[PATCH v3 21/24] Extend "x" and "print" commands to support memory tagging

[Luis Machado via Gdb-patches <gdb-patches@sourceware.org>]

Extend the "x" and "print" commands to make use of memory tagging
functionality, if supported by the architecture.

The "print" command will point out any possible tag mismatches it finds
when dealing with pointers, in case such a pointer is tagged.  No additional
modifiers are needed.

Suppose we have a pointer "p" with value 0x1234 (logical tag 0x0) and that we
have an allocation tag of 0x1 for that particular area of memory. This is the
expected output:

(gdb) p/x p
Logical tag (0x0) does not match the allocation tag (0x1).
$1 = 0x1234

The "x" command has a new 'm' modifier that will enable displaying of
allocation tags alongside the data dump.  It will display one allocation
tag per line.

AArch64 has a tag granule of 16 bytes, which means we can have one tag for
every 16 bytes of memory. In this case, this is what the "x" command will
display with the new 'm' modifier:

(gdb) x/32bxm p
<Allocation Tag 0x1 for range [0x1230,0x1240)>
0x1234:	0x01	0x02	0x00	0x00	0x00	0x00	0x00	0x00
0x123c:	0x00	0x00	0x00	0x00	0x00	0x00	0x00	0x00
<Allocation Tag 0x1 for range [0x1240,0x1250)>
0x1244:	0x00	0x00	0x00	0x00	0x00	0x00	0x00	0x00
0x124c:	0x00	0x00	0x00	0x00	0x00	0x00	0x00	0x00

(gdb) x/4gxm a
<Allocation Tag 0x1 for range [0x1230,0x1240)>
0x1234:	0x0000000000000201	0x0000000000000000
<Allocation Tag 0x1 for range [0x1240,0x1250)>
0x1244:	0x0000000000000000	0x0000000000000000

gdb/ChangeLog:

YYYY-MM-DD  Luis Machado  <luis.machado@linaro.org>

	* printcmd.c (decode_format): Handle the 'm' modifier.
	(do_examine): Display allocation tags when required/supported.
	(should_validate_memtags): New function.
	(print_command_1): Display memory tag mismatches.
	* valprint.h (struct format_data) <print_tags>: New field.
---
 gdb/printcmd.c | 83 +++++++++++++++++++++++++++++++++++++++++++++++++-
 gdb/valprint.h |  1 +
 2 files changed, 83 insertions(+), 1 deletion(-)

diff --git a/gdb/printcmd.c b/gdb/printcmd.c
index 6949678235..38b51c64ab 100644
--- a/gdb/printcmd.c
+++ b/gdb/printcmd.c
@@ -54,6 +54,7 @@
 #include "gdbsupport/byte-vector.h"
 #include "gdbsupport/gdb_optional.h"
 #include "gdbsupport/rsp-low.h"
+#include "infrun.h"		/* For memtag setting.  */
 
 /* Chain containing all defined mtag subcommands.  */
 
@@ -210,6 +211,7 @@ decode_format (const char **string_ptr, int oformat, int osize)
   val.size = '?';
   val.count = 1;
   val.raw = 0;
+  val.print_tags = false;
 
   if (*p == '-')
     {
@@ -232,6 +234,11 @@ decode_format (const char **string_ptr, int oformat, int osize)
 	  val.raw = 1;
 	  p++;
 	}
+      else if (*p == 'm')
+	{
+	  val.print_tags = true;
+	  p++;
+	}
       else if (*p >= 'a' && *p <= 'z')
 	val.format = *p++;
       else
@@ -1116,12 +1123,47 @@ do_examine (struct format_data fmt, struct gdbarch *gdbarch, CORE_ADDR addr)
       need_to_update_next_address = 1;
     }
 
+  /* Whether we need to print the memory tag information for the current
+     address range.  */
+  bool print_range_tag = true;
+  uint32_t gsize = gdbarch_memtag_granule_size (gdbarch);
+
   /* Print as many objects as specified in COUNT, at most maxelts per line,
      with the address of the next one at the start of each line.  */
 
   while (count > 0)
     {
       QUIT;
+
+      CORE_ADDR tag_laddr = 0, tag_haddr = 0;
+
+      /* Print the memory tag information if requested.  */
+      if (fmt.print_tags && print_range_tag && memtag
+	  && target_supports_memory_tagging ())
+	{
+	  tag_laddr = align_down (next_address, gsize);
+	  tag_haddr = align_down (next_address + gsize, gsize);
+
+	  struct value *v_addr
+	    = value_from_ulongest (builtin_type (gdbarch)->builtin_data_ptr,
+				   tag_laddr);
+
+	  if (gdbarch_tagged_address_p (target_gdbarch (), v_addr))
+	    {
+	      std::string atag = gdbarch_memtag_to_string (gdbarch, v_addr,
+							   tag_allocation);
+
+	      if (!atag.empty ())
+		{
+		  printf_filtered (_("<Allocation Tag %s for range [%s,%s)>\n"),
+				   atag.c_str (),
+				   paddress (gdbarch, tag_laddr),
+				   paddress (gdbarch, tag_haddr));
+		}
+	    }
+	  print_range_tag = false;
+	}
+
       if (format == 'i')
 	fputs_filtered (pc_prefix (next_address), gdb_stdout);
       print_address (next_gdbarch, next_address, gdb_stdout);
@@ -1152,6 +1194,11 @@ do_examine (struct format_data fmt, struct gdbarch *gdbarch, CORE_ADDR addr)
 	  /* Display any branch delay slots following the final insn.  */
 	  if (format == 'i' && count == 1)
 	    count += branch_delay_insns;
+
+	  /* Update the tag range based on the current address being
+	     processed.  */
+	  if (tag_haddr <= next_address)
+	      print_range_tag = true;
 	}
       printf_filtered ("\n");
     }
@@ -1224,6 +1271,26 @@ print_value (value *val, const value_print_options &opts)
   annotate_value_history_end ();
 }
 
+/* Returns true if memory tags should be validated.  False otherwise.  */
+
+static bool
+should_validate_memtags (struct value *value)
+{
+  if (memtag && target_supports_memory_tagging ()
+      && gdbarch_tagged_address_p (target_gdbarch (), value))
+    {
+      gdb_assert (value && value_type (value));
+
+      enum type_code code = value_type (value)->code ();
+
+      return (code == TYPE_CODE_PTR
+	      || code == TYPE_CODE_REF
+	      || code == TYPE_CODE_METHODPTR
+	      || code == TYPE_CODE_MEMBERPTR);
+    }
+  return false;
+}
+
 /* Helper for parsing arguments for print_command_1.  */
 
 static struct value *
@@ -1259,7 +1326,21 @@ print_command_1 (const char *args, int voidprint)
 
   if (voidprint || (val && value_type (val) &&
 		    value_type (val)->code () != TYPE_CODE_VOID))
-    print_value (val, print_opts);
+    {
+      /* If memory tagging validation is on, check if the tag is valid.  */
+      if (should_validate_memtags (val)
+	  && gdbarch_memtag_mismatch_p (target_gdbarch (), val))
+	{
+	  std::string ltag = gdbarch_memtag_to_string (target_gdbarch (),
+						       val, tag_logical);
+	  std::string atag = gdbarch_memtag_to_string (target_gdbarch (),
+						       val, tag_allocation);
+	  printf_filtered (_("Logical tag (%s) does not match the "
+			     "allocation tag (%s).\n"),
+			   ltag.c_str (), atag.c_str ());
+	}
+      print_value (val, print_opts);
+    }
 }
 
 /* See valprint.h.  */
diff --git a/gdb/valprint.h b/gdb/valprint.h
index ef9ebfa84f..fca58ad084 100644
--- a/gdb/valprint.h
+++ b/gdb/valprint.h
@@ -255,6 +255,7 @@ struct format_data
     int count;
     char format;
     char size;
+    bool print_tags;
 
     /* True if the value should be printed raw -- that is, bypassing
        python-based formatters.  */
-- 
2.17.1