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std: uefi: Add basic Env variables
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- Implement environment variable functions
- Using EFI Shell GUID for reading/storing variables.

Signed-off-by: Ayush Singh <[email protected]>
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@Ayush1325
Ayush1325 committed Aug 28, 2024
1 parent ac77e88 commit f114cd9
Showing 1 changed file with 186 additions and 14 deletions.
200 changes: 186 additions & 14 deletions library/std/src/sys/pal/uefi/os.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@ use crate::error::Error as StdError;
use crate::ffi::{OsStr, OsString};
use crate::marker::PhantomData;
use crate::os::uefi;
use crate::os::uefi::ffi::OsStringExt;
use crate::path::{self, PathBuf};
use crate::ptr::NonNull;
use crate::{fmt, io};
Expand Down Expand Up @@ -171,44 +172,70 @@ pub fn current_exe() -> io::Result<PathBuf> {
helpers::device_path_to_text(protocol).map(PathBuf::from)
}

pub struct Env(!);
#[derive(Clone)]
pub struct Env {
last_var_name: Vec<u16>,
last_var_guid: r_efi::efi::Guid,
}

impl Env {
// FIXME(https://github.com/rust-lang/rust/issues/114583): Remove this when <OsStr as Debug>::fmt matches <str as Debug>::fmt.
pub fn str_debug(&self) -> impl fmt::Debug + '_ {
let Self(inner) = self;
match *inner {}
self
}
}

impl Iterator for Env {
type Item = (OsString, OsString);

fn next(&mut self) -> Option<(OsString, OsString)> {
self.0
let (key, guid) =
uefi_vars::get_next_variable_name(&self.last_var_name, self.last_var_guid).ok()?;

self.last_var_name = key;
self.last_var_guid = guid;

if self.last_var_guid == uefi_vars::SHELL_VARIABLE_GUID {
let k = OsString::from_wide(&self.last_var_name[..(self.last_var_name.len() - 1)]);
let v = uefi_vars::get(self.last_var_name.as_mut_slice())?;

Some((k, v))
} else {
self.next()
}
}
}

impl fmt::Debug for Env {
fn fmt(&self, _: &mut fmt::Formatter<'_>) -> fmt::Result {
let Self(inner) = self;
match *inner {}
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let iter: Env = self.clone();
let mut list = f.debug_list();
for (a, b) in iter {
list.entry(&(a.to_str().unwrap(), b.to_str().unwrap()));
}
list.finish()
}
}

pub fn env() -> Env {
panic!("not supported on this platform")
Env { last_var_name: Vec::from([0]), last_var_guid: uefi_vars::SHELL_VARIABLE_GUID }
}

pub fn getenv(_: &OsStr) -> Option<OsString> {
None
pub fn getenv(key: &OsStr) -> Option<OsString> {
let mut key = uefi_vars::key(key)?;
uefi_vars::get(key.as_mut_slice())
}

pub unsafe fn setenv(_: &OsStr, _: &OsStr) -> io::Result<()> {
Err(io::const_io_error!(io::ErrorKind::Unsupported, "cannot set env vars on this platform"))
pub unsafe fn setenv(k: &OsStr, v: &OsStr) -> io::Result<()> {
let mut k =
uefi_vars::key(k).ok_or(io::const_io_error!(io::ErrorKind::InvalidInput, "Invalid key"))?;
uefi_vars::set(k.as_mut_slice(), v)
}

pub unsafe fn unsetenv(_: &OsStr) -> io::Result<()> {
Err(io::const_io_error!(io::ErrorKind::Unsupported, "cannot unset env vars on this platform"))
pub unsafe fn unsetenv(k: &OsStr) -> io::Result<()> {
let mut k =
uefi_vars::key(k).ok_or(io::const_io_error!(io::ErrorKind::InvalidInput, "Invalid key"))?;
uefi_vars::unset(k.as_mut_slice())
}

pub fn temp_dir() -> PathBuf {
Expand Down Expand Up @@ -239,3 +266,148 @@ pub fn exit(code: i32) -> ! {
pub fn getpid() -> u32 {
panic!("no pids on this platform")
}

mod uefi_vars {
use super::helpers;
use crate::ffi::{OsStr, OsString};
use crate::io;
use crate::mem::size_of;
use crate::os::uefi::ffi::{OsStrExt, OsStringExt};
use crate::ptr::NonNull;

// Using Shell Variable Guid from edk2/ShellPkg
// https://github.com/tianocore/edk2/blob/master/ShellPkg/Include/Guid/ShellVariableGuid.h
pub(crate) const SHELL_VARIABLE_GUID: r_efi::efi::Guid = r_efi::efi::Guid::from_fields(
0x158def5a,
0xf656,
0x419c,
0xb0,
0x27,
&[0x7a, 0x31, 0x92, 0xc0, 0x79, 0xd2],
);

pub(crate) fn key(k: &OsStr) -> Option<Vec<u16>> {
let key = k.encode_wide().chain(Some(0)).collect::<Vec<u16>>();
if key[..key.len() - 1].contains(&0) {
return None;
} else {
Some(key)
}
}

pub(crate) fn get(key: &mut [u16]) -> Option<OsString> {
let rt: NonNull<r_efi::efi::RuntimeServices> =
helpers::runtime_services().expect("UEFI Runtime Services Missing").cast();

let mut len = 0usize;
let mut guid = SHELL_VARIABLE_GUID;

let ret = unsafe {
((*rt.as_ptr()).get_variable)(
key.as_mut_ptr(),
&mut guid,
crate::ptr::null_mut(),
&mut len,
crate::ptr::null_mut(),
)
};

if ret != r_efi::efi::Status::BUFFER_TOO_SMALL {
return None;
}

let mut val = Vec::<u16>::with_capacity(len / size_of::<u16>());
let ret = unsafe {
((*rt.as_ptr()).get_variable)(
key.as_mut_ptr(),
&mut guid,
crate::ptr::null_mut(),
&mut len,
val.as_mut_ptr().cast(),
)
};

if ret.is_error() {
None
} else {
unsafe { val.set_len(len / size_of::<u16>()) };
Some(OsString::from_wide(&val))
}
}

pub(crate) fn set(key: &mut [u16], val: &OsStr) -> io::Result<()> {
// UEFI variable value does not need to be NULL terminated.
let mut val = val.encode_wide().collect::<Vec<u16>>();
let rt: NonNull<r_efi::efi::RuntimeServices> =
helpers::runtime_services().expect("UEFI Runtime Services Missing").cast();
let mut guid = SHELL_VARIABLE_GUID;

let r = unsafe {
((*rt.as_ptr()).set_variable)(
key.as_mut_ptr(),
&mut guid,
r_efi::efi::VARIABLE_BOOTSERVICE_ACCESS,
val.len() * size_of::<u16>(),
val.as_mut_ptr().cast(),
)
};

if r.is_error() { Err(io::Error::from_raw_os_error(r.as_usize())) } else { Ok(()) }
}

pub(crate) fn unset(key: &mut [u16]) -> io::Result<()> {
let rt: NonNull<r_efi::efi::RuntimeServices> =
helpers::runtime_services().expect("UEFI Runtime Services Missing").cast();
let mut guid = SHELL_VARIABLE_GUID;

let r = unsafe {
((*rt.as_ptr()).set_variable)(
key.as_mut_ptr(),
&mut guid,
r_efi::efi::VARIABLE_BOOTSERVICE_ACCESS,
0,
crate::ptr::null_mut(),
)
};

if r.is_error() { Err(io::Error::from_raw_os_error(r.as_usize())) } else { Ok(()) }
}

pub(crate) fn get_next_variable_name(
last_var_name: &[u16],
last_guid: r_efi::efi::Guid,
) -> io::Result<(Vec<u16>, r_efi::efi::Guid)> {
let mut var_name = Vec::from(last_var_name);
let mut var_size = var_name.capacity() * size_of::<u16>();
let mut guid: r_efi::efi::Guid = last_guid;
let rt: NonNull<r_efi::efi::RuntimeServices> =
helpers::runtime_services().expect("UEFI Runtime Services Missing").cast();

let r = unsafe {
((*rt.as_ptr()).get_next_variable_name)(&mut var_size, var_name.as_mut_ptr(), &mut guid)
};

if !r.is_error() {
unsafe { var_name.set_len(var_size / size_of::<u16>()) };
return Ok((var_name, guid));
}

if r != r_efi::efi::Status::BUFFER_TOO_SMALL {
return Err(io::Error::from_raw_os_error(r.as_usize()));
}

var_name.reserve((var_size / size_of::<u16>()) - var_name.capacity() + 1);
var_size = var_name.capacity() * size_of::<u16>();

let r = unsafe {
((*rt.as_ptr()).get_next_variable_name)(&mut var_size, var_name.as_mut_ptr(), &mut guid)
};

if r.is_error() {
Err(io::Error::from_raw_os_error(r.as_usize()))
} else {
unsafe { var_name.set_len(var_size / size_of::<u16>()) };
Ok((var_name, guid))
}
}
}

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