[Mammoth] Write a custom buddy allocator to replace libc malloc.
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@ -1,6 +1,5 @@
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add_library(c STATIC
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src/malloc.cpp
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src/string.cpp
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)
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@ -1,5 +0,0 @@
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#pragma once
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#include "stddef.h"
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void* malloc(size_t size);
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@ -1,46 +0,0 @@
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#include <zcall.h>
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#include <zglobal.h>
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#include "stdlib.h"
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namespace {
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class NaiveAllocator {
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public:
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constexpr static uint64_t kSize = 0x10000;
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NaiveAllocator() {}
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bool is_init() { return next_addr_ != 0; }
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void Init() {
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uint64_t vmmo_cap;
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uint64_t err = ZMemoryObjectCreate(kSize, &vmmo_cap);
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if (err != 0) {
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(void)ZProcessExit(err);
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}
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err = ZAddressSpaceMap(gSelfVmasCap, 0, vmmo_cap, 0, &next_addr_);
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max_addr_ = next_addr_ + kSize;
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}
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void* Allocate(size_t size) {
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uint64_t addr = next_addr_;
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next_addr_ += size;
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if (next_addr_ >= max_addr_) {
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(void)ZProcessExit(0xBEEF);
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return 0;
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}
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return reinterpret_cast<void*>(addr);
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}
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private:
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uint64_t next_addr_ = 0;
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uint64_t max_addr_ = 0;
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};
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NaiveAllocator gAlloc;
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} // namespace
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void* malloc(size_t size) {
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if (!gAlloc.is_init()) {
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gAlloc.Init();
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}
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return gAlloc.Allocate(size);
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}
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@ -1,8 +1,166 @@
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#include <glacier/container/intrusive_list.h>
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#include <glacier/string/str_format.h>
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#include <stdint.h>
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#include <stdlib.h>
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#include <zcall.h>
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#include <zglobal.h>
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[[nodiscard]] void* operator new(uint64_t size) { return malloc(size); }
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[[nodiscard]] void* operator new[](uint64_t size) { return malloc(size); }
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#include "util/debug.h"
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namespace {
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class PageAllocator {
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public:
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static uint64_t AllocatePagePair() {
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uint64_t mem_cap;
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check(ZMemoryObjectCreate(0x2000, &mem_cap));
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uint64_t vaddr;
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check(ZAddressSpaceMap(gSelfVmasCap, 0, mem_cap, /* align= */ 0x2000,
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&vaddr));
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// The address space mapping will keep this memory capability alive.
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check(ZCapRelease(mem_cap));
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return vaddr;
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}
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};
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struct BuddySlot {
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BuddySlot* next;
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BuddySlot* prev;
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uint64_t size;
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};
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uint64_t NeededSize(uint64_t size) {
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uint64_t needed = size + sizeof(BuddySlot);
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// Start at 32 because sizeof(BuddySlot) is already 24;
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uint64_t pow2 = 32;
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while (pow2 < needed) {
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pow2 <<= 1;
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}
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return pow2;
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}
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class BuddyAllocator {
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public:
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BuddyAllocator() {}
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void Init() {
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free_front_ = nullptr;
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AddPage();
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check(ZMutexCreate(&mutex_cap_));
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}
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void* Allocate(uint64_t size) {
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check(ZMutexLock(mutex_cap_));
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if (size > (0x2000 - sizeof(BuddySlot))) {
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crash("Can't allocate greater than one page", glcr::UNIMPLEMENTED);
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}
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if (free_front_ == nullptr) {
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AddPage();
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}
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BuddySlot* slot = free_front_;
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uint64_t needed = NeededSize(size);
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BuddySlot* best_fit = nullptr;
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while (slot != nullptr) {
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bool fits = slot->size >= needed;
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bool better = best_fit == nullptr || slot->size < best_fit->size;
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if (fits && better) {
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best_fit = slot;
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}
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slot = slot->next;
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}
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if (best_fit == nullptr) {
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AddPage();
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best_fit = free_front_;
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}
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while (best_fit->size > needed) {
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best_fit = Split(best_fit);
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}
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Remove(best_fit);
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// TODO: We may need to align the pointer here.
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void* ptr = reinterpret_cast<uint8_t*>(best_fit) + sizeof(BuddySlot);
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check(ZMutexRelease(mutex_cap_));
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return ptr;
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}
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private:
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BuddySlot* free_front_ = nullptr;
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z_cap_t mutex_cap_ = 0;
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void AddPage() {
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uint64_t vaddr = PageAllocator::AllocatePagePair();
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BuddySlot* slot = reinterpret_cast<BuddySlot*>(vaddr);
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slot->prev = nullptr;
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slot->next = free_front_;
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free_front_ = slot;
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slot->size = 0x2000;
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}
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BuddySlot* Split(BuddySlot* slot) {
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if (slot->size <= 32) {
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crash("Splitting smallest buddy chunk", glcr::INTERNAL);
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}
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slot->size /= 2;
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BuddySlot* new_slot = reinterpret_cast<BuddySlot*>(
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reinterpret_cast<uint64_t>(slot) ^ slot->size);
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new_slot->size = slot->size;
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new_slot->next = slot->next;
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new_slot->prev = slot;
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if (slot->next) {
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slot->next->prev = new_slot;
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}
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slot->next = new_slot;
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return slot;
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}
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void Remove(BuddySlot* slot) {
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if (slot->prev) {
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slot->prev->next = slot->next;
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}
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if (slot->next) {
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slot->next->prev = slot->prev;
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}
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if (free_front_ == slot) {
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free_front_ = slot->next;
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}
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slot->next = nullptr;
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slot->prev = nullptr;
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}
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};
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BuddyAllocator gAllocator;
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bool gHasInit = false;
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// FIXME: Race condition.
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void* Allocate(uint64_t size) {
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if (!gHasInit) {
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// Call Init since we don't call global constructors yet.
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gAllocator.Init();
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gHasInit = true;
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}
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void* ptr = gAllocator.Allocate(size);
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char buffer[64];
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// glcr::FixedStringBuilder builder(buffer, 64);
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// glcr::StrFormatIntoBuffer(builder, "Allocated {x}", (uint64_t)ptr);
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// dbgln(builder.operator glcr::StringView());
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return ptr;
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}
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} // namespace
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[[nodiscard]] void* operator new(uint64_t size) { return Allocate(size); }
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[[nodiscard]] void* operator new[](uint64_t size) { return Allocate(size); }
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void operator delete(void*, uint64_t) {}
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void operator delete[](void*) {}
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@ -6,7 +6,6 @@
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#include <mammoth/util/debug.h>
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#include <mammoth/util/init.h>
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#include <mammoth/util/memory_region.h>
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#include <stdlib.h>
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#include <zcall.h>
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#include "hw/gpt.h"
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