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Do not attempt to allocate >= 4 GiB on 32-bit systems #99

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Jul 9, 2019
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Do not attempt to allocate >= 4 GiB on 32-bit systems #99

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2 changes: 1 addition & 1 deletion doc/configuration.md
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Expand Up @@ -31,7 +31,7 @@ Not all of the parameters can be changed safely and most parameters have some co
This parameter determines the amount of memory needed in the light mode. Memory is specified in KiB (1 KiB = 1024 bytes).

#### Permitted values
Any integer power of 2.
Integer powers of 2 in the range 1 - 2097152.

#### Notes
Lower sizes will reduce the memory-hardness of the algorithm.
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1 change: 1 addition & 0 deletions src/common.hpp
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Expand Up @@ -38,6 +38,7 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
namespace randomx {

static_assert(RANDOMX_ARGON_MEMORY > 0, "RANDOMX_ARGON_MEMORY must be greater than 0.");
static_assert(RANDOMX_ARGON_MEMORY <= 2097152, "RANDOMX_ARGON_MEMORY must not exceed 2097152.");
static_assert((RANDOMX_ARGON_MEMORY & (RANDOMX_ARGON_MEMORY - 1)) == 0, "RANDOMX_ARGON_MEMORY must be a power of 2.");
static_assert(RANDOMX_DATASET_BASE_SIZE >= 64, "RANDOMX_DATASET_BASE_SIZE must be at least 64.");
static_assert((RANDOMX_DATASET_BASE_SIZE & (RANDOMX_DATASET_BASE_SIZE - 1)) == 0, "RANDOMX_DATASET_BASE_SIZE must be a power of 2.");
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7 changes: 7 additions & 0 deletions src/randomx.cpp
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Expand Up @@ -34,6 +34,7 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#include "vm_compiled_light.hpp"
#include "blake2/blake2.h"
#include <cassert>
#include <limits>

extern "C" {

Expand Down Expand Up @@ -102,6 +103,12 @@ extern "C" {
}

randomx_dataset *randomx_alloc_dataset(randomx_flags flags) {

//fail on 32-bit systems if DatasetSize is >= 4 GiB
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Shouldn't the failure threshold be much smaller? At 4GiB there is no room in the address space for any other code or data.

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If the computer doesn't have enough virtual memory (which is likely) then the allocation will fail naturally.

This condition is in place to prevent an overflow which could make the allocation to falsely succeed. For example if DatasetSize is 4.5 GiB, it will overflow to 0.5 GiB on 32-bit systems and only 0.5 GiB will be allocated, leading to runtime crashes.

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ok

if (randomx::DatasetSize > std::numeric_limits<size_t>::max()) {
return nullptr;
}

randomx_dataset *dataset;

try {
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