Fix --kernel and --initrd options w.r.t. sparse mem_t implementation

For some reason, the old accessors for the non-sparse version were left
dangling.  These methods are used by the --kernel and --initrd options,
and so those options were just broken.

This also fixes a memory leak and refactors the implementation a bit.

riscv/devices.cc

@@ -1,5 +1,6 @@
 #include "devices.h"
 #include "mmu.h"
+#include <stdexcept>
 
 void bus_t::add_device(reg_t addr, abstract_device_t* dev)
 {
@@ -90,17 +91,49 @@ bool mmio_plugin_device_t::store(reg_t addr, size_t len, const uint8_t* bytes)
   return (*plugin.store)(user_data, addr, len, bytes);
 }
 
-char* mem_t::contents() {
-    return data;
+mem_t::mem_t(reg_t size)
+  : sz(size)
+{
+  if (size == 0 || size % PGSIZE != 0)
+    throw std::runtime_error("memory size must be a positive multiple of 4 KiB");
+}
+
+mem_t::~mem_t()
+{
+  for (auto& entry : sparse_memory_map)
+    free(entry.second);
+}
+
+bool mem_t::load_store(reg_t addr, size_t len, uint8_t* bytes, bool store)
+{
+  if (addr + len < addr || addr + len > sz)
+    return false;
+
+  while (len > 0) {
+    auto n = std::min(PGSIZE - (addr % PGSIZE), len);
+
+    if (store)
+      memcpy(this->contents(addr), bytes, n);
+    else
+      memcpy(bytes, this->contents(addr), n);
+
+    addr += n;
+    bytes += n;
+    len -= n;
+  }
+
+  return true;
 }
 
 char* mem_t::contents(reg_t addr) {
-    reg_t pg_idx = addr & ~reg_t(PGSIZE - 1);
-    auto search = acc_tbl.find(pg_idx);
-    if (search == acc_tbl.end() || !search->second.second) {
-        char* mem_ptr = (char*)calloc(PGSIZE, sizeof(char));
-        acc_tbl[pg_idx] = std::make_pair(mem_ptr, true);
-    }
-    auto offset = addr & (PGSIZE - 1);
-    return acc_tbl[pg_idx].first + offset;
+  reg_t ppn = addr >> PGSHIFT, pgoff = addr % PGSIZE;
+  auto search = sparse_memory_map.find(ppn);
+  if (search == sparse_memory_map.end()) {
+    auto res = (char*)calloc(PGSIZE, 1);
+    if (res == nullptr)
+      throw std::bad_alloc();
+    sparse_memory_map[ppn] = res;
+    return res + pgoff;
+  }
+  return search->second + pgoff;
 }

riscv/devices.h

@@ -7,7 +7,6 @@
 #include <string>
 #include <map>
 #include <vector>
-#include <stdexcept>
 #include <utility>
 
 class processor_t;
@@ -43,26 +42,20 @@ class rom_device_t : public abstract_device_t {
 
 class mem_t : public abstract_device_t {
  public:
-  mem_t(size_t size) : len(size) {
-    if (!size)
-      throw std::runtime_error("zero bytes of target memory requested");
-    data = nullptr;
-  }
+  mem_t(reg_t size);
   mem_t(const mem_t& that) = delete;
-  ~mem_t() {
-        free(data);
-  }
+  ~mem_t();
 
-  bool load(reg_t addr, size_t len, uint8_t* bytes) { return false; }
-  bool store(reg_t addr, size_t len, const uint8_t* bytes) { return false; }
-  char* contents();
+  bool load(reg_t addr, size_t len, uint8_t* bytes) { return load_store(addr, len, bytes, false); }
+  bool store(reg_t addr, size_t len, const uint8_t* bytes) { return load_store(addr, len, const_cast<uint8_t*>(bytes), true); }
   char* contents(reg_t addr);
-  size_t size() { return len; }
+  reg_t size() { return sz; }
 
  private:
-  std::map<reg_t, std::pair<char*, bool>> acc_tbl;
-  char* data;
-  size_t len;
+  bool load_store(reg_t addr, size_t len, uint8_t* bytes, bool store);
+
+  std::map<reg_t, char*> sparse_memory_map;
+  reg_t sz;
 };
 
 class clint_t : public abstract_device_t {

riscv/sim.cc

@@ -353,7 +353,7 @@ char* sim_t::addr_to_mem(reg_t addr) {
   auto desc = bus.find_device(addr);
   if (auto mem = dynamic_cast<mem_t*>(desc.second))
     if (addr - desc.first < mem->size())
-      return mem->contents(addr);
+      return mem->contents(addr - desc.first);
   return NULL;
 }
 

spike_main/spike.cc

@@ -89,11 +89,14 @@ static std::ifstream::pos_type get_file_size(const char *filename)
 }
 
 static void read_file_bytes(const char *filename,size_t fileoff,
-                            char *read_buf, size_t read_sz)
+                            mem_t* mem, size_t memoff, size_t read_sz)
 {
   std::ifstream in(filename, std::ios::in | std::ios::binary);
   in.seekg(fileoff, std::ios::beg);
-  in.read(read_buf, read_sz);
+
+  std::vector<char> read_buf(read_sz, 0);
+  in.read(&read_buf[0], read_sz);
+  mem->store(memoff, read_sz, (uint8_t*)&read_buf[0]);
 }
 
 bool sort_mem_region(const std::pair<reg_t, mem_t*> &a,
@@ -374,7 +377,7 @@ int main(int argc, char** argv)
       kernel_offset = 0x400000;
     for (auto& m : mems) {
       if (kernel_size && (kernel_offset + kernel_size) < m.second->size()) {
-         read_file_bytes(kernel, 0, m.second->contents() + kernel_offset, kernel_size);
+         read_file_bytes(kernel, 0, m.second, kernel_offset, kernel_size);
          break;
       }
     }
@@ -386,7 +389,7 @@ int main(int argc, char** argv)
       if (initrd_size && (initrd_size + 0x1000) < m.second->size()) {
          initrd_end = m.first + m.second->size() - 0x1000;
          initrd_start = initrd_end - initrd_size;
-         read_file_bytes(initrd, 0, m.second->contents() + (initrd_start - m.first), initrd_size);
+         read_file_bytes(initrd, 0, m.second, initrd_start - m.first, initrd_size);
          break;
       }
     }