bjoernager/rust
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do direct splice syscall and probe availability to get android builds to work

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Android builds use feature level 14, the libc wrapper for splice is gated
on feature level 21+ so we have to invoke the syscall directly.
Additionally the emulator doesn't seem to support it so we also have to
add ENOSYS checks.
This commit is contained in:
The8472 2020-11-06 23:36:23 +01:00
parent 3dfc377aa1
commit 4854d418a5
2 changed files with 72 additions and 4 deletions
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42
library/std/src/sys/unix/kernel_copy.rs
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@ -58,6 +58,7 @@ use crate::os::unix::fs::FileTypeExt;
use crate::os::unix::io::{AsRawFd, FromRawFd, RawFd};
use crate::process::{ChildStderr, ChildStdin, ChildStdout};
use crate::ptr;
use crate::sync::atomic::{AtomicBool, Ordering};
use crate::sys::cvt;
#[cfg(test)]
@ -440,7 +441,6 @@ pub(super) enum CopyResult {
/// If the initial file offset was 0 then `Fallback` will only contain `0`.
pub(super) fn copy_regular_files(reader: RawFd, writer: RawFd, max_len: u64) -> CopyResult {
use crate::cmp;
use crate::sync::atomic::{AtomicBool, Ordering};
// Kernel prior to 4.5 don't have copy_file_range
// We store the availability in a global to avoid unnecessary syscalls
@ -534,6 +534,30 @@ enum SpliceMode {
/// performs splice or sendfile between file descriptors
/// Does _not_ fall back to a generic copy loop.
fn sendfile_splice(mode: SpliceMode, reader: RawFd, writer: RawFd, len: u64) -> CopyResult {
static HAS_SENDFILE: AtomicBool = AtomicBool::new(true);
static HAS_SPLICE: AtomicBool = AtomicBool::new(true);
syscall! {
fn splice(
srcfd: libc::c_int,
src_offset: *const i64,
dstfd: libc::c_int,
dst_offset: *const i64,
len: libc::size_t,
flags: libc::c_int
) -> libc::ssize_t
}
match mode {
SpliceMode::Sendfile if !HAS_SENDFILE.load(Ordering::Relaxed) => {
return CopyResult::Fallback(0);
}
SpliceMode::Splice if !HAS_SPLICE.load(Ordering::Relaxed) => {
return CopyResult::Fallback(0);
}
_ => (),
}
let mut written = 0u64;
while written < len {
let chunk_size = crate::cmp::min(len - written, 0x7ffff000_u64) as usize;
@ -543,7 +567,7 @@ fn sendfile_splice(mode: SpliceMode, reader: RawFd, writer: RawFd, len: u64) ->
cvt(unsafe { libc::sendfile(writer, reader, ptr::null_mut(), chunk_size) })
}
SpliceMode::Splice => cvt(unsafe {
libc::splice(reader, ptr::null_mut(), writer, ptr::null_mut(), chunk_size, 0)
splice(reader, ptr::null_mut(), writer, ptr::null_mut(), chunk_size, 0)
}),
};
@ -552,8 +576,18 @@ fn sendfile_splice(mode: SpliceMode, reader: RawFd, writer: RawFd, len: u64) ->
Ok(ret) => written += ret as u64,
Err(err) => {
return match err.raw_os_error() {
Some(os_err) if os_err == libc::EINVAL => {
// splice/sendfile do not support this particular file descritor (EINVAL)
Some(libc::ENOSYS | libc::EPERM) => {
// syscall not supported (ENOSYS)
// syscall is disallowed, e.g. by seccomp (EPERM)
match mode {
SpliceMode::Sendfile => HAS_SENDFILE.store(false, Ordering::Relaxed),
SpliceMode::Splice => HAS_SPLICE.store(false, Ordering::Relaxed),
}
assert_eq!(written, 0);
CopyResult::Fallback(0)
}
Some(libc::EINVAL) => {
// splice/sendfile do not support this particular file descriptor (EINVAL)
assert_eq!(written, 0);
CopyResult::Fallback(0)
}