From a855622c498c9a588043f02160dc6dd88f143f71 Mon Sep 17 00:00:00 2001
From: George Rimar <grimar@accesssoftek.com>
Date: Tue, 5 Mar 2019 13:07:43 +0000
Subject: [PATCH] [llvm-objcopy] - Simplify `isCompressable` and fix the issue
 relative.

When --compress-debug-sections is given, llvm-objcopy do not compress
sections that have "ZLIB" header in data. Normally this signature is used
in zlib-gnu compression format. But if zlib-gnu used then the name of the compressed
section should start from .z* (e.g .zdebug_info). If it does not, then it is not
a zlib-gnu format and section should be treated as a normal uncompressed section.

Differential revision: https://reviews.llvm.org/D58908


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@355399 91177308-0d34-0410-b5e6-96231b3b80d8
---
 .../ELF/compress-debug-sections-zlib-header.test   | 41 ++++++++++++++++++++++
 tools/llvm-objcopy/ELF/ELFObjcopy.cpp              | 13 ++-----
 2 files changed, 43 insertions(+), 11 deletions(-)
 create mode 100644 test/tools/llvm-objcopy/ELF/compress-debug-sections-zlib-header.test

diff --git a/test/tools/llvm-objcopy/ELF/compress-debug-sections-zlib-header.test b/test/tools/llvm-objcopy/ELF/compress-debug-sections-zlib-header.test
new file mode 100644
index 00000000000..0e7d713aebc
--- /dev/null
+++ b/test/tools/llvm-objcopy/ELF/compress-debug-sections-zlib-header.test
@@ -0,0 +1,41 @@
+# REQUIRES: zlib
+
+# RUN: yaml2obj %s -o %t1.o
+# RUN: llvm-objcopy --compress-debug-sections %t1.o %t2.o
+# RUN: llvm-readobj -s %t2.o | FileCheck %s
+
+# Non-.zdebug* sections whose data does start with "ZLIB" should
+# not be considered as zlib-gnu compressed sections.
+
+# In this test we have 2 normal sections, one of them starts with "ZLIB",
+# another starts with "ZZZZ". Check we compress both as expected.
+
+# CHECK:        Name: .debug_foo
+# CHECK-NEXT:   Type: SHT_PROGBITS
+# CHECK-NEXT:   Flags [
+# CHECK-NEXT:     SHF_COMPRESSED
+# CHECK-NEXT:   ]
+
+# CHECK:        Name: .debug_bar
+# CHECK-NEXT:   Type: SHT_PROGBITS
+# CHECK-NEXT:   Flags [
+# CHECK-NEXT:     SHF_COMPRESSED
+# CHECK-NEXT:   ]
+
+--- !ELF
+FileHeader:      
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  Type:            ET_REL
+  Machine:         EM_X86_64
+Sections:        
+  - Name:            .debug_foo
+    Type:            SHT_PROGBITS
+    AddressAlign:    0x0000000000000001
+    # "ZLIB"
+    Content:         5A4C49420000000000000000
+  - Name:            .debug_bar
+    Type:            SHT_PROGBITS
+    AddressAlign:    0x0000000000000001
+    # "ZZZZ"
+    Content:         5A5A5A5A0000000000000000
diff --git a/tools/llvm-objcopy/ELF/ELFObjcopy.cpp b/tools/llvm-objcopy/ELF/ELFObjcopy.cpp
index 1132aa18589..6f21db9db60 100644
--- a/tools/llvm-objcopy/ELF/ELFObjcopy.cpp
+++ b/tools/llvm-objcopy/ELF/ELFObjcopy.cpp
@@ -223,18 +223,9 @@ static Error dumpSectionToFile(StringRef SecName, StringRef Filename,
   return createStringError(object_error::parse_failed, "Section not found");
 }
 
-static bool isCompressed(const SectionBase &Section) {
-  const char *Magic = "ZLIB";
-  return StringRef(Section.Name).startswith(".zdebug") ||
-         (Section.OriginalData.size() > strlen(Magic) &&
-          !strncmp(reinterpret_cast<const char *>(Section.OriginalData.data()),
-                   Magic, strlen(Magic))) ||
-         (Section.Flags & ELF::SHF_COMPRESSED);
-}
-
 static bool isCompressable(const SectionBase &Section) {
-  return !isCompressed(Section) && isDebugSection(Section) &&
-         Section.Name != ".gdb_index";
+  return !(Section.Flags & ELF::SHF_COMPRESSED) &&
+         StringRef(Section.Name).startswith(".debug");
 }
 
 static void replaceDebugSections(
-- 
2.11.0