From 463cec95495084b45afcc8cc8b8ba51ebbd0d83d Mon Sep 17 00:00:00 2001
From: George Rimar <grimar@accesssoftek.com>
Date: Fri, 24 May 2019 11:12:50 +0000
Subject: [PATCH] [llvm-readelf] - Allow dumping of the .dynamic section even
 if there is no PT_DYNAMIC header.

It is now possible after D61937 was landed and was discussed
in it's review comments. It is not consistent with GNU, which
does not output .dynamic section content in this case for
no visible reason.

Differential revision: https://reviews.llvm.org/D62179

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@361630 91177308-0d34-0410-b5e6-96231b3b80d8
---
 .../elf-dynamic-no-pt-dynamic.test             | 15 +++++++++++----
 tools/llvm-readobj/ELFDumper.cpp               | 18 +++++++++---------
 2 files changed, 20 insertions(+), 13 deletions(-)

diff --git a/test/tools/llvm-readobj/elf-dynamic-no-pt-dynamic.test b/test/tools/llvm-readobj/elf-dynamic-no-pt-dynamic.test
index 3ef293714a8..5a03d04ab4d 100644
--- a/test/tools/llvm-readobj/elf-dynamic-no-pt-dynamic.test
+++ b/test/tools/llvm-readobj/elf-dynamic-no-pt-dynamic.test
@@ -1,16 +1,23 @@
-# Show that no dumping occurs if there is no PT_DYNAMIC header.
+## Show that dumping occurs even if there is no PT_DYNAMIC header.
+## This is inconsistent with the GNU behavior, but seems to be more reasonable.
 # RUN: yaml2obj %s -o %t.no-phdr
 # RUN: llvm-readobj --dynamic-table %t.no-phdr | FileCheck %s --check-prefix=LLVM
-# RUN: llvm-readelf --dynamic-table %t.no-phdr | FileCheck %s --check-prefix=GNU --allow-empty
+# RUN: llvm-readelf --dynamic-table %t.no-phdr | FileCheck %s --check-prefix=GNU
 
 # LLVM:      File: {{.*}}.no-phdr
 # LLVM-NEXT: Format: ELF64-x86-64
 # LLVM-NEXT: Arch: x86_64
 # LLVM-NEXT: AddressSize: 64bit
 # LLVM-NEXT: LoadName:{{ *}}
-# LLVM-NOT:  {{.}}
+# LLVM-NEXT: DynamicSection [ (1 entries)
+# LLVM-NEXT:   Tag                Type Name/Value
+# LLVM-NEXT:   0x0000000000000000 NULL 0x0
+# LLVM-NEXT: ]
 
-# GNU-NOT: {{.}}
+# GNU:      DynamicSection [ (1 entries)
+# GNU-NEXT:   Tag                Type Name/Value
+# GNU-NEXT:   0x0000000000000000 NULL 0x0
+# GNU-NEXT: ]
 
 --- !ELF
 FileHeader:
diff --git a/tools/llvm-readobj/ELFDumper.cpp b/tools/llvm-readobj/ELFDumper.cpp
index 159e300de30..b86a6c192ca 100644
--- a/tools/llvm-readobj/ELFDumper.cpp
+++ b/tools/llvm-readobj/ELFDumper.cpp
@@ -1331,6 +1331,7 @@ static const char *getElfMipsOptionsOdkType(unsigned Odk) {
 
 template <typename ELFT>
 void ELFDumper<ELFT>::loadDynamicTable(const ELFFile<ELFT> *Obj) {
+  // Try to locate the PT_DYNAMIC header.
   const Elf_Phdr *DynamicPhdr = nullptr;
   for (const Elf_Phdr &Phdr : unwrapOrError(Obj->program_headers())) {
     if (Phdr.p_type != ELF::PT_DYNAMIC)
@@ -1339,11 +1340,6 @@ void ELFDumper<ELFT>::loadDynamicTable(const ELFFile<ELFT> *Obj) {
     break;
   }
 
-  // We do not want to dump dynamic section if we have no PT_DYNAMIC header.
-  // This matches GNU's behavior.
-  if (!DynamicPhdr)
-    return;
-
   // Try to locate the .dynamic section in the sections header table.
   const Elf_Shdr *DynamicSec = nullptr;
   for (const Elf_Shdr &Sec : unwrapOrError(Obj->sections())) {
@@ -1358,9 +1354,16 @@ void ELFDumper<ELFT>::loadDynamicTable(const ELFFile<ELFT> *Obj) {
   // Ignore sh_entsize and use the expected value for entry size explicitly.
   // This allows us to dump the dynamic sections with a broken sh_entsize
   // field.
-  if (DynamicSec)
+  if (DynamicSec) {
     DynamicTable = checkDRI({ObjF->getELFFile()->base() + DynamicSec->sh_offset,
                              DynamicSec->sh_size, sizeof(Elf_Dyn)});
+    parseDynamicTable();
+  }
+
+  // If we have a PT_DYNAMIC header, we will either check the found dynamic
+  // section or take the dynamic table data directly from the header.
+  if (!DynamicPhdr)
+    return;
 
   if (DynamicPhdr->p_offset + DynamicPhdr->p_filesz >
       ObjF->getMemoryBufferRef().getBufferSize())
@@ -1374,7 +1377,6 @@ void ELFDumper<ELFT>::loadDynamicTable(const ELFFile<ELFT> *Obj) {
   }
 
   StringRef Name = unwrapOrError(Obj->getSectionName(DynamicSec));
-
   if (DynamicSec->sh_addr + DynamicSec->sh_size >
           DynamicPhdr->p_vaddr + DynamicPhdr->p_memsz ||
       DynamicSec->sh_addr < DynamicPhdr->p_vaddr)
@@ -1386,8 +1388,6 @@ void ELFDumper<ELFT>::loadDynamicTable(const ELFFile<ELFT> *Obj) {
     reportWarning("The SHT_DYNAMIC section '" + Name +
                   "' is not at the start of "
                   "PT_DYNAMIC segment");
-
-  parseDynamicTable();
 }
 
 template <typename ELFT>
-- 
2.50.1