[PING][PATCH] Move vgdb special case into remote_filesystem_is_local

[Gary Benson <gbenson at redhat dot com>]

Ping:
https://sourceware.org/ml/gdb-patches/2015-04/msg00991.html

Gary Benson wrote:
> Hi all,
> 
> Valgrind GDB (vgdb) presents itself as a remote target but works on
> the local filesystem.  gdb_bfd_open contained a special case to make
> vgdb work with "target:" sysroots, but the implementation meant that
> GDB would fall back to the local filesystem if *any* to_fileio_open
> method failed with ENOSYS for *any* reason.  This commit moves the
> vgdb special case to remote_filesystem_is_local to allow the fallback
> to be restricted only to the specific case that remote file transfer
> is unsupported.  This commit also adds a warning which is displayed
> the first time the fallback is used.
> 
> Built and regtested on RHEL6.6 x86_64.
> 
> Ok to commit?
> 
> Cheers,
> Gary
> 
> 
> gdb/ChangeLog:
> 
> 	* gdb_bfd.c (gdb_bfd_open): Move vgdb special case to...
> 	* remote.c (remote_filesystem_is_local): ...here.
> ---
>  gdb/ChangeLog |    5 ++++
>  gdb/gdb_bfd.c |   16 +-------------
>  gdb/remote.c  |   62 ++++++++++++++++++++++++++++++++++++++++++++++++--------
>  3 files changed, 59 insertions(+), 24 deletions(-)
> 
> diff --git a/gdb/gdb_bfd.c b/gdb/gdb_bfd.c
> index 3d5d23f..2cd91ef 100644
> --- a/gdb/gdb_bfd.c
> +++ b/gdb/gdb_bfd.c
> @@ -326,25 +326,11 @@ gdb_bfd_open (const char *name, const char *target, int fd)
>  	{
>  	  gdb_assert (fd == -1);
>  
> -	  abfd = gdb_bfd_openr_iovec (name, target,
> +	  return gdb_bfd_openr_iovec (name, target,
>  				      gdb_bfd_iovec_fileio_open, NULL,
>  				      gdb_bfd_iovec_fileio_pread,
>  				      gdb_bfd_iovec_fileio_close,
>  				      gdb_bfd_iovec_fileio_fstat);
> -
> -	  if (abfd != NULL || errno != ENOSYS)
> -	    return abfd;
> -
> -	  /* gdb_bfd_iovec_fileio_open failed with ENOSYS.  This can
> -	     happen, for example, with vgdb (Valgrind GDB), which
> -	     presents itself as a remote target but works on the local
> -	     filesystem: it does not implement remote get and users
> -	     are not expected to set gdb_sysroot.  To handle this case
> -	     we fall back to trying the local filesystem iff
> -	     gdb_sysroot is exactly TARGET_SYSROOT_PREFIX.  */
> -	  if (gdb_sysroot == NULL
> -	      || strcmp (gdb_sysroot, TARGET_SYSROOT_PREFIX) != 0)
> -	    return NULL;
>  	}
>  
>        name += strlen (TARGET_SYSROOT_PREFIX);
> diff --git a/gdb/remote.c b/gdb/remote.c
> index 3b2325f..099ddbb 100644
> --- a/gdb/remote.c
> +++ b/gdb/remote.c
> @@ -9879,15 +9879,6 @@ remote_hostio_send_command (int command_bytes, int which_packet,
>    return ret;
>  }
>  
> -/* Return nonzero if the filesystem accessed by the target_fileio_*
> -   methods is the local filesystem, zero otherwise.  */
> -
> -static int
> -remote_filesystem_is_local (struct target_ops *self)
> -{
> -  return 0;
> -}
> -
>  /* Open FILENAME on the remote target, using FLAGS and MODE.  Return a
>     remote file descriptor, or -1 if an error occurs (and set
>     *REMOTE_ERRNO).  */
> @@ -10125,6 +10116,59 @@ remote_hostio_fstat (struct target_ops *self,
>    return 0;
>  }
>  
> +/* Return nonzero if the filesystem accessed by the target_fileio_*
> +   methods is the local filesystem, zero otherwise.  */
> +
> +static int
> +remote_filesystem_is_local (struct target_ops *self)
> +{
> +  /* Valgrind GDB presents itself as a remote target but works
> +     on the local filesystem: it does not implement remote get
> +     and users are not expected to set a sysroot.  To handle
> +     this case we treat the remote filesystem as local if the
> +     sysroot is exactly TARGET_SYSROOT_PREFIX and if the stub
> +     does not support vFile:open.  */
> +  if (gdb_sysroot != NULL
> +      && strcmp (gdb_sysroot, TARGET_SYSROOT_PREFIX) == 0)
> +    {
> +      enum packet_support ps = packet_support (PACKET_vFile_open);
> +
> +      if (ps == PACKET_SUPPORT_UNKNOWN)
> +	{
> +	  int fd, remote_errno;
> +
> +	  /* Try opening a file to probe support.  The supplied
> +	     filename is irrelevant, we only care about whether
> +	     the stub recognizes the packet or not.  */
> +	  fd = remote_hostio_open (self, "just probing",
> +				   FILEIO_O_RDONLY, 0700,
> +				   &remote_errno);
> +
> +	  if (fd >= 0)
> +	    remote_hostio_close (self, fd, &remote_errno);
> +
> +	  ps = packet_support (PACKET_vFile_open);
> +	}
> +
> +      if (ps == PACKET_DISABLE)
> +	{
> +	  static int warning_issued = 0;
> +
> +	  if (!warning_issued)
> +	    {
> +	      warning (_("remote target does not support file"
> +			 " transfer, attempting to access files"
> +			 " from local filesystem."));
> +	      warning_issued = 1;
> +	    }
> +
> +	  return 1;
> +	}
> +    }
> +
> +  return 0;
> +}
> +
>  static int
>  remote_fileio_errno_to_host (int errnum)
>  {
> -- 
> 1.7.1
> 

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