[PATCH 2/6] gdb/ser-pipe.c: Duplicate the file descriptors

["Alexandra Hájková" <ahajkova@redhat.com>]

Duplicate the numbers of STDOUT/STDIN/STDERR file descriptors
GDB is connected to. Preserved numbers of the file descriptors
could be then sent to the GDBserver. If GDBserver is run locally
and will accept he numbers of the file descriptors, it can start
the inferior connected to the same STDIN/OUT/ERR, GDB is connected to.
---
 gdb/ser-pipe.c | 25 +++++++++++++++++++++++++
 gdb/serial.c   |  4 ++++
 gdb/serial.h   |  4 ++++
 3 files changed, 33 insertions(+)

diff --git a/gdb/ser-pipe.c b/gdb/ser-pipe.c
index 47ccd33cece..84253cf2e2c 100644
--- a/gdb/ser-pipe.c
+++ b/gdb/ser-pipe.c
@@ -77,6 +77,16 @@ pipe_open (struct serial *scb, const char *name)
       return -1;
     }
 
+  /* Preserve STDIN/STDOUT/STDERR so they won't be closed on
+     exec later, after we fork.  */
+  int saved_stdin = dup (STDIN_FILENO);
+  int saved_stdout = dup (STDOUT_FILENO);
+  int saved_stderr = dup (STDERR_FILENO);
+
+  scb->fds[0] = saved_stdin;
+  scb->fds[1] = saved_stdout;
+  scb->fds[2] = saved_stderr;
+
   /* Create the child process to run the command in.  Note that the
      apparent call to vfork() below *might* actually be a call to
      fork() due to the fact that autoconf will ``#define vfork fork''
@@ -90,6 +100,12 @@ pipe_open (struct serial *scb, const char *name)
       close (pdes[1]);
       close (err_pdes[0]);
       close (err_pdes[1]);
+      close (saved_stdout);
+      close (saved_stdin);
+      close (saved_stderr);
+      scb->fds[0] = -1;
+      scb->fds[1] = -1;
+      scb->fds[2] = -1;
       return -1;
     }
 
@@ -128,6 +144,10 @@ pipe_open (struct serial *scb, const char *name)
 	  close (err_pdes[1]);
 	}
 
+      mark_fd_no_cloexec (saved_stdout);
+      mark_fd_no_cloexec (saved_stdin);
+      mark_fd_no_cloexec (saved_stderr);
+
       close_most_fds ();
 
       const char *shellfile = get_shell ();
@@ -139,6 +159,11 @@ pipe_open (struct serial *scb, const char *name)
   close (pdes[1]);
   if (err_pdes[1] != -1)
     close (err_pdes[1]);
+
+  close (saved_stdout);
+  close (saved_stdin);
+  close (saved_stderr);
+
   /* :end chunk */
   state = XNEW (struct pipe_state);
   state->pid = pid;
diff --git a/gdb/serial.c b/gdb/serial.c
index 8a8bab46ead..a2bbe9a972d 100644
--- a/gdb/serial.c
+++ b/gdb/serial.c
@@ -182,6 +182,10 @@ new_serial (const struct serial_ops *ops)
 
   scb->ops = ops;
 
+  scb->fds[0] = -1;
+  scb->fds[1] = -1;
+  scb->fds[2] = -1;
+
   scb->bufp = scb->buf;
   scb->error_fd = -1;
   scb->refcnt = 1;
diff --git a/gdb/serial.h b/gdb/serial.h
index 3b861200302..113f7360a55 100644
--- a/gdb/serial.h
+++ b/gdb/serial.h
@@ -254,6 +254,10 @@ struct serial
     int async_state;		/* Async internal state.  */
     void *async_context;	/* Async event thread's context */
     serial_event_ftype *async_handler;/* Async event handler */
+
+    /* File descriptors for preserved STDIN/STDOUT/STDERR
+       to be sent to GDBserver when run locally.  */
+    int fds[3];
   };
 
 struct serial_ops
-- 
2.41.0