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Assert on NX bit

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This commit is contained in:
Fabian 2022-01-14 13:45:12 -06:00
parent f72d0a9ca0
commit ff22df3f9c
1 changed files with 19 additions and 18 deletions
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37
src/rust/cpu/cpu.rs
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@ -1797,20 +1797,17 @@ pub unsafe fn do_page_translation(addr: i32, for_writing: bool, user: bool) -> O
}
}
/*
* 32-bit paging:
* - 10 bits PD | 10 bits PT | 12 bits offset
* - 10 bits PD | 22 bits offset (4MB huge page)
*
* PAE paging:
* - 2 bits PDPT | 9 bits PD | 9 bits PT | 12 bits offset
* - 2 bits PDPT | 9 bits PD | 21 bits offset (2MB huge page)
*
* Note that PAE entries are 64-bit, and can describe physical addresses over 32
* bits. However, since we support only 32-bit physical addresses, we require
* the high half of the entry to be 0 (except for the execute-disable bit in
* PDE and PTE).
*/
// 32-bit paging:
// - 10 bits PD | 10 bits PT | 12 bits offset
// - 10 bits PD | 22 bits offset (4MB huge page)
//
// PAE paging:
// - 2 bits PDPT | 9 bits PD | 9 bits PT | 12 bits offset
// - 2 bits PDPT | 9 bits PD | 21 bits offset (2MB huge page)
//
// Note that PAE entries are 64-bit, and can describe physical addresses over 32
// bits. However, since we support only 32-bit physical addresses, we require
// the high half of the entry to be 0.
pub unsafe fn do_page_walk(
addr: i32,
for_writing: bool,
@ -2015,12 +2012,14 @@ unsafe fn walk_page_directory(pae: bool, addr: i32) -> Option<(i32, i32)> {
let page_dir_addr = ((pdpt_entry as u32 & 0xFFFFF000)>> 2).wrapping_add(page_dir_idx << 1);
let page_dir_entry = read_aligned64(page_dir_addr);
// Note that the highest bit of PDE specifies execute-disable, and can
// be set (we'll ignore it anyway).
dbg_assert!(
page_dir_entry as u64 & 0x7FFF_FFFF_0000_0000 == 0,
"Unsupported: Page directory entry larger than 32 bits"
);
dbg_assert!(
page_dir_entry & 0x8000_0000_0000_0000u64 as i64 == 0,
"Unsupported: NX bit"
);
return Some((page_dir_addr as i32, page_dir_entry as i32));
}
@ -2041,12 +2040,14 @@ unsafe fn walk_page_table(
let page_table_idx = (addr as u32 >> 12) & 0x1FF;
let page_table_addr = page_table.wrapping_add(page_table_idx << 1);
let page_table_entry = read_aligned64(page_table_addr);
// Note that the highest bit of PTE specifies execute-disable, and can
// be set (we'll ignore it anyway).
dbg_assert!(
page_table_entry as u64 & 0x7FFF_FFFF_0000_0000 == 0,
"Unsupported: Page table entry larger than 32 bits"
);
dbg_assert!(
page_table_entry & 0x8000_0000_0000_0000u64 as i64 == 0,
"Unsupported: NX bit"
);
return (page_table_addr as i32, page_table_entry as i32);
}