Add function to pre-populate large heap objects PML4.

This becomes necessary once we made dispatcher allocation
lazy. Since we didn't have this PT slot initialized before
we spawned an ELF binary.

Author: gz

Cargo.lock

@@ -46,7 +46,7 @@ bit_field = "0.10"
 crossbeam-queue = { version = "0.3", default-features = false, features = ["alloc"] }
 arrayvec = { version = "0.7.0", default-features = false }
 memoffset = { version = "0.6.5", features = ["unstable_const"] }
-fallible_collections = { git = "https://github.com/gz/fallible_collections.git", branch = "allocator_api2", features = ["unstable", "rust_1_57"] }
+fallible_collections = { git = "https://github.com/gz/fallible_collections.git", branch = "allocator_api3", features = ["unstable", "rust_1_57"] }
 # Should be optional (but currently aren't, TODO)
 gimli = { version = "0.26", default-features = false, features = ["read", "endian-reader"] }
 gdbstub = { git = "https://github.com/daniel5151/gdbstub.git", branch = "dev/0.6", default-features = false, features = ["alloc"] }

kernel/Cargo.toml

@@ -372,6 +372,8 @@ fn _start(argc: isize, _argv: *const *const u8) -> isize {
     dyn_mem.set_global_pmem(&global_memory_static);
     core::mem::forget(dyn_mem);
 
+    unsafe { vspace::init_large_objects_pml4() };
+
     // Set-up interrupt routing drivers (I/O APIC controllers)
     irq::ioapic_initialize();
 

kernel/src/arch/x86_64/mod.rs

@@ -7,7 +7,7 @@ use core::ops::Bound::*;
 use fallible_collections::btree::BTreeMap;
 use lazy_static::lazy_static;
 use spin::Mutex;
-use x86::current::paging::{PDFlags, PDPTFlags, PTFlags};
+use x86::current::paging::{PDFlags, PDPTFlags, PTFlags, PML4Flags, PML4Entry};
 
 mod debug;
 pub mod page_table; /* TODO(encapsulation): This should be a private module but we break encapsulation in a few places */
@@ -18,7 +18,7 @@ use crate::error::KError;
 use crate::memory::{detmem::DA, vspace::*};
 use crate::memory::{Frame, PAddr, VAddr};
 
-use page_table::PageTable;
+use page_table::{PT_LAYOUT, PageTable};
 
 lazy_static! {
     /// A handle to the initial kernel address space (created for us by the
@@ -83,6 +83,27 @@ lazy_static! {
     };
 }
 
+/// We insert a pml4 slot for the big kernel allocated objects, this ensures
+/// that the PML4 entry is already there when we create a ELF process and
+/// patch-in the kernel mappings. Otherwise we don't have a mapping and lose
+/// access to big malloc'd objects in the kernel once we switch to a user-space
+/// page-table.
+///
+/// # TODO
+/// - This clearly needs a better solution. See also the part where we patch
+///   this into the process page-table.
+pub(crate) unsafe fn init_large_objects_pml4() {
+    log::info!("init_large_objects_pml4()");
+    let mut vspace = INITIAL_VSPACE.lock();
+    let frame_ptr = alloc::alloc::alloc(PT_LAYOUT);
+
+    let vaddr = VAddr::from(frame_ptr as *const u8 as u64);
+    let paddr = crate::arch::memory::kernel_vaddr_to_paddr(vaddr);
+    let mut frame = Frame::new(paddr, PT_LAYOUT.size(), 0);
+    frame.zero();
+    (*vspace.pml4)[132] = PML4Entry::new(frame.base, PML4Flags::P | PML4Flags::RW);
+}
+
 pub(crate) struct VSpace {
     pub mappings: BTreeMap<VAddr, MappingInfo>,
     pub page_table: PageTable,

kernel/src/arch/x86_64/vspace/mod.rs

@@ -17,7 +17,7 @@ use crate::memory::vspace::*;
 use crate::memory::{kernel_vaddr_to_paddr, paddr_to_kernel_vaddr, Frame, PAddr, VAddr};
 
 /// Describes a potential modification operation on existing page tables.
-const PT_LAYOUT: Layout =
+pub(super) const PT_LAYOUT: Layout =
     unsafe { Layout::from_size_align_unchecked(BASE_PAGE_SIZE, BASE_PAGE_SIZE) };
 // Safety (size not overflowing when rounding up is given with size == align):
 static_assertions::const_assert!(BASE_PAGE_SIZE > 0); // align must not be zero