[PATCH] D116769: [ifs] Allow llvm-ifs to generate text stub from elf stub

[Roland McGrath via Phabricator via llvm-commits]

mcgrathr added inline comments.


================
Comment at: llvm/lib/InterfaceStub/ELFObjHandler.cpp:538
   // Get pointer to in-memory location of .dynstr section.
-  Expected<const uint8_t *> DynStrPtr = ElfFile.toMappedAddr(DynEnt.StrTabAddr);
-  if (!DynStrPtr)
-    return appendToError(DynStrPtr.takeError(),
-                         "when locating .dynstr section contents");
-
-  StringRef DynStr(reinterpret_cast<const char *>(DynStrPtr.get()),
-                   DynEnt.StrSize);
+  const uint8_t *DynStrPtr = ElfFile.base() + DynEnt.StrTabAddr;
+  if (HasPhdr) {
----------------
This value cannot be safely used at all.  The DT_STRTAB address is not something that can be presumed to be an offset into the file, even if that's often true.

The behavior I'd expect here is to first look for section headers.  If there are section headers at all, then purely look for the SHT_DYNSYM section and follow its sh_link to its SHT_STRTAB section and use its sh_offset and sh_size.  If there are section headers at all, but no SHT_DYNSYM section or its sh_link doesn't point to an SHT_STRTAB section, then you don't need to handle this input file.  It's invalid or empty.

Only if there are no section headers at all should you fall back to decoding based on phdrs.  This should be the same for finding the SHT_DYNAMIC section in the first place, only falling back to PT_DYNAMIC if there are no section headers at all.

Also note that for DT_NEEDED et al, strings pointed to by SHT_DYNAMIC entries, technically it's the sh_link of the SHT_DYNAMIC that tells you what string table section to use.  In practice, it's always the same one as the one that SHT_DYNSYM's sh_link points to, but by the spec they can be separate when dealing with sections.



================
Comment at: llvm/lib/InterfaceStub/ELFObjHandler.cpp:583
     // Get pointer to in-memory location of .dynsym section.
-    Expected<const uint8_t *> DynSymPtr =
-        ElfFile.toMappedAddr(DynEnt.DynSymAddr);
-    if (!DynSymPtr)
-      return appendToError(DynSymPtr.takeError(),
-                           "when locating .dynsym section contents");
+    const uint8_t *DynSymPtr = ElfFile.base() + DynEnt.DynSymAddr;
+    if (HasPhdr) {
----------------
Same issues here.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D116769/new/

https://reviews.llvm.org/D116769