[asan, myriad] Support environment variables

[alekseyshl]

compiler-rt/lib/sanitizer_common/sanitizer_rtems.cc

257

What if name_len > env_len - 2?

261

name == "" and env="=x\0" will work and return "x", but maybe it's not that a bad thing.

[vitalybuka]

compiler-rt/lib/sanitizer_common/sanitizer_rtems.cc

39

why?

41

Howe about making it static and add __sanitizer::SetEnvForTest()

253

how this can happen?

259

for (uptr i = 0; i <= end; i += internal_strlen(env) + 1)

[waltl]

Sorry for the overly complicated initial patch. We've decided to get
setenv() to work in our test enviroment (using similar approach to the
initial patch here), so now the sanitizer run-time can just call that.

compiler-rt/lib/sanitizer_common/sanitizer_rtems.cc

 #include <string.h>
 #include <unistd.h>
 
 // There is no mmap on RTEMS.  Use memalign, etc.
 #define __mmap_alloc_aligned posix_memalign
 #define __mmap_free free
 #define __mmap_memset memset
 
+static const __asan::uptr __sanitizer_env_len = 1024;
+// This variable needs to not be in .bss because we don't want
+// zero-initialization by the OS.
+char __sanitizer_env[__sanitizer_env_len] __attribute__((section(".data")));
+
 namespace __sanitizer {
 
 #include "sanitizer_syscall_generic.inc"
 
 void NORETURN internal__exit(int exitcode) {
   _exit(exitcode);
 }
 

 void ReleaseMemoryPagesToOS(uptr beg, uptr end) {}
 void DumpProcessMap() {}
 
 // There is no page protection so everything is "accessible."
 bool IsAccessibleMemoryRange(uptr beg, uptr size) {
   return true;
 }
 
-char **GetArgv() { return NULL; }
-const char *GetEnv(const char *name) { return NULL; }
+char **GetArgv() { return nullptr; }
+
+const char *GetEnv(const char *name) {
+  char *const env = __sanitizer_env;
+  uptr env_len = __sanitizer_env_len;
+  // To avoid buffer overrun, give up if buffer is not null terminated.
+  if (env[env_len - 1] != '\0')
+    return nullptr;
+
+  uptr name_len = internal_strlen(name);
+  uptr end = env_len - name_len - 2;
+  uptr i = 0;
+  while (i <= end) {
+    if (internal_strncmp(&env[i], name, name_len) == 0 &&
+        env[i + name_len] == '=')
+      return &env[i + name_len + 1];
+    i += internal_strlen(env) + 1;
+  }
+  return nullptr;
+}
 
 uptr ReadBinaryName(/*out*/char *buf, uptr buf_len) {
   internal_strncpy(buf, "StubBinaryName", buf_len);
   return internal_strlen(buf);
 }
 
 uptr ReadLongProcessName(/*out*/ char *buf, uptr buf_len) {
   internal_strncpy(buf, "StubProcessName", buf_len);