[lld] b8a3c61 - [ELF] Allow misaligned SHT_GNU_verneed

[Fangrui Song via llvm-commits]

Author: Fangrui Song
Date: 2020-05-26T11:18:19-07:00
New Revision: b8a3c618d6c5df081cad69b5ffb386a7a7b0361f

URL: https://github.com/llvm/llvm-project/commit/b8a3c618d6c5df081cad69b5ffb386a7a7b0361f
DIFF: https://github.com/llvm/llvm-project/commit/b8a3c618d6c5df081cad69b5ffb386a7a7b0361f.diff

LOG: [ELF] Allow misaligned SHT_GNU_verneed

Bazel created interface shared objects (.ifso) may be misaligned.  We use
llvm::support::detail::packed_endian_specific_integral under the hood
which allows reading of misaligned values, so there is not a need to
diagnose (in LLD we don't intend to support sophisticated parsing for
SHT_GNU_*).

Added: 
    lld/test/ELF/invalid/verneed-shared.test

Modified: 
    lld/ELF/InputFiles.cpp

Removed: 
    lld/test/ELF/invalid/verneed-shared.yaml


################################################################################
diff  --git a/lld/ELF/InputFiles.cpp b/lld/ELF/InputFiles.cpp
index 9fdd0547ddca..c451aee1f921 100644
--- a/lld/ELF/InputFiles.cpp
+++ b/lld/ELF/InputFiles.cpp
@@ -1224,14 +1224,12 @@ std::vector<uint32_t> SharedFile::parseVerneed(const ELFFile<ELFT> &obj,
   ArrayRef<uint8_t> data = CHECK(obj.getSectionContents(sec), this);
   const uint8_t *verneedBuf = data.begin();
   for (unsigned i = 0; i != sec->sh_info; ++i) {
-    if (verneedBuf + sizeof(typename ELFT::Verneed) > data.end() ||
-        uintptr_t(verneedBuf) % sizeof(uint32_t) != 0)
+    if (verneedBuf + sizeof(typename ELFT::Verneed) > data.end())
       fatal(toString(this) + " has an invalid Verneed");
     auto *vn = reinterpret_cast<const typename ELFT::Verneed *>(verneedBuf);
     const uint8_t *vernauxBuf = verneedBuf + vn->vn_aux;
     for (unsigned j = 0; j != vn->vn_cnt; ++j) {
-      if (vernauxBuf + sizeof(typename ELFT::Vernaux) > data.end() ||
-          uintptr_t(vernauxBuf) % sizeof(uint32_t) != 0)
+      if (vernauxBuf + sizeof(typename ELFT::Vernaux) > data.end())
         fatal(toString(this) + " has an invalid Vernaux");
       auto *aux = reinterpret_cast<const typename ELFT::Vernaux *>(vernauxBuf);
       if (aux->vna_name >= this->stringTable.size())

diff  --git a/lld/test/ELF/invalid/verneed-shared.yaml b/lld/test/ELF/invalid/verneed-shared.test
similarity index 89%
rename from lld/test/ELF/invalid/verneed-shared.yaml
rename to lld/test/ELF/invalid/verneed-shared.test
index 18315fe8a2df..916b8c1a5d95 100644
--- a/lld/test/ELF/invalid/verneed-shared.yaml
+++ b/lld/test/ELF/invalid/verneed-shared.test
@@ -6,7 +6,7 @@
 ## sh_offset(SHT_GNU_verneed) is out of bounds.
 # RUN: yaml2obj --docnum=1 %s -o %t1.so
 # RUN: not ld.lld %t.o %t1.so -o /dev/null 2>&1 | FileCheck --check-prefix=SHOFFSET %s
-# SHOFFSET: error: {{.*}}.so: section [index 1] has a sh_offset (0xffffffff) + sh_size (0x0) that is greater than the file size (0x228)
+# SHOFFSET: error: {{.*}}.so: section [index 1] has a sh_offset (0xffffffff) + sh_size (0x0) that is greater than the file size (0x168)
 --- !ELF
 FileHeader:
   Class:   ELFCLASS64
@@ -17,12 +17,14 @@ Sections:
   - Name:  .gnu.version_r
     Type:  SHT_GNU_verneed
     Flags: [ SHF_ALLOC ]
+    Info:  1
     ShOffset: 0xFFFFFFFF
 
-## A Verneed entry is misaligned (not a multiple of 4).
+## A Verneed entry is misaligned (not a multiple of 4). This may happen
+## some interface shared objects. We use memcpy to read the fields, so
+## misalignment isn't a problem and there is no need to diagnose.
 # RUN: yaml2obj --docnum=2 %s -o %t2.so
-# RUN: not ld.lld %t.o %t2.so -o /dev/null 2>&1 | FileCheck --check-prefix=VN-MISALIGNED %s
-# VN-MISALIGNED: {{.*}}.so has an invalid Verneed
+# RUN: ld.lld %t.o %t2.so -o /dev/null
 --- !ELF
 FileHeader:
   Class:   ELFCLASS64