std: xous: add support for args and env

Process arguments and environment variables are both passed by way of
Application Parameters. These are a TLV format that gets passed in as
the second process argument.

This patch combines both as they are very similar in their decode.

Signed-off-by: Sean Cross <sean@osdyne.com>

library/std/src/sys/pal/xous/args.rs

@@ -0,0 +1,53 @@
+use crate::ffi::OsString;
+use crate::sys::pal::xous::os::get_application_parameters;
+use crate::sys::pal::xous::os::params::ArgumentList;
+use crate::{fmt, vec};
+
+pub struct Args {
+    parsed_args_list: vec::IntoIter<OsString>,
+}
+
+pub fn args() -> Args {
+    let Some(params) = get_application_parameters() else {
+        return Args { parsed_args_list: vec![].into_iter() };
+    };
+
+    for param in params {
+        if let Ok(args) = ArgumentList::try_from(&param) {
+            let mut parsed_args = vec![];
+            for arg in args {
+                parsed_args.push(arg.into());
+            }
+            return Args { parsed_args_list: parsed_args.into_iter() };
+        }
+    }
+    Args { parsed_args_list: vec![].into_iter() }
+}
+
+impl fmt::Debug for Args {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        self.parsed_args_list.as_slice().fmt(f)
+    }
+}
+
+impl Iterator for Args {
+    type Item = OsString;
+    fn next(&mut self) -> Option<OsString> {
+        self.parsed_args_list.next()
+    }
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.parsed_args_list.size_hint()
+    }
+}
+
+impl DoubleEndedIterator for Args {
+    fn next_back(&mut self) -> Option<OsString> {
+        self.parsed_args_list.next_back()
+    }
+}
+
+impl ExactSizeIterator for Args {
+    fn len(&self) -> usize {
+        self.parsed_args_list.len()
+    }
+}

library/std/src/sys/pal/xous/mod.rs

@@ -1,6 +1,5 @@
 #![forbid(unsafe_op_in_unsafe_fn)]
 
-#[path = "../unsupported/args.rs"]
 pub mod args;
 #[path = "../unsupported/env.rs"]
 pub mod env;

library/std/src/sys/pal/xous/os.rs

@@ -1,29 +1,35 @@
 use super::unsupported;
+use crate::collections::HashMap;
 use crate::error::Error as StdError;
 use crate::ffi::{OsStr, OsString};
 use crate::marker::PhantomData;
 use crate::os::xous::ffi::Error as XousError;
 use crate::path::{self, PathBuf};
-use crate::{fmt, io};
+use crate::sync::atomic::{AtomicPtr, AtomicUsize, Ordering};
+use crate::sync::{Mutex, Once};
+use crate::{fmt, io, vec};
+
+pub(crate) mod params;
+
+static PARAMS_ADDRESS: AtomicPtr<u8> = AtomicPtr::new(core::ptr::null_mut());
 
 #[cfg(not(test))]
 #[cfg(feature = "panic_unwind")]
 mod eh_unwinding {
-    pub(crate) struct EhFrameFinder(usize /* eh_frame */);
-    pub(crate) static mut EH_FRAME_SETTINGS: EhFrameFinder = EhFrameFinder(0);
-    impl EhFrameFinder {
-        pub(crate) unsafe fn init(&mut self, eh_frame: usize) {
-            unsafe {
-                EH_FRAME_SETTINGS.0 = eh_frame;
-            }
-        }
-    }
+    pub(crate) struct EhFrameFinder;
+    pub(crate) static mut EH_FRAME_ADDRESS: usize = 0;
+    pub(crate) static EH_FRAME_SETTINGS: EhFrameFinder = EhFrameFinder;
+
     unsafe impl unwind::EhFrameFinder for EhFrameFinder {
         fn find(&self, _pc: usize) -> Option<unwind::FrameInfo> {
-            Some(unwind::FrameInfo {
-                text_base: None,
-                kind: unwind::FrameInfoKind::EhFrame(self.0),
-            })
+            if unsafe { EH_FRAME_ADDRESS == 0 } {
+                None
+            } else {
+                Some(unwind::FrameInfo {
+                    text_base: None,
+                    kind: unwind::FrameInfoKind::EhFrame(unsafe { EH_FRAME_ADDRESS }),
+                })
+            }
         }
     }
 }
@@ -41,12 +47,21 @@ mod c_compat {
     }
 
     #[no_mangle]
-    pub extern "C" fn _start(eh_frame: usize) {
+    pub extern "C" fn _start(eh_frame: usize, params_address: usize) {
         #[cfg(feature = "panic_unwind")]
-        unsafe {
-            super::eh_unwinding::EH_FRAME_SETTINGS.init(eh_frame);
+        {
+            unsafe { super::eh_unwinding::EH_FRAME_ADDRESS = eh_frame };
             unwind::set_custom_eh_frame_finder(&super::eh_unwinding::EH_FRAME_SETTINGS).ok();
         }
+
+        if params_address != 0 {
+            let params_address = crate::ptr::with_exposed_provenance_mut::<u8>(params_address);
+            if unsafe {
+                super::params::ApplicationParameters::new_from_ptr(params_address).is_some()
+            } {
+                super::PARAMS_ADDRESS.store(params_address, core::sync::atomic::Ordering::Relaxed);
+            }
+        }
         exit(unsafe { main() });
     }
 
@@ -116,44 +131,103 @@ pub fn current_exe() -> io::Result<PathBuf> {
     unsupported()
 }
 
-pub struct Env(!);
+pub(crate) fn get_application_parameters() -> Option<params::ApplicationParameters> {
+    let params_address = PARAMS_ADDRESS.load(Ordering::Relaxed);
+    unsafe { params::ApplicationParameters::new_from_ptr(params_address) }
+}
+
+// ---------- Environment handling ---------- //
+static ENV: AtomicUsize = AtomicUsize::new(0);
+static ENV_INIT: Once = Once::new();
+type EnvStore = Mutex<HashMap<OsString, OsString>>;
+
+fn get_env_store() -> &'static EnvStore {
+    ENV_INIT.call_once(|| {
+        let env_store = EnvStore::default();
+        if let Some(params) = get_application_parameters() {
+            for param in params {
+                if let Ok(envs) = params::EnvironmentBlock::try_from(&param) {
+                    let mut env_store = env_store.lock().unwrap();
+                    for env in envs {
+                        env_store.insert(env.key.into(), env.value.into());
+                    }
+                    break;
+                }
+            }
+        }
+        ENV.store(Box::into_raw(Box::new(env_store)) as _, Ordering::Relaxed)
+    });
+    unsafe { &*core::ptr::with_exposed_provenance::<EnvStore>(ENV.load(Ordering::Relaxed)) }
+}
+
+pub struct Env {
+    iter: vec::IntoIter<(OsString, OsString)>,
+}
+
+// FIXME(https://github.com/rust-lang/rust/issues/114583): Remove this when <OsStr as Debug>::fmt matches <str as Debug>::fmt.
+pub struct EnvStrDebug<'a> {
+    slice: &'a [(OsString, OsString)],
+}
+
+impl fmt::Debug for EnvStrDebug<'_> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let Self { slice } = self;
+        f.debug_list()
+            .entries(slice.iter().map(|(a, b)| (a.to_str().unwrap(), b.to_str().unwrap())))
+            .finish()
+    }
+}
 
 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 {}
+        let Self { iter } = self;
+        EnvStrDebug { slice: iter.as_slice() }
     }
 }
 
 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 Self { iter } = self;
+        f.debug_list().entries(iter.as_slice()).finish()
     }
 }
 
+impl !Send for Env {}
+impl !Sync for Env {}
+
 impl Iterator for Env {
     type Item = (OsString, OsString);
     fn next(&mut self) -> Option<(OsString, OsString)> {
-        self.0
+        self.iter.next()
+    }
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.iter.size_hint()
     }
 }
 
 pub fn env() -> Env {
-    panic!("not supported on this platform")
+    let clone_to_vec = |map: &HashMap<OsString, OsString>| -> Vec<_> {
+        map.iter().map(|(k, v)| (k.clone(), v.clone())).collect()
+    };
+
+    let iter = clone_to_vec(&*get_env_store().lock().unwrap()).into_iter();
+    Env { iter }
 }
 
-pub fn getenv(_: &OsStr) -> Option<OsString> {
-    None
+pub fn getenv(k: &OsStr) -> Option<OsString> {
+    get_env_store().lock().unwrap().get(k).cloned()
 }
 
-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 (k, v) = (k.to_owned(), v.to_owned());
+    get_env_store().lock().unwrap().insert(k, v);
+    Ok(())
 }
 
-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<()> {
+    get_env_store().lock().unwrap().remove(k);
+    Ok(())
 }
 
 pub fn temp_dir() -> PathBuf {

library/std/src/sys/pal/xous/os/params.rs

@@ -0,0 +1,271 @@
+/// Xous passes a pointer to the parameter block as the second argument.
+/// This is used for passing flags such as environment variables. The
+/// format of the argument block is:
+///
+/// #[repr(C)]
+/// struct BlockHeader {
+///     /// Magic number that identifies this block. Must be printable ASCII.
+///     magic: [u8; 4],
+///
+///     /// The size of the data block. Does not include this header. May be 0.
+///     size: u32,
+///
+///     /// The contents of this block. Varies depending on the block type.
+///     data: [u8; 0],
+/// }
+///
+/// There is a BlockHeader at the start that has magic `AppP`, and the data
+/// that follows is the number of blocks present:
+///
+/// #[repr(C)]
+/// struct ApplicationParameters {
+///     magic: b"AppP",
+///     size: 4u32,
+///
+///     /// The size of the entire application slice, in bytes, including all headers
+///     length: u32,
+///
+///     /// Number of application parameters present. Must be at least 1 (this block)
+///     entries: (parameter_count as u32).to_bytes_le(),
+/// }
+///
+/// #[repr(C)]
+/// struct EnvironmentBlock {
+///     magic: b"EnvB",
+///
+///     /// Total number of bytes, excluding this header
+///     size: 2+data.len(),
+///
+///     /// The number of environment variables
+///     count: u16,
+///
+///     /// Environment variable iteration
+///     data: [u8; 0],
+/// }
+///
+/// Environment variables are present in an `EnvB` block. The `data` section is
+/// a sequence of bytes of the form:
+///
+///      (u16 /* key_len */; [0u8; key_len as usize] /* key */,
+///       u16 /* val_len */ [0u8; val_len as usize])
+///
+/// #[repr(C)]
+/// struct ArgumentList {
+///     magic: b"ArgL",
+///
+///     /// Total number of bytes, excluding this header
+///     size: 2+data.len(),
+///
+///     /// The number of arguments variables
+///     count: u16,
+///
+///     /// Argument variable iteration
+///     data: [u8; 0],
+/// }
+///
+/// Args are just an array of strings that represent command line arguments.
+/// They are a sequence of the form:
+///
+///      (u16 /* val_len */ [0u8; val_len as usize])
+use core::slice;
+
+use crate::ffi::OsString;
+
+/// Magic number indicating we have an environment block
+const ENV_MAGIC: [u8; 4] = *b"EnvB";
+
+/// Command line arguments list
+const ARGS_MAGIC: [u8; 4] = *b"ArgL";
+
+/// Magic number indicating the loader has passed application parameters
+const PARAMS_MAGIC: [u8; 4] = *b"AppP";
+
+#[cfg(test)]
+mod tests;
+
+pub(crate) struct ApplicationParameters {
+    data: &'static [u8],
+    offset: usize,
+    _entries: usize,
+}
+
+impl ApplicationParameters {
+    pub(crate) unsafe fn new_from_ptr(data: *const u8) -> Option<ApplicationParameters> {
+        if data.is_null() {
+            return None;
+        }
+
+        let magic = unsafe { core::slice::from_raw_parts(data, 4) };
+        let block_length = unsafe {
+            u32::from_le_bytes(slice::from_raw_parts(data.add(4), 4).try_into().ok()?) as usize
+        };
+        let data_length = unsafe {
+            u32::from_le_bytes(slice::from_raw_parts(data.add(8), 4).try_into().ok()?) as usize
+        };
+        let entries = unsafe {
+            u32::from_le_bytes(slice::from_raw_parts(data.add(12), 4).try_into().ok()?) as usize
+        };
+
+        // Check for the main header
+        if data_length < 16 || magic != PARAMS_MAGIC || block_length != 8 {
+            return None;
+        }
+
+        let data = unsafe { slice::from_raw_parts(data, data_length) };
+
+        Some(ApplicationParameters { data, offset: 0, _entries: entries })
+    }
+}
+
+impl Iterator for ApplicationParameters {
+    type Item = ApplicationParameter;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        // Fetch magic, ensuring we don't run off the end
+        if self.offset + 4 > self.data.len() {
+            return None;
+        }
+        let magic = &self.data[self.offset..self.offset + 4];
+        self.offset += 4;
+
+        // Fetch header size
+        if self.offset + 4 > self.data.len() {
+            return None;
+        }
+        let size = u32::from_le_bytes(self.data[self.offset..self.offset + 4].try_into().unwrap())
+            as usize;
+        self.offset += 4;
+
+        // Fetch data contents
+        if self.offset + size > self.data.len() {
+            return None;
+        }
+        let data = &self.data[self.offset..self.offset + size];
+        self.offset += size;
+
+        Some(ApplicationParameter { data, magic: magic.try_into().unwrap() })
+    }
+}
+
+pub(crate) struct ApplicationParameter {
+    data: &'static [u8],
+    magic: [u8; 4],
+}
+
+pub(crate) struct ApplicationParameterError;
+
+pub(crate) struct EnvironmentBlock {
+    _count: usize,
+    data: &'static [u8],
+    offset: usize,
+}
+
+impl TryFrom<&ApplicationParameter> for EnvironmentBlock {
+    type Error = ApplicationParameterError;
+
+    fn try_from(value: &ApplicationParameter) -> Result<Self, Self::Error> {
+        if value.data.len() < 2 || value.magic != ENV_MAGIC {
+            return Err(ApplicationParameterError);
+        }
+
+        let count = u16::from_le_bytes(value.data[0..2].try_into().unwrap()) as usize;
+
+        Ok(EnvironmentBlock { data: &value.data[2..], offset: 0, _count: count })
+    }
+}
+
+pub(crate) struct EnvironmentEntry {
+    pub key: &'static str,
+    pub value: &'static str,
+}
+
+impl Iterator for EnvironmentBlock {
+    type Item = EnvironmentEntry;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.offset + 2 > self.data.len() {
+            return None;
+        }
+        let key_len =
+            u16::from_le_bytes(self.data[self.offset..self.offset + 2].try_into().ok()?) as usize;
+        self.offset += 2;
+
+        if self.offset + key_len > self.data.len() {
+            return None;
+        }
+        let key = core::str::from_utf8(&self.data[self.offset..self.offset + key_len]).ok()?;
+        self.offset += key_len;
+
+        if self.offset + 2 > self.data.len() {
+            return None;
+        }
+        let value_len =
+            u16::from_le_bytes(self.data[self.offset..self.offset + 2].try_into().ok()?) as usize;
+        self.offset += 2;
+
+        if self.offset + value_len > self.data.len() {
+            return None;
+        }
+        let value = core::str::from_utf8(&self.data[self.offset..self.offset + value_len]).ok()?;
+        self.offset += value_len;
+
+        Some(EnvironmentEntry { key, value })
+    }
+}
+
+pub(crate) struct ArgumentList {
+    data: &'static [u8],
+    _count: usize,
+    offset: usize,
+}
+
+impl TryFrom<&ApplicationParameter> for ArgumentList {
+    type Error = ApplicationParameterError;
+
+    fn try_from(value: &ApplicationParameter) -> Result<Self, Self::Error> {
+        if value.data.len() < 2 || value.magic != ARGS_MAGIC {
+            return Err(ApplicationParameterError);
+        }
+        let count =
+            u16::from_le_bytes(value.data[0..2].try_into().or(Err(ApplicationParameterError))?)
+                as usize;
+        Ok(ArgumentList { data: &value.data[2..], _count: count, offset: 0 })
+    }
+}
+
+pub(crate) struct ArgumentEntry {
+    value: &'static str,
+}
+
+impl Into<&str> for ArgumentEntry {
+    fn into(self) -> &'static str {
+        self.value
+    }
+}
+
+impl Into<OsString> for ArgumentEntry {
+    fn into(self) -> OsString {
+        self.value.into()
+    }
+}
+
+impl Iterator for ArgumentList {
+    type Item = ArgumentEntry;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.offset + 2 > self.data.len() {
+            return None;
+        }
+        let value_len =
+            u16::from_le_bytes(self.data[self.offset..self.offset + 2].try_into().ok()?) as usize;
+        self.offset += 2;
+
+        if self.offset + value_len > self.data.len() {
+            return None;
+        }
+        let value = core::str::from_utf8(&self.data[self.offset..self.offset + value_len]).ok()?;
+        self.offset += value_len;
+
+        Some(ArgumentEntry { value })
+    }
+}

library/std/src/sys/pal/xous/os/params/tests.rs

@@ -0,0 +1,75 @@
+use super::*;
+use crate::collections::HashMap;
+use crate::io::Write;
+
+fn create_args_test() -> std::io::Result<Vec<u8>> {
+    let mut sample_data = vec![];
+    let mut h = HashMap::new();
+
+    h.insert("foo", "bar");
+    h.insert("baz", "qux");
+    h.insert("some", "val");
+
+    // Magic number
+    sample_data.write_all(&PARAMS_MAGIC)?;
+    // Size of the AppP block
+    sample_data.write_all(&4u32.to_le_bytes())?;
+    // Number of blocks
+    sample_data.write_all(&2u32.to_le_bytes())?;
+
+    // Magic number
+    sample_data.write_all(&ENV_MAGIC)?;
+    let mut data = vec![];
+    for (key, value) in h.iter() {
+        data.extend_from_slice(&(key.len() as u16).to_le_bytes());
+        data.extend_from_slice(key.as_bytes());
+        data.extend_from_slice(&(value.len() as u16).to_le_bytes());
+        data.extend_from_slice(value.as_bytes());
+    }
+    // Size of the EnvB block
+    sample_data.write_all(&(data.len() as u32 + 2).to_le_bytes())?;
+
+    // Number of environment variables
+    sample_data.write_all(&(h.len() as u16).to_le_bytes())?;
+
+    // Environment variables
+    sample_data.write_all(&data)?;
+
+    // Write command line arguments
+    let args = vec!["some", "command", "line variable", "entries"];
+    sample_data.write_all(&ARGS_MAGIC)?;
+    let mut args_size = 0;
+    for entry in args.iter() {
+        args_size += entry.len() + 2;
+    }
+    sample_data.write_all(&(args_size as u32 + 2).to_le_bytes())?;
+    sample_data.write_all(&(args.len() as u16).to_le_bytes())?;
+    for entry in args {
+        sample_data.write_all(&(entry.len() as u16).to_le_bytes())?;
+        sample_data.write_all(entry.as_bytes())?;
+    }
+
+    Ok(sample_data)
+}
+
+#[test]
+fn basic_arg_parsing() {
+    let arg_data = create_args_test().expect("couldn't create test data");
+    for byte in &arg_data {
+        print!("{:02x} ", byte);
+    }
+    println!();
+
+    let args = ApplicationParameters::new(&arg_data).expect("Unable to parse arguments");
+    for arg in args {
+        if let Ok(env) = EnvironmentBlock::try_from(&arg) {
+            for env in env {
+                println!("{}={}", env.key, env.value);
+            }
+        } else if let Ok(args) = ArgumentList::try_from(&arg) {
+            for arg in args {
+                println!("Arg: {}", arg.value);
+            }
+        }
+    }
+}