From 73ad16d367de9e0966dbeeddf2cf23eb22473d07 Mon Sep 17 00:00:00 2001
From: Sean Cross <sean@xobs.io>
Date: Mon, 6 Apr 2020 15:29:37 +0800
Subject: [PATCH] loader: fix loading when init spans pages

Due to an issue withow MiniELF files were loaded, one page was mapped to
two addresses rather than having two adjacent addresses mapped.  This
occurred when a small section spanned two pages.

This has now been corrected, and an additional test binary will be added
to demonstrate the issue.

Signed-off-by: Sean Cross <sean@xobs.io>
---
 loader/src/main.rs | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/loader/src/main.rs b/loader/src/main.rs
index 00af11acf..18ca2ea08 100644
--- a/loader/src/main.rs
+++ b/loader/src/main.rs
@@ -200,6 +200,7 @@ impl MiniElf {
     /// The process will have been already loaded in stage 1.  This simply assigns
     /// memory maps as necessary.
     pub fn load(&self, allocator: &mut BootConfig, load_offset: usize, pid: XousPid) -> usize {
+        println!("Mapping PID {} starting at offset {:08x}", pid, load_offset);
         let mut allocated_bytes = 0;
 
         let mut page_addr: usize = 0;
@@ -291,6 +292,7 @@ impl MiniElf {
 
             // Part 3: Copy the final residual partial page
             if bytes_to_copy > 0 {
+                let this_page = (section.virt as usize + section.len()) & !(PAGE_SIZE - 1);
                 allocator.map_page(satp, top as usize, this_page, flag_defaults);
                 allocated_bytes += PAGE_SIZE;
                 top -= PAGE_SIZE;
@@ -632,6 +634,8 @@ fn copy_processes(cfg: &mut BootConfig) {
 
                     // Zero out the page, if necessary.
                     unsafe { bzero(top, top.add(section.virt as usize & (PAGE_SIZE - 1))) };
+                } else {
+                    println!("Reusing existing page @ {:08x}", this_page);
                 }
 
                 // Part 1: Copy the first chunk over.