Rustc panicked struct cannot be packed and aligned #83107
Labels
A-layout
Area: Memory layout of types
C-bug
Category: This is a bug.
glacier
ICE tracked in rust-lang/glacier.
I-ICE
Issue: The compiler panicked, giving an Internal Compilation Error (ICE) ❄️
P-medium
Medium priority
T-compiler
Relevant to the compiler team, which will review and decide on the PR/issue.
Comments
Andy-Python-Programmer
added
C-bug
|
Can't reproduce, can you provide the full code that's needed to reproduce this? |
|
Sure //! This file contains the source for the GDT (Global Descriptor Table).
//! The GDT contains entries telling the CPU about memory segments.
//!
//! **Notes**: https://wiki.osdev.org/Global_Descriptor_Table
use core::intrinsics::size_of;
use lazy_static::lazy_static;
// TODO: Each GDT for every different arch.
// TODO: https://github.com/rust-lang/rust/issues/83107
/// The GDT Descriptor containing the size of offset of the table.
#[repr(C, packed)]
struct GDTDescriptor {
/// The size of the table subtracted by 1.
/// The size of the table is subtracted by 1 as the maximum value
/// of `size` is 65535, while the GDT can be up to 65536 bytes.
size: u16,
/// The linear address of the table.
offset: u64,
}
impl GDTDescriptor {
/// Create a new GDT descriptor.
#[inline]
pub fn new(size: u16, offset: u64) -> Self {
Self { size, offset }
}
}
/// A GDT entry.
#[repr(C)]
struct GDTEntry {
limit_low: u16,
base_low: u16,
base_middle: u8,
access_byte: u8,
/// Four bits of the variable is the limit and rest four bits of the
/// variable are the flags.
limit_hi_flags: u8,
base_high: u8,
}
impl GDTEntry {
/// Create a new GDT entry.
#[inline]
fn new(
limit_low: u16,
base_low: u16,
base_middle: u8,
access_byte: u8,
limit_hi_flags: u8,
base_high: u8,
) -> Self {
Self {
limit_low,
base_low,
base_middle,
access_byte,
limit_hi_flags,
base_high,
}
}
}
/// The GDT.
#[repr(C, packed, align(0x1000))]
struct GDT {
/// The kernel null segment: `0x00`.
kernel_null: GDTEntry,
/// The kernel code segment: `0x08`.
kernel_code: GDTEntry,
/// The kernel data segment: `0x10`.
kernel_data: GDTEntry,
/// The user null segment.
user_null: GDTEntry,
/// The user code segment.
user_code: GDTEntry,
/// The user data segment.
user_data: GDTEntry,
}
/// Initialize the GDT.
pub fn init() {
unsafe {
let gdt_descriptor = GDTDescriptor::new(
(size_of::<GDT>() - 1) as u16,
(&GLOBAL_DESCRIPTOR_TABLE as *const _) as u64,
);
}
}
lazy_static! {
/// The GDT (Global Descriptor Table).
static ref GLOBAL_DESCRIPTOR_TABLE: GDT = GDT {
kernel_null: GDTEntry::new(0, 0, 0, 0x00, 0x00, 0),
kernel_code: GDTEntry::new(0, 0, 0, 0x9a, 0xa0, 0),
kernel_data: GDTEntry::new(0, 0, 0, 0x92, 0xa0, 0),
user_null: GDTEntry::new(0, 0, 0, 0x00, 0x00, 0),
user_code: GDTEntry::new(0, 0, 0, 0x9a, 0xa0, 0),
user_data: GDTEntry::new(0, 0, 0, 0x92, 0xa0, 0)
};
} |
jonas-schievink
added
A-layout
|
MCVE: #[repr(packed, align(0x1000))]
pub struct Foo {
val: u16,
}
static BAR: Foo = Foo {
val: 0,
};
fn main() {} |
|
Assigning @rustbot label -I-prioritize +P-medium |
rustbot
added
P-medium
|
bisection: searched nightlies: from nightly-2020-06-01 to nightly-2021-03-17 bisected with cargo-bisect-rustc v0.6.0Host triple: x86_64-unknown-linux-gnu cargo bisect-rustc --start=2020-06-01 --regress=ice |
fanninpm
added a commit
to fanninpm/glacier
that referenced
this issue
Mar 19, 2021
Issue: rust-lang/rust#83107
GuillaumeGomez
added a commit
to GuillaumeGomez/rust
that referenced
this issue
Jul 15, 2021
Layout error instead of an ICE for packed and aligned types Fixes rust-lang#83107.
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rustc --version --verbose:Error output
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