sys: Add arm_compat::sys_read_uninit and mips::{mips_read_uninit,mips…

…_pread_uninit}

src/sys/arm_compat/mod.rs

@@ -16,6 +16,8 @@ pub(crate) mod errno;
 pub(crate) mod fs;
 pub mod syscall;
 
+#[cfg(any(feature = "stdio", feature = "fs"))]
+use core::slice;
 use core::{
     ffi::{c_void, CStr},
     mem::{self, MaybeUninit},
@@ -296,9 +298,8 @@ pub(crate) fn should_close(_fd: &OwnedFd) -> bool {
     true
 }
 
-// TODO: Add read_uninit?
 /// [SYS_READ (0x06)](https://github.com/ARM-software/abi-aa/blob/2024Q3/semihosting/semihosting.rst#sys-read-0x06)
-pub fn sys_read(fd: BorrowedFd<'_>, buf: &mut [MaybeUninit<u8>]) -> Result<usize> {
+pub fn sys_read_uninit(fd: BorrowedFd<'_>, buf: &mut [MaybeUninit<u8>]) -> Result<usize> {
     let len = buf.len();
     let mut args = [ParamRegW::fd(fd), ParamRegW::buf(buf), ParamRegW::usize(len)];
     let res = unsafe { syscall(OperationNumber::SYS_READ, ParamRegW::block(&mut args)) };
@@ -308,15 +309,19 @@ pub fn sys_read(fd: BorrowedFd<'_>, buf: &mut [MaybeUninit<u8>]) -> Result<usize
         Err(Error::from_raw_os_error(sys_errno()))
     }
 }
+// TODO: make sys_read take initialized buf in the next breaking release (e.i., rename sys_read_init to sys_read and make it public).
+pub use sys_read_uninit as sys_read;
 #[cfg(any(feature = "stdio", feature = "fs"))]
-pub(crate) fn read(fd: BorrowedFd<'_>, buf: &mut [u8]) -> Result<usize> {
-    use core::slice;
-
+pub(crate) fn sys_read_init(fd: BorrowedFd<'_>, buf: &mut [u8]) -> Result<usize> {
     let len = buf.len();
     // SAFETY: transmuting initialized u8 to MaybeUninit<u8> is always safe.
     let buf = unsafe { slice::from_raw_parts_mut(buf.as_mut_ptr().cast::<MaybeUninit<u8>>(), len) };
-    sys_read(fd, buf)
+    sys_read_uninit(fd, buf)
 }
+// #[cfg(any(feature = "stdio", feature = "fs"))]
+// pub(crate) use self::sys_read_uninit as read_uninit;
+#[cfg(any(feature = "stdio", feature = "fs"))]
+pub(crate) use self::sys_read_init as read;
 
 /// [SYS_READC (0x07)](https://github.com/ARM-software/abi-aa/blob/2024Q3/semihosting/semihosting.rst#sys-readc-0x07)
 pub fn sys_readc() -> u8 {

src/sys/mips/mod.rs

@@ -15,7 +15,8 @@ pub mod syscall;
 
 use core::{
     ffi::{self, CStr},
-    mem,
+    mem::{self, MaybeUninit},
+    slice,
 };
 
 use self::syscall::{
@@ -150,7 +151,7 @@ pub unsafe fn mips_close(fd: RawFd) -> Result<()> {
 }
 pub(crate) use self::mips_close as close;
 
-pub fn mips_read(fd: BorrowedFd<'_>, buf: &mut [u8]) -> Result<usize> {
+pub fn mips_read_uninit(fd: BorrowedFd<'_>, buf: &mut [MaybeUninit<u8>]) -> Result<usize> {
     let len = buf.len();
     let (res, errno) = unsafe {
         syscall3(
@@ -167,6 +168,14 @@ pub fn mips_read(fd: BorrowedFd<'_>, buf: &mut [u8]) -> Result<usize> {
         Ok(res.usize())
     }
 }
+pub fn mips_read(fd: BorrowedFd<'_>, buf: &mut [u8]) -> Result<usize> {
+    let len = buf.len();
+    // SAFETY: transmuting initialized u8 to MaybeUninit<u8> is always safe.
+    let buf = unsafe { slice::from_raw_parts_mut(buf.as_mut_ptr().cast::<MaybeUninit<u8>>(), len) };
+    mips_read_uninit(fd, buf)
+}
+// #[cfg(any(feature = "stdio", feature = "fs"))]
+// pub(crate) use mips_read_uninit as read_uninit;
 #[cfg(any(feature = "stdio", feature = "fs"))]
 pub(crate) use self::mips_read as read;
 
@@ -261,7 +270,11 @@ pub unsafe fn mips_argn(n: usize, buf: *mut u8) -> Result<()> {
 // TODO: UHI_PLOG
 // TODO: UHI_ASSERT
 
-pub fn mips_pread(fd: BorrowedFd<'_>, buf: &mut [u8], offset: usize) -> Result<usize> {
+pub fn mips_pread_uninit(
+    fd: BorrowedFd<'_>,
+    buf: &mut [MaybeUninit<u8>],
+    offset: usize,
+) -> Result<usize> {
     let len = buf.len();
     let (res, errno) = unsafe {
         syscall4(
@@ -279,6 +292,12 @@ pub fn mips_pread(fd: BorrowedFd<'_>, buf: &mut [u8], offset: usize) -> Result<u
         Ok(res.usize())
     }
 }
+pub fn mips_pread(fd: BorrowedFd<'_>, buf: &mut [u8], offset: usize) -> Result<usize> {
+    let len = buf.len();
+    // SAFETY: transmuting initialized u8 to MaybeUninit<u8> is always safe.
+    let buf = unsafe { slice::from_raw_parts_mut(buf.as_mut_ptr().cast::<MaybeUninit<u8>>(), len) };
+    mips_pread_uninit(fd, buf, offset)
+}
 
 pub fn mips_pwrite(fd: BorrowedFd<'_>, buf: &[u8], offset: usize) -> Result<usize> {
     let (res, errno) = unsafe {