Document the memory_tagged argument for memory region callbacks

There were no comments in some instances (gdb/defs.h, gdb/core.c and
gdb/linux-tdep.c), so address that by adding comments where those are missing.

gdb/defs.h

@@ -340,8 +340,12 @@ extern const char *pc_prefix (CORE_ADDR);
 /* * Process memory area starting at ADDR with length SIZE.  Area is
    readable iff READ is non-zero, writable if WRITE is non-zero,
    executable if EXEC is non-zero.  Area is possibly changed against
-   its original file based copy if MODIFIED is non-zero.  DATA is
-   passed without changes from a caller.  */
+   its original file based copy if MODIFIED is non-zero.
+
+   MEMORY_TAGGED is true if the memory region contains memory tags, false
+   otherwise.
+
+   DATA is passed without changes from a caller.  */
 
 typedef int (*find_memory_region_ftype) (CORE_ADDR addr, unsigned long size,
 					 int read, int write, int exec,

gdb/gcore.c

@@ -372,8 +372,12 @@ make_output_phdrs (bfd *obfd, asection *osec)
   bfd_record_phdr (obfd, p_type, 1, p_flags, 0, 0, 0, 0, 1, &osec);
 }
 
-/* find_memory_region_ftype implementation.  DATA is 'bfd *' for the core file
-   GDB is creating.  */
+/* find_memory_region_ftype implementation.
+
+   MEMORY_TAGGED is true if the memory region contains memory tags, false
+   otherwise.
+
+   DATA is 'bfd *' for the core file GDB is creating.  */
 
 static int
 gcore_create_callback (CORE_ADDR vaddr, unsigned long size, int read,
@@ -462,6 +466,10 @@ gcore_create_callback (CORE_ADDR vaddr, unsigned long size, int read,
 }
 
 /* gdbarch_find_memory_region callback for creating a memory tag section.
+
+   MEMORY_TAGGED is true if the memory region contains memory tags, false
+   otherwise.
+
    DATA is 'bfd *' for the core file GDB is creating.  */
 
 static int

gdb/linux-tdep.c

@@ -1695,7 +1695,10 @@ struct linux_make_mappings_data
 static linux_find_memory_region_ftype linux_make_mappings_callback;
 
 /* A callback for linux_find_memory_regions_full that updates the
-   mappings data for linux_make_mappings_corefile_notes.  */
+   mappings data for linux_make_mappings_corefile_notes.
+
+   MEMORY_TAGGED is true if the memory region contains memory tags, false
+   otherwise.  */
 
 static int
 linux_make_mappings_callback (ULONGEST vaddr, ULONGEST size,