[NFC][libomptarget] Reduce the dependency on libelf

[vzakhari]

Summary

This change-set removes libelf usage from elf_common part of the plugins. libelf is still used in x86_64 generic plugin code and in some plugins (e.g. amdgpu) - these will have to be cleaned up in separate checkins.

[JonChesterfield]

Looks functionally correct. Always in favour of moving stuff out of headers where we can, though as an unrelated change we might want to start building plugins with flto or similar to ensure that remains free.

Either myself or @pdhaliwal will do equivalent handling for the amdgpu plugin.

There was some discussion on the mailing list about failing to link against llvm libs but I didn't see the resolution to it. Suggest we continue as planned.

openmp/libomptarget/plugins/common/elf_common/elf_common.cpp

23

A bit surprised that GETNAME handles spaces. Have you done a debug build of this to check the DP() handling compiles cleanly?

66

Maybe a helper function for this setup code? It's very similar to the above function. Thinking something along the lines of:

ELFObjectFileBase * tbd(char * bytes, size_t size); // return nullptr if it can't make one

but it's possible memory management will thwart that, in which case it may be easier callback style:

template <typename F>
int withBytesAsElf(char * bytes, size_t size, F f)
{
 ///
int rc = f(Object);
///
return rc;
}

[vzakhari]

openmp/libomptarget/plugins/common/elf_common/elf_common.cpp

23

Sure, other plugins also use TARGET_NAME with spaces. And I did verify that LIBOMPTARGET_DEBUG output worked, e.g.:

TARGET ELF Common --> Unknown ELF format or not an ELF image!

[JonChesterfield]

Thanks!

[vzakhari]

Just a rebase.

[JonChesterfield]

Are you expecting to land this soon?

[vzakhari]

In D103545#2821456, @JonChesterfield wrote:

Are you expecting to land this soon?

Yes, I am going to merge it in 24 hours.

[JonChesterfield]

Great, thanks! I'll (try to) find some time to start cutting the dependency out of the amdgpu plugin next week.

[tianshilei1992]

This patch seems to break the link of libomptarget.rtl.cuda.so. Here is the error on my machine.

[46/48] Linking CXX shared library libomptarget/libomptarget.rtl.x86_64.so
FAILED: libomptarget/libomptarget.rtl.x86_64.so
: && /home/shiltian/Documents/deploy/llvm/release/bin/clang++ -fPIC -Wall -Wcast-qual -Wformat-pedantic -Wimplicit-fallthrough -Wsign-compare -Wno-extra -Wno-pedantic -std=gnu++14 -g   -shared -Wl,-soname,libomptarget.rtl.x86_64.so -o libomptarget/libomptarget.rtl.x86_64.so libomptarget/plugins/common/elf_common/CMakeFiles/elf_common.dir/elf_common.cpp.o libomptarget/plugins/x86_64/CMakeFiles/omptarget.rtl.x86_64.dir/__/generic-elf-64bit/src/rtl.cpp.o  /usr/lib64/libffi.so  /usr/lib64/libelf.so  -ldl  -lpthread  -Wl,--version-script=/home/shiltian/Documents/vscode/llvm-project/openmp/libomptarget/plugins/x86_64/../exports  /home/shiltian/Documents/deploy/llvm/release/lib/libLLVMObject.a  /home/shiltian/Documents/deploy/llvm/release/lib/libLLVMBitReader.a  /home/shiltian/Documents/deploy/llvm/release/lib/libLLVMCore.a  /home/shiltian/Documents/deploy/llvm/release/lib/libLLVMRemarks.a  /home/shiltian/Documents/deploy/llvm/release/lib/libLLVMBitstreamReader.a  /home/shiltian/Documents/deploy/llvm/release/lib/libLLVMMCParser.a  /home/shiltian/Documents/deploy/llvm/release/lib/libLLVMMC.a  /home/shiltian/Documents/deploy/llvm/release/lib/libLLVMDebugInfoCodeView.a  /home/shiltian/Documents/deploy/llvm/release/lib/libLLVMTextAPI.a  /home/shiltian/Documents/deploy/llvm/release/lib/libLLVMBinaryFormat.a  /home/shiltian/Documents/deploy/llvm/release/lib/libLLVMSupport.a  -lrt  -lm  /usr/lib64/libz.so  /usr/lib64/libtinfo.so  /home/shiltian/Documents/deploy/llvm/release/lib/libLLVMDemangle.a  -ldl  -lpthread && :
/usr/bin/ld: libomptarget/plugins/common/elf_common/CMakeFiles/elf_common.dir/elf_common.cpp.o: relocation R_X86_64_32S against symbol `stderr@@GLIBC_2.2.5' can not be used when making a shared object; recompile with -fPIC
clang-13: error: linker command failed with exit code 1 (use -v to see invocation)
[47/48] Linking CXX shared library libomptarget/libomptarget.rtl.cuda.so

I checked its parent commit that there is no problem.

[ye-luo]

@tianshilei1992 what is your OS?

[ronlieb]

[AMD Official Use Only]

I am seeing similar errors after merging down the latest llvm.
I had to add a cmake option to find the include files and I am now seeing the relocation issues

I am on ubuntu 18.04

I build openmp for target in a separate step after llvm is built.

[JonChesterfield]

It appears the static llvm libraries were not built with fPIC, thus can't be linked into a shared library. Forcing fPIC on everything would verify that (as in stuff would work, maybe slightly slower) if the cmake controls are opaque.

I think there's a linker bug/feature in this area too, I remember running into this on a previous toolchain where the objects had all been built with fPIC, but the relocation error remained. I think that was solved by passing a linker flag or using gold, but that is going back a few years and the details are hazy.

[tianshilei1992]

In D103545#2825804, @ye-luo wrote:

@tianshilei1992 what is your OS?

➜  lsb_release -a
LSB Version:    :core-4.1-amd64:core-4.1-noarch:cxx-4.1-amd64:cxx-4.1-noarch:desktop-4.1-amd64:desktop-4.1-noarch:languages-4.1-amd64:languages-4.1-noarch:printing-4.1-amd64:printing-4.1-noarch
Distributor ID: Fedora
Description:    Fedora release 32 (Thirty Two)
Release:        32
Codename:       ThirtyTwo

[vzakhari]

Can you please provide the CMake command to reproduce this? I cannot reproduce this with an ordinary in-tree build.

[ronlieb]

[AMD Official Use Only]

Trunk as of this morning
work/rlieberm/mono-repo/llvm-project/openmp/libomptarget/plugins/common/elf_common/elf_common.cpp
/work/rlieberm/mono-repo/llvm-project/openmp/libomptarget/plugins/common/elf_common/elf_common.cpp:15:10: fatal error: 'llvm/BinaryFormat/Magic.h' file not found
#include "llvm/BinaryFormat/Magic.h"

^~~~~~~~~~~~~~~~~~~~~~~~~~~

1 error generated.
[182/204] Building CXX object openmp/tools/archer/CMakeFiles/archer.dir/ompt-tsan.cpp.o

Cmake command, you can probably drop the CMAKE_INSTALL_PREFIX

cmake -DCMAKE_INSTALL_PREFIX=/home/rlieberm/rocm/trunk_1.0 \

-DCMAKE_BUILD_TYPE=Release \
-DLLVM_ENABLE_PROJECTS="clang;lld" \
-DLLVM_TARGETS_TO_BUILD="X86;AMDGPU" \
-DLLVM_ENABLE_ASSERTIONS=ON                        \
-DLLVM_ENABLE_RUNTIMES="openmp" \
-DCLANG_DEFAULT_LINKER=lld                         \
../llvm -GNinja

[ronlieb]

i forgot to mention that the first problem i encountered with this patch is that elf_common.cpp has difficulties finding its LLVM header files.
i am reporting that issue. For me, the fPIC relocatables might be a downstream issue, still looking into that one.

for the header file issue, i cobbled this up
add to end of file openmp/libomptarget/plugins/common/elf_common/CMakeLists.txt
include_directories(${LIBOMPTARGET_LLVM_INCLUDE_DIRS})

and added a cmake definition kind of like:
-DLIBOMPTARGET_LLVM_INCLUDE_DIRS=/<blah>/llvm-project/llvm/include

A person more versed in CMake might have a better solution, hope so.

[vzakhari]

In D103545#2826676, @ronlieb wrote:

[AMD Official Use Only]

Trunk as of this morning
work/rlieberm/mono-repo/llvm-project/openmp/libomptarget/plugins/common/elf_common/elf_common.cpp
/work/rlieberm/mono-repo/llvm-project/openmp/libomptarget/plugins/common/elf_common/elf_common.cpp:15:10: fatal error: 'llvm/BinaryFormat/Magic.h' file not found
#include "llvm/BinaryFormat/Magic.h"

^~~~~~~~~~~~~~~~~~~~~~~~~~~

1 error generated.
[182/204] Building CXX object openmp/tools/archer/CMakeFiles/archer.dir/ompt-tsan.cpp.o

Cmake command, you can probably drop the CMAKE_INSTALL_PREFIX

cmake -DCMAKE_INSTALL_PREFIX=/home/rlieberm/rocm/trunk_1.0 \

-DCMAKE_BUILD_TYPE=Release \
-DLLVM_ENABLE_PROJECTS="clang;lld" \
-DLLVM_TARGETS_TO_BUILD="X86;AMDGPU" \
-DLLVM_ENABLE_ASSERTIONS=ON                        \
-DLLVM_ENABLE_RUNTIMES="openmp" \
-DCLANG_DEFAULT_LINKER=lld                         \
../llvm -GNinja

Thank you, @ronlieb! I am able to reproduce it. It seems that LLVM_ENABLE_RUNTIMES behavior is quite different from the -DLLVM_ENABLE_PROJECTS="openmp" that I use (so I did not see this issue before). It seems to me that in LLVM_ENABLE_RUNTIMES mode, openmp is configured/built as a standalone project using clang built by the "main" cmake/build step, but for some reason OPENMP_STANDALONE_BUILD is false. I am not sure about the right solution yet. Can you please add openmp to your -DLLVM_ENABLE_PROJECTS="clang;lld" and remove "-DLLVM_ENABLE_RUNTIMES="openmp" as a temporary workaround?

[vzakhari]

In D103545#2826828, @ronlieb wrote:

i forgot to mention that the first problem i encountered with this patch is that elf_common.cpp has difficulties finding its LLVM header files.
i am reporting that issue. For me, the fPIC relocatables might be a downstream issue, still looking into that one.

for the header file issue, i cobbled this up
add to end of file openmp/libomptarget/plugins/common/elf_common/CMakeLists.txt
include_directories(${LIBOMPTARGET_LLVM_INCLUDE_DIRS})

and added a cmake definition kind of like:
-DLIBOMPTARGET_LLVM_INCLUDE_DIRS=/<blah>/llvm-project/llvm/include

A person more versed in CMake might have a better solution, hope so.

Please check if D104535 fixes the header files issue.
As to the PIC issue, I do not see it. @tianshilei1992 please provide cmake commands so that I can reproduce the issue.

[tianshilei1992]

I build my LLVM with the command:

cmake -G Ninja -DCMAKE_INSTALL_PREFIX=$HOME/Documents/deploy/llvm/release -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_PROJECTS="clang" -DLLVM_INSTALL_UTILS=ON -DLLVM_INCLUDE_BENCHMARKS=OFF -DLLVM_INCLUDE_TESTS=ON -DLLVM_INCLUDE_EXAMPLES=OFF -DLLVM_ENABLE_ASSERTIONS=ON $HOME/Documents/vscode/llvm-project/llvm

And then have a separate configure for OpenMP:

cmake -G Ninja -DCMAKE_INSTALL_PREFIX=$HOME/Documents/deploy/openmp/debug -DCMAKE_BUILD_TYPE=Debug -DCMAKE_C_COMPILER=$HOME/Documents/deploy/llvm/release/bin/clang -DCMAKE_CXX_COMPILER=$HOME/Documents/deploy/llvm/release/bin/clang++ -DLIBOMPTARGET_NVPTX_COMPUTE_CAPABILITIES=75 -DOPENMP_NOT_EXECUTABLE=$HOME/Documents/deploy/llvm/release/bin/not -DCUDA_TOOLKIT_ROOT_DIR=/usr/local/cuda -DLLVM_ROOT=$HOME/Documents/deploy/llvm/release -DLIBOMPTARGET_LLVM_INCLUDE_DIRS=$HOME/Documents/vscode/llvm-project/llvm/include $HOME/Documents/vscode/llvm-project/openm

[ronlieb]

Thank you, @ronlieb! I am able to reproduce it. It seems that LLVM_ENABLE_RUNTIMES behavior is quite different from the -DLLVM_ENABLE_PROJECTS="openmp" that I use (so I did not see this issue before). It seems to me that in LLVM_ENABLE_RUNTIMES mode, openmp is configured/built as a standalone project using clang built by the "main" cmake/build step, but for some reason OPENMP_STANDALONE_BUILD is false. I am not sure about the right solution yet. Can you please add openmp to your -DLLVM_ENABLE_PROJECTS="clang;lld" and remove "-DLLVM_ENABLE_RUNTIMES="openmp" as a temporary workaround?

i added openmp to PROJECTS, and removed -DLLVM_ENABLE_RUNTIMES="openmp"

results in error

CMake Error at cmake/modules/LLVMExternalProjectUtils.cmake:358 (add_custom_target):

add_custom_target cannot create target "check-openmp" because another
target with the same name already exists.  The existing target is a custom
target created in source directory
"/work/rlieberm/mono-repo/llvm-project/openmp".  See documentation for
policy CMP0002 for more details.

Call Stack (most recent call first):

runtimes/CMakeLists.txt:226 (llvm_ExternalProject_Add)
runtimes/CMakeLists.txt:353 (runtime_default_target)

[vzakhari]

In D103545#2827177, @ronlieb wrote:

Thank you, @ronlieb! I am able to reproduce it. It seems that LLVM_ENABLE_RUNTIMES behavior is quite different from the -DLLVM_ENABLE_PROJECTS="openmp" that I use (so I did not see this issue before). It seems to me that in LLVM_ENABLE_RUNTIMES mode, openmp is configured/built as a standalone project using clang built by the "main" cmake/build step, but for some reason OPENMP_STANDALONE_BUILD is false. I am not sure about the right solution yet. Can you please add openmp to your -DLLVM_ENABLE_PROJECTS="clang;lld" and remove "-DLLVM_ENABLE_RUNTIMES="openmp" as a temporary workaround?

i added openmp to PROJECTS, and removed -DLLVM_ENABLE_RUNTIMES="openmp"

results in error

CMake Error at cmake/modules/LLVMExternalProjectUtils.cmake:358 (add_custom_target):

add_custom_target cannot create target "check-openmp" because another
target with the same name already exists.  The existing target is a custom
target created in source directory
"/work/rlieberm/mono-repo/llvm-project/openmp".  See documentation for
policy CMP0002 for more details.

Call Stack (most recent call first):

runtimes/CMakeLists.txt:226 (llvm_ExternalProject_Add)
runtimes/CMakeLists.txt:353 (runtime_default_target)

This is weird. The following command works for me: cmake -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_PROJECTS="clang;lld;openmp" -DLLVM_TARGETS_TO_BUILD="X86;AMDGPU" -DLLVM_ENABLE_ASSERTIONS=ON -DCLANG_DEFAULT_LINKER=lld ../llvm -GNinja
It looks like your cmake invocation still uses the LLVM_ENABLE_RUNTIMES path. Did you remove cmake cache before the reconfiguration? Anyway, I believe D104535 should fix the LLVM_ENABLE_RUNTIMES build.

[vzakhari]

In D103545#2827091, @tianshilei1992 wrote:

I build my LLVM with the command:

cmake -G Ninja -DCMAKE_INSTALL_PREFIX=$HOME/Documents/deploy/llvm/release -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_PROJECTS="clang" -DLLVM_INSTALL_UTILS=ON -DLLVM_INCLUDE_BENCHMARKS=OFF -DLLVM_INCLUDE_TESTS=ON -DLLVM_INCLUDE_EXAMPLES=OFF -DLLVM_ENABLE_ASSERTIONS=ON $HOME/Documents/vscode/llvm-project/llvm

And then have a separate configure for OpenMP:

cmake -G Ninja -DCMAKE_INSTALL_PREFIX=$HOME/Documents/deploy/openmp/debug -DCMAKE_BUILD_TYPE=Debug -DCMAKE_C_COMPILER=$HOME/Documents/deploy/llvm/release/bin/clang -DCMAKE_CXX_COMPILER=$HOME/Documents/deploy/llvm/release/bin/clang++ -DLIBOMPTARGET_NVPTX_COMPUTE_CAPABILITIES=75 -DOPENMP_NOT_EXECUTABLE=$HOME/Documents/deploy/llvm/release/bin/not -DCUDA_TOOLKIT_ROOT_DIR=/usr/local/cuda -DLLVM_ROOT=$HOME/Documents/deploy/llvm/release -DLIBOMPTARGET_LLVM_INCLUDE_DIRS=$HOME/Documents/vscode/llvm-project/llvm/include $HOME/Documents/vscode/llvm-project/openm

Thank you, @tianshilei1992. I believe D104545 should fix the issue.

[tianshilei1992]

In D103545#2827232, @vzakhari wrote:

Thank you, @tianshilei1992. I believe D104545 should fix the issue.

Confirmed. Works for me.

openmp/libomptarget/plugins/amdgpu/CMakeLists.txt

 install(TARGETS omptarget.rtl.amdgpu LIBRARY DESTINATION "lib${OPENMP_LIBDIR_SUFFIX}")
 
 set_property(TARGET omptarget.rtl.amdgpu PROPERTY INSTALL_RPATH "$ORIGIN")
 target_link_libraries(
   omptarget.rtl.amdgpu
   PRIVATE
   elf_common
   hsa-runtime64::hsa-runtime64
-  pthread dl elf
+  dl
+  ${LIBOMPTARGET_DEP_LIBELF_LIBRARIES}
+  ${OPENMP_PTHREAD_LIB}
   "-Wl,--version-script=${CMAKE_CURRENT_SOURCE_DIR}/../exports"
   "-Wl,-z,defs"
   )
 
 if (LLVM_BINARY_DIR)
   # for in-tree build using LLVM_ENABLE_RUNTIMES
   set(AMDGPU_ARCH_TOOL "${LLVM_BINARY_DIR}/bin/amdgpu-arch")
 elseif (OPENMP_LLVM_TOOLS_DIR)

openmp/libomptarget/plugins/common/elf_common/CMakeLists.txt

 ##===----------------------------------------------------------------------===##
 #
 # Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 # See https://llvm.org/LICENSE.txt for license information.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 #
 ##===----------------------------------------------------------------------===##
 #
 # Common ELF functionality for target plugins
 #
 ##===----------------------------------------------------------------------===##
 
-add_library(elf_common INTERFACE)
+add_library(elf_common OBJECT elf_common.cpp)
 
+llvm_update_compile_flags(elf_common)
+set(LINK_LLVM_LIBS LLVMBinaryFormat LLVMObject LLVMSupport)
+target_link_libraries(elf_common INTERFACE ${LINK_LLVM_LIBS} ${LIBOMPTARGET_DEP_LIBELF_LIBRARIES})
+add_dependencies(elf_common ${LINK_LLVM_LIBS})
+
+# The code uses Debug.h, which requires threads support.
+target_link_libraries(elf_common INTERFACE ${OPENMP_PTHREAD_LIB})
+
+# Expose elf_common.h directory to the users of this library.
 target_include_directories(elf_common INTERFACE ${CMAKE_CURRENT_SOURCE_DIR})

openmp/libomptarget/plugins/common/elf_common/elf_common.h

-//===-- elf_common.h - Common ELF functionality -------------------*- C -*-===//
+//===-- elf_common.h - Common ELF functionality -----------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // Common ELF functionality for target plugins.
-// Must be included in the plugin source file AFTER omptarget.h has been
-// included and macro DP(...) has been defined.
-// .
 //
 //===----------------------------------------------------------------------===//
 
-#if !(defined(_OMPTARGET_DEBUG_H))
-#error Include elf_common.h in the plugin source AFTER Debug.h has\
- been included.
-#endif
+#ifndef LLVM_OPENMP_LIBOMPTARGET_PLUGINS_COMMON_ELF_COMMON_ELF_COMMON_H
+#define LLVM_OPENMP_LIBOMPTARGET_PLUGINS_COMMON_ELF_COMMON_ELF_COMMON_H
 
-#include <elf.h>
-#include <libelf.h>
+#include "omptargetplugin.h"
+#include <cstdint>
 
-// Check whether an image is valid for execution on target_id
-static inline int32_t elf_check_machine(__tgt_device_image *image,
-                                        uint16_t target_id) {
+/// Return non-zero, if the given \p image is an ELF object, which
+/// e_machine matches \p target_id; return zero otherwise.
+EXTERN int32_t elf_check_machine(__tgt_device_image *image, uint16_t target_id);
 
-  // Is the library version incompatible with the header file?
-  if (elf_version(EV_CURRENT) == EV_NONE) {
-    DP("Incompatible ELF library!\n");
-    return 0;
-  }
+/// Return non-zero, if the given \p image is an ET_DYN ELF object;
+/// return zero otherwise.
+EXTERN int32_t elf_is_dynamic(__tgt_device_image *image);
 
-  char *img_begin = (char *)image->ImageStart;
-  char *img_end = (char *)image->ImageEnd;
-  size_t img_size = img_end - img_begin;
-
-  // Obtain elf handler
-  Elf *e = elf_memory(img_begin, img_size);
-  if (!e) {
-    DP("Unable to get ELF handle: %s!\n", elf_errmsg(-1));
-    return 0;
-  }
-
-  // Check if ELF is the right kind.
-  if (elf_kind(e) != ELF_K_ELF) {
-    DP("Unexpected ELF type!\n");
-    elf_end(e);
-    return 0;
-  }
-  Elf64_Ehdr *eh64 = elf64_getehdr(e);
-  Elf32_Ehdr *eh32 = elf32_getehdr(e);
-
-  if (!eh64 && !eh32) {
-    DP("Unable to get machine ID from ELF file!\n");
-    elf_end(e);
-    return 0;
-  }
-
-  uint16_t MachineID;
-  if (eh64 && !eh32)
-    MachineID = eh64->e_machine;
-  else if (eh32 && !eh64)
-    MachineID = eh32->e_machine;
-  else {
-    DP("Ambiguous ELF header!\n");
-    elf_end(e);
-    return 0;
-  }
-
-  elf_end(e);
-  return MachineID == target_id;
-}
-
-static inline int32_t elf_is_dynamic(__tgt_device_image *image) {
-
-  char *img_begin = (char *)image->ImageStart;
-  char *img_end = (char *)image->ImageEnd;
-  size_t img_size = img_end - img_begin;
-
-  // Obtain elf handler
-  Elf *e = elf_memory(img_begin, img_size);
-  if (!e) {
-    DP("Unable to get ELF handle: %s!\n", elf_errmsg(-1));
-    return 0;
-  }
-
-  Elf64_Ehdr *eh64 = elf64_getehdr(e);
-  Elf32_Ehdr *eh32 = elf32_getehdr(e);
-
-  if (!eh64 && !eh32) {
-    DP("Unable to get machine ID from ELF file!\n");
-    elf_end(e);
-    return 0;
-  }
-
-  uint16_t Type;
-  if (eh64 && !eh32)
-    Type = eh64->e_type;
-  else if (eh32 && !eh64)
-    Type = eh32->e_type;
-  else {
-    DP("Ambiguous ELF header!\n");
-    elf_end(e);
-    return 0;
-  }
-
-  elf_end(e);
-  DP("ELF Type: %d\n", Type);
-  return Type == ET_DYN;
-}
+#endif // LLVM_OPENMP_LIBOMPTARGET_PLUGINS_COMMON_ELF_COMMON_ELF_COMMON_H

openmp/libomptarget/plugins/common/elf_common/elf_common.cpp

+//===-- elf_common.cpp - Common ELF functionality -------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Common ELF functionality for target plugins.
+//
+//===----------------------------------------------------------------------===//
+#include "elf_common.h"
+#include "Debug.h"
+
+#include "llvm/BinaryFormat/Magic.h"
+#include "llvm/Object/Binary.h"
+#include "llvm/Object/ELFObjectFile.h"
+#include "llvm/Object/ELFTypes.h"
+#include "llvm/Object/ObjectFile.h"
+#include "llvm/Support/MemoryBuffer.h"
+
+#ifndef TARGET_NAME
+#define TARGET_NAME ELF Common
+#endif
+#define DEBUG_PREFIX "TARGET " GETNAME(TARGET_NAME)
+
+using namespace llvm;
+using namespace llvm::ELF;
+using namespace llvm::object;
+
+/// If the given range of bytes [\p BytesBegin, \p BytesEnd) represents
+/// a valid ELF, then invoke \p Callback on the ELFObjectFileBase
+/// created from this range, otherwise, return 0.
+/// If \p Callback is invoked, then return whatever value \p Callback returns.
+template <typename F>
+static int32_t withBytesAsElf(char *BytesBegin, char *BytesEnd, F Callback) {
+  size_t Size = BytesEnd - BytesBegin;
+  StringRef StrBuf(BytesBegin, Size);
+
+  auto Magic = identify_magic(StrBuf);
+  if (Magic != file_magic::elf && Magic != file_magic::elf_relocatable &&
+      Magic != file_magic::elf_executable &&
+      Magic != file_magic::elf_shared_object && Magic != file_magic::elf_core) {
+    DP("Not an ELF image!\n");
+    return 0;
+  }
+
+  std::unique_ptr<MemoryBuffer> MemBuf =
+      MemoryBuffer::getMemBuffer(StrBuf, "", false);
+  Expected<std::unique_ptr<ObjectFile>> BinOrErr =
+      ObjectFile::createELFObjectFile(MemBuf->getMemBufferRef(),
+                                      /*InitContent=*/false);
+  if (!BinOrErr) {
+    DP("Unable to get ELF handle: %s!\n",
+       toString(BinOrErr.takeError()).c_str());
+    return 0;
+  }
+
+  auto *Object = dyn_cast<const ELFObjectFileBase>(BinOrErr->get());
+
+  if (!Object) {
+    DP("Unknown ELF format!\n");
+    return 0;
+  }
+
+  return Callback(Object);
+}
+
+// Check whether an image is valid for execution on target_id
+int32_t elf_check_machine(__tgt_device_image *image, uint16_t target_id) {
+  auto CheckMachine = [target_id](const ELFObjectFileBase *Object) {
+    return target_id == Object->getEMachine();
+  };
+  return withBytesAsElf(reinterpret_cast<char *>(image->ImageStart),
+                        reinterpret_cast<char *>(image->ImageEnd),
+                        CheckMachine);
+}
+
+int32_t elf_is_dynamic(__tgt_device_image *image) {
+  auto CheckDynType = [](const ELFObjectFileBase *Object) {
+    uint16_t Type = Object->getEType();
+    DP("ELF Type: %d\n", Type);
+    return Type == ET_DYN;
+  };
+  return withBytesAsElf(reinterpret_cast<char *>(image->ImageStart),
+                        reinterpret_cast<char *>(image->ImageEnd),
+                        CheckDynType);
+}

openmp/libomptarget/plugins/remote/server/CMakeLists.txt

 ##===----------------------------------------------------------------------===##
 #
 # Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 # See https://llvm.org/LICENSE.txt for license information.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 #
 ##===----------------------------------------------------------------------===##
 #
 # Build server for remote offloading.
 #
 ##===----------------------------------------------------------------------===##
 
-include_directories(${LIBOMPTARGET_DEP_LIBELF_INCLUDE_DIRS})
 include_directories(${LIBOMPTARGET_SRC_DIR})
 include_directories(${LIBOMPTARGET_INCLUDE_DIR})
 include_directories(${GRPC_INCLUDE_DIR})
 include_directories(${RPC_INCLUDE_DIR})
 
 add_executable(openmp-offloading-server
         ${LIBOMPTARGET_SRC_FILES}
         ${GRPC_SRC_FILES}
         ${RPC_SRC_DIR}/Utils.cpp
         Server.cpp
         OffloadingServer.cpp
 )
 
 target_link_libraries(openmp-offloading-server
         grpc++
         protobuf
         ${OPENMP_PTHREAD_LIB}
-        "-ldl" "-lomp" "-fopenmp" "-Wl,--version-script=${CMAKE_CURRENT_SOURCE_DIR}/../../exports" ${LIBOMPTARGET_DEP_LIBELF_LIBRARIES})
+        "-ldl" "-lomp" "-fopenmp" "-Wl,--version-script=${CMAKE_CURRENT_SOURCE_DIR}/../../exports")