From 106e3eba38979e3cbfec333e3badbeebb4da717d Mon Sep 17 00:00:00 2001
From: Rupert Swarbrick <rswarbrick@gmail.com>
Date: Fri, 18 Feb 2022 11:50:54 +0000
Subject: Add simple error checking to DTB parsing code

This catches silly mistakes like accidentally passing a DTS file when
it should have been a DTB.

Now, you get something like this:

    $ /opt/spike/latest/bin/spike --dtb=bogus.dtb -l obj.o
    Failed to read DTB from `bogus.dtb': FDT_ERR_BADMAGIC.
---
 riscv/sim.cc | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/riscv/sim.cc b/riscv/sim.cc
index 97b3746..2ee05d6 100644
--- a/riscv/sim.cc
+++ b/riscv/sim.cc
@@ -6,6 +6,7 @@
 #include "remote_bitbang.h"
 #include "byteorder.h"
 #include "platform.h"
+#include "libfdt.h"
 #include <fstream>
 #include <map>
 #include <iostream>
@@ -296,6 +297,18 @@ void sim_t::make_dtb()
     dts = make_dts(INSNS_PER_RTC_TICK, CPU_HZ, initrd_start, initrd_end, bootargs, procs, mems);
     dtb = dts_compile(dts);
   }
+
+  int fdt_code = fdt_check_header(dtb.c_str());
+  if (fdt_code) {
+    std::cerr << "Failed to read DTB from ";
+    if (dtb_file.empty()) {
+      std::cerr << "auto-generated DTS string";
+    } else {
+      std::cerr << "`" << dtb_file << "'";
+    }
+    std::cerr << ": " << fdt_strerror(fdt_code) << ".\n";
+    exit(-1);
+  }
 }
 
 void sim_t::set_rom()
-- 
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