read/elf: exclude zero sized STT_NOTYPE symbols from is_definition

These are generally markers, not definitions.
In particular, this excludes ARM mapping symbols ('$*').

Additionally, since we are treating non-zero sized STT_NOTYPE
symbols as definitions, that means they are not SymbolKind::Label.

crates/examples/testfiles/elf/base-aarch64.o.objdump

@@ -40,6 +40,4 @@ Dynamic symbols
 Dynamic relocations
 
 Symbol map
-0x0 "$d"
-0x0 "$x"
 0x0 "main"

crates/examples/testfiles/elf/base-aarch64.objdump

@@ -163,52 +163,23 @@ Import { library: "", name: "_ITM_registerTMCloneTable" }
 Import { library: "", name: "printf" }
 
 Symbol map
-0x21c "$d"
-0x598 "$x"
 0x598 "_init"
-0x5a4 "$x"
-0x5b0 "$x"
-0x620 "$x"
 0x620 "_start"
-0x658 "$x"
 0x658 "call_weak_fn"
-0x670 "$x"
 0x670 "deregister_tm_clones"
 0x6a0 "register_tm_clones"
 0x6d8 "__do_global_dtors_aux"
 0x720 "frame_dummy"
-0x724 "$x"
 0x724 "main"
-0x748 "$x"
 0x748 "__libc_csu_init"
 0x7c8 "__libc_csu_fini"
-0x7cc "$x"
 0x7cc "_fini"
-0x7d4 "$x"
-0x7e0 "$d"
 0x7e0 "_IO_stdin_used"
-0x7e8 "$d"
-0x7f8 "$d"
 0x7f8 "__FRAME_END__"
-0x10d80 "$d"
 0x10d80 "__frame_dummy_init_array_entry"
-0x10d80 "__init_array_start"
-0x10d88 "$d"
 0x10d88 "__do_global_dtors_aux_fini_array_entry"
-0x10d88 "__init_array_end"
 0x10d90 "_DYNAMIC"
 0x10fc0 "_GLOBAL_OFFSET_TABLE_"
-0x11000 "data_start"
-0x11000 "__data_start"
-0x11008 "$d"
 0x11008 "__dso_handle"
 0x11010 "completed.8500"
-0x11010 "$d"
-0x11010 "__bss_start__"
-0x11010 "_edata"
-0x11010 "__bss_start"
 0x11010 "__TMC_END__"
-0x11018 "_bss_end__"
-0x11018 "__bss_end__"
-0x11018 "_end"
-0x11018 "__end__"

crates/examples/testfiles/elf/base.objdump

@@ -143,19 +143,11 @@ Symbol map
 0x710 "__libc_csu_fini"
 0x714 "_fini"
 0x720 "_IO_stdin_used"
-0x734 "__GNU_EH_FRAME_HDR"
 0x874 "__FRAME_END__"
 0x200da8 "__frame_dummy_init_array_entry"
-0x200da8 "__init_array_start"
 0x200db0 "__do_global_dtors_aux_fini_array_entry"
-0x200db0 "__init_array_end"
 0x200db8 "_DYNAMIC"
 0x200fb8 "_GLOBAL_OFFSET_TABLE_"
-0x201000 "data_start"
-0x201000 "__data_start"
 0x201008 "__dso_handle"
 0x201010 "completed.7698"
-0x201010 "_edata"
-0x201010 "__bss_start"
 0x201010 "__TMC_END__"
-0x201018 "_end"

src/read/elf/symbol.rs

@@ -354,7 +354,8 @@ impl<'data, 'file, Elf: FileHeader, R: ReadRef<'data>> ObjectSymbol<'data>
     fn kind(&self) -> SymbolKind {
         match self.symbol.st_type() {
             elf::STT_NOTYPE if self.index.0 == 0 => SymbolKind::Null,
-            elf::STT_NOTYPE => SymbolKind::Label,
+            elf::STT_NOTYPE if self.size() == 0 => SymbolKind::Label,
+            elf::STT_NOTYPE => SymbolKind::Unknown,
             elf::STT_OBJECT | elf::STT_COMMON => SymbolKind::Data,
             elf::STT_FUNC | elf::STT_GNU_IFUNC => SymbolKind::Text,
             elf::STT_SECTION => SymbolKind::Section,
@@ -478,9 +479,14 @@ pub trait Sym: Debug + Pod {
 
     /// Return true if the symbol is a definition of a function or data object.
     fn is_definition(&self, endian: Self::Endian) -> bool {
-        let st_type = self.st_type();
-        (st_type == elf::STT_NOTYPE || st_type == elf::STT_FUNC || st_type == elf::STT_OBJECT)
-            && self.st_shndx(endian) != elf::SHN_UNDEF
+        if self.st_shndx(endian) == elf::SHN_UNDEF {
+            return false;
+        }
+        match self.st_type() {
+            elf::STT_NOTYPE => self.st_size(endian).into() != 0,
+            elf::STT_FUNC | elf::STT_OBJECT => true,
+            _ => false,
+        }
     }
 }