Add options for base dir and redirecting files to IRT open resource and use it.

src/untrusted/irt/irt_core_resource.c

Index: src/untrusted/irt/irt_core_resource.c
diff --git a/src/untrusted/irt/irt_core_resource.c b/src/untrusted/irt/irt_core_resource.c
index eb0ceebaafadd5647363e236bf8863059182f9b9..b591a1ecef41facd771aa2f3ec65a36d27007568 100644
--- a/src/untrusted/irt/irt_core_resource.c
+++ b/src/untrusted/irt/irt_core_resource.c
@@ -4,13 +4,73 @@
  * found in the LICENSE file.
  */
 
+#include <errno.h>
 #include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
 
 #include "native_client/src/untrusted/irt/irt.h"
 #include "native_client/src/untrusted/nacl/syscall_bindings_trampoline.h"
 
+/*
+ * An open resource implementation used for testing PNaCl's sandboxed

[Mark Seaborn, 2014/12/02 00:42:07]

Nit: "open resource" -> "open_resource()"

[jvoung (off chromium), 2014/12/02 16:24:08]

Done.

+ * translator (the linker), outside of chromium.

[Mark Seaborn, 2014/12/02 00:42:07]

Nit: capitalise as "Chromium"

[jvoung (off chromium), 2014/12/02 16:24:08]

Done.

+ *
+ * This code will prepend the |base_dir| to |pathname|. That is useful if,
+ * say, |pathname| is the basename of a library, and |base_dir| is a directory.
+ * holding library files. The |base_dir| is assumed to already have a
+ * separator char at the end.
+ *
+ * PNaCl's sandboxed linker also has hardcoded the name of a shim library.
+ * That will open the chromium PPAPI shim when used with chromium, but when
+ * testing outside of chromium we want to open a dummy shim library instead.
+ * |file_remap| is used to redirect the hardcoded shim library name to the
+ * dummy shim. This is specified as an environment variable, e.g.:
+ * "NACL_IRT_OPEN_RESOURCE_REMAPPED=lib_orig.a:lib_dummy.a"
+ */
+static int nacl_irt_open_resource_remapped(const char *pathname,
+                                           const char *base_dir,
+                                           const char *file_remap) {
+  if (file_remap != NULL) {
+    const char *delim_ptr = strchr(file_remap, ':');
+    if (delim_ptr != NULL) {
+      if (strcmp(pathname, file_remap) == 0) {
+        pathname = delim_ptr + 1;
+      }
+    } else {
+      fprintf(
+          stderr,
+          "NACL_IRT_OPEN_RESOURCE_REMAP expects <from>:<to> instead of %s\n",
+          file_remap);
+      abort();
+    }
+  }
+  size_t base_len = strlen(base_dir);
+  size_t pathname_len = strlen(pathname);
+  char *merged_path = (char *)malloc(

[Mark Seaborn, 2014/12/02 00:42:07]

Nit: add space after "(char *)"

[jvoung (off chromium), 2014/12/02 16:24:08]

Done.

+      sizeof(char) * (base_len + pathname_len + 1));
+  if (merged_path == NULL) {
+    errno = ENOMEM;
+    return -1;
+  }
+  merged_path[0] = '\0';

[Mark Seaborn, 2014/12/02 00:42:07]

Use strcpy() instead of this + strcat()?

[jvoung (off chromium), 2014/12/02 16:24:08]

Done.

+  strcat(merged_path, base_dir);
+  strcat(merged_path, pathname);
+  int rv = NACL_GC_WRAP_SYSCALL(NACL_SYSCALL(open)(merged_path, O_RDONLY, 0));
+  free(merged_path);
+  return rv;
+}
+
 static int nacl_irt_open_resource(const char *pathname, int *newfd) {
-  int rv = NACL_GC_WRAP_SYSCALL(NACL_SYSCALL(open)(pathname, O_RDONLY, 0));
+  char *base_dir = getenv("NACL_IRT_OPEN_RESOURCE_BASE");
+  char *file_remap = getenv("NACL_IRT_OPEN_RESOURCE_REMAP");
+  int rv;
+  if (base_dir == NULL) {
+    rv = NACL_GC_WRAP_SYSCALL(NACL_SYSCALL(open)(pathname, O_RDONLY, 0));
+  } else {
+    rv = nacl_irt_open_resource_remapped(pathname, base_dir, file_remap);
+  }
   if (rv < 0)
     return -rv;
   *newfd = rv;