Bananymous/banan-os
1
1
Fork 1
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Kernel: Add barebones per process virtual addresses

Browse Source 
We now assign every (userspace) process its own MMU which we load
in scheduler. This allows every process to have separate virtual
address space.

This is very hackish implementations but it works for now
This commit is contained in:
Bananymous
2023-04-20 00:45:41 +03:00
parent b3eeb6412f
commit 3aa0eeb4a3
8 changed files with 134 additions and 33 deletions
Download Patch File Download Diff File Expand all files Collapse all files

81
kernel/arch/x86_64/MMU.cpp
View File

@@ -8,15 +8,18 @@
#define CLEANUP_STRUCTURE(s) \
for (uint64_t i = 0; i < 512; i++) \
if (s[i] & Flags::Present) \
goto cleanup_done; \
return; \
kfree(s)
static MMU* s_instance = nullptr;
void MMU::intialize()
void MMU::initialize()
{
ASSERT(s_instance == nullptr);
s_instance = new MMU();
ASSERT(s_instance);
s_instance->initialize_kernel();
s_instance->load();
}
MMU& MMU::get()
@@ -33,10 +36,14 @@ static uint64_t* allocate_page_aligned_page()
return (uint64_t*)page;
}
MMU::MMU()
extern uint8_t g_kernel_end[];
void MMU::initialize_kernel()
{
// FIXME: We should just identity map until g_kernel_end
ASSERT((uintptr_t)g_kernel_end <= 6 * (1 << 20));
// Identity map from 0 -> 6 MiB
m_highest_paging_struct = allocate_page_aligned_page();
@@ -57,9 +64,55 @@ MMU::MMU()
// Unmap 0 -> 4 KiB
uint64_t* pt1 = (uint64_t*)(pd[0] & PAGE_MASK);
pt1[0] = 0;
}
// Load the new pml4
asm volatile("movq %0, %%cr3" :: "r"(m_highest_paging_struct));
MMU::MMU()
{
if (s_instance == nullptr)
return;
// Here we copy the s_instances paging structs since they are
// global for every process
uint64_t* global_pml4 = s_instance->m_highest_paging_struct;
uint64_t* pml4 = allocate_page_aligned_page();
for (uint32_t pml4e = 0; pml4e < 512; pml4e++)
{
if (!(global_pml4[pml4e] & Flags::Present))
continue;
uint64_t* global_pdpt = (uint64_t*)(global_pml4[pml4e] & PAGE_MASK);
uint64_t* pdpt = allocate_page_aligned_page();
pml4[pml4e] = (uint64_t)pdpt | (global_pml4[pml4e] & ~PAGE_MASK);
for (uint32_t pdpte = 0; pdpte < 512; pdpte++)
{
if (!(global_pdpt[pdpte] & Flags::Present))
continue;
uint64_t* global_pd = (uint64_t*)(global_pdpt[pdpte] & PAGE_MASK);
uint64_t* pd = allocate_page_aligned_page();
pdpt[pdpte] = (uint64_t)pd | (global_pdpt[pdpte] & ~PAGE_MASK);
for (uint32_t pde = 0; pde < 512; pde++)
{
if (!(global_pd[pde] & Flags::Present))
continue;
uint64_t* global_pt = (uint64_t*)(global_pd[pde] & PAGE_MASK);
uint64_t* pt = allocate_page_aligned_page();
pd[pde] = (uint64_t)pt | (global_pd[pde] & ~PAGE_MASK);
memcpy(pt, global_pt, PAGE_SIZE);
}
}
}
m_highest_paging_struct = pml4;
}
MMU::~MMU()
@@ -88,6 +141,11 @@ MMU::~MMU()
kfree(pml4);
}
void MMU::load()
{
asm volatile("movq %0, %%cr3" :: "r"(m_highest_paging_struct));
}
void MMU::map_page(uintptr_t address, uint8_t flags)
{
address &= PAGE_MASK;
@@ -137,9 +195,6 @@ void MMU::unmap_page(uintptr_t address)
pdpt[pdpte] = 0;
CLEANUP_STRUCTURE(pdpt);
pml4[pml4e] = 0;
cleanup_done:
asm volatile("invlpg (%0)" :: "r"(address) : "memory");
}
void MMU::unmap_range(uintptr_t address, ptrdiff_t size)
@@ -159,7 +214,6 @@ void MMU::map_page_at(paddr_t paddr, vaddr_t vaddr, uint8_t flags)
ASSERT((vaddr & ~PAGE_MASK) == 0);;
ASSERT(flags & Flags::Present);
bool should_invalidate = false;
uint64_t pml4e = (vaddr >> 39) & 0x1FF;
uint64_t pdpte = (vaddr >> 30) & 0x1FF;
@@ -172,7 +226,6 @@ void MMU::map_page_at(paddr_t paddr, vaddr_t vaddr, uint8_t flags)
if (!(pml4[pml4e] & Flags::Present))
pml4[pml4e] = (uint64_t)allocate_page_aligned_page();
pml4[pml4e] = (pml4[pml4e] & PAGE_MASK) | flags;
should_invalidate = true;
}
uint64_t* pdpt = (uint64_t*)(pml4[pml4e] & PAGE_MASK);
@@ -181,7 +234,6 @@ void MMU::map_page_at(paddr_t paddr, vaddr_t vaddr, uint8_t flags)
if (!(pdpt[pdpte] & Flags::Present))
pdpt[pdpte] = (uint64_t)allocate_page_aligned_page();
pdpt[pdpte] = (pdpt[pdpte] & PAGE_MASK) | flags;
should_invalidate = true;
}
uint64_t* pd = (uint64_t*)(pdpt[pdpte] & PAGE_MASK);
@@ -190,16 +242,9 @@ void MMU::map_page_at(paddr_t paddr, vaddr_t vaddr, uint8_t flags)
if (!(pd[pde] & Flags::Present))
pd[pde] = (uint64_t)allocate_page_aligned_page();
pd[pde] = (pd[pde] & PAGE_MASK) | flags;
should_invalidate = true;
}
uint64_t* pt = (uint64_t*)(pd[pde] & PAGE_MASK);
if ((pt[pte] & flags) != flags)
{
pt[pte] = paddr | flags;
should_invalidate = true;
}
if (should_invalidate)
asm volatile("movq %0, %%cr3" :: "r"(m_highest_paging_struct));
}