Re: [PATCH v2] gdbserver: widen the stat fields returned by the vFile packets

[Abhay Kandpal <abhay@linux.ibm.com>]

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Hi Andrew,

Ping.  Let me know if the vFile-only scope looks right to you.

Thanks,
Abhay


On 04/09/26 14:02, Abhay Kandpal wrote:
> The struct sent by the vFile:fstat, vFile:stat and vFile:lstat packets
> declares st_dev, st_ino, st_nlink, st_rdev and the three timestamps as
> 4-byte fields, while the corresponding struct stat members are 8 bytes
> on a 64-bit host.  The values are silently truncated.
>
> This is not visible on a filesystem whose inode numbers stay below
> 2^32, but it is on a large one.  On an 86 TB xfs volume,
> gdb.server/fileio-packets.exp fails because the inode reported by
> vFile:lstat does not match the one reported locally:
>
>    remote = {..., 'st_ino': 2161233200, ...}
>    local  = {..., 'st_ino': 122420317488, ...}
>
> The field widths cannot simply be changed, as that would alter the wire
> layout and break communication between different versions of GDB and
> gdbserver.  Add a new 'stat64' qSupported feature instead.  When both
> sides report it, the vFile stat packets return struct fio_stat_wide, in
> which the six too-narrow fields are 8 bytes; otherwise the existing
> struct fio_stat is used, exactly as before.
>
> Internally both GDB and gdbserver now work with the wide struct, and
> the conversion happens at the wire boundary: gdbserver narrows the
> result before sending it if the feature was not negotiated, and GDB
> selects the unpacker by the length of the reply.  Narrowing a value
> which does not fit now produces a warning rather than truncating
> silently.
>
> Only the vFile packets are changed.  The F-packet file-i/o protocol
> uses the same struct, but writes it directly into inferior memory,
> where the target reads it as the layout documented in the manual under
> "struct stat"; that layout is left alone.
>
> While here, drop a duplicate include of gdbsupport/fileio.h from
> gdbserver/hostio.cc.
>
> Tested on powerpc64le-linux; gdb.server/fileio-packets.exp now passes on
> a filesystem with inode numbers above 2^32 and continues to pass on one
> without, with no unexpected failures in the full testsuite.
>
> gdb/
> 	* NEWS: Mention the stat64 feature.
> 	* doc/gdb.texinfo (General Query Packets): Document the stat64
> 	feature.
> 	(Host I/O Packets): Mention the wide reply format.
> 	(struct stat64): New node.
> 	* remote-fileio.c (remote_fileio_to_host_ulong8): New function.
> 	(remote_fileio_wide_to_host_stat): New function.
> 	* remote-fileio.h (remote_fileio_wide_to_host_stat): Declare.
> 	* remote.c (PACKET_stat64_feature): New enum value.
> 	(remote_features::stat64_feature): New method.
> 	(remote_protocol_features): Add stat64.
> 	(remote_target::remote_query_supported): Send stat64+.
> 	(fileio_process_fstat_and_lstat_reply): Handle both formats.
> 	(INIT_GDB_FILE): Add the stat64-feature packet command.
> 	* testsuite/gdb.server/fileio-packets.py (decode_stat_reply):
> 	Handle both the narrow and wide reply formats.
>
> gdbserver/
> 	* hostio.cc (handle_fstat, handle_stat, handle_lstat): Send the
> 	wide struct when the feature is negotiated.
> 	* server.cc (handle_query): Handle and report stat64.
> 	* server.h (client_state::stat64_feature): New member.
>
> gdbsupport/
> 	* fileio.cc (host_to_fileio_stat_wide): New function.
> 	(narrow_field, fileio_stat_wide_to_narrow): New functions.
> 	* fileio.h (struct fio_stat_wide): New struct.
> 	(bigendian_to_host): New function.
> 	(host_to_fileio_stat_wide, fileio_stat_wide_to_narrow): Declare.
>
> Bug:https://sourceware.org/bugzilla/show_bug.cgi?id=34567
> Reviewed-By: Eli Zaretskii<eliz@gnu.org>
> ---
> This patch is reg tested.
>
>   gdb/NEWS                                   |  13 +++
>   gdb/doc/gdb.texinfo                        |  50 ++++++++++
>   gdb/remote-fileio.c                        |  35 ++++++-
>   gdb/remote-fileio.h                        |   4 +
>   gdb/remote.c                               |  36 +++++--
>   gdb/testsuite/gdb.server/fileio-packets.py |  59 +++++++-----
>   gdbserver/hostio.cc                        | 106 +++++++++++++++------
>   gdbserver/server.cc                        |   4 +-
>   gdbserver/server.h                         |   5 +
>   gdbsupport/fileio.cc                       |  70 ++++++++++++++
>   gdbsupport/fileio.h                        |  54 ++++++++++-
>   11 files changed, 370 insertions(+), 66 deletions(-)
>
> diff --git a/gdb/NEWS b/gdb/NEWS
> index 222f38e3d52..7c1a09752a9 100644
> --- a/gdb/NEWS
> +++ b/gdb/NEWS
> @@ -3,6 +3,19 @@
>   
>   *** Changes since GDB 18
>   
> +* Changed remote packets
> +
> +stat64 in qSupported
> +
> +  The new stat64 feature within the qSupported packet allows GDB and
> +  the stub to agree on a wider form of the stat structure returned by
> +  the vFile:fstat, vFile:stat and vFile:lstat packets, in which st_dev,
> +  st_ino, st_nlink, st_rdev and the three timestamps are 8 bytes rather
> +  than 4.  The wider form is used only when both sides report the
> +  feature; otherwise the existing format is used and values which do
> +  not fit are truncated as before.  Note that the narrow form reads
> +  timestamps as unsigned, so it overflows in 2106 rather than 2038.
> +
>   *** Changes in GDB 18
>   
>   * Support for the Common Trace Format (CTF) has been removed.  GDB now
> diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
> index 0030698dcee..355153212f0 100644
> --- a/gdb/doc/gdb.texinfo
> +++ b/gdb/doc/gdb.texinfo
> @@ -46112,6 +46112,11 @@ inspected, if @samp{qIsAddressTagged} (@pxref{qIsAddressTagged}) packet
>   is not supported by the stub.  Access to the @file{/proc/@var{pid}/smaps}
>   file is done via @samp{vFile} requests.
>   
> +@item stat64
> +The remote stub supports the wider form of the stat structure returned
> +by the @samp{vFile:fstat}, @samp{vFile:stat} and @samp{vFile:lstat}
> +packets (@pxref{struct stat64}).
> +
>   @item error-message
>   The remote stub supports replying with an error in a
>   @samp{E.@var{errtext}} (@xref{textual error reply}) format from the
> @@ -47358,6 +47363,9 @@ On success the information is returned as a binary attachment
>   and the return value is the size of this attachment in bytes.
>   If an error occurs the return value is -1.  The format of the
>   returned binary attachment is as described in @ref{struct stat}.
> +If both @value{GDBN} and the stub report the @samp{stat64} feature in
> +the @samp{qSupported} exchange, the wider format is used instead
> +(@pxref{struct stat64}).
>   
>   @item vFile:stat: @var{filename}
>   Get information about the file @var{filename} on the target as if from
> @@ -47365,6 +47373,9 @@ a @samp{stat} call.  On success the information is returned as a binary
>   attachment and the return value is the size of this attachment in
>   bytes.  If an error occurs the return value is -1.  The format of the
>   returned binary attachment is as described in @ref{struct stat}.
> +If both @value{GDBN} and the stub report the @samp{stat64} feature in
> +the @samp{qSupported} exchange, the wider format is used instead
> +(@pxref{struct stat64}).
>   
>   If @var{filename} is a symbolic link, then the information returned is
>   about the file the link refers to, this is inline with the @samp{stat}
> @@ -47376,6 +47387,9 @@ an @samp{lstat} call.  On success the information is returned as a
>   binary attachment and the return value is the size of this attachment
>   in bytes.  If an error occurs the return value is -1.  The format of
>   the returned binary attachment is as described in @ref{struct stat}.
> +If both @value{GDBN} and the stub report the @samp{stat64} feature in
> +the @samp{qSupported} exchange, the wider format is used instead
> +(@pxref{struct stat64}).
>   
>   This packet is identical to @samp{vFile:stat}, except if
>   @var{filename} is a symbolic link, then this packet returns
> @@ -48570,6 +48584,7 @@ protocol.
>   * Pointer Values::
>   * Memory Transfer::
>   * struct stat::
> +* struct stat64::
>   * struct timeval::
>   @end menu
>   
> @@ -48696,6 +48711,41 @@ Note that due to size differences between the host, target, and protocol
>   representations of @code{struct stat} members, these members could eventually
>   get truncated on the target.
>   
> +@node struct stat64
> +@unnumberedsubsubsec struct stat64
> +@cindex struct stat64, in file-i/o protocol
> +
> +When the @samp{stat64} feature has been negotiated, the buffer returned
> +by the @samp{vFile:fstat}, @samp{vFile:stat} and @samp{vFile:lstat}
> +packets uses the following representation instead:
> +
> +@smallexample
> +struct stat64 @{
> +    uint64_t      st_dev;      /* device */
> +    uint64_t      st_ino;      /* inode */
> +    mode_t        st_mode;     /* protection */
> +    uint64_t      st_nlink;    /* number of hard links */
> +    unsigned int  st_uid;      /* user ID of owner */
> +    unsigned int  st_gid;      /* group ID of owner */
> +    uint64_t      st_rdev;     /* device type (if inode device) */
> +    uint64_t      st_size;     /* total size, in bytes */
> +    uint64_t      st_blksize;  /* blocksize for filesystem I/O */
> +    uint64_t      st_blocks;   /* number of blocks allocated */
> +    uint64_t      st_atime;    /* time of last access */
> +    uint64_t      st_mtime;    /* time of last modification */
> +    uint64_t      st_ctime;    /* time of last change */
> +@};
> +@end smallexample
> +
> +This structure is of size 92 bytes.  The fields have the same meanings
> +as in the narrow form (@pxref{struct stat}), but @code{st_dev},
> +@code{st_ino}, @code{st_nlink}, @code{st_rdev} and the three timestamps
> +are wide enough to hold the values found on a 64-bit host without
> +truncation.
> +
> +This representation is only used by the @samp{vFile} packets; the
> +File-I/O protocol always uses the narrow form (@pxref{struct stat}).
> +
>   @node struct timeval
>   @unnumberedsubsubsec struct timeval
>   @cindex struct timeval, in file-i/o protocol
> diff --git a/gdb/remote-fileio.c b/gdb/remote-fileio.c
> index a151161371d..76deb80d10a 100644
> --- a/gdb/remote-fileio.c
> +++ b/gdb/remote-fileio.c
> @@ -1220,7 +1220,40 @@ remote_fileio_to_host_stat (struct fio_stat *fst, struct stat *st)
>     st->st_mtime = remote_fileio_to_host_time (fst->fst_mtime);
>     st->st_ctime = remote_fileio_to_host_time (fst->fst_ctime);
>   }
> -\f
> +
> +/* Unpack an 8-byte protocol field.  */
> +
> +static ULONGEST
> +remote_fileio_to_host_ulong8 (const char *fnum)
> +{
> +  return extract_unsigned_integer ((const gdb_byte *) fnum, 8,
> +				   BFD_ENDIAN_BIG);
> +}
> +
> +/* See remote-fileio.h.  */
> +
> +void
> +remote_fileio_wide_to_host_stat (struct fio_stat_wide *fst, struct stat *st)
> +{
> +  memset (st, 0, sizeof (struct stat));
> +  st->st_dev = remote_fileio_to_host_ulong8 (fst->fst_dev);
> +  st->st_ino = remote_fileio_to_host_ulong8 (fst->fst_ino);
> +  st->st_mode = remote_fileio_to_host_mode (fst->fst_mode);
> +  st->st_nlink = remote_fileio_to_host_ulong8 (fst->fst_nlink);
> +  st->st_uid = remote_fileio_to_host_uint (fst->fst_uid);
> +  st->st_gid = remote_fileio_to_host_uint (fst->fst_gid);
> +  st->st_rdev = remote_fileio_to_host_ulong8 (fst->fst_rdev);
> +  st->st_size = remote_fileio_to_host_ulong8 (fst->fst_size);
> +#ifdef HAVE_STRUCT_STAT_ST_BLKSIZE
> +  st->st_blksize = remote_fileio_to_host_ulong8 (fst->fst_blksize);
> +#endif
> +#if HAVE_STRUCT_STAT_ST_BLOCKS
> +  st->st_blocks = remote_fileio_to_host_ulong8 (fst->fst_blocks);
> +#endif
> +  st->st_atime = remote_fileio_to_host_ulong8 (fst->fst_atime);
> +  st->st_mtime = remote_fileio_to_host_ulong8 (fst->fst_mtime);
> +  st->st_ctime = remote_fileio_to_host_ulong8 (fst->fst_ctime);
> +}
>   
>   static void
>   set_system_call_allowed (const char *args, int from_tty)
> diff --git a/gdb/remote-fileio.h b/gdb/remote-fileio.h
> index d01b3df92ca..95fb042fc9d 100644
> --- a/gdb/remote-fileio.h
> +++ b/gdb/remote-fileio.h
> @@ -44,4 +44,8 @@ extern void initialize_remote_fileio (
>   extern void remote_fileio_to_host_stat (struct fio_stat *fst,
>   					struct stat *st);
>   
> +/* Unpack a struct fio_stat_wide.  */
> +extern void remote_fileio_wide_to_host_stat (struct fio_stat_wide *fst,
> +					     struct stat *st);
> +
>   #endif /* GDB_REMOTE_FILEIO_H */
> diff --git a/gdb/remote.c b/gdb/remote.c
> index 76cf6b5234f..03cb8a074b7 100644
> --- a/gdb/remote.c
> +++ b/gdb/remote.c
> @@ -389,6 +389,8 @@ enum {
>        packets and the tag violation stop replies.  */
>     PACKET_memory_tagging_feature,
>   
> +  PACKET_stat64_feature,
> +
>     /* Support for the qIsAddressTagged packet.  */
>     PACKET_qIsAddressTagged,
>   
> @@ -844,6 +846,9 @@ struct remote_features
>     bool remote_memory_tagging_p () const
>     { return packet_support (PACKET_memory_tagging_feature) == PACKET_ENABLE; }
>   
> +  bool stat64_feature () const
> +  { return packet_support (PACKET_stat64_feature) == PACKET_ENABLE; }
> +
>     /* Returns true if there is support for sending vRun inferior arguments
>        as a single string.  */
>     bool remote_vrun_single_arg_p () const
> @@ -6199,6 +6204,8 @@ static const struct protocol_feature remote_protocol_features[] = {
>     { "no-resumed", PACKET_DISABLE, remote_supported_packet, PACKET_no_resumed },
>     { "memory-tagging", PACKET_DISABLE, remote_supported_packet,
>       PACKET_memory_tagging_feature },
> +  { "stat64", PACKET_DISABLE, remote_supported_packet,
> +    PACKET_stat64_feature },
>     { "error-message", PACKET_ENABLE, remote_supported_packet,
>       PACKET_accept_error_message },
>     { "binary-upload", PACKET_DISABLE, remote_supported_packet, PACKET_x },
> @@ -6309,6 +6316,10 @@ remote_target::remote_query_supported ()
>   	  != AUTO_BOOLEAN_FALSE)
>   	remote_query_supported_append (&q, "QThreadOptions+");
>   
> +      if (m_features.packet_set_cmd_state (PACKET_stat64_feature)
> +	  != AUTO_BOOLEAN_FALSE)
> +	remote_query_supported_append (&q, "stat64+");
> +
>         if (m_features.packet_set_cmd_state (PACKET_no_resumed)
>   	  != AUTO_BOOLEAN_FALSE)
>   	remote_query_supported_append (&q, "no-resumed+"); @@ -13663,29 +13674,35 @@ remote_target::fileio_readlink (struct 
> inferior *inf, const char *filename, remote syscall reply. 
> EXPECTED_LEN is the length returned from the fstat or stat call, this 
> the length of the returned data (in ATTACHMENT) once it has been 
> decoded. The fstat/stat result (from the ATTACHMENT - data) is to be 
> placed in ST. */ + data) is to be placed in ST. + The reply holds 
> either a struct fio_stat or, if the stat64 feature was + negotiated, 
> the wider struct fio_stat_wide; the two are distinguished + by their 
> length. */ static int fileio_process_fstat_and_lstat_reply (const char 
> *attachment, int attachment_len, int expected_len, struct stat *st) { 
> - struct fio_stat fst; + gdb_byte buf[sizeof (struct fio_stat_wide)]; 
> int read_len = remote_unescape_input ((gdb_byte *) attachment, 
> attachment_len, - (gdb_byte *) &fst, sizeof (fst)); + buf, sizeof 
> (buf)); if (read_len != expected_len) error (_("vFile:fstat returned %d, but %d bytes."),
>   	   expected_len, read_len);
>   
> -  if (read_len != sizeof (fst))
> -    error (_("vFile:fstat returned %d bytes, but expecting %d."),
> -	   read_len, (int) sizeof (fst));
> -
> -  remote_fileio_to_host_stat (&fst, st);
> +  if (read_len == sizeof (struct fio_stat_wide))
> +    remote_fileio_wide_to_host_stat ((struct fio_stat_wide *) buf, st);
> +  else if (read_len == sizeof (struct fio_stat))
> +    remote_fileio_to_host_stat ((struct fio_stat *) buf, st);
> +  else
> +    error (_("vFile:fstat returned %d bytes, but expecting %d or %d."), + read_len, (int) sizeof (struct fio_stat), + (int) sizeof (struct 
> fio_stat_wide)); return 0; } @@ -17039,6 +17056,9 @@ Show the maximum 
> size of the address (in bits) in a memory packet."), NULL,
>     add_packet_config_cmd (PACKET_memory_tagging_feature,
>   			 "memory-tagging-feature", "memory-tagging-feature", 0);
>   
> +  add_packet_config_cmd (PACKET_stat64_feature,
> +			 "stat64-feature", "stat64-feature", 0);
> +
>     add_packet_config_cmd (PACKET_qIsAddressTagged,
>   			 "qIsAddressTagged", "memory-tagging-address-check", 0);
>   
> diff --git a/gdb/testsuite/gdb.server/fileio-packets.py b/gdb/testsuite/gdb.server/fileio-packets.py
> index 54ae56fa68a..2d06edcdbf7 100644
> --- a/gdb/testsuite/gdb.server/fileio-packets.py
> +++ b/gdb/testsuite/gdb.server/fileio-packets.py
> @@ -57,33 +57,48 @@ def decode_stat_reply(buf, byteorder="big"):
>   
>       buf = unescape_remote_data(buf)
>   
> -    if (
> -        buf[0] != ord("F")
> -        or buf[1] != ord("4")
> -        or buf[2] != ord("0")
> -        or buf[3] != ord(";")
> -        or len(buf) != 68
> -    ):
> +    if buf[0:4] == b"F40;" and len(buf) == 68:
> +        wide = False
> +    elif buf[0:4] == b"F5c;" and len(buf) == 96:
> +        wide = True
> +    else:
>           print(f"decode_stat_reply failed: {buf}\t(length = {len(buf)})")
>           return None
>   
> -    # Discard the 'F40;' prefix.  The rest is the 64 bytes of data to
> -    # be decoded.
> +    # Discard the 'FNN;' prefix.
>       buf = buf[4:]
>   
> -    st_dev = int.from_bytes(buf[0:4], byteorder=byteorder)
> -    st_ino = int.from_bytes(buf[4:8], byteorder=byteorder)
> -    st_mode = int.from_bytes(buf[8:12], byteorder=byteorder)
> -    st_nlink = int.from_bytes(buf[12:16], byteorder=byteorder)
> -    st_uid = int.from_bytes(buf[16:20], byteorder=byteorder)
> -    st_gid = int.from_bytes(buf[20:24], byteorder=byteorder)
> -    st_rdev = int.from_bytes(buf[24:28], byteorder=byteorder)
> -    st_size = int.from_bytes(buf[28:36], byteorder=byteorder)
> -    st_blksize = int.from_bytes(buf[36:44], byteorder=byteorder)
> -    st_blocks = int.from_bytes(buf[44:52], byteorder=byteorder)
> -    st_atime = int.from_bytes(buf[52:56], byteorder=byteorder)
> -    st_mtime = int.from_bytes(buf[56:60], byteorder=byteorder)
> -    st_ctime = int.from_bytes(buf[60:64], byteorder=byteorder)
> +    def field(off, size):
> +        return int.from_bytes(buf[off : off + size], byteorder=byteorder)
> +
> +    if wide:
> +        st_dev     = field(0, 8)
> +        st_ino     = field(8, 8)
> +        st_mode    = field(16, 4)
> +        st_nlink   = field(20, 8)
> +        st_uid     = field(28, 4)
> +        st_gid     = field(32, 4)
> +        st_rdev    = field(36, 8)
> +        st_size    = field(44, 8)
> +        st_blksize = field(52, 8)
> +        st_blocks  = field(60, 8)
> +        st_atime   = field(68, 8)
> +        st_mtime   = field(76, 8)
> +        st_ctime   = field(84, 8)
> +    else:
> +        st_dev     = field(0, 4)
> +        st_ino     = field(4, 4)
> +        st_mode    = field(8, 4)
> +        st_nlink   = field(12, 4)
> +        st_uid     = field(16, 4)
> +        st_gid     = field(20, 4)
> +        st_rdev    = field(24, 4)
> +        st_size    = field(28, 8)
> +        st_blksize = field(36, 8)
> +        st_blocks  = field(44, 8)
> +        st_atime   = field(52, 4)
> +        st_mtime   = field(56, 4)
> +        st_ctime   = field(60, 4)
>   
>       return {
>           "st_dev": st_dev,
> diff --git a/gdbserver/hostio.cc b/gdbserver/hostio.cc
> index b9ca27c2ff4..34def5d22da 100644
> --- a/gdbserver/hostio.cc
> +++ b/gdbserver/hostio.cc
> @@ -26,7 +26,6 @@
>   #include <unistd.h>
>   #include <sys/types.h>
>   #include <sys/stat.h>
> -#include "gdbsupport/fileio.h"
>   
>   struct fd_list
>   {
> @@ -465,7 +464,7 @@ handle_fstat (char *own_buf, int *new_packet_len)
>     int fd, bytes_sent;
>     char *p;
>     struct stat st;
> -  struct fio_stat fst;
> +  client_state &cs = get_client_state ();
>   
>     p = own_buf + strlen ("vFile:fstat:");
>   
> @@ -483,16 +482,31 @@ handle_fstat (char *own_buf, int *new_packet_len)
>         return;
>       }
>   
> -  host_to_fileio_stat (&st, &fst);
> -
> -  bytes_sent = hostio_reply_with_data (own_buf,
> -				       (char *) &fst, sizeof (fst),
> -				       new_packet_len);
> +  struct fio_stat_wide wide;
> +  host_to_fileio_stat_wide (&st, &wide);
>   
> -  /* If the response does not fit into a single packet, do not attempt
> -     to return a partial response, but simply fail.  */
> -  if (bytes_sent < sizeof (fst))
> -    write_enn (own_buf);
> +  /* Send the wide form if GDB understands it, otherwise narrow the
> +     result first.  */
> +  if (cs.stat64_feature)
> +    {
> +      bytes_sent = hostio_reply_with_data (own_buf, (char *) &wide,
> +					   sizeof (wide), new_packet_len);
> +      /* If the response does not fit into a single packet, do not attempt
> +	 to return a partial response, but simply fail.  */
> +      if (bytes_sent < sizeof (wide))
> +	write_enn (own_buf);
> +    }
> +  else
> +    {
> +      struct fio_stat narrow;
> +      fileio_stat_wide_to_narrow (&wide, &narrow);
> +      bytes_sent = hostio_reply_with_data (own_buf, (char *) &narrow,
> +					   sizeof (narrow), new_packet_len);
> +      /* If the response does not fit into a single packet, do not attempt
> +	 to return a partial response, but simply fail.  */
> +      if (bytes_sent < sizeof (narrow))
> +	write_enn (own_buf);
> +    }
>   }
>   
>   static void
> @@ -501,8 +515,8 @@ handle_stat (char *own_buf, int *new_packet_len)
>     int bytes_sent;
>     char *p;
>     struct stat st;
> -  struct fio_stat fst;
>     char filename[HOSTIO_PATH_MAX];
> +  client_state &cs = get_client_state ();
>   
>     p = own_buf + strlen ("vFile:stat:");
>   
> @@ -519,16 +533,31 @@ handle_stat (char *own_buf, int *new_packet_len)
>         return;
>       }
>   
> -  host_to_fileio_stat (&st, &fst);
> -
> -  bytes_sent = hostio_reply_with_data (own_buf,
> -				       (char *) &fst, sizeof (fst),
> -				       new_packet_len);
> +  struct fio_stat_wide wide;
> +  host_to_fileio_stat_wide (&st, &wide);
>   
> -  /* If the response does not fit into a single packet, do not attempt
> -     to return a partial response, but simply fail.  */
> -  if (bytes_sent < sizeof (fst))
> -    write_enn (own_buf);
> +  /* Send the wide form if GDB understands it, otherwise narrow the
> +     result first.  */
> +  if (cs.stat64_feature)
> +    {
> +      bytes_sent = hostio_reply_with_data (own_buf, (char *) &wide,
> +					   sizeof (wide), new_packet_len);
> +      /* If the response does not fit into a single packet, do not attempt
> +	 to return a partial response, but simply fail.  */
> +      if (bytes_sent < sizeof (wide))
> +	write_enn (own_buf);
> +    }
> +  else
> +    {
> +      struct fio_stat narrow;
> +      fileio_stat_wide_to_narrow (&wide, &narrow);
> +      bytes_sent = hostio_reply_with_data (own_buf, (char *) &narrow,
> +					   sizeof (narrow), new_packet_len);
> +      /* If the response does not fit into a single packet, do not attempt
> +	 to return a partial response, but simply fail.  */
> +      if (bytes_sent < sizeof (narrow))
> +	write_enn (own_buf);
> +    }
>   }
>   
>   static void
> @@ -537,8 +566,8 @@ handle_lstat (char *own_buf, int *new_packet_len)
>     int ret, bytes_sent;
>     char *p;
>     struct stat st;
> -  struct fio_stat fst;
>     char filename[HOSTIO_PATH_MAX];
> +  client_state &cs = get_client_state ();
>   
>     p = own_buf + strlen ("vFile:lstat:");
>   
> @@ -560,16 +589,31 @@ handle_lstat (char *own_buf, int *new_packet_len)
>         return;
>       }
>   
> -  host_to_fileio_stat (&st, &fst);
> -
> -  bytes_sent = hostio_reply_with_data (own_buf,
> -				       (char *) &fst, sizeof (fst),
> -				       new_packet_len);
> +  struct fio_stat_wide wide;
> +  host_to_fileio_stat_wide (&st, &wide);
>   
> -  /* If the response does not fit into a single packet, do not attempt
> -     to return a partial response, but simply fail.  */
> -  if (bytes_sent < sizeof (fst))
> -    write_enn (own_buf);
> +  /* Send the wide form if GDB understands it, otherwise narrow the
> +     result first.  */
> +  if (cs.stat64_feature)
> +    {
> +      bytes_sent = hostio_reply_with_data (own_buf, (char *) &wide,
> +					   sizeof (wide), new_packet_len);
> +      /* If the response does not fit into a single packet, do not attempt
> +	 to return a partial response, but simply fail.  */
> +      if (bytes_sent < sizeof (wide))
> +	write_enn (own_buf);
> +    }
> +  else
> +    {
> +      struct fio_stat narrow;
> +      fileio_stat_wide_to_narrow (&wide, &narrow);
> +      bytes_sent = hostio_reply_with_data (own_buf, (char *) &narrow,
> +					   sizeof (narrow), new_packet_len);
> +      /* If the response does not fit into a single packet, do not attempt
> +	 to return a partial response, but simply fail.  */
> +      if (bytes_sent < sizeof (narrow))
> +	write_enn (own_buf);
> +    }
>   }
>   
>   static void
> diff --git a/gdbserver/server.cc b/gdbserver/server.cc
> index a208e24d09f..dfa24617847 100644
> --- a/gdbserver/server.cc
> +++ b/gdbserver/server.cc
> @@ -2746,6 +2746,8 @@ handle_query (char *own_buf, int packet_len, int *new_packet_len_p)
>   		cs.single_inferior_argument = true;
>   	      else if (feature == "multi-wp-addr+")
>   		cs.multiple_wp_addr_feature = true;
> +	      else if (feature == "stat64+")
> +		cs.stat64_feature = true;
>   	      else
>   		{
>   		  /* Move the unknown features all together.  */
> @@ -2762,7 +2764,7 @@ handle_query (char *own_buf, int packet_len, int *new_packet_len_p)
>   	       "PacketSize=%x;QPassSignals+;QProgramSignals+;"
>   	       "QStartupWithShell+;QEnvironmentHexEncoded+;"
>   	       "QEnvironmentReset+;QEnvironmentUnset+;"
> -	       "QSetWorkingDir+;binary-upload+",
> +	       "QSetWorkingDir+;binary-upload+;stat64+", PBUFSIZ - 1); if (target_supports_catch_syscall ()) diff --git 
> a/gdbserver/server.h b/gdbserver/server.h index 
> bbba3650de7..cf811f228fa 100644 --- a/gdbserver/server.h +++ 
> b/gdbserver/server.h @@ -192,6 +192,11 @@ struct client_state /* If 
> true, memory tagging features are supported. */ bool 
> memory_tagging_feature = false; + /* True if GDB supports the wide 
> form of struct stat in the vFile + fstat, stat and lstat replies. When 
> false, gdbserver narrows the + result to struct fio_stat before 
> sending it. */ + bool stat64_feature = false; + /* If true then 
> E.errtext style errors are supported everywhere, including for the 
> qRcmd and m packet. When false E.errtext errors are not supported with 
> qRcmd and m packets, but are still supported diff --git 
> a/gdbsupport/fileio.cc b/gdbsupport/fileio.cc index 
> 6d2ffb14544..bab2c4c8efe 100644 --- a/gdbsupport/fileio.cc +++ 
> b/gdbsupport/fileio.cc @@ -20,6 +20,7 @@ #include "fileio.h"
>   #include <sys/stat.h>
>   #include <fcntl.h>
> +#include "gdbsupport/errors.h"
>   
>   /* See fileio.h.  */
>   
> @@ -305,3 +306,72 @@ host_to_fileio_stat (struct stat *st, struct fio_stat *fst)
>     host_to_fileio_time (st->st_mtime, fst->fst_mtime);
>     host_to_fileio_time (st->st_ctime, fst->fst_ctime);
>   }
> +
> +/* See fileio.h.  */
> +
> +void
> +host_to_fileio_stat_wide (struct stat *st, struct fio_stat_wide *fst)
> +{
> +  LONGEST blksize;
> +
> +  host_to_bigendian ((LONGEST) st->st_dev, (char *) fst->fst_dev, 8);
> +  host_to_bigendian ((LONGEST) st->st_ino, (char *) fst->fst_ino, 8);
> +  host_to_fileio_mode (st->st_mode, fst->fst_mode);
> +  host_to_bigendian ((LONGEST) st->st_nlink, (char *) fst->fst_nlink, 8);
> +  host_to_fileio_uint ((long) st->st_uid, fst->fst_uid);
> +  host_to_fileio_uint ((long) st->st_gid, fst->fst_gid);
> +  host_to_bigendian ((LONGEST) st->st_rdev, (char *) fst->fst_rdev, 8);
> +  host_to_bigendian ((LONGEST) st->st_size, (char *) fst->fst_size, 8);
> +#ifdef HAVE_STRUCT_STAT_ST_BLKSIZE
> +  blksize = st->st_blksize;
> +#else
> +  blksize = 512;
> +#endif
> +  host_to_bigendian (blksize, (char *) fst->fst_blksize, 8);
> +#if HAVE_STRUCT_STAT_ST_BLOCKS
> +  host_to_bigendian ((LONGEST) st->st_blocks, (char *) fst->fst_blocks, 8);
> +#else
> +  host_to_bigendian (((LONGEST) st->st_size + blksize - 1) / blksize,
> +		     (char *) fst->fst_blocks, 8);
> +#endif
> +  host_to_bigendian ((LONGEST) st->st_atime, (char *) fst->fst_atime, 8);
> +  host_to_bigendian ((LONGEST) st->st_mtime, (char *) fst->fst_mtime, 8);
> +  host_to_bigendian ((LONGEST) st->st_ctime, (char *) fst->fst_ctime, 8);
> +}
> +
> +/* Copy the 8-byte value in FROM into the 4-byte field TO, warning if
> +   the value does not fit.  WHAT names the field, for the warning.  */
> +
> +static void
> +narrow_field (const char *from, char *to, const char *what)
> +{
> +  ULONGEST num = bigendian_to_host (from, 8);
> +
> +  if (num != (ULONGEST) (uint32_t) num)
> +    warning (_("file-i/o: %s value %s does not fit in 32 bits; "
> +	       "the value seen by the peer will be truncated"),
> +	     what, pulongest (num));
> +
> +  host_to_bigendian ((LONGEST) num, to, 4);
> +}
> +
> +/* See fileio.h.  */
> +
> +void
> +fileio_stat_wide_to_narrow (const struct fio_stat_wide *wide,
> +			    struct fio_stat *narrow)
> +{
> +  narrow_field (wide->fst_dev, narrow->fst_dev, "st_dev");
> +  narrow_field (wide->fst_ino, narrow->fst_ino, "st_ino");
> +  memcpy (narrow->fst_mode, wide->fst_mode, 4);
> +  narrow_field (wide->fst_nlink, narrow->fst_nlink, "st_nlink");
> +  memcpy (narrow->fst_uid, wide->fst_uid, 4);
> +  memcpy (narrow->fst_gid, wide->fst_gid, 4);
> +  narrow_field (wide->fst_rdev, narrow->fst_rdev, "st_rdev");
> +  memcpy (narrow->fst_size, wide->fst_size, 8);
> +  memcpy (narrow->fst_blksize, wide->fst_blksize, 8);
> +  memcpy (narrow->fst_blocks, wide->fst_blocks, 8);
> +  narrow_field (wide->fst_atime, narrow->fst_atime, "st_atime");
> +  narrow_field (wide->fst_mtime, narrow->fst_mtime, "st_mtime");
> +  narrow_field (wide->fst_ctime, narrow->fst_ctime, "st_ctime");
> +}
> diff --git a/gdbsupport/fileio.h b/gdbsupport/fileio.h
> index c2592cf8c15..fa5de54dd40 100644
> --- a/gdbsupport/fileio.h
> +++ b/gdbsupport/fileio.h
> @@ -120,9 +120,11 @@ using fio_time_t = char[FIO_TIME_LEN];
>   using fio_long_t = char[FIO_LONG_LEN];
>   using fio_ulong_t = char[FIO_ULONG_LEN];
>   
> -/* Struct stat as used in protocol.  For complete independence
> -   of host/target systems, it's defined as an array with offsets
> -   to the members. */
> +/* Struct stat as used in the protocol.  This is the format used by the
> +   F-packet file-i/o protocol, and by the vFile stat packets when the
> +   stat64 feature has not been negotiated.  Several fields are too narrow
> +   to hold the corresponding struct stat member on a 64-bit host; see
> +   struct fio_stat_wide.  */
>   
>   struct fio_stat
>   {
> @@ -141,6 +143,29 @@ struct fio_stat
>     fio_time_t  fst_ctime;
>   };
>   
> +/* Struct stat as used in the wide form of the protocol.  The fields
> +   which cannot hold the corresponding struct stat member on a 64-bit
> +   host are widened to 8 bytes.  This layout is only used by the vFile
> +   stat packets, and only when the stat64 feature has been negotiated
> +   with the peer.  */
> +
> +struct fio_stat_wide
> +{
> +  fio_ulong_t fst_dev;
> +  fio_ulong_t fst_ino;
> +  fio_mode_t  fst_mode;
> +  fio_ulong_t fst_nlink;
> +  fio_uint_t  fst_uid;
> +  fio_uint_t  fst_gid;
> +  fio_ulong_t fst_rdev;
> +  fio_ulong_t fst_size;
> +  fio_ulong_t fst_blksize;
> +  fio_ulong_t fst_blocks;
> +  fio_ulong_t fst_atime;
> +  fio_ulong_t fst_mtime;
> +  fio_ulong_t fst_ctime;
> +};
> +
>   struct fio_timeval
>   {
>     fio_time_t  ftv_sec;
> @@ -179,6 +204,20 @@ host_to_bigendian (LONGEST num, char *buf, int bytes)
>       buf[i] = (num >> (8 * (bytes - i - 1))) & 0xff;
>   }
>   
> +/* Unpack an integer of BYTES bytes from BUF, which holds it in
> +   big-endian, protocol format.  */
> +
> +static inline ULONGEST
> +bigendian_to_host (const char *buf, int bytes)
> +{
> +  ULONGEST num = 0;
> +  int i;
> +
> +  for (i = 0; i < bytes; ++i)
> +    num = (num << 8) | (unsigned char) buf[i];
> +  return num;
> +}
> +
>   /* Pack a host-format integer into an fio_uint_t.  */
>   
>   static inline void
> @@ -199,4 +238,13 @@ host_to_fileio_time (time_t num, fio_time_t fnum)
>   
>   extern void host_to_fileio_stat (struct stat *st, struct fio_stat *fst);
>   
> +/* Pack a host-format struct stat into a struct fio_stat_wide.  */
> +extern void host_to_fileio_stat_wide (struct stat *st,
> +				      struct fio_stat_wide *fst);
> +
> +/* Narrow a struct fio_stat_wide into a struct fio_stat, warning if any
> +   value does not fit.  */
> +extern void fileio_stat_wide_to_narrow (const struct fio_stat_wide *wide,
> +					struct fio_stat *narrow);
> +
>   #endif /* GDBSUPPORT_FILEIO_H */

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