obtain verdefnum from verdef section header

Similarly to #611 Rust's ELF raw-dylibs do not contain the information
about verdef count.
This goes against LSB, but all the other linkers can handle it,
presumably by using `st_info` of`.gnu.version_d` section.


I'm not sure if this is the right thing to do, maybe `sh_info` should be
 used just a fallback when `.dynamic` doesn't have `DT_VERDEFNUM` tag?

On current main `tests/ui/linkage-attr/raw-dylib/elf/glibc-x86_64.rs`
fails with:
```
wild: error: Failed to load symbols from `/tmp/rustcnCgdWG/raw-dylibs/lib105m6f543m4qw1t7khnttg751.so`
  Caused by:
    Invalid version index 1
```

Author: mati865

libwild/src/elf.rs

@@ -16,7 +16,6 @@ use linker_utils::elf::extract_bits;
 use linker_utils::elf::sht;
 use object::LittleEndian;
 use object::read::elf::CompressionHeader;
-use object::read::elf::Dyn;
 use object::read::elf::FileHeader as _;
 use object::read::elf::RelocationSections;
 use object::read::elf::SectionHeader as _;
@@ -63,8 +62,8 @@ pub(crate) struct File<'data> {
     /// An iterator over the version definitions and the corresponding linked string table index.
     pub(crate) verdef: Option<(VerdefIterator<'data>, object::SectionIndex)>,
 
-    /// Number of verdef versions according to the dynamic table.
-    pub(crate) verdefnum: u64,
+    /// Number of verdef versions according to `sh_info` of `.gnu._version_d` section.
+    pub(crate) verdefnum: u32,
 
     /// e_flags from the header.
     pub(crate) eflags: u32,
@@ -85,10 +84,9 @@ impl<'data> File<'data> {
         let mut symbols = SymbolTable::default();
         let mut versym: &[Versym] = &[];
         let mut verdef = None;
-        let mut dynamic = None;
         let mut verdefnum = 0;
 
-        // Find all the sections that we're interested in in a single scan of the section table so
+        // Find all the sections that we're interested in a single scan of the section table so
         // as to avoid multiple scans.
         for (section_index, section) in sections.enumerate() {
             match SectionType::from_header(section) {
@@ -103,22 +101,12 @@ impl<'data> File<'data> {
                 }
                 sht::GNU_VERDEF => {
                     verdef = section.gnu_verdef(endian, data)?;
-                }
-                sht::DYNAMIC => {
-                    dynamic = section.dynamic(endian, data)?;
+                    verdefnum = section.sh_info(endian);
                 }
                 _ => {}
             }
         }
 
-        if let Some((dynamic, _)) = dynamic {
-            for dy in dynamic {
-                if dy.d_tag(endian) == u64::from(object::elf::DT_VERDEFNUM) {
-                    verdefnum = dy.d_val(endian);
-                }
-            }
-        }
-
         Ok(Self {
             arch: architecture,
             data,

libwild/src/layout.rs

@@ -5282,9 +5282,9 @@ impl<'data> DynamicLayoutState<'data> {
         resources: &GraphResources<'data, '_>,
         queue: &mut LocalWorkQueue,
     ) -> Result {
-        let dt_info = DynamicTagValues::read(self.object)?;
-        self.symbol_versions_needed = vec![false; dt_info.verdefnum as usize];
+        self.symbol_versions_needed = vec![false; self.object.verdefnum as usize];
 
+        let dt_info = DynamicTagValues::read(self.object)?;
         if let Some(soname) = dt_info.soname {
             self.lib_name = soname;
         }