Support for the GNU note with the AARCH64 CPU features (#527)

* Support for AARCH64 features GNU note

* Missing D_TAG

* Missing D_TAG, extra GNU CFA opcode

* DW_CFA_AARCH64_negate_ra_state

---------

Co-authored-by: Seva Alekseyev <sevaa@nih.gov>

elftools/dwarf/callframe.py

@@ -199,7 +199,7 @@ def _parse_instructions(self, structs, offset, end_offset):
                 args = [primary_arg]
             # primary == 0 and real opcode is extended
             elif opcode in (DW_CFA_nop, DW_CFA_remember_state,
-                            DW_CFA_restore_state):
+                            DW_CFA_restore_state, DW_CFA_AARCH64_negate_ra_state):
                 args = []
             elif opcode == DW_CFA_set_loc:
                 args = [
@@ -236,6 +236,7 @@ def _parse_instructions(self, structs, offset, end_offset):
                     struct_parse(structs.Dwarf_sleb128(''), self.stream)]
             elif opcode == DW_CFA_GNU_args_size:
                 args = [struct_parse(structs.Dwarf_uleb128(''), self.stream)]
+
             else:
                 dwarf_assert(False, 'Unknown CFI opcode: 0x%x' % opcode)
 

elftools/dwarf/constants.py

@@ -208,6 +208,8 @@
 DW_CFA_val_offset = 0x14
 DW_CFA_val_offset_sf = 0x15
 DW_CFA_val_expression = 0x16
+DW_CFA_GNU_window_save = 0x2d # Used on SPARC, not in the corpus
+DW_CFA_AARCH64_negate_ra_state = 0x2d
 DW_CFA_GNU_args_size = 0x2e
 
 

elftools/dwarf/descriptions.py

@@ -89,7 +89,7 @@ def _full_reg_name(regnum):
                 name, factored_offset, factored_offset + pc)
             pc += factored_offset
         elif name in (  'DW_CFA_remember_state', 'DW_CFA_restore_state',
-                        'DW_CFA_nop'):
+                        'DW_CFA_nop', 'DW_CFA_AARCH64_negate_ra_state'):
             s += '  %s\n' % name
         elif name == 'DW_CFA_def_cfa':
             s += '  %s: %s ofs %s\n' % (

elftools/elf/descriptions.py

@@ -200,7 +200,7 @@ def describe_ver_flags(x):
         VER_FLAGS.VER_FLG_INFO) if x & flag)
 
 
-def describe_note(x):
+def describe_note(x, machine):
     n_desc = x['n_desc']
     desc = ''
     if x['n_type'] == 'NT_GNU_ABI_TAG':
@@ -215,7 +215,7 @@ def describe_note(x):
     elif x['n_type'] == 'NT_GNU_GOLD_VERSION':
         desc = '\n    Version: %s' % (n_desc)
     elif x['n_type'] == 'NT_GNU_PROPERTY_TYPE_0':
-        desc = '\n      Properties: ' + describe_note_gnu_properties(x['n_desc'])
+        desc = '\n      Properties: ' + describe_note_gnu_properties(x['n_desc'], machine)
     else:
         desc = '\n      description data: {}'.format(bytes2hex(n_desc))
 
@@ -269,30 +269,14 @@ def describe_attr_tag_riscv(tag, val, extra):
     else:
         return _DESCR_ATTR_TAG_RISCV[tag] + d_entry[val]
 
-
-
-def describe_note_gnu_property_x86_feature_1(value):
-    descs = []
-    for mask, desc in _DESCR_NOTE_GNU_PROPERTY_X86_FEATURE_1_FLAGS:
-        if value & mask:
-            descs.append(desc)
-    return 'x86 feature: ' + ', '.join(descs)
-
-def describe_note_gnu_property_x86_feature_2_used(value):
-    descs = []
-    for mask, desc in _DESCR_NOTE_GNU_PROPERTY_X86_FEATURE_2_FLAGS:
-        if value & mask:
-            descs.append(desc)
-    return 'x86 feature used: ' + ', '.join(descs)
-
-def describe_note_gnu_property_x86_isa_1(value, verb):
+def describe_note_gnu_property_bitmap_and(values, prefix, value):
     descs = []
-    for mask, desc in _DESCR_NOTE_GNU_PROPERTY_X86_ISA_1_FLAGS:
+    for mask, desc in values:
         if value & mask:
             descs.append(desc)
-    return 'x86 ISA %s: %s' % (verb, ', '.join(descs))
+    return '%s: %s' % (prefix, ', '.join(descs))
 
-def describe_note_gnu_properties(properties):
+def describe_note_gnu_properties(properties, machine):
     descriptions = []
     for prop in properties:
         t, d, sz = prop.pr_type, prop.pr_data, prop.pr_datasz
@@ -310,22 +294,27 @@ def describe_note_gnu_properties(properties):
             if sz != 4:
                 prop_desc = ' <corrupt length: 0x%x>' % sz
             else:
-                prop_desc = describe_note_gnu_property_x86_feature_1(d)
+                prop_desc = describe_note_gnu_property_bitmap_and(_DESCR_NOTE_GNU_PROPERTY_X86_FEATURE_1_FLAGS, 'x86 feature', d)
         elif t == 'GNU_PROPERTY_X86_FEATURE_2_USED':
             if sz != 4:
                 prop_desc = ' <corrupt length: 0x%x>' % sz
             else:
-                prop_desc = describe_note_gnu_property_x86_feature_2_used(d)                
+                prop_desc = describe_note_gnu_property_bitmap_and(_DESCR_NOTE_GNU_PROPERTY_X86_FEATURE_2_FLAGS, 'x86 feature used', d)                
         elif t == 'GNU_PROPERTY_X86_ISA_1_NEEDED':
             if sz != 4:
                 prop_desc = ' <corrupt length: 0x%x>' % sz
             else:
-                prop_desc = describe_note_gnu_property_x86_isa_1(d, "needed")
+                prop_desc = describe_note_gnu_property_bitmap_and(_DESCR_NOTE_GNU_PROPERTY_X86_ISA_1_FLAGS, 'x86 ISA needed', d)
         elif t == 'GNU_PROPERTY_X86_ISA_1_USED':
             if sz != 4:
                 prop_desc = ' <corrupt length: 0x%x>' % sz
             else:
-                prop_desc = describe_note_gnu_property_x86_isa_1(d, "used")
+                prop_desc = describe_note_gnu_property_bitmap_and(_DESCR_NOTE_GNU_PROPERTY_X86_ISA_1_FLAGS, 'x86 ISA used', d)
+        elif t == 'GNU_PROPERTY_AARCH64_FEATURE_1_AND' and machine == 'EM_AARCH64':
+            if sz != 4:
+                prop_desc = ' <corrupt length: 0x%x>' % sz
+            else:
+                prop_desc = describe_note_gnu_property_bitmap_and(_DESCR_NOTE_GNU_PROPERTY_AARCH64_FEATURE_1_AND, 'aarch64 feature', d)
         elif _DESCR_NOTE_GNU_PROPERTY_TYPE_LOPROC <= t <= _DESCR_NOTE_GNU_PROPERTY_TYPE_HIPROC:
             prop_desc = '<processor-specific type 0x%x data: %s >' % (t, bytes2hex(d, sep=' '))
         elif _DESCR_NOTE_GNU_PROPERTY_TYPE_LOUSER <= t <= _DESCR_NOTE_GNU_PROPERTY_TYPE_HIUSER:
@@ -673,6 +662,11 @@ def describe_note_gnu_properties(properties):
     # TODO; there is a long list
 )
 
+# Same for GNU_PROPERTY_AARCH64_FEATURE_1_AND
+_DESCR_NOTE_GNU_PROPERTY_AARCH64_FEATURE_1_AND = (
+    (1, 'bti'),
+    (2, 'pac'),
+)
 
 def _reverse_dict(d, low_priority=()):
     """

elftools/elf/enums.py

@@ -619,6 +619,10 @@
     DT_MIPS_RLD_MAP_REL=0x70000035,
 )
 
+ENUM_D_TAG_AARCH64 = dict(
+    DT_AARCH64_BTI_PLT=0x70000001,
+)
+
 # Here is the mapping from e_machine enum to the extra dynamic tags which it
 # validates. Solaris is missing from this list because its inclusion is not
 # controlled by e_machine but rather e_ident[EI_OSABI].
@@ -628,6 +632,7 @@
 ENUMMAP_EXTRA_D_TAG_MACHINE = dict(
     EM_MIPS=ENUM_D_TAG_MIPS,
     EM_MIPS_RS3_LE=ENUM_D_TAG_MIPS,
+    EM_AARCH64=ENUM_D_TAG_AARCH64
 )
 
 # Here is the full combined mapping from tag name to value
@@ -1065,6 +1070,7 @@
     GNU_PROPERTY_X86_ISA_1_NEEDED=0xc0008002,
     GNU_PROPERTY_X86_FEATURE_2_USED=0xc0010001,
     GNU_PROPERTY_X86_ISA_1_USED=0xc0010002,
+    GNU_PROPERTY_AARCH64_FEATURE_1_AND=0xc0000000,
     _default_=Pass,
 )
 

elftools/elf/structs.py

@@ -404,6 +404,8 @@ def classify_pr_data(ctx):
                 return None
             if ctx.pr_type.startswith('GNU_PROPERTY_X86_'):
                 return ('GNU_PROPERTY_X86_*', 4, 0)
+            elif ctx.pr_type.startswith('GNU_PROPERTY_AARCH64_'):
+                return ('GNU_PROPERTY_AARCH64_*', 4, 0)            
             return (ctx.pr_type, ctx.pr_datasz, self.elfclass)
 
         self.Elf_Prop = Struct('Elf_Prop',
@@ -413,6 +415,7 @@ def classify_pr_data(ctx):
                     ('GNU_PROPERTY_STACK_SIZE', 4, 32): self.Elf_word('pr_data'),
                     ('GNU_PROPERTY_STACK_SIZE', 8, 64): self.Elf_word64('pr_data'),
                     ('GNU_PROPERTY_X86_*', 4, 0): self.Elf_word('pr_data'),
+                    ('GNU_PROPERTY_AARCH64_*', 4, 0): self.Elf_word('pr_data'),
                 },
                 default=Field('pr_data', lambda ctx: ctx.pr_datasz)
             ),

scripts/readelf.py

@@ -549,6 +549,8 @@ def display_dynamic_tags(self):
                 elif tag.entry.d_tag in ('DT_MIPS_SYMTABNO',
                                          'DT_MIPS_LOCAL_GOTNO'):
                     parsed = str(tag.entry.d_val)
+                elif tag.entry.d_tag == 'DT_AARCH64_BTI_PLT':
+                    parsed = ''
                 else:
                     parsed = '%#x' % tag['d_val']
 
@@ -573,7 +575,7 @@ def display_notes(self):
                       self._emitline('  %s %s\t%s' % (
                           note['n_name'].ljust(20),
                           self._format_hex(note['n_descsz'], fieldsize=8),
-                          describe_note(note)))
+                          describe_note(note, self.elffile.header.e_machine)))
 
     def display_relocations(self):
         """ Display the relocations contained in the file