Implement vFile:setfs in gdbserver

From: Gary Benson <gbenson@redhat.com>

This commit implements the "vFile:setfs" packet in gdbserver.

gdb/gdbserver/ChangeLog:

	* target.h (struct target_ops) <multifs_open>: New field.

	<multifs_unlink>: Likewise.

	<multifs_readlink>: Likewise.

	* linux-low.c (nat/linux-namespaces.h): New include.

	(linux_target_ops): Initialize the_target->multifs_open,

	the_target->multifs_unlink and the_target->multifs_readlink.

	* hostio.h (hostio_handle_new_gdb_connection): New declaration.

	* hostio.c (hostio_fs_pid): New static variable.

	(hostio_handle_new_gdb_connection): New function.

	(handle_setfs): Likewise.

	(handle_open): Use the_target->multifs_open as appropriate.

	(handle_unlink): Use the_target->multifs_unlink as appropriate.

	(handle_readlink): Use the_target->multifs_readlink as

	appropriate.

	(handle_vFile): Handle vFile:setfs packets.

	* server.c (handle_query): Call hostio_handle_new_gdb_connection

	after target_handle_new_gdb_connection.

---

 gdb/gdbserver/ChangeLog   |   20 +++++++++++++

 gdb/gdbserver/hostio.c    |   70 +++++++++++++++++++++++++++++++++++++++++++--

 gdb/gdbserver/linux-low.c |    4 +++

 gdb/gdbserver/server.c    |    2 +

 gdb/gdbserver/target.h    |   21 ++++++++++++++

 5 files changed, 114 insertions(+), 3 deletions(-)

Index: gdb-7.6.1/gdb/gdbserver/hostio.c

===================================================================

--- gdb-7.6.1.orig/gdb/gdbserver/hostio.c	2013-01-01 07:33:00.000000000 +0100

+++ gdb-7.6.1/gdb/gdbserver/hostio.c	2016-03-06 23:38:57.315483217 +0100

@@ -263,6 +263,55 @@

   return 0;

 }

+/* Process ID of inferior whose filesystem hostio functions

+   that take FILENAME arguments will use.  Zero means to use

+   our own filesystem.  */

+

+static int hostio_fs_pid;

+

+/* See hostio.h.  */

+

+void

+hostio_handle_new_gdb_connection (void)

+{

+  hostio_fs_pid = 0;

+}

+

+/* Handle a "vFile:setfs:" packet.  */

+

+static void

+handle_setfs (char *own_buf)

+{

+  char *p;

+  int pid;

+

+  /* If the target doesn't have any of the in-filesystem-of methods

+     then there's no point in GDB sending "vFile:setfs:" packets.  We

+     reply with an empty packet (i.e. we pretend we don't understand

+     "vFile:setfs:") and that should stop GDB sending any more.  */

+  if (the_target->multifs_open == NULL

+      && the_target->multifs_unlink == NULL

+      && the_target->multifs_readlink == NULL)

+    {

+      own_buf[0] = '\0';

+      return;

+    }

+

+  p = own_buf + strlen ("vFile:setfs:");

+

+  if (require_int (&p, &pid)

+      || pid < 0

+      || require_end (p))

+    {

+      hostio_packet_error (own_buf);

+      return;

+    }

+

+  hostio_fs_pid = pid;

+

+  hostio_reply (own_buf, 0);

+}

+

 static void

 handle_open (char *own_buf)

 {

@@ -287,7 +336,11 @@

   /* We do not need to convert MODE, since the fileio protocol

      uses the standard values.  */

-  fd = open (filename, flags, mode);

+  if (hostio_fs_pid != 0 && the_target->multifs_open != NULL)

+    fd = the_target->multifs_open (hostio_fs_pid, filename,

+				   flags, mode);

+  else

+    fd = open (filename, flags, mode);

   if (fd == -1)

     {

@@ -455,7 +508,10 @@

       return;

     }

-  ret = unlink (filename);

+  if (hostio_fs_pid != 0 && the_target->multifs_unlink != NULL)

+    ret = the_target->multifs_unlink (hostio_fs_pid, filename);

+  else

+    ret = unlink (filename);

   if (ret == -1)

     {

@@ -483,7 +539,13 @@

       return;

     }

-  ret = readlink (filename, linkname, sizeof (linkname) - 1);

+  if (hostio_fs_pid != 0 && the_target->multifs_readlink != NULL)

+    ret = the_target->multifs_readlink (hostio_fs_pid, filename,

+					linkname,

+					sizeof (linkname) - 1);

+  else

+    ret = readlink (filename, linkname, sizeof (linkname) - 1);

+

   if (ret == -1)

     {

       hostio_error (own_buf);

@@ -518,6 +580,8 @@

     handle_unlink (own_buf);

   else if (strncmp (own_buf, "vFile:readlink:", 15) == 0)

     handle_readlink (own_buf, new_packet_len);

+  else if (strncmp (own_buf, "vFile:setfs:", 12) == 0)

+    handle_setfs (own_buf);

   else

     return 0;

Index: gdb-7.6.1/gdb/gdbserver/linux-low.c

===================================================================

--- gdb-7.6.1.orig/gdb/gdbserver/linux-low.c	2016-03-06 23:38:57.259482835 +0100

+++ gdb-7.6.1/gdb/gdbserver/linux-low.c	2016-03-06 23:38:57.317483230 +0100

@@ -50,6 +50,7 @@

    definition of elf_fpregset_t.  */

 #include <elf.h>

 #endif

+#include "../nat/linux-namespaces.h"

 #ifndef SPUFS_MAGIC

 #define SPUFS_MAGIC 0x23c9b64e

@@ -6019,6 +6020,9 @@

   NULL,

 #endif

   linux_proc_pid_to_exec_file,

+  linux_mntns_open_cloexec,

+  linux_mntns_unlink,

+  linux_mntns_readlink,

 };

 static void

Index: gdb-7.6.1/gdb/gdbserver/server.c

===================================================================

--- gdb-7.6.1.orig/gdb/gdbserver/server.c	2016-03-06 23:38:57.278482965 +0100

+++ gdb-7.6.1/gdb/gdbserver/server.c	2016-03-06 23:41:53.678684044 +0100

@@ -1873,6 +1873,11 @@

       if (the_target->pid_to_exec_file != NULL)

 	strcat (own_buf, ";qXfer:exec-file:read+");

+      /* Reinitialize components as needed for the new connection.  */

+{

+extern void hostio_handle_new_gdb_connection (void);

+      hostio_handle_new_gdb_connection ();

+}

       return;

     }

Index: gdb-7.6.1/gdb/gdbserver/target.h

===================================================================

--- gdb-7.6.1.orig/gdb/gdbserver/target.h	2016-03-06 23:38:57.261482849 +0100

+++ gdb-7.6.1/gdb/gdbserver/target.h	2016-03-06 23:38:57.318483237 +0100

@@ -421,6 +421,27 @@

      string should be copied into a buffer by the client if the string

      will not be immediately used, or if it must persist.  */

   char *(*pid_to_exec_file) (int pid);

+

+  /* Multiple-filesystem-aware open.  Like open(2), but operating in

+     the filesystem as it appears to process PID.  Systems where all

+     processes share a common filesystem should set this to NULL.

+     If NULL, the caller should fall back to open(2).  */

+  int (*multifs_open) (int pid, const char *filename,

+		       int flags, mode_t mode);

+

+  /* Multiple-filesystem-aware unlink.  Like unlink(2), but operates

+     in the filesystem as it appears to process PID.  Systems where

+     all processes share a common filesystem should set this to NULL.

+     If NULL, the caller should fall back to unlink(2).  */

+  int (*multifs_unlink) (int pid, const char *filename);

+

+  /* Multiple-filesystem-aware readlink.  Like readlink(2), but

+     operating in the filesystem as it appears to process PID.

+     Systems where all processes share a common filesystem should

+     set this to NULL.  If NULL, the caller should fall back to

+     readlink(2).  */

+  ssize_t (*multifs_readlink) (int pid, const char *filename,

+			       char *buf, size_t bufsiz);

 };

 extern struct target_ops *the_target;