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fix(mman): don't deallocate PROT_NONE frames #2008

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Merged
merged 2 commits into from
Oct 23, 2025
Merged

fix(mman): don't deallocate PROT_NONE frames #2008

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d08e3c2
style(mman): rename variables for clarity
mkroening Oct 22, 2025
0cc67df
fix(mman): don't deallocate PROT_NONE frames
mkroening Oct 22, 2025
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24 changes: 17 additions & 7 deletions src/syscalls/mman.rs
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Original file line number Diff line number Diff line change
@@ -1,7 +1,8 @@
use core::ffi::{c_int, c_void};

use align_address::Align;
use free_list::{PageLayout, PageRange};
use free_list::{FreeList, PageLayout, PageRange};
use hermit_sync::SpinMutex;
use memory_addresses::{PhysAddr, VirtAddr};

use crate::arch;
Expand All @@ -26,6 +27,8 @@ bitflags! {
}
}

static PROT_NONE_FREE_LIST: SpinMutex<FreeList<16>> = SpinMutex::new(FreeList::new());

/// Creates a new virtual memory mapping of the `size` specified with
/// protection bits specified in `prot_flags`.
#[hermit_macro::system(errno)]
Expand All @@ -37,6 +40,9 @@ pub extern "C" fn sys_mmap(size: usize, prot_flags: MemoryProtection, ret: &mut
let virtual_address = VirtAddr::from(page_range.start());
if prot_flags.is_empty() {
*ret = virtual_address.as_mut_ptr();
unsafe {
PROT_NONE_FREE_LIST.lock().deallocate(page_range).unwrap();
}
return 0;
}
let frame_layout = PageLayout::from_size(size).unwrap();
Expand Down Expand Up @@ -67,6 +73,11 @@ pub extern "C" fn sys_mmap(size: usize, prot_flags: MemoryProtection, ret: &mut
pub extern "C" fn sys_munmap(ptr: *mut u8, size: usize) -> i32 {
let virtual_address = VirtAddr::from_ptr(ptr);
let size = size.align_up(BasePageSize::SIZE as usize);
let page_range = PageRange::from_start_len(virtual_address.as_usize(), size).unwrap();

if PROT_NONE_FREE_LIST.lock().allocate_at(page_range).is_ok() {
return 0;
}

if let Some(physical_address) = arch::mm::paging::virtual_to_physical(virtual_address) {
arch::mm::paging::unmap::<BasePageSize>(
Expand All @@ -75,16 +86,15 @@ pub extern "C" fn sys_munmap(ptr: *mut u8, size: usize) -> i32 {
);
debug!("Unmapping {virtual_address:X} ({size}) -> {physical_address:X}");

let range = PageRange::from_start_len(physical_address.as_u64() as usize, size).unwrap();
if let Err(_err) = unsafe { PHYSICAL_FREE_LIST.lock().deallocate(range) } {
// FIXME: return EINVAL instead, once wasmtime can handle it
error!("Unable to deallocate {range:?}");
let frame_range =
PageRange::from_start_len(physical_address.as_u64() as usize, size).unwrap();
unsafe {
PHYSICAL_FREE_LIST.lock().deallocate(frame_range).unwrap();
}
}

let range = PageRange::from_start_len(virtual_address.as_usize(), size).unwrap();
unsafe {
KERNEL_FREE_LIST.lock().deallocate(range).unwrap();
KERNEL_FREE_LIST.lock().deallocate(page_range).unwrap();
}

0
Expand Down