5 files changed, 37 insertions, 21 deletions
diff --git a/src/common/compat.c b/src/common/compat.c
index 6fb15e3794..8e301a0edd 100644
--- a/src/common/compat.c
+++ b/src/common/compat.c
@@ -113,14 +113,19 @@ const char compat_c_id[] =
 #endif
 
 #ifdef HAVE_SYS_MMAN_H
+typedef struct tor_mmap_impl_t {
+  tor_mmap_t base;
+  size_t mapping_size; /**< Size of the actual mapping. (This is this file
+                        * size, rounded up to the nearest page.) */
+} tor_mmap_impl_t;
 tor_mmap_t *
 tor_mmap_file(const char *filename)
 {
   int fd; /* router file */
   char *string;
   int page_size;
-  tor_mmap_t *res;
-  size_t size;
+  tor_mmap_impl_t *res;
+  size_t size, filesize;
 
   tor_assert(filename);
 
@@ -130,7 +135,7 @@ tor_mmap_file(const char *filename)
     return NULL;
   }
 
-  size = lseek(fd, 0, SEEK_END);
+  size = filesize = lseek(fd, 0, SEEK_END);
   lseek(fd, 0, SEEK_SET);
   /* ensure page alignment */
   page_size = getpagesize();
@@ -146,28 +151,31 @@ tor_mmap_file(const char *filename)
 
   close(fd);
 
-  res = tor_malloc_zero(sizeof(tor_mmap_t));
-  res->data = string;
-  res->size = size;
+  res = tor_malloc_zero(sizeof(tor_mmap_impl_t));
+  res->base.data = string;
+  res->base.size = filesize;
+  res->mapping_size = size;
 
-  return res;
+  return &(res->base);
 }
 void
 tor_munmap_file(tor_mmap_t *handle)
 {
-  munmap((char*)handle->data, handle->size);
-  tor_free(handle);
+  tor_mmap_impl_t *h = (tor_mmap_impl_t*)
+    (((char*)handle) - STRUCT_OFFSET(tor_mmap_impl_t, base));
+  munmap((char*)h->base.data, h->mapping_size);
+  tor_free(h);
 }
 #elif defined(MS_WINDOWS)
 typedef struct win_mmap_t {
   tor_mmap_t base;
   HANDLE file_handle;
   HANDLE mmap_handle;
-} tor_mmap_impl_t;
+} win_mmap_t;
 tor_mmap_t *
 tor_mmap_file(const char *filename)
 {
-  struct win_mmap_t *res = tor_malloc_zero(sizeof(struct win_mmap_t));
+  win_mmap_t *res = tor_malloc_zero(sizeof(win_mmap_t));
   res->mmap_handle = res->file_handle = INVALID_HANDLE_VALUE;
 
   res->file_handle = CreateFile(filename,
@@ -208,8 +216,8 @@ tor_mmap_file(const char *filename)
 void
 tor_munmap_file(tor_mmap_t *handle)
 {
-  struct win_mmap_t *h = (struct win_mmap_t*)
-    (((char*)handle) - STRUCT_OFFSET(struct win_mmap_t, base));
+  win_mmap_t *h = (win_mmap_t*)
+    (((char*)handle) - STRUCT_OFFSET(win_mmap_t, base));
   if (handle->data)
 
   /*this is an ugly cast, but without it, "data" in struct tor_mmap_t would
@@ -226,13 +234,14 @@ tor_munmap_file(tor_mmap_t *handle)
 tor_mmap_t *
 tor_mmap_file(const char *filename)
 {
-  char *res = read_file_to_str(filename, 1);
+  size_t size;
+  char *res = read_file_to_str(filename, 1, &size);
   tor_mmap_t *handle;
   if (! res)
     return NULL;
   handle = tor_malloc_zero(sizeof(tor_mmap_t));
   handle->data = res;
-  handle->size = strlen(res) + 1;
+  handle->size = size;
   return handle;
 }
 void
diff --git a/src/common/compat.h b/src/common/compat.h
index 5567f5e9c1..79825fc057 100644
--- a/src/common/compat.h
+++ b/src/common/compat.h
@@ -129,10 +129,11 @@ size_t strlcpy(char *dst, const char *src, size_t siz) ATTR_NONNULL((1,2));
 #define U64_LITERAL(n) (n ## llu)
 #endif
 
-/** Opaque bookkeeping type used for mmap accounting. */
+/** Represents an mmaped file. Allocated via tor_mmap_file; freed with
+ * tor_munmap_file. */
 typedef struct tor_mmap_t {
-  const char *data;
-  size_t size;
+  const char *data; /**< Mapping of the file's contents. */
+  size_t size; /**< Size of the file. */
 } tor_mmap_t;
 
 tor_mmap_t *tor_mmap_file(const char *filename) ATTR_NONNULL((1));
diff --git a/src/common/crypto.c b/src/common/crypto.c
index 9aea7506ae..c7e5d4587f 100644
--- a/src/common/crypto.c
+++ b/src/common/crypto.c
@@ -460,7 +460,7 @@ crypto_pk_read_private_key_from_filename(crypto_pk_env_t *env,
   int r;
 
   /* Read the file into a string. */
-  contents = read_file_to_str(keyfile, 0);
+  contents = read_file_to_str(keyfile, 0, NULL);
   if (!contents) {
     log_warn(LD_CRYPTO, "Error reading private key from \"%s\"", keyfile);
     return -1;
diff --git a/src/common/util.c b/src/common/util.c
index 50211917b3..d5a71d2743 100644
--- a/src/common/util.c
+++ b/src/common/util.c
@@ -1288,6 +1288,9 @@ append_bytes_to_file(const char *fname, const char *str, size_t len,
 
 /** Read the contents of <b>filename</b> into a newly allocated
  * string; return the string on success or NULL on failure.
+ *
+ * If <b>size_out</b> is provided, store the length of the result in
+ * <b>size_out</b>
  */
 /*
  * This function <em>may</em> return an erroneous result if the file
@@ -1297,7 +1300,7 @@ append_bytes_to_file(const char *fname, const char *str, size_t len,
  * be truncated.
  */
 char *
-read_file_to_str(const char *filename, int bin)
+read_file_to_str(const char *filename, int bin, size_t *size_out)
 {
   int fd; /* router file */
   struct stat statbuf;
@@ -1351,6 +1354,8 @@ read_file_to_str(const char *filename, int bin)
   }
 #endif
   close(fd);
+  if (size_out)
+    *size_out = (size_t) r;
 
   return string;
 }
diff --git a/src/common/util.h b/src/common/util.h
index 082e9db51a..13d51b4413 100644
--- a/src/common/util.h
+++ b/src/common/util.h
@@ -180,7 +180,8 @@ int write_chunks_to_file(const char *fname, const struct smartlist_t *chunks,
 int append_bytes_to_file(const char *fname, const char *str, size_t len,
                          int bin);
 
-char *read_file_to_str(const char *filename, int bin) ATTR_MALLOC;
+char *read_file_to_str(const char *filename, int bin, size_t *size_out)
+  ATTR_MALLOC;
 char *parse_line_from_str(char *line, char **key_out, char **value_out);
 char *expand_filename(const char *filename);
 struct smartlist_t *tor_listdir(const char *dirname);