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https://gitlab.freedesktop.org/mesa/mesa.git
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e0b1193361
This is intended to a Rust analog to "src/util", which has
many utilities used by Mesa developers. This is mostly
a copy of ${crosvm} rutabaga_gfx/src/rutabaga_os (which will
be deleted in favor of this crate).
Key constructs include:
- SharedMemory
- MemoryMapping
- Tube (sockets, essentially)
- OwnedDescriptor (HANDLE or fd-based)
- WaitContext (epoll, ..)
As one would expect, Linux implementations are the most complete.
Acked-by: Aaron Ruby <aruby@qnx.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/35210>
93 lines
2.5 KiB
Rust
93 lines
2.5 KiB
Rust
// Copyright 2025 Google
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// SPDX-License-Identifier: MIT
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use std::ffi::c_void;
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use std::os::fd::AsFd;
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use std::ptr::null_mut;
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use rustix::mm::mmap;
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use rustix::mm::munmap;
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use rustix::mm::MapFlags;
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use rustix::mm::ProtFlags;
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use crate::MesaError;
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use crate::MesaResult;
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use crate::OwnedDescriptor;
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use crate::MESA_MAP_ACCESS_MASK;
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use crate::MESA_MAP_ACCESS_READ;
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use crate::MESA_MAP_ACCESS_RW;
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use crate::MESA_MAP_ACCESS_WRITE;
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/// Wraps an anonymous shared memory mapping in the current process. Provides
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/// RAII semantics including munmap when no longer needed.
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#[derive(Debug)]
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pub struct MemoryMapping {
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pub addr: *mut c_void,
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pub size: usize,
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}
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// SAFETY:
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// MemoryMapping user must ensure it is used by one thread at a time.
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unsafe impl Sync for MemoryMapping {}
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// SAFETY:
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// MemoryMapping user must ensure it is used by one thread at a time.
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unsafe impl Send for MemoryMapping {}
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impl Drop for MemoryMapping {
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fn drop(&mut self) {
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// SAFETY:
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// This is safe because we mmap the area at addr ourselves, and nobody
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// else is holding a reference to it.
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unsafe {
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munmap(self.addr, self.size).unwrap();
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}
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}
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}
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impl MemoryMapping {
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fn do_mmap(
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descriptor: &OwnedDescriptor,
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offset: usize,
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size: usize,
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map_info: u32,
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) -> MesaResult<MemoryMapping> {
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let prot = match map_info & MESA_MAP_ACCESS_MASK {
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MESA_MAP_ACCESS_READ => ProtFlags::READ,
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MESA_MAP_ACCESS_WRITE => ProtFlags::WRITE,
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MESA_MAP_ACCESS_RW => ProtFlags::READ | ProtFlags::WRITE,
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_ => return Err(MesaError::WithContext("incorrect access flags")),
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};
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// SAFETY:
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// The inputs to the mmap() system call have been verified, and
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// the kernel is trusted to deliver a correct result.
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let addr = unsafe {
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mmap(
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null_mut(),
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size,
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prot,
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MapFlags::SHARED,
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descriptor.as_fd(),
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offset.try_into().unwrap(),
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)?
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};
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Ok(MemoryMapping { addr, size })
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}
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pub fn from_safe_descriptor(
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descriptor: OwnedDescriptor,
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size: usize,
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map_info: u32,
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) -> MesaResult<MemoryMapping> {
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Self::do_mmap(&descriptor, 0, size, map_info)
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}
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pub fn from_offset(
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descriptor: &OwnedDescriptor,
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offset: usize,
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size: usize,
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) -> MesaResult<MemoryMapping> {
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Self::do_mmap(descriptor, offset, size, MESA_MAP_ACCESS_RW)
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}
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}
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