New memory-tag commands

Add new commands under the "memory-tag" prefix to allow users to inspect,
modify and check memory tags in different ways.

The available subcommands are the following:

- memory-tag print-logical-tag <expression>: Prints the logical tag for a
  particular address.

- memory-tag withltag <expression> <tag>: Prints the address tagged with the
  logical tag <tag>.

- memory-tag print-allocation-tag <expression>: Prints the allocation tag for
  a particular address.

- memory-tag setatag <expression> <length> <tags>: Sets one or more allocation
  tags to the specified tags.

- memory-tag check <expression>: Checks if the logical tag in <address>
  matches its allocation tag.

These commands make use of the memory tagging gdbarch methods, and are still
available, but disabled, when memory tagging is not supported by the
architecture.

I've pondered about a way to make these commands invisible when memory tagging
is not available, but given the check is at runtime (and support may come and go
based on a process' configuration), that is a bit too late in the process to
either not include the commands or get rid of them.

Ideas are welcome.

gdb/ChangeLog:

2021-03-24  Luis Machado  <luis.machado@linaro.org>

	* printcmd.c: Include gdbsupport/rsp-low.h.
	(memory_tag_list): New static global.
	(process_print_command_args): Factored out of
	print_command_1.
	(print_command_1): Use process_print_command_args.
	(show_addr_not_tagged, show_memory_tagging_unsupported)
	(memory_tag_command, memory_tag_print_tag_command)
	(memory_tag_print_logical_tag_command)
	(memory_tag_print_allocation_tag_command, parse_with_logical_tag_input)
	(memory_tag_with_logical_tag_command, parse_set_allocation_tag_input)
	(memory_tag_set_allocation_tag_command, memory_tag_check_command): New
	functions.
	(_initialize_printcmd): Add "memory-tag" prefix and subcommands.

gdbsupport/ChangeLog:

2021-03-24  Luis Machado  <luis.machado@linaro.org>

	* rsp-low.cc (fromhex, hex2bin): Move to ...
	* common-utils.cc: ... here.
	(fromhex) Change error message text to not be RSP-specific.
	* rsp-low.h (fromhex, hex2bin): Move to ...
	* common-utils.h: ... here.

1 files changed, 15 insertions, 0 deletions

diff --git a/gdbsupport/common-utils.h b/gdbsupport/common-utils.h
index 1de747f186d..224e1f31222 100644
--- a/gdbsupport/common-utils.h
+++ b/gdbsupport/common-utils.h
@@ -22,6 +22,7 @@
 
 #include <string>
 #include <vector>
+#include "gdbsupport/byte-vector.h"
 
 #include "poison.h"
 
@@ -191,4 +192,18 @@ in_inclusive_range (T value, T low, T high)
 extern ULONGEST align_up (ULONGEST v, int n);
 extern ULONGEST align_down (ULONGEST v, int n);
 
+/* Convert hex digit A to a number, or throw an exception.  */
+extern int fromhex (int a);
+
+/* HEX is a string of characters representing hexadecimal digits.
+   Convert pairs of hex digits to bytes and store sequentially into
+   BIN.  COUNT is the maximum number of characters to convert.  This
+   will convert fewer characters if the number of hex characters
+   actually seen is odd, or if HEX terminates before COUNT characters.
+   Returns the number of characters actually converted.  */
+extern int hex2bin (const char *hex, gdb_byte *bin, int count);
+
+/* Like the above, but return a gdb::byte_vector.  */
+gdb::byte_vector hex2bin (const char *hex);
+
 #endif /* COMMON_COMMON_UTILS_H */