From dfd191367991cb157b53767dcc05824c826b5abd Mon Sep 17 00:00:00 2001
From: Iman Hosseini <hosseini.iman@yahoo.com>
Date: Tue, 20 Sep 2022 00:05:00 -0400
Subject: detects the loading of isa-incompatible (i.e. 32 bit code to 64bit
 HART) code and emits an error message to help avoid unintentionally loading
 wrong elf.

---
 fesvr/elfloader.cc |  6 +++++-
 fesvr/elfloader.h  |  2 +-
 fesvr/htif.cc      | 10 ++++++++--
 fesvr/htif.h       |  4 ++--
 fesvr/memif.h      |  8 ++++++++
 riscv/sim.cc       |  1 +
 6 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/fesvr/elfloader.cc b/fesvr/elfloader.cc
index 76cd6da..1bdccd3 100644
--- a/fesvr/elfloader.cc
+++ b/fesvr/elfloader.cc
@@ -16,7 +16,7 @@
 #include <vector>
 #include <map>
 
-std::map<std::string, uint64_t> load_elf(const char* fn, memif_t* memif, reg_t* entry)
+std::map<std::string, uint64_t> load_elf(const char* fn, memif_t* memif, reg_t* entry, unsigned required_xlen = 0)
 {
   int fd = open(fn, O_RDONLY);
   struct stat s;
@@ -32,6 +32,10 @@ std::map<std::string, uint64_t> load_elf(const char* fn, memif_t* memif, reg_t*
   assert(size >= sizeof(Elf64_Ehdr));
   const Elf64_Ehdr* eh64 = (const Elf64_Ehdr*)buf;
   assert(IS_ELF32(*eh64) || IS_ELF64(*eh64));
+  unsigned xlen = IS_ELF32(*eh64) ? 32 : 64;
+  if (required_xlen != 0 && required_xlen != xlen) {
+    throw incompat_xlen(required_xlen, xlen);
+  }
   assert(IS_ELFLE(*eh64) || IS_ELFBE(*eh64));
   assert(IS_ELF_EXEC(*eh64));
   assert(IS_ELF_RISCV(*eh64) || IS_ELF_EM_NONE(*eh64));
diff --git a/fesvr/elfloader.h b/fesvr/elfloader.h
index 696ef47..ae4ee78 100644
--- a/fesvr/elfloader.h
+++ b/fesvr/elfloader.h
@@ -8,6 +8,6 @@
 #include <string>
 
 class memif_t;
-std::map<std::string, uint64_t> load_elf(const char* fn, memif_t* memif, reg_t* entry);
+std::map<std::string, uint64_t> load_elf(const char* fn, memif_t* memif, reg_t* entry, unsigned required_xlen = 0);
 
 #endif
diff --git a/fesvr/htif.cc b/fesvr/htif.cc
index ead309c..29eb7d8 100644
--- a/fesvr/htif.cc
+++ b/fesvr/htif.cc
@@ -82,8 +82,14 @@ htif_t::~htif_t()
 
 void htif_t::start()
 {
-  if (!targs.empty() && targs[0] != "none")
+  if (!targs.empty() && targs[0] != "none") {
+    try {
       load_program();
+    } catch (const incompat_xlen & err) {
+      fprintf(stderr, "Error: cannot execute %d-bit program on RV%d hart\n", err.actual_xlen, err.expected_xlen);
+      exit(1);
+    }
+  }
 
   reset();
 }
@@ -129,7 +135,7 @@ std::map<std::string, uint64_t> htif_t::load_payload(const std::string& payload,
   } preload_aware_memif(this);
 
   try {
-    return load_elf(path.c_str(), &preload_aware_memif, entry);
+    return load_elf(path.c_str(), &preload_aware_memif, entry, expected_xlen);
   } catch (mem_trap_t& t) {
     bad_address("loading payload " + payload, t.get_tval());
     abort();
diff --git a/fesvr/htif.h b/fesvr/htif.h
index ca5b362..cf8b2d5 100644
--- a/fesvr/htif.h
+++ b/fesvr/htif.h
@@ -26,7 +26,7 @@ class htif_t : public chunked_memif_t
   int run();
   bool done();
   int exit_code();
-
+  void set_expected_xlen(unsigned int m) { expected_xlen = m; }
   virtual memif_t& memif() { return mem; }
 
   template<typename T> inline T from_target(target_endian<T> n) const
@@ -74,7 +74,7 @@ class htif_t : public chunked_memif_t
   void parse_arguments(int argc, char ** argv);
   void register_devices();
   void usage(const char * program_name);
-
+  unsigned int expected_xlen = 0;
   memif_t mem;
   reg_t entry;
   bool writezeros;
diff --git a/fesvr/memif.h b/fesvr/memif.h
index 001c425..3f9bd2d 100644
--- a/fesvr/memif.h
+++ b/fesvr/memif.h
@@ -5,6 +5,7 @@
 
 #include <stdint.h>
 #include <stddef.h>
+#include <stdexcept>
 #include "byteorder.h"
 
 typedef uint64_t reg_t;
@@ -79,4 +80,11 @@ protected:
   chunked_memif_t* cmemif;
 };
 
+class incompat_xlen : public std::exception {
+public:
+  const unsigned expected_xlen;
+  const unsigned actual_xlen;
+  incompat_xlen(unsigned _expected_xlen, unsigned _actual_xlen) : expected_xlen(_expected_xlen), actual_xlen(_actual_xlen) {}
+};
+
 #endif // __MEMIF_H
diff --git a/riscv/sim.cc b/riscv/sim.cc
index 0000537..0ef13b8 100644
--- a/riscv/sim.cc
+++ b/riscv/sim.cc
@@ -202,6 +202,7 @@ int sim_t::run()
 {
   host = context_t::current();
   target.init(sim_thread_main, this);
+  htif_t::set_expected_xlen(isa.get_max_xlen());
   return htif_t::run();
 }
 
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