[SOL] Temporarily patch BPF ELF file header with SBF machine code

Author: dmakarov

compiler/rustc_codegen_ssa/src/back/link.rs

@@ -2064,9 +2064,23 @@ fn add_linked_symbol_object(
     if let Err(error) = result {
         sess.dcx().emit_fatal(errors::FailedToWrite { path, error });
     }
+    if sess.target.arch == "sbf" {
+        patch_synthetic_object_file(sess, &path);
+    }
     cmd.add_object(&path);
 }
 
+fn patch_synthetic_object_file(sess: &Session, path: &PathBuf) {
+    const EM_SBF: [u8; 2] = [0x07, 0x01];
+    if let Ok(mut sf) = fs::OpenOptions::new().write(true).open(path) {
+        if let Ok(_) = sf.seek(SeekFrom::Start(0x12)) {
+            sf.write(&EM_SBF).unwrap();
+        }
+    } else {
+        sess.fatal(&format!("failed to patch {}", path.display()));
+    }
+}
+
 /// Add object files containing code from the current crate.
 fn add_local_crate_regular_objects(cmd: &mut dyn Linker, codegen_results: &CodegenResults) {
     for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) {