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[kernel] Move the page table cache into page_table

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Further chipping away at page_manager: the cache of pages to be used as
page tables gets moved to a static in page_table.
This commit is contained in:
Justin C. Miller
2020-09-17 21:30:05 -07:00
parent 09575370ce
commit ac67111b83
7 changed files with 86 additions and 71 deletions
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58
src/kernel/page_table.cpp
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@@ -8,6 +8,11 @@
using memory::page_offset;
using level = page_table::level;
extern frame_allocator &g_frame_allocator;
free_page_header * page_table::s_page_cache = nullptr;
size_t page_table::s_cache_count = 0;
// Flags: 0 0 0 0 0 0 0 0 0 0 1 1 = 0x0003
// IGNORED | | | | | | | +- Present
// | | | | | | +--- Writeable
@@ -20,6 +25,7 @@ using level = page_table::level;
/// Page table entry flags for entries pointing at another table
constexpr uint16_t table_flags = 0x003;
page_table::iterator::iterator(uintptr_t virt, page_table *pml4) :
m_table {pml4, 0, 0, 0}
{
@@ -157,9 +163,6 @@ page_table::iterator::ensure_table(level l)
if (l == level::pml4 || l > level::pt) return;
if (check_table(l)) return;
// TODO: a better way to get at the frame allocator
extern frame_allocator g_frame_allocator;
uintptr_t phys = 0;
size_t n = g_frame_allocator.allocate(1, &phys);
kassert(n, "Failed to allocate a page table");
@@ -195,6 +198,55 @@ page_table::set(int i, page_table *p, uint16_t flags)
(flags & 0xfff);
}
struct free_page_header { free_page_header *next; };
page_table *
page_table::get_table_page()
{
if (!s_cache_count)
fill_table_page_cache();
free_page_header *page = s_page_cache;
s_page_cache = s_page_cache->next;
--s_cache_count;
return reinterpret_cast<page_table*>(page);
}
void
page_table::free_table_page(page_table *pt)
{
free_page_header *page =
reinterpret_cast<free_page_header*>(pt);
page->next = s_page_cache;
s_page_cache = page->next;
++s_cache_count;
}
void
page_table::fill_table_page_cache()
{
constexpr size_t min_pages = 16;
while (s_cache_count < min_pages) {
uintptr_t phys = 0;
size_t n = g_frame_allocator.allocate(min_pages - s_cache_count, &phys);
free_page_header *start =
memory::to_virtual<free_page_header>(phys);
for (int i = 0; i < n - 1; ++i)
kutil::offset_pointer(start, i * memory::frame_size)
->next = kutil::offset_pointer(start, (i+1) * memory::frame_size);
free_page_header *end =
kutil::offset_pointer(start, (n-1) * memory::frame_size);
end->next = s_page_cache;
s_page_cache = start;
s_cache_count += n;
}
}
void
page_table::dump(page_table::level lvl, bool recurse)