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raw pointer dance for memory allocations and extra allocations
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this is probably the most significant source of consternation but
also this code path has been fairly well-trodden.

That being said it might be worth considering if there is any
way to use some of the new Rust const based reasoning logic
to see if we can't tighten this up someday, but today is not
that day.
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@bunnie
bunnie committed Dec 2, 2024
1 parent b591771 commit 4f21bf3
Showing 1 changed file with 37 additions and 32 deletions.
69 changes: 37 additions & 32 deletions kernel/src/mem.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -94,7 +94,7 @@ static mut EXTRA_REGIONS: &[MemoryRangeExtra] = &[];
/// MEM_ALLOCATIONS variable. The loop is likewise marked unsafe, because it accesses this static mut.
pub unsafe fn renormalize_allocs() -> u32 {
#[cfg(feature = "debug-swap-verbose")]
for (i, alloc) in MEMORY_ALLOCATIONS.iter().enumerate() {
for (i, alloc) in (&mut *(&raw mut MEMORY_ALLOCATIONS)).iter().enumerate() {
if alloc.get_raw_vpn() != 0 || alloc.get_timestamp() != 0 {
println!(" {:x}: {:08x}[{:x}]", i, alloc.get_raw_vpn(), alloc.get_timestamp());
}
Expand All @@ -104,13 +104,13 @@ pub unsafe fn renormalize_allocs() -> u32 {
let mut min_search_limit = 0;
loop {
let mut ms = crate::utils::MinSet::new();
for d in MEMORY_ALLOCATIONS.iter() {
for d in (&mut *(&raw mut MEMORY_ALLOCATIONS)).iter() {
if d.get_timestamp() >= min_search_limit {
ms.insert(d.get_timestamp());
}
}
// remap elements in d that match the minset
for d in MEMORY_ALLOCATIONS.iter_mut() {
for d in (&mut *(&raw mut MEMORY_ALLOCATIONS)).iter_mut() {
if let Some(i) = ms.index_of(d.get_timestamp()) {
d.set_timestamp(i as u32 + min_search_limit);
}
Expand All @@ -121,12 +121,12 @@ pub unsafe fn renormalize_allocs() -> u32 {
}
}
#[cfg(feature = "debug-swap-verbose")]
for (i, alloc) in MEMORY_ALLOCATIONS.iter().enumerate() {
for (i, alloc) in (&mut *(&raw mut MEMORY_ALLOCATIONS)).iter().enumerate() {
if alloc.get_raw_vpn() != 0 || alloc.get_timestamp() != 0 {
println!(" {:x}: {:08x}[{:x}]", i, alloc.get_raw_vpn(), alloc.get_timestamp());
}
}
MEMORY_ALLOCATIONS.iter().max().unwrap().get_timestamp()
(&mut *(&raw mut MEMORY_ALLOCATIONS)).iter().max().unwrap().get_timestamp()
}

/// Initialize the memory map.
Expand Down Expand Up @@ -191,7 +191,11 @@ impl MemoryManager {
let mut args_iter = args.iter();
let xarg_def = args_iter.next().expect("mm: no kernel arguments found");
unsafe {
assert!(EXTRA_REGIONS.is_empty(), "mm: self.extra.len() was {}, not 0", EXTRA_REGIONS.len());
assert!(
(&mut *(&raw mut EXTRA_REGIONS)).is_empty(),
"mm: self.extra.len() was {}, not 0",
(&mut *(&raw mut EXTRA_REGIONS)).len()
);
}
assert!(xarg_def.name == u32::from_le_bytes(*b"XArg"), "mm: first tag wasn't XArg");
assert!(xarg_def.data[1] == 1, "mm: XArg had unexpected version");
Expand All @@ -205,12 +209,12 @@ impl MemoryManager {
if tag.name == u32::from_le_bytes(*b"MREx") {
unsafe {
assert!(
EXTRA_REGIONS.is_empty(),
(&mut *(&raw mut EXTRA_REGIONS)).is_empty(),
"mm: MREx tag appears twice! self.extra.len() is {}, not 0",
EXTRA_REGIONS.len()
(&mut *(&raw mut EXTRA_REGIONS)).len()
);
let ptr = tag.data.as_ptr() as *mut MemoryRangeExtra;
EXTRA_REGIONS = slice::from_raw_parts_mut(
*(&mut *(&raw mut EXTRA_REGIONS)) = slice::from_raw_parts_mut(
ptr,
tag.data.len() * 4 / core::mem::size_of::<MemoryRangeExtra>(),
)
Expand All @@ -219,7 +223,7 @@ impl MemoryManager {
}

unsafe {
for range in EXTRA_REGIONS.iter() {
for range in (&mut *(&raw mut EXTRA_REGIONS)).iter() {
extra_size += range.mem_size as usize / PAGE_SIZE;
}
}
Expand Down Expand Up @@ -251,7 +255,7 @@ impl MemoryManager {
#[cfg(baremetal)]
#[cfg(not(feature = "swap"))]
unsafe {
for owner in &MEMORY_ALLOCATIONS[0..self.ram_size / PAGE_SIZE] {
for owner in &(&mut *(&raw mut MEMORY_ALLOCATIONS))[0..self.ram_size / PAGE_SIZE] {
if owner == &Some(pid) {
owned_bytes += PAGE_SIZE;
}
Expand All @@ -260,7 +264,7 @@ impl MemoryManager {
#[cfg(baremetal)]
#[cfg(feature = "swap")]
unsafe {
for owner in &MEMORY_ALLOCATIONS[0..self.ram_size / PAGE_SIZE] {
for owner in &(&mut *(&raw mut MEMORY_ALLOCATIONS))[0..self.ram_size / PAGE_SIZE] {
if owner.is_pid(pid) {
owned_bytes += PAGE_SIZE;
}
Expand All @@ -270,9 +274,10 @@ impl MemoryManager {
}

#[cfg(all(baremetal, feature = "debug-print"))]
#[allow(dead_code)]
pub fn print_ownership(&self) {
println!("Ownership ({} bytes in all):", unsafe {
MEMORY_ALLOCATIONS.len() + EXTRA_ALLOCATIONS.len()
(&mut *(&raw mut MEMORY_ALLOCATIONS)).len() + (&mut *(&raw mut EXTRA_ALLOCATIONS)).len()
});

let mut offset = 0;
Expand All @@ -292,24 +297,22 @@ impl MemoryManager {
};
#[cfg(feature = "swap")]
for o in 0..self.ram_size / PAGE_SIZE {
unsafe {
println!(
" {:08x} => {:?}",
self.ram_size + o * PAGE_SIZE,
MEMORY_ALLOCATIONS[offset + o].get_pid()
);
}
println!(
" {:08x} => {:?}",
self.ram_size + o * PAGE_SIZE,
(&mut *(&raw mut MEMORY_ALLOCATIONS))[offset + o].get_pid()
);
}

offset = 0;

// Go through additional regions looking for this address, and claim it
// if it's not in use.
unsafe {
for region in EXTRA_REGIONS {
for region in (&mut *(&raw mut EXTRA_REGIONS)).iter() {
println!(" Region {}:", region);
for o in 0..(region.mem_size as usize) / PAGE_SIZE {
if let Some(allocation) = EXTRA_ALLOCATIONS[offset + o] {
if let Some(allocation) = (&mut *(&raw mut EXTRA_ALLOCATIONS))[offset + o] {
println!(
" {:08x} => {}",
(region.mem_start as usize) + o * PAGE_SIZE,
Expand All @@ -332,10 +335,10 @@ impl MemoryManager {
unsafe {
let end_point = self.ram_size / PAGE_SIZE;
let starting_point = self.last_ram_page.max(end_point);
for (allocation, index) in MEMORY_ALLOCATIONS[starting_point..end_point]
for (allocation, index) in (&mut *(&raw mut MEMORY_ALLOCATIONS))[starting_point..end_point]
.iter_mut()
.zip(starting_point..)
.chain(MEMORY_ALLOCATIONS[..starting_point].iter_mut().zip(0..))
.chain((&mut *(&raw mut MEMORY_ALLOCATIONS))[..starting_point].iter_mut().zip(0..))
{
if allocation.is_none() {
*allocation = Some(pid);
Expand All @@ -355,7 +358,7 @@ impl MemoryManager {
pub fn touch(&self, paddr: usize) {
if paddr >= self.ram_start && paddr < self.ram_start + self.ram_size {
unsafe {
MEMORY_ALLOCATIONS[(paddr - self.ram_start) / PAGE_SIZE].touch();
(&mut *(&raw mut MEMORY_ALLOCATIONS))[(paddr - self.ram_start) / PAGE_SIZE].touch();
}
}
}
Expand All @@ -366,7 +369,7 @@ impl MemoryManager {

#[cfg(feature = "debug-swap")]
#[allow(dead_code)]
pub fn rpt_base(&self) -> usize { unsafe { MEMORY_ALLOCATIONS.as_ptr() as usize } }
pub fn rpt_base(&self) -> usize { unsafe { (&mut *(&raw mut MEMORY_ALLOCATIONS)).as_ptr() as usize } }

#[cfg(feature = "debug-swap")]
#[allow(dead_code)]
Expand All @@ -375,7 +378,9 @@ impl MemoryManager {
/// other context.
pub unsafe fn get_timestamp(&self, paddr: usize) -> u32 {
if paddr >= self.ram_start && paddr < self.ram_start + self.ram_size {
unsafe { MEMORY_ALLOCATIONS[(paddr - self.ram_start) / PAGE_SIZE].get_timestamp() }
unsafe {
(&mut *(&raw mut MEMORY_ALLOCATIONS))[(paddr - self.ram_start) / PAGE_SIZE].get_timestamp()
}
} else {
0xDEAD_BEEF
}
Expand All @@ -396,10 +401,10 @@ impl MemoryManager {
unsafe {
let end_point = self.ram_size / PAGE_SIZE;
let starting_point = self.last_ram_page.max(end_point);
for (allocation, index) in MEMORY_ALLOCATIONS[starting_point..end_point]
for (allocation, index) in (&mut *(&raw mut MEMORY_ALLOCATIONS))[starting_point..end_point]
.iter_mut()
.zip(starting_point..)
.chain(MEMORY_ALLOCATIONS[..starting_point].iter_mut().zip(0..))
.chain((&mut *(&raw mut MEMORY_ALLOCATIONS))[..starting_point].iter_mut().zip(0..))
{
if allocation.is_none() {
allocation.update(Some(pid), vaddr);
Expand Down Expand Up @@ -623,7 +628,7 @@ impl MemoryManager {
let mut range_start: Option<usize> = None;
let mut current_run = 0;
unsafe {
for (index, entry) in MEMORY_ALLOCATIONS.iter().enumerate() {
for (index, entry) in (&mut *(&raw mut MEMORY_ALLOCATIONS)).iter().enumerate() {
if entry.is_none() {
if let Some(_start) = range_start {
current_run += 1;
Expand Down Expand Up @@ -1021,7 +1026,7 @@ impl MemoryManager {
pub unsafe fn release_all_memory_for_process(&mut self, _pid: PID) {
// release the main memory allocs
#[cfg(baremetal)]
for (idx, owner) in MEMORY_ALLOCATIONS.iter_mut().enumerate() {
for (idx, owner) in (&mut *(&raw mut MEMORY_ALLOCATIONS)).iter_mut().enumerate() {
// If this address has been allocated to this process, consider
// freeing it or reparenting it.
#[cfg(not(feature = "swap"))]
Expand Down Expand Up @@ -1051,7 +1056,7 @@ impl MemoryManager {
}
// release the extra allocs
#[cfg(baremetal)]
for (idx, owner) in EXTRA_ALLOCATIONS.iter_mut().enumerate() {
for (idx, owner) in (&mut *(&raw mut EXTRA_ALLOCATIONS)).iter_mut().enumerate() {
if owner == &mut Some(_pid) {
let phys_addr = self.allocation_offset_to_address_extra(idx).unwrap();
if crate::arch::mem::page_is_lent(phys_addr as *mut u8) {
Expand Down

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