85 lines
2.6 KiB
C
Executable File
85 lines
2.6 KiB
C
Executable File
// Yet another shot at a frame manager... This time, instead of focusing on
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// something unnecessarily complex, I'll try something simpler: an alloc-only
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// frame manager. I wasn't even freeing them anyway, and I don't think I'll ever
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// need that. All the hardcore memory allocation will be done on the kernel heap
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// anyway.
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//
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// tl;dr - want to free a frame? memory leaks ahoy.
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//
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// I want this to be as simple as a 'top' pointer, pointing to the next address
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// of the physical memory that is free. There are two things to watch out for,
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// though:
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// o unusable memory regions
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// o max memory size
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// We'll solve the first problem by asking system.c whether we can use a provided
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// region. It used to work the previosu way around, but I'm not going to keep a
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// list of unusable regions both here and in system.c...
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// The second problem is solved by also keeping a max memory size, and throwing
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// a kernel panic when we reach it. It could use an exception system, but since
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// this code will only be called from low-level system routines, if it actually
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// happens that we run out of memory... We're probably badly screwed, anyway.
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#include "Tier0/physmem.h"
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#include "Tier0/system.h"
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#include "Tier0/kstdio.h"
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#include "Tier0/panic.h"
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#include "Tier0/paging.h"
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// The amount of memory in the system, or the top usable pointer.
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u64 g_MemorySize;
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// The current pointer to the top of the frame stack.
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u64 g_TopFrame;
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void physmem_init(u64 MemorySize)
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{
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g_TopFrame = 0;
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g_MemorySize = MemorySize;
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}
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u64 physmem_allocate_page(void)
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{
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u64 NextPageStart = g_TopFrame;
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while (!system_memory_available(NextPageStart, PHYSMEM_PAGE_SIZE))
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{
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NextPageStart += PHYSMEM_PAGE_SIZE;
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if (NextPageStart > g_MemorySize)
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PANIC("Out of memory!");
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}
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return NextPageStart / PHYSMEM_PAGE_SIZE;
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}
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u64 physmem_page_to_physical(u64 Page)
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{
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return Page * PHYSMEM_PAGE_SIZE;
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}
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u64 physmem_physical_to_page(u64 Physical)
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{
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return Physical / PHYSMEM_PAGE_SIZE;
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}
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void physmem_read(u64 Base, u64 Size, void *Destination)
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{
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u8 *DataSource = (u8 *)paging_temp_page_get_virtual();
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u64 OffsetInSource = Base & 0xFFF;
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u64 PreviousPageBase = Base & ~((u64)0xFFF);
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paging_temp_page_set_physical(PreviousPageBase);
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for (u64 i = 0; i < Size; i++)
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{
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u64 PageBase = (Base + i) & ~((u64)0xFFF);
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if (PageBase != PreviousPageBase)
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paging_temp_page_set_physical(PageBase);
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PreviousPageBase = PageBase;
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*((u8 *)Destination + i) = DataSource[OffsetInSource % 4096];
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OffsetInSource++;
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}
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}
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