[llvm] e0fb9f5 - [llvm-objdump] Fix alignment issues when dumping offloading sections

[Joseph Huber via llvm-commits]

Author: Joseph Huber
Date: 2022-07-08T14:30:06-04:00
New Revision: e0fb9f55b63ce5a1d38bf2468b0593d8cca040dc

URL: https://github.com/llvm/llvm-project/commit/e0fb9f55b63ce5a1d38bf2468b0593d8cca040dc
DIFF: https://github.com/llvm/llvm-project/commit/e0fb9f55b63ce5a1d38bf2468b0593d8cca040dc.diff

LOG: [llvm-objdump] Fix alignment issues when dumping offloading sections

Summary:
The `.llvm.offloading` section should always be aligned by `8`. However,
we may want to show the offloading data stored in a static library. In
this case, even though the section's alignment is correct, the offset
inside the archive will result in the memory buffer being misaligned. TO
combat this we simply check if the buffer does not have the proper
alignment and copies it to a new buffer if not. This copy should have
the proper alignment.

Added: 
    llvm/test/tools/llvm-objdump/Offloading/alignment.test

Modified: 
    llvm/tools/llvm-objdump/OffloadDump.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/test/tools/llvm-objdump/Offloading/alignment.test b/llvm/test/tools/llvm-objdump/Offloading/alignment.test
new file mode 100644
index 0000000000000..d949d5916ea20
--- /dev/null
+++ b/llvm/test/tools/llvm-objdump/Offloading/alignment.test
@@ -0,0 +1,22 @@
+## Ensure we can read the contents even if the alignment is bad.
+# RUN: yaml2obj %s -o %t.elf
+# RUN: yaml2obj %S/Inputs/binary.yaml -o %t.bin
+# RUN: llvm-objcopy --update-section .llvm.offloading=%t.bin %t.elf
+# RUN: llvm-objdump --offloading %t.elf | FileCheck %s -DFILENAME=%t
+
+!ELF
+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  Type:            ET_EXEC
+Sections:
+  - Name:            .misaligned
+    Type:            SHT_PROGBITS
+    AddressAlign:    0x0000000000000001
+    Content:         "41424300"
+  - Name:            .llvm.offloading
+    Type:            SHT_LLVM_OFFLOADING
+    Flags:           [ SHF_EXCLUDE ]
+    AddressAlign:    0x0000000000000001
+
+# CHECK-NOT: error: '[[FILENAME]]': while extracting offloading files: Invalid data was encountered while parsing the file

diff  --git a/llvm/tools/llvm-objdump/OffloadDump.cpp b/llvm/tools/llvm-objdump/OffloadDump.cpp
index b3302d40e2bcb..46334c249070d 100644
--- a/llvm/tools/llvm-objdump/OffloadDump.cpp
+++ b/llvm/tools/llvm-objdump/OffloadDump.cpp
@@ -13,6 +13,7 @@
 #include "OffloadDump.h"
 #include "llvm-objdump.h"
 #include "llvm/Object/ELFObjectFile.h"
+#include "llvm/Support/Alignment.h"
 
 using namespace llvm;
 using namespace llvm::object;
@@ -79,8 +80,13 @@ void llvm::dumpOffloadBinary(const ObjectFile &O) {
     if (!Contents)
       reportError(Contents.takeError(), O.getFileName());
 
-    MemoryBufferRef Buffer = MemoryBufferRef(*Contents, O.getFileName());
-    auto BinaryOrErr = OffloadBinary::create(Buffer);
+    std::unique_ptr<MemoryBuffer> Buffer =
+        MemoryBuffer::getMemBuffer(*Contents, O.getFileName(), false);
+    if (!isAddrAligned(Align(OffloadBinary::getAlignment()),
+                       Buffer->getBufferStart()))
+      Buffer = MemoryBuffer::getMemBufferCopy(Buffer->getBuffer(),
+                                              Buffer->getBufferIdentifier());
+    auto BinaryOrErr = OffloadBinary::create(*Buffer);
     if (!BinaryOrErr)
       reportError(O.getFileName(), "while extracting offloading files: " +
                                        toString(BinaryOrErr.takeError()));