[llvm] [llvm-objdump][ELF]Fix crash when reading strings from .dynstr (PR #125679)

[Ruoyu Qiu via llvm-commits]

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@@ -221,6 +221,28 @@ template <class ELFT> void ELFDumper<ELFT>::printDynamicSection() {
   std::string TagFmt = "  %-" + std::to_string(MaxLen) + "s ";
 
   outs() << "\nDynamic Section:\n";
+  typename ELFT::Xword StringTableSize{0};
+  for (const typename ELFT::Shdr &Sec : cantFail(Elf.sections())) {
+    if (Sec.sh_type == ELF::SHT_DYNSYM) {
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cabbaken wrote:

> This will work because it happens to be the same section in pretty much any normal ELF, but is not technically correct. You should check `SHT_DYNAMIC`, since the strings referenced by the dynamic section are the ones you need (not the dynamic symbol names).

That’s true, but `private-headers.test` will fail if `SHT_DYNAMIC` is used since there’s no `Link` to `.dynstr` in this test. I chose `SHT_DYNSYM` to align with `llvm/llvm/tools/llvm-objdump/ELFDump.cpp:61: getDynamicStrTab()`, as they function similarly.
In fact, I'm curious why using `SHT_DYNSYM` allows the test to pass. It seems that `yaml2obj` add the `SHT_DYNSYM` to the generated ELF.
Maybe I should use
```
    if (Sec.sh_type == ELF::SHT_DYNSYM||Sec.sh_type == ELF::SHT_DYNAMIC)
```
here?

https://github.com/llvm/llvm-project/pull/125679