-14 15:03:32 -08:00
commit 254fd89d39
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1 changed files with 5 additions and 5 deletions
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10
src/random.cpp
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@ -126,7 +126,7 @@ uint64_t GetRdRand() noexcept
{ {
// RdRand may very rarely fail. Invoke it up to 10 times in a loop to reduce this risk. // RdRand may very rarely fail. Invoke it up to 10 times in a loop to reduce this risk.
#ifdef __i386__ #ifdef __i386__
uint8_t ok; uint8_t ok = 0;
// Initialize to 0 to silence a compiler warning that r1 or r2 may be used // Initialize to 0 to silence a compiler warning that r1 or r2 may be used
// uninitialized. Even if rdrand fails (!ok) it will set the output to 0, // uninitialized. Even if rdrand fails (!ok) it will set the output to 0,
// but there is no way that the compiler could know that. // but there is no way that the compiler could know that.
@ -141,7 +141,7 @@ uint64_t GetRdRand() noexcept
} }
return (((uint64_t)r2) << 32) | r1; return (((uint64_t)r2) << 32) | r1;
#elif defined(__x86_64__) || defined(__amd64__) #elif defined(__x86_64__) || defined(__amd64__)
uint8_t ok; uint8_t ok = 0;
uint64_t r1 = 0; // See above why we initialize to 0. uint64_t r1 = 0; // See above why we initialize to 0.
for (int i = 0; i < 10; ++i) { for (int i = 0; i < 10; ++i) {
__asm__ volatile (".byte 0x48, 0x0f, 0xc7, 0xf0; setc %1" : "=a"(r1), "=q"(ok) :: "cc"); // rdrand %rax __asm__ volatile (".byte 0x48, 0x0f, 0xc7, 0xf0; setc %1" : "=a"(r1), "=q"(ok) :: "cc"); // rdrand %rax
@ -162,7 +162,7 @@ uint64_t GetRdSeed() noexcept
// RdSeed may fail when the HW RNG is overloaded. Loop indefinitely until enough entropy is gathered, // RdSeed may fail when the HW RNG is overloaded. Loop indefinitely until enough entropy is gathered,
// but pause after every failure. // but pause after every failure.
#ifdef __i386__ #ifdef __i386__
uint8_t ok; uint8_t ok = 0;
uint32_t r1, r2; uint32_t r1, r2;
do { do {
__asm__ volatile (".byte 0x0f, 0xc7, 0xf8; setc %1" : "=a"(r1), "=q"(ok) :: "cc"); // rdseed %eax __asm__ volatile (".byte 0x0f, 0xc7, 0xf8; setc %1" : "=a"(r1), "=q"(ok) :: "cc"); // rdseed %eax
@ -215,7 +215,7 @@ void ReportHardwareRand()
*/ */
uint64_t GetRNDR() noexcept uint64_t GetRNDR() noexcept
{ {
uint8_t ok; uint8_t ok = 0;
uint64_t r1; uint64_t r1;
do { do {
// https://developer.arm.com/documentation/ddi0601/2022-12/AArch64-Registers/RNDR--Random-Number // https://developer.arm.com/documentation/ddi0601/2022-12/AArch64-Registers/RNDR--Random-Number
@ -233,7 +233,7 @@ uint64_t GetRNDR() noexcept
*/ */
uint64_t GetRNDRRS() noexcept uint64_t GetRNDRRS() noexcept
{ {
uint8_t ok; uint8_t ok = 0;
uint64_t r1; uint64_t r1;
do { do {
// https://developer.arm.com/documentation/ddi0601/2022-12/AArch64-Registers/RNDRRS--Reseeded-Random-Number // https://developer.arm.com/documentation/ddi0601/2022-12/AArch64-Registers/RNDRRS--Reseeded-Random-Number