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Address code review feedback

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- Define EFI_MEMORY_DESCRIPTOR struct for better code clarity
- Use PAGE_SIZE constant instead of magic number 4096
- Add check in freePage() to prevent usedPages underflow

Co-authored-by: johndoe6345789 <224850594+johndoe6345789@users.noreply.github.com>
This commit is contained in:
copilot-swe-agent[bot]
2025-12-28 23:22:08 +00:00
parent 4051edd198
commit 90ccd7c4db
1 changed files with 16 additions and 9 deletions
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25
kernel/src/memory.cpp
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@@ -12,6 +12,15 @@
// Physical memory bitmap constants // Physical memory bitmap constants
#define BITMAP_SIZE 2097152 // Supports up to 64GB with 4KB pages (64GB / 4KB = 16M pages, 16M bits = 2MB bitmap) #define BITMAP_SIZE 2097152 // Supports up to 64GB with 4KB pages (64GB / 4KB = 16M pages, 16M bits = 2MB bitmap)
// EFI Memory Descriptor structure (from UEFI spec)
struct EFI_MEMORY_DESCRIPTOR {
uint32_t Type;
uint64_t PhysicalStart;
uint64_t VirtualStart;
uint64_t NumberOfPages;
uint64_t Attribute;
};
/* PhysicalMemoryManager class implementation */ /* PhysicalMemoryManager class implementation */
/** /**
@@ -68,14 +77,7 @@ void PhysicalMemoryManager::init(BootInfo* bootInfo) {
// First pass: find highest usable address and mark free pages // First pass: find highest usable address and mark free pages
for (uint64_t i = 0; i < num_descriptors; i++) { for (uint64_t i = 0; i < num_descriptors; i++) {
// Cast to EFI_MEMORY_DESCRIPTOR structure EFI_MEMORY_DESCRIPTOR* desc = (EFI_MEMORY_DESCRIPTOR*)(map + i * descriptor_size);
struct {
uint32_t Type;
uint64_t PhysicalStart;
uint64_t VirtualStart;
uint64_t NumberOfPages;
uint64_t Attribute;
}* desc = (decltype(desc))(map + i * descriptor_size);
// Check if this is a usable memory type // Check if this is a usable memory type
bool is_usable = (desc->Type == EfiConventionalMemory || bool is_usable = (desc->Type == EfiConventionalMemory ||
@@ -86,7 +88,7 @@ void PhysicalMemoryManager::init(BootInfo* bootInfo) {
if (is_usable) { if (is_usable) {
uint64_t region_start = desc->PhysicalStart; uint64_t region_start = desc->PhysicalStart;
uint64_t region_size = desc->NumberOfPages * 4096; // EFI pages are 4KB uint64_t region_size = desc->NumberOfPages * PAGE_SIZE; // EFI pages are 4KB
uint64_t region_end = region_start + region_size; uint64_t region_end = region_start + region_size;
// Only consider memory at or above MEMORY_BASE // Only consider memory at or above MEMORY_BASE
@@ -211,6 +213,11 @@ void PhysicalMemoryManager::freePage(void* page) {
return; return;
} }
// Check if page is already free to prevent underflow
if (!(pageBitmap[byte] & (1 << bit))) {
return; // Already free, nothing to do
}
// Mark as free // Mark as free
pageBitmap[byte] &= ~(1 << bit); pageBitmap[byte] &= ~(1 << bit);
usedPages--; usedPages--;