From 1fea2afbf46d2641d77f2db3d6108e0897431a84 Mon Sep 17 00:00:00 2001
From: Andrew Waterman <andrew@sifive.com>
Date: Thu, 17 Mar 2022 15:45:19 -0700
Subject: Improve error message when HTIF accesses invalid memory

...which includes program loading.
---
 fesvr/htif.cc | 51 +++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 41 insertions(+), 10 deletions(-)

(limited to 'fesvr')

diff --git a/fesvr/htif.cc b/fesvr/htif.cc
index 7150039..f81878d 100644
--- a/fesvr/htif.cc
+++ b/fesvr/htif.cc
@@ -5,12 +5,14 @@
 #include "elfloader.h"
 #include "platform.h"
 #include "byteorder.h"
+#include "trap.h"
 #include <algorithm>
 #include <assert.h>
 #include <vector>
 #include <queue>
 #include <iostream>
 #include <fstream>
+#include <sstream>
 #include <iomanip>
 #include <stdio.h>
 #include <unistd.h>
@@ -86,6 +88,13 @@ void htif_t::start()
   reset();
 }
 
+static void bad_address(const std::string& situation, reg_t addr)
+{
+  std::cerr << "Access exception occurred while " << situation << ":\n";
+  std::cerr << "Memory address 0x" << std::hex << addr << " is invalid\n";
+  exit(-1);
+}
+
 std::map<std::string, uint64_t> htif_t::load_payload(const std::string& payload, reg_t* entry)
 {
   std::string path;
@@ -119,7 +128,12 @@ std::map<std::string, uint64_t> htif_t::load_payload(const std::string& payload,
     htif_t* htif;
   } preload_aware_memif(this);
 
-  return load_elf(path.c_str(), &preload_aware_memif, entry);
+  try {
+    return load_elf(path.c_str(), &preload_aware_memif, entry);
+  } catch (mem_trap_t& t) {
+    bad_address("loading payload " + payload, t.get_tval());
+    abort();
+  }
 }
 
 void htif_t::load_program()
@@ -218,19 +232,36 @@ int htif_t::run()
 
   while (!signal_exit && exitcode == 0)
   {
-    if (auto tohost = from_target(mem.read_uint64(tohost_addr))) {
-      mem.write_uint64(tohost_addr, target_endian<uint64_t>::zero);
-      command_t cmd(mem, tohost, fromhost_callback);
-      device_list.handle_command(cmd);
+    uint64_t tohost;
+
+    try {
+      if ((tohost = from_target(mem.read_uint64(tohost_addr))) != 0)
+        mem.write_uint64(tohost_addr, target_endian<uint64_t>::zero);
+    } catch (mem_trap_t& t) {
+      bad_address("accessing tohost", t.get_tval());
+    }
+
+    if (tohost != 0) {
+      try {
+        command_t cmd(mem, tohost, fromhost_callback);
+        device_list.handle_command(cmd);
+        device_list.tick();
+      } catch (mem_trap_t& t) {
+        std::stringstream tohost_hex;
+        tohost_hex << std::hex << tohost;
+        bad_address("host was accessing memory on behalf of target (tohost = 0x" + tohost_hex.str() + ")", t.get_tval());
+      }
     } else {
       idle();
     }
 
-    device_list.tick();
-
-    if (!fromhost_queue.empty() && !mem.read_uint64(fromhost_addr)) {
-      mem.write_uint64(fromhost_addr, to_target(fromhost_queue.front()));
-      fromhost_queue.pop();
+    try {
+      if (!fromhost_queue.empty() && !mem.read_uint64(fromhost_addr)) {
+        mem.write_uint64(fromhost_addr, to_target(fromhost_queue.front()));
+        fromhost_queue.pop();
+      }
+    } catch (mem_trap_t& t) {
+      bad_address("accessing fromhost", t.get_tval());
     }
   }
 
-- 
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