[BROKEN] 32-bit x86 (i386) support

arch/um/Kconfig

@@ -28,7 +28,7 @@ config UML
 	select TRACE_IRQFLAGS_SUPPORT
 	select TTY # Needed for line.c
 	select HAVE_ARCH_VMAP_STACK
-	select HAVE_RUST			if X86_64
+	select HAVE_RUST
 
 config MMU
 	bool

arch/x86/Kconfig

@@ -263,7 +263,7 @@ config X86
 	select HAVE_STATIC_CALL_INLINE		if HAVE_OBJTOOL
 	select HAVE_PREEMPT_DYNAMIC_CALL
 	select HAVE_RSEQ
-	select HAVE_RUST			if X86_64
+	select HAVE_RUST
 	select HAVE_SYSCALL_TRACEPOINTS
 	select HAVE_UACCESS_VALIDATION		if HAVE_OBJTOOL
 	select HAVE_UNSTABLE_SCHED_CLOCK

arch/x86/lib/Makefile

@@ -63,6 +63,7 @@ ifeq ($(CONFIG_X86_32),y)
 ifneq ($(CONFIG_X86_CMPXCHG64),y)
         lib-y += cmpxchg8b_emu.o atomic64_386_32.o
 endif
+	lib-y += moddiv_32.o
 else
         obj-y += iomap_copy_64.o
 ifneq ($(CONFIG_GENERIC_CSUM),y)

arch/x86/lib/moddiv_32.c

@@ -0,0 +1,13 @@
+#include <linux/math64.h>
+
+unsigned long long __udivdi3(unsigned long long a, unsigned long long b)
+{
+	return div64_u64(a, b);
+}
+
+unsigned long long __umoddi3(unsigned long long a, unsigned long long b)
+{
+	unsigned long long rem;
+	div64_u64_rem(a, b, &rem);
+	return rem;
+}

scripts/generate_rust_target.rs

@@ -211,6 +211,19 @@ fn main() {
         ts.push("features", features);
         ts.push("llvm-target", "x86_64-linux-gnu");
         ts.push("target-pointer-width", "64");
+    } else if cfg.has("X86_32") {
+        ts.push("arch", "x86");
+        ts.push(
+            "data-layout",
+            "e-m:e-p:32:32-p270:32:32-p271:32:32-p272:64:64-f64:32:64-f80:32-n8:16:32-S128",
+        );
+        let mut features = "-3dnow,-3dnowa,-mmx,+soft-float".to_string();
+        if cfg.has("RETPOLINE") {
+            features += ",+retpoline-external-thunk";
+        }
+        ts.push("features", features);
+        ts.push("llvm-target", "i386-unknown-linux-gnu");
+        ts.push("target-pointer-width", "32");
     } else {
         panic!("Unsupported architecture");
     }