From 94344d130c2c2db90bcc47e12870d1d58f020ecf Mon Sep 17 00:00:00 2001
From: Philipp Stephani <phst@google.com>
Date: Sun, 10 Jan 2021 22:28:31 +0100
Subject: [PATCH] Add functions to open a file without quitting.

In some situations, e.g. when the Lisp machinery isn't available, we
can't quit.  Don't check the quit flags in such situations, in case
they contain garbage.

* src/sysdep.c (emacs_open_noquit, emacs_openat_noquit): New variants
of 'emacs_open' and 'emacs_openat' that don't check the quit flags.

* src/emacs.c (main, Fdaemon_initialized):
* src/pdumper.c (pdumper_load):
* src/w32term.c (w32_initialize):
* src/buffer.c (mmap_init):
* src/callproc.c (emacs_spawn): Use them where we can't quit.
---
 src/buffer.c   |  2 +-
 src/callproc.c |  2 +-
 src/emacs.c    |  4 ++--
 src/lisp.h     |  1 +
 src/pdumper.c  |  2 +-
 src/sysdep.c   | 22 ++++++++++++++++++++++
 src/w32term.c  |  3 ++-
 7 files changed, 30 insertions(+), 6 deletions(-)

diff --git a/src/buffer.c b/src/buffer.c
index 71ad5edd527..80c799e719b 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -4785,7 +4785,7 @@ mmap_init (void)
   if (mmap_fd <= 0)
     {
       /* No anonymous mmap -- we need the file descriptor.  */
-      mmap_fd = emacs_open ("/dev/zero", O_RDONLY, 0);
+      mmap_fd = emacs_open_noquit ("/dev/zero", O_RDONLY, 0);
       if (mmap_fd == -1)
 	fatal ("Cannot open /dev/zero: %s", emacs_strerror (errno));
     }
diff --git a/src/callproc.c b/src/callproc.c
index 1da315bef18..cb72b070b7b 100644
--- a/src/callproc.c
+++ b/src/callproc.c
@@ -1336,7 +1336,7 @@ emacs_spawn (pid_t *newpid, int std_in, int std_out, int std_err,
 	     would work?  */
 	  if (std_in >= 0)
 	    emacs_close (std_in);
-	  std_out = std_in = emacs_open (pty, O_RDWR, 0);
+          std_out = std_in = emacs_open_noquit (pty, O_RDWR, 0);
 
 	  if (std_in < 0)
 	    {
diff --git a/src/emacs.c b/src/emacs.c
index 69d10821fae..77114271b27 100644
--- a/src/emacs.c
+++ b/src/emacs.c
@@ -1275,7 +1275,7 @@ main (int argc, char **argv)
 	{
 	  emacs_close (STDIN_FILENO);
 	  emacs_close (STDOUT_FILENO);
-	  int result = emacs_open (term, O_RDWR, 0);
+	  int result = emacs_open_noquit (term, O_RDWR, 0);
 	  if (result != STDIN_FILENO
 	      || (fcntl (STDIN_FILENO, F_DUPFD_CLOEXEC, STDOUT_FILENO)
 		  != STDOUT_FILENO))
@@ -2847,7 +2847,7 @@ from the parent process and its tty file descriptors.  */)
       int nfd;
 
       /* Get rid of stdin, stdout and stderr.  */
-      nfd = emacs_open ("/dev/null", O_RDWR, 0);
+      nfd = emacs_open_noquit ("/dev/null", O_RDWR, 0);
       err |= nfd < 0;
       err |= dup2 (nfd, STDIN_FILENO) < 0;
       err |= dup2 (nfd, STDOUT_FILENO) < 0;
diff --git a/src/lisp.h b/src/lisp.h
index 86be25852a6..9d8dbbd629f 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -4577,6 +4577,7 @@ extern AVOID emacs_abort (void) NO_INLINE;
 extern int emacs_fstatat (int, char const *, void *, int);
 extern int emacs_openat (int, char const *, int, int);
 extern int emacs_open (const char *, int, int);
+extern int emacs_open_noquit (const char *, int, int);
 extern int emacs_pipe (int[2]);
 extern int emacs_close (int);
 extern ptrdiff_t emacs_read (int, void *, ptrdiff_t);
diff --git a/src/pdumper.c b/src/pdumper.c
index 116cc28dbba..c1388ebbb37 100644
--- a/src/pdumper.c
+++ b/src/pdumper.c
@@ -5273,7 +5273,7 @@ pdumper_load (const char *dump_filename)
   eassert (!dump_loaded_p ());
 
   int err;
-  int dump_fd = emacs_open (dump_filename, O_RDONLY, 0);
+  int dump_fd = emacs_open_noquit (dump_filename, O_RDONLY, 0);
   if (dump_fd < 0)
     {
       err = (errno == ENOENT || errno == ENOTDIR
diff --git a/src/sysdep.c b/src/sysdep.c
index a49f1775ebd..941b4e2fa24 100644
--- a/src/sysdep.c
+++ b/src/sysdep.c
@@ -2320,6 +2320,28 @@ emacs_open (char const *file, int oflags, int mode)
   return emacs_openat (AT_FDCWD, file, oflags, mode);
 }
 
+/* Same as above, but doesn't allow the user to quit.  */
+
+static int
+emacs_openat_noquit (int dirfd, const char *file, int oflags,
+                     int mode)
+{
+  int fd;
+  if (! (oflags & O_TEXT))
+    oflags |= O_BINARY;
+  oflags |= O_CLOEXEC;
+  do
+    fd = openat (dirfd, file, oflags, mode);
+  while (fd < 0 && errno == EINTR);
+  return fd;
+}
+
+int
+emacs_open_noquit (char const *file, int oflags, int mode)
+{
+  return emacs_openat_noquit (AT_FDCWD, file, oflags, mode);
+}
+
 /* Open FILE as a stream for Emacs use, with mode MODE.
    Act like emacs_open with respect to threads, signals, and quits.  */
 
diff --git a/src/w32term.c b/src/w32term.c
index e5a8a823b48..109aa58d732 100644
--- a/src/w32term.c
+++ b/src/w32term.c
@@ -7507,7 +7507,8 @@ w32_initialize (void)
     }
 
 #ifdef CYGWIN
-  if ((w32_message_fd = emacs_open ("/dev/windows", O_RDWR, 0)) == -1)
+  if ((w32_message_fd = emacs_open_noquit ("/dev/windows", O_RDWR, 0))
+      == -1)
     fatal ("opening /dev/windows: %s", strerror (errno));
 #endif /* CYGWIN */
 
-- 
2.39.5