Revert "[CommandLine][Linux] Don't read argv from /proc/self/cmdline."

Author: jckarter

stdlib/public/CommandLineSupport/CommandLine.cpp

@@ -172,151 +172,7 @@ static char **swift::getUnsafeArgvArgc(int *outArgLen) {
 
 template <typename F>
 static void swift::enumerateUnsafeArgv(const F& body) { }
-#elif defined(__linux__)
-// On Linux, there is no easy way to get the argument vector pointer outside
-// of the main() function.  However, the ABI specifications dictate the layout
-// of the process's initial stack, which looks something like:
-//
-// stack top ----> ┌────────────────────────┐
-//                 │ Unspecified            │
-//                 ┊                        ┊
-//                 ├┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┤
-//                 │ Information block      │
-//                 │ (argument strings,     │
-//                 │ environment strings,   │
-//                 │ auxiliary information) │
-//                 ┊                        ┊
-//                 ├┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┤
-//                 │ Unspecified            │
-//                 ┊                        ┊
-//                 ├┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┤
-//                 │ NULL                   │
-//                 ├┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┤
-//                 │ Auxiliary Vector       │
-//                 ┊                        ┊
-//                 ├┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┤
-//                 │ NULL                   │
-//                 ├┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┤
-//                 │ Environment Pointers   │
-//                 ┊                        ┊
-// environ ------> ├┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┤
-//                 │ NULL                   │
-//                 ├┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┤
-//                 │ Argument Pointers      │
-//                 ┊                        ┊
-//                 ├┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┤
-//                 │ Argument Count         │
-//                 ├┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┤
-//                 ┊                        ┊
-//
-//                 See https://gitlab.com/x86-psABIs/x86-64-ABI,
-//                     https://gitlab.com/x86-psABIs/i386-ABI
-//
-// The upshot is that if we can get hold of `environ` before anything has
-// had a chance to change it, we can find the `argv` array and also the
-// argument count, `argc`, by walking back up the stack.
-//
-// (Note that Linux uses this same layout for all platforms, not just x86-based
-// ones.  It also has a fixed layout for the data at the top of the stack, but
-// we don't need to take advantage of that here and can stick to things that
-// are defined in the ABI specs.)
-
-// We'll need this in a minute
-extern char **environ;
-
-namespace {
-
-struct ArgvGrabber {
-  char **argv;
-  int argc;
-
-  ArgvGrabber();
-
-private:
-  struct stack {
-    void *base;
-    void *top;
-
-    stack() : base(nullptr), top(nullptr) {}
-    stack(void *b, void *t) : base(b), top(t) {}
-  };
-
-  stack findStack();
-  void findArgv(stack s);
-};
-
-// Find the stack by looking at /proc/self/maps
-ArgvGrabber::stack ArgvGrabber::findStack(void) {
-  FILE *maps = fopen("/proc/self/maps", "r");
-  if (!maps)
-    return stack();
-
-  char line[256];
-  void *base = NULL, *top = NULL;
-  bool found = false;
-  while (fgets(line, sizeof(line), maps)) {
-    // line is on the stack, so we know we're looking at the right
-    // region if line is between base and top.
-    //
-    // Note that we can't look for [stack], because Rosetta and qemu
-    // set up a separate stack for the emulated code.
-    if (sscanf(line, "%p-%p", &base, &top) == 2
-        && (void *)line >= base && (void *)line < top) {
-      found = true;
-      break;
-    }
-  }
-
-  fclose(maps);
-
-  if (!found)
-    return stack();
-
-  return stack(base, top);
-}
-
-// Find argv by walking backwards from environ
-void ArgvGrabber::findArgv(ArgvGrabber::stack stack) {
-  if (!stack.base)
-    return;
-
-  // Check that environ points to the stack
-  char **envp = environ;
-  if ((void *)envp < stack.base || (void *)envp >= stack.top)
-    return;
-
-  char **ptr = envp - 1;
-
-// We're now pointing at the NULL that terminates argv.  Keep going back
-  // while we're seeing pointers (values greater than envp).
-  while ((void *)(ptr - 1) > stack.base) {
-    --ptr;
-
-    // The first thing less than envp must be the argc value
-    if ((void *)*ptr < (void *)envp) {
-      argc = (int)(intptr_t)*ptr++;
-      argv = ptr;
-      return;
-    }
-  }
-}
-
-ArgvGrabber::ArgvGrabber() : argv(nullptr), argc(0) {
-  findArgv(findStack());
-}
-
-ArgvGrabber argvGrabber;
-
-} // namespace
-
-static char **swift::getUnsafeArgvArgc(int *outArgLen) {
-  *outArgLen = argvGrabber.argc;
-  return argvGrabber.argv;
-}
-
-template <typename F>
-static void swift::enumerateUnsafeArgv(const F& body) { }
-#elif defined(__CYGWIN__)
+#elif defined(__linux__) || defined(__CYGWIN__)
 static char **swift::getUnsafeArgvArgc(int *outArgLen) {
   return nullptr;
 }