Re: [PATCH 2/3] gdb: Add per-remote target variables for memory read and write config

[Andrew Burgess <aburgess@redhat.com>]

* Christina Schimpe via Gdb-patches <gdb-patches@sourceware.org> [2022-01-13 16:21:17 +0100]:

> This patch adds per-remote target variables for the configuration of
> memory read- and write packet size. It is a further change in addition
> to commit "gdb: Make global feature array a per-remote target array"
> to apply the fixme notes described in commit 5b6d1e4.
> 
> The former global variables for that configuration are still available
> to allow the command line configuration for all future remote
> connections.  Similar to the command line configuration of the per-
> remote target feature array, the commands
> 
> - set remotewritesize (deprecated)
> - set remote memory-read-packet-size
> - set remote memory-write-packet-size
> 
> will configure the current target (if available) and future remote
> connections. The show command will display the global configuration
> and the packet size of the current remote target, if available.
> 
> It is required to adapt the test gdb.base/remote.exp which is failing
> for --target_board=native-extended-gdbserver.  With that board GDB
> connects to gdbserver at gdb start time.  Due to this patch two loggings
> "The target may not be able to.." are shown if the command 'set remote
> memory-write-packet-size fixed' is executed while a target is connected
> for the current inferior.  To fix this, the clean_restart command is
> moved to a later time point of the test.  It is sufficient to be
> connected to the server when "runto_main" is executed.  Now the
> connection time is similar to a testrun with
> --target_board=native-gdbserver.
> 
> To allow the user to distinguish between the packet-size configuration
> for future connections and for the currently selected target, the
> logging of the command 'set remote memory-write-packet-size fixed' is
> adapted.
> ---
>  gdb/remote.c                      | 94 +++++++++++++++++++------------
>  gdb/testsuite/gdb.base/remote.exp |  7 ++-
>  2 files changed, 61 insertions(+), 40 deletions(-)

This needs a NEWS entry and a docs update.

Like with the previous patch, I think we should consider having the
set/show commands print more informative messages about which targets
are being changed or displayed.

> 
> diff --git a/gdb/remote.c b/gdb/remote.c
> index 10f9226827..a270cb688c 100644
> --- a/gdb/remote.c
> +++ b/gdb/remote.c
> @@ -563,8 +563,31 @@ struct packet_config
>      enum packet_support support;
>    };
>  
> -/* This global array contains the default configuration for every new
> -   per-remote target array.  */
> +/* User configurable variables for the number of characters in a
> +   memory read/write packet.  MIN (rsa->remote_packet_size,
> +   rsa->sizeof_g_packet) is the default.  Some targets need smaller
> +   values (fifo overruns, et.al.) and some users need larger values
> +   (speed up transfers).  The variables ``preferred_*'' (the user
> +   request), ``current_*'' (what was actually set) and ``forced_*''
> +   (Positive - a soft limit, negative - a hard limit).  */
> +
> +struct memory_packet_config
> +{
> +  const char *name;
> +  long size;
> +  int fixed_p;
> +};
> +
> +/* These global variables contain the default configuration for every new
> +   remote_feature object.  */
> +static memory_packet_config memory_read_packet_config =
> +{
> +  "memory-read-packet-size",
> +};
> +static memory_packet_config memory_write_packet_config =
> +{
> +  "memory-write-packet-size",
> +};
>  static packet_config remote_protocol_packets[PACKET_MAX];
>  
>  class remote_features
> @@ -573,6 +596,9 @@ class remote_features
>  
>    remote_features ()
>    {
> +    m_memory_read_packet_config = memory_read_packet_config;
> +    m_memory_write_packet_config = memory_write_packet_config;
> +
>      std::copy (std::begin (remote_protocol_packets),
>  	       std::end (remote_protocol_packets),
>  	       std::begin (m_protocol_packets));
> @@ -591,6 +617,9 @@ class remote_features
>  
>    void reset_all_packet_configs_support (void);
>  
> +  memory_packet_config m_memory_read_packet_config;
> +  memory_packet_config m_memory_write_packet_config;

Comment new fields please.

> +
>    packet_config m_protocol_packets[PACKET_MAX];
>  };
>  
> @@ -1842,21 +1871,6 @@ show_remotebreak (struct ui_file *file, int from_tty,
>  static unsigned int remote_address_size;
>  
>  \f
> -/* User configurable variables for the number of characters in a
> -   memory read/write packet.  MIN (rsa->remote_packet_size,
> -   rsa->sizeof_g_packet) is the default.  Some targets need smaller
> -   values (fifo overruns, et.al.) and some users need larger values
> -   (speed up transfers).  The variables ``preferred_*'' (the user
> -   request), ``current_*'' (what was actually set) and ``forced_*''
> -   (Positive - a soft limit, negative - a hard limit).  */
> -
> -struct memory_packet_config
> -{
> -  const char *name;
> -  long size;
> -  int fixed_p;
> -};
> -
>  /* The default max memory-write-packet-size, when the setting is
>     "fixed".  The 16k is historical.  (It came from older GDB's using
>     alloca for buffers and the knowledge (folklore?) that some hosts
> @@ -1922,7 +1936,8 @@ remote_target::get_memory_packet_size (struct memory_packet_config *config)
>     something really big then do a sanity check.  */
>  
>  static void
> -set_memory_packet_size (const char *args, struct memory_packet_config *config)
> +set_memory_packet_size (const char *args, struct memory_packet_config *config,
> +			bool target_connected)
>  {
>    int fixed_p = config->fixed_p;
>    long size = config->size;
> @@ -1956,9 +1971,16 @@ set_memory_packet_size (const char *args, struct memory_packet_config *config)
>  			 ? DEFAULT_MAX_MEMORY_PACKET_SIZE_FIXED
>  			 : size);
>  
> -      if (! query (_("The target may not be able to correctly handle a %s\n"
> -		   "of %ld bytes. Change the packet size? "),
> -		   config->name, query_size))
> +      if (target_connected
> +	  && ! query (_("The target may not be able to correctly handle a %s\n"

The space after '!' is not gdb style, could you remove it please.
Also the two below please.

Thanks,
Andrew

> +		      "of %ld bytes.  Change the packet size? "),
> +		      config->name, query_size))
> +	error (_("Packet size not changed."));
> +      else if (! target_connected
> +	       && ! query (_("Future targets may not be able to correctly "
> +			   "handle a %s\nof %ld bytes.  Change the packet size "
> +			   "for future remote targets? "),
> +			   config->name, query_size))
>  	error (_("Packet size not changed."));
>      }
>    /* Update the config.  */
> @@ -1989,16 +2011,15 @@ show_memory_packet_size (struct memory_packet_config *config)
>      }
>  }
>  
> -/* FIXME: needs to be per-remote-target.  */
> -static struct memory_packet_config memory_write_packet_config =
> -{
> -  "memory-write-packet-size",
> -};
> -
>  static void
>  set_memory_write_packet_size (const char *args, int from_tty)
>  {
> -  set_memory_packet_size (args, &memory_write_packet_config);
> +  remote_target *remote = get_current_remote_target ();
> +  if (remote != nullptr)
> +    set_memory_packet_size
> +      (args, &remote->m_features.m_memory_write_packet_config, true);
> +
> +  set_memory_packet_size (args, &memory_write_packet_config, false);
>  }
>  
>  static void
> @@ -2060,19 +2081,18 @@ show_remote_packet_max_chars (struct ui_file *file, int from_tty,
>  long
>  remote_target::get_memory_write_packet_size ()
>  {
> -  return get_memory_packet_size (&memory_write_packet_config);
> +  return get_memory_packet_size (&m_features.m_memory_write_packet_config);
>  }
>  
> -/* FIXME: needs to be per-remote-target.  */
> -static struct memory_packet_config memory_read_packet_config =
> -{
> -  "memory-read-packet-size",
> -};
> -
>  static void
>  set_memory_read_packet_size (const char *args, int from_tty)
>  {
> -  set_memory_packet_size (args, &memory_read_packet_config);
> +  remote_target *remote = get_current_remote_target ();
> +  if (remote != nullptr)
> +    set_memory_packet_size
> +      (args, &remote->m_features.m_memory_read_packet_config, true);
> +
> +  set_memory_packet_size (args, &memory_read_packet_config, false);
>  }
>  
>  static void
> @@ -2084,7 +2104,7 @@ show_memory_read_packet_size (const char *args, int from_tty)
>  long
>  remote_target::get_memory_read_packet_size ()
>  {
> -  long size = get_memory_packet_size (&memory_read_packet_config);
> +  long size = get_memory_packet_size (&m_features.m_memory_read_packet_config);
>  
>    /* FIXME: cagney/1999-11-07: Functions like getpkt() need to get an
>       extra buffer size argument before the memory read size can be
> diff --git a/gdb/testsuite/gdb.base/remote.exp b/gdb/testsuite/gdb.base/remote.exp
> index 1f0869433f..31c5adfd0d 100644
> --- a/gdb/testsuite/gdb.base/remote.exp
> +++ b/gdb/testsuite/gdb.base/remote.exp
> @@ -62,7 +62,7 @@ gdb_test "show remote memory-write-packet-size" \
>  
>  set test "set remote memory-write-packet-size fixed"
>  gdb_test_multiple $test $test {
> -    -re "Change the packet size. .y or n. " {
> +    -re "Change the packet size for future remote targets. .y or n. " {
>  	gdb_test_multiple "y" $test {
>  	    -re "$gdb_prompt $" {
>  		pass $test
> @@ -70,6 +70,7 @@ gdb_test_multiple $test $test {
>  	}
>      }
>  }
> +
>  gdb_test "show remote memory-write-packet-size" \
>  	"The memory-write-packet-size is 0 \\(default\\). Packets are fixed at 16384 bytes\." \
>  	"write-packet default fixed"
> @@ -129,8 +130,6 @@ proc gdb_load_timed {executable class writesize} {
>      pass $test
>  }
>  
> -clean_restart $binfile
> -
>  # These download tests won't actually download anything on !is_remote
>  # target boards, but we run them anyway because it's simpler, and
>  # harmless.
> @@ -155,6 +154,8 @@ gdb_load_timed $binfile "limit" 0
>  # Get the size of random_data table (defaults to 48K).
>  set sizeof_random_data [get_sizeof "random_data" 48*1024]
>  
> +clean_restart $binfile
> +
>  #
>  # Part THREE: Check the upload behavour
>  #
> -- 
> 2.25.1
> 
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