Use append_panic_message syscall on panic

Author: eupn

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

@@ -5,7 +5,7 @@ pub struct Stdout {}
 pub struct Stderr;
 
 use crate::os::xous::ffi::{lend, try_lend, try_scalar, Connection};
-use crate::os::xous::services::{log_server, try_connect, LogLend, LogScalar};
+use crate::os::xous::services::{log_server, LogLend, LogScalar};
 
 impl Stdin {
     pub const fn new() -> Stdin {
@@ -87,6 +87,11 @@ pub struct PanicWriter {
 
 impl io::Write for PanicWriter {
     fn write(&mut self, s: &[u8]) -> core::result::Result<usize, io::Error> {
+        // Save the panic text in the kernel in groups of 6 words
+        for c in s.chunks(core::mem::size_of::<usize>() * 6) {
+            xous::append_panic_message(c).ok();
+        }
+
         for c in s.chunks(core::mem::size_of::<usize>() * 4) {
             // Text is grouped into 4x `usize` words. The id is 1100 plus
             // the number of characters in this message.

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

@@ -35,7 +35,7 @@ impl Thread {
                 None,
                 None,
                 GUARD_PAGE_SIZE + stack_size + GUARD_PAGE_SIZE,
-                MemoryFlags::R | MemoryFlags::W | MemoryFlags::X,
+                MemoryFlags::W | MemoryFlags::X,
             )
         }
         .map_err(|code| io::Error::from_raw_os_error(code as i32))?;

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

@@ -104,7 +104,7 @@ fn tls_table() -> &'static mut [*mut u8] {
             None,
             None,
             TLS_MEMORY_SIZE / core::mem::size_of::<*mut u8>(),
-            MemoryFlags::R | MemoryFlags::W,
+            MemoryFlags::W,
         )
         .expect("Unable to allocate memory for thread local storage")
     };