rt: implement i686 signal entry stub

lib/runtime/src/process/signal.rs

@@ -164,6 +164,8 @@ pub fn setup_signal_full(size: usize) -> Result<(), Error> {
 // TODO
 #[cfg(any(target_arch = "x86", rust_analyzer))]
 mod imp {
+    use super::common_signal_entry;
+
     // i686 is a bit tricky: cdecl ABI requires the arguments to be passed on the stack, while
     //  the kernel does the easy thing and just puts it into %eax, so a fixup needs to be done
     //  before entering a proper handler. The wrapper also aligns the stack nicely.
@@ -172,9 +174,13 @@ mod imp {
         // %eax - SignalEntryData pointer
         core::arch::naked_asm!(
             r#"
-            jmp .
+            // Align the stack
+            and $~0xF, %esp
+            push %eax
+            call {entry}
         "#,
-            options(att_syntax)
+            options(att_syntax),
+            entry = sym common_signal_entry
         );
     }
 }