[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, 96 insertions, 0 deletions

diff --git a/gdb/gdbarch.c b/gdb/gdbarch.c
index 68ef048..5d14aec 100644
--- a/gdb/gdbarch.c
+++ b/gdb/gdbarch.c
@@ -171,6 +171,9 @@ struct gdbarch
   gdbarch_iterate_over_regset_sections_ftype *iterate_over_regset_sections;
   gdbarch_make_corefile_notes_ftype *make_corefile_notes;
   gdbarch_find_memory_regions_ftype *find_memory_regions;
+  gdbarch_create_memtag_section_ftype *create_memtag_section;
+  gdbarch_fill_memtag_section_ftype *fill_memtag_section;
+  gdbarch_decode_memtag_section_ftype *decode_memtag_section;
   gdbarch_core_xfer_shared_libraries_ftype *core_xfer_shared_libraries;
   gdbarch_core_xfer_shared_libraries_aix_ftype *core_xfer_shared_libraries_aix;
   gdbarch_core_pid_to_str_ftype *core_pid_to_str;
@@ -527,6 +530,9 @@ verify_gdbarch (struct gdbarch *gdbarch)
   /* Skip verify of iterate_over_regset_sections, has predicate.  */
   /* Skip verify of make_corefile_notes, has predicate.  */
   /* Skip verify of find_memory_regions, has predicate.  */
+  /* Skip verify of create_memtag_section, has predicate.  */
+  /* Skip verify of fill_memtag_section, has predicate.  */
+  /* Skip verify of decode_memtag_section, has predicate.  */
   /* Skip verify of core_xfer_shared_libraries, has predicate.  */
   /* Skip verify of core_xfer_shared_libraries_aix, has predicate.  */
   /* Skip verify of core_pid_to_str, has predicate.  */
@@ -1097,6 +1103,24 @@ gdbarch_dump (struct gdbarch *gdbarch, struct ui_file *file)
                       "gdbarch_dump: find_memory_regions = <%s>\n",
                       host_address_to_string (gdbarch->find_memory_regions));
   gdb_printf (file,
+                      "gdbarch_dump: gdbarch_create_memtag_section_p() = %d\n",
+                      gdbarch_create_memtag_section_p (gdbarch));
+  gdb_printf (file,
+                      "gdbarch_dump: create_memtag_section = <%s>\n",
+                      host_address_to_string (gdbarch->create_memtag_section));
+  gdb_printf (file,
+                      "gdbarch_dump: gdbarch_fill_memtag_section_p() = %d\n",
+                      gdbarch_fill_memtag_section_p (gdbarch));
+  gdb_printf (file,
+                      "gdbarch_dump: fill_memtag_section = <%s>\n",
+                      host_address_to_string (gdbarch->fill_memtag_section));
+  gdb_printf (file,
+                      "gdbarch_dump: gdbarch_decode_memtag_section_p() = %d\n",
+                      gdbarch_decode_memtag_section_p (gdbarch));
+  gdb_printf (file,
+                      "gdbarch_dump: decode_memtag_section = <%s>\n",
+                      host_address_to_string (gdbarch->decode_memtag_section));
+  gdb_printf (file,
                       "gdbarch_dump: gdbarch_core_xfer_shared_libraries_p() = %d\n",
                       gdbarch_core_xfer_shared_libraries_p (gdbarch));
   gdb_printf (file,
@@ -3745,6 +3769,78 @@ set_gdbarch_find_memory_regions (struct gdbarch *gdbarch,
 }
 
 bool
+gdbarch_create_memtag_section_p (struct gdbarch *gdbarch)
+{
+  gdb_assert (gdbarch != NULL);
+  return gdbarch->create_memtag_section != NULL;
+}
+
+asection *
+gdbarch_create_memtag_section (struct gdbarch *gdbarch, bfd *obfd, CORE_ADDR address, size_t size)
+{
+  gdb_assert (gdbarch != NULL);
+  gdb_assert (gdbarch->create_memtag_section != NULL);
+  if (gdbarch_debug >= 2)
+    gdb_printf (gdb_stdlog, "gdbarch_create_memtag_section called\n");
+  return gdbarch->create_memtag_section (gdbarch, obfd, address, size);
+}
+
+void
+set_gdbarch_create_memtag_section (struct gdbarch *gdbarch,
+                                   gdbarch_create_memtag_section_ftype create_memtag_section)
+{
+  gdbarch->create_memtag_section = create_memtag_section;
+}
+
+bool
+gdbarch_fill_memtag_section_p (struct gdbarch *gdbarch)
+{
+  gdb_assert (gdbarch != NULL);
+  return gdbarch->fill_memtag_section != NULL;
+}
+
+bool
+gdbarch_fill_memtag_section (struct gdbarch *gdbarch, asection *osec)
+{
+  gdb_assert (gdbarch != NULL);
+  gdb_assert (gdbarch->fill_memtag_section != NULL);
+  if (gdbarch_debug >= 2)
+    gdb_printf (gdb_stdlog, "gdbarch_fill_memtag_section called\n");
+  return gdbarch->fill_memtag_section (gdbarch, osec);
+}
+
+void
+set_gdbarch_fill_memtag_section (struct gdbarch *gdbarch,
+                                 gdbarch_fill_memtag_section_ftype fill_memtag_section)
+{
+  gdbarch->fill_memtag_section = fill_memtag_section;
+}
+
+bool
+gdbarch_decode_memtag_section_p (struct gdbarch *gdbarch)
+{
+  gdb_assert (gdbarch != NULL);
+  return gdbarch->decode_memtag_section != NULL;
+}
+
+gdb::byte_vector
+gdbarch_decode_memtag_section (struct gdbarch *gdbarch, bfd_section *section, int type, CORE_ADDR address, size_t length)
+{
+  gdb_assert (gdbarch != NULL);
+  gdb_assert (gdbarch->decode_memtag_section != NULL);
+  if (gdbarch_debug >= 2)
+    gdb_printf (gdb_stdlog, "gdbarch_decode_memtag_section called\n");
+  return gdbarch->decode_memtag_section (gdbarch, section, type, address, length);
+}
+
+void
+set_gdbarch_decode_memtag_section (struct gdbarch *gdbarch,
+                                   gdbarch_decode_memtag_section_ftype decode_memtag_section)
+{
+  gdbarch->decode_memtag_section = decode_memtag_section;
+}
+
+bool
 gdbarch_core_xfer_shared_libraries_p (struct gdbarch *gdbarch)
 {
   gdb_assert (gdbarch != NULL);