[AArch64] MTE corefile support

Teach GDB how to dump memory tags for AArch64 when using the gcore command
and how to read memory tag data back from a core file generated by GDB
(via gcore) or by the Linux kernel.

The format is documented in the Linux Kernel documentation [1].

Each tagged memory range (listed in /proc/<pid>/smaps) gets dumped to its
own PT_AARCH64_MEMTAG_MTE segment. A section named ".memtag" is created for each
of those segments when reading the core file back.

To save a little bit of space, given MTE tags only take 4 bits, the memory tags
are stored packed as 2 tags per byte.

When reading the data back, the tags are unpacked.

I've added a new testcase to exercise the feature.

Build-tested with --enable-targets=all and regression tested on aarch64-linux
Ubuntu 20.04.

[1] Documentation/arm64/memory-tagging-extension.rst (Core Dump Support)

1 files changed, 2 insertions, 1 deletions

diff --git a/gdb/defs.h b/gdb/defs.h
index 99a03fb..e5b6c78 100644
--- a/gdb/defs.h
+++ b/gdb/defs.h
@@ -345,7 +345,8 @@ extern const char *pc_prefix (CORE_ADDR);
 
 typedef int (*find_memory_region_ftype) (CORE_ADDR addr, unsigned long size,
 					 int read, int write, int exec,
-					 int modified, void *data);
+					 int modified, bool memory_tagged,
+					 void *data);
 
 /* * Possible lvalue types.  Like enum language, this should be in
    value.h, but needs to be here for the same reason.  */