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[kernel] Implement VMA page tracking

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The previous method of VMA page tracking relied on the VMA always being
mapped at least into one space and just kept track of pages in the
spaces' page tables. This had a number of drawbacks, and the mapper
system was too complex without much benefit.

Now make VMAs themselves keep track of spaces that they're a part of,
and make them responsible for knowing what page goes where. This
simplifies most types of VMA greatly. The new vm_area_open (nee
vm_area_shared, but there is now no reason for most VMAs to be
explicitly shareable) adds a 64-ary radix tree for tracking allocated
pages.

The page_tree cannot yet handle taking pages away, but this isn't
something jsix can do yet anyway.
This commit is contained in:
Justin C. Miller
2021-01-31 22:18:44 -08:00
parent c364e30240
commit 634a1c5f6a
14 changed files with 412 additions and 411 deletions
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60
src/kernel/vm_space.cpp
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@@ -45,15 +45,15 @@ vm_space::vm_space() :
vm_space::~vm_space()
{
for (auto &a : m_areas)
a.area->mapper().remove(this);
for (auto &a : m_areas) {
bool free = a.area->remove_from(this);
clear(*a.area, 0, memory::page_count(a.area->size()), free);
a.area->handle_release();
}
kassert(!is_kernel(), "Kernel vm_space destructor!");
vm_space &kernel = kernel_space();
if (active())
kernel.activate();
kernel_space().activate();
// All VMAs have been removed by now, so just
// free all remaining pages and tables
@@ -71,7 +71,7 @@ vm_space::add(uintptr_t base, vm_area *area)
{
//TODO: check for collisions
m_areas.sorted_insert({base, area});
area->mapper().add(this);
area->add_to(this);
area->handle_retain();
return true;
}
@@ -81,8 +81,9 @@ vm_space::remove(vm_area *area)
{
for (auto &a : m_areas) {
if (a.area == area) {
bool free = area->remove_from(this);
clear(*area, 0, memory::page_count(area->size()), free);
m_areas.remove(a);
area->mapper().remove(this);
area->handle_release();
return true;
}
@@ -257,30 +258,6 @@ vm_space::initialize_tcb(TCB &tcb)
~memory::page_offset;
}
size_t
vm_space::allocate(uintptr_t virt, size_t count, uintptr_t *phys)
{
uintptr_t base = 0;
vm_area *area = get(virt, &base);
uintptr_t offset = (virt & ~0xfffull) - base;
if (!area || !area->allowed(offset))
return 0;
uintptr_t addr = 0;
size_t n = frame_allocator::get().allocate(count, &addr);
void *mem = memory::to_virtual<void>(addr);
if (area->flags() && vm_flags::zero)
kutil::memset(mem, 0, count * memory::frame_size);
area->commit(addr, offset, 1);
if (phys)
*phys = addr;
return n;
}
bool
vm_space::handle_fault(uintptr_t addr, fault_type fault)
{
@@ -288,9 +265,22 @@ vm_space::handle_fault(uintptr_t addr, fault_type fault)
if (fault && fault_type::present)
return false;
size_t n = allocate(addr, 1, nullptr);
kassert(n, "Failed to allocate a new page during page fault");
return n;
uintptr_t base = 0;
vm_area *area = get(addr, &base);
if (!area)
return false;
uintptr_t offset = (addr & ~0xfffull) - base;
uintptr_t phys_page = 0;
if (!area->get_page(offset, phys_page))
return false;
void *mem = memory::to_virtual<void>(phys_page);
if (area->flags() && vm_flags::zero)
kutil::memset(mem, 0, memory::frame_size);
page_in(*area, offset, phys_page, 1);
return true;
}
size_t