From a9d8abbf5357ee0f176af3e1985a6425fb3ffda4 Mon Sep 17 00:00:00 2001
From: Ulrich Weigand <ulrich.weigand@de.ibm.com>
Date: Mon, 9 Nov 2020 17:59:30 +0100
Subject: [PATCH] Support big-endian hosts with GuestType (#2383)

The GuestType trait is used to access data elements in guest memory.
According to the WebAssembly spec, those are always stored in
little-endian byte order, even on big-endian hosts.  Accessing such
elements on big-endian hosts therefore requires byte swapping.

Fixed by adding from_le_bytes / to_le_bytes.
---
 crates/wiggle/src/guest_type.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/crates/wiggle/src/guest_type.rs b/crates/wiggle/src/guest_type.rs
index 7eabd0f025..422c3f2394 100644
--- a/crates/wiggle/src/guest_type.rs
+++ b/crates/wiggle/src/guest_type.rs
@@ -88,7 +88,7 @@ macro_rules! primitives {
                 if ptr.mem().is_borrowed(region) {
                     return Err(GuestError::PtrBorrowed(region));
                 }
-                Ok(unsafe { *host_ptr.cast::<Self>() })
+                Ok(unsafe { <$i>::from_le_bytes(*host_ptr.cast::<[u8; mem::size_of::<Self>()]>()) })
             }
 
             #[inline]
@@ -108,7 +108,7 @@ macro_rules! primitives {
                     return Err(GuestError::PtrBorrowed(region));
                 }
                 unsafe {
-                    *host_ptr.cast::<Self>() = val;
+                    *host_ptr.cast::<[u8; mem::size_of::<Self>()]>() = <$i>::to_le_bytes(val);
                 }
                 Ok(())
             }