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[boot] Add PD tables for all kernel PML4 entries

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Process PML4s all point their high (kernelspace) entries at the same set
of PDs, but that copying only happens on process creation. New PDs added
to the kernel PML4 won't get shared among other PML4s. This change
instantiates empty PDs for all PML4 entries in the higher half to make
sure this can't happen.
This commit is contained in:
Justin C. Miller
2020-08-02 18:06:41 -07:00
parent 911b4c0b10
commit cf582c4ce4
1 changed files with 20 additions and 2 deletions
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22
src/boot/paging.cpp
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@@ -11,6 +11,8 @@ namespace boot {
namespace paging {
using memory::page_size;
using ::memory::pml4e_kernel;
using ::memory::table_entries;
// Flags: 0 0 0 1 0 0 0 0 0 0 1 1 = 0x0103
// IGN | | | | | | | | +- Present
@@ -157,6 +159,16 @@ add_offset_mappings(page_table *pml4, void *&page_cache, uint32_t &num_pages)
}
}
static void
add_kernel_pds(page_table *pml4, void *&page_cache, uint32_t &num_pages)
{
for (unsigned i = pml4e_kernel; i < table_entries; ++i) {
pml4->set(i, page_cache, table_flags);
page_cache = offset_ptr<void>(page_cache, page_size);
num_pages--;
}
}
void
add_current_mappings(page_table *new_pml4)
{
@@ -177,8 +189,13 @@ allocate_tables(kernel::args::header *args, uefi::boot_services *bs)
{
status_line status(L"Allocating initial page tables");
static constexpr size_t offset_map_tables = 128 + 1;
static constexpr size_t tables_needed = offset_map_tables + 49;
static constexpr size_t pd_tables = 256; // number of pages for kernelspace PDs
static constexpr size_t extra_tables = 49; // number of extra pages
// number of pages for kernelspace PDs + PML4
static constexpr size_t kernel_tables = pd_tables + 1;
static constexpr size_t tables_needed = kernel_tables + extra_tables;
void *addr = nullptr;
try_or_raise(
@@ -201,6 +218,7 @@ allocate_tables(kernel::args::header *args, uefi::boot_services *bs)
args->page_table_cache = offset_ptr<void>(addr, page_size);
page_table *pml4 = reinterpret_cast<page_table*>(addr);
add_kernel_pds(pml4, args->page_table_cache, args->num_free_tables);
add_offset_mappings(pml4, args->page_table_cache, args->num_free_tables);
console::print(L" Set up initial mappings, %d spare tables.\r\n", args->num_free_tables);