From f00717d56cb3078d90fb096f7771d17b4fa19fb5 Mon Sep 17 00:00:00 2001
From: Manuel Bentele
Date: Fri, 20 Nov 2020 08:16:25 +0100
Subject: [BUILD] add support for atomic operations not supported by hardware

This change links the dnbd3-server with 'libatomic' to add support for
atomic operations not supported by hardware (especially 32-bit hardware
architectures, such as ARM). Thus the dnbd3-server can also run on a
Raspberry Pi 1 running Rasperry Pi OS.

Note that the dnbd3-server is still linked to the libatomic, even if the
hardware supports atomic operations. In this case, the compiler resolves
atomic operations and replaces them automatically with specific built-in
functions. This unnecessary linkage can be removed in the future if the
GCC supports an upcoming option called automatic linking of libatomic
(--enable-autolink-libatomic).
---
 CMakeLists.txt            |  4 ++--
 README.md                 | 14 ++++++++++++++
 src/server/CMakeLists.txt |  2 +-
 3 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index bad9c00..65b9ebb 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -132,7 +132,7 @@ if(CMAKE_BUILD_TYPE MATCHES Release)
     set(CPACK_RESOURCE_FILE_README ${CMAKE_CURRENT_SOURCE_DIR}/README.md)
 
     # set DEB generator specific packaging options
-    set(CPACK_DEBIAN_PACKAGE_DEPENDS "libc6, libfuse2, libjansson4")
+    set(CPACK_DEBIAN_PACKAGE_DEPENDS "libc6, libfuse2, libjansson4, libatomic1")
     if(DNBD3_KERNEL_MODULE)
         file(WRITE ${CMAKE_CURRENT_BINARY_DIR}/package/deb/postinst "depmod -a\n")
         file(WRITE ${CMAKE_CURRENT_BINARY_DIR}/package/deb/postrm "depmod -a\n")
@@ -141,7 +141,7 @@ if(CMAKE_BUILD_TYPE MATCHES Release)
     endif(DNBD3_KERNEL_MODULE)
 
     # set RPM generator specific packaging options
-    set(CPACK_RPM_PACKAGE_REQUIRES "glibc, fuse-libs, jansson")
+    set(CPACK_RPM_PACKAGE_REQUIRES "glibc, fuse-libs, jansson, libatomic")
     set(CPACK_RPM_EXCLUDE_FROM_AUTO_FILELIST_ADDITION "/lib"
                                                       "/lib/modules"
                                                       "/lib/modules/${CMAKE_SYSTEM_VERSION}"
diff --git a/README.md b/README.md
index 1e60477..954fbe9 100644
--- a/README.md
+++ b/README.md
@@ -12,6 +12,7 @@ This repository contains the source code for the following dnbd3 components:
 The dnbd3 components can be built for the following Linux kernel versions and Unix distributions:
 
   - Archlinux with **Linux kernel 5.9.x** or **5.4.x**
+  - Raspberry Pi OS with **Linux kernel 5.4.x**
   - Ubuntu 20.04 with **Linux kernel 5.4.x**
   - Ubuntu 18.04 with **Linux kernel 4.19.x**
   - CentOS 8 with **Linux kernel 4.18.x**
@@ -37,6 +38,19 @@ pacman -S git \
           rpm-tools
 ```
 
+#### Raspberry Pi OS with Linux kernel 5.4.x
+```shell
+apt-get install git \
+                make \
+                cmake \
+                gcc \
+                raspberrypi-kernel-headers \
+				libfuse-dev \
+				libjansson-dev \
+                afl \
+                rpm
+```
+
 #### Ubuntu 20.04 with Linux kernel 5.4.x
 ```shell
 apt-get install git \
diff --git a/src/server/CMakeLists.txt b/src/server/CMakeLists.txt
index 463f944..038d626 100644
--- a/src/server/CMakeLists.txt
+++ b/src/server/CMakeLists.txt
@@ -55,7 +55,7 @@ add_executable(dnbd3-server ${CMAKE_CURRENT_SOURCE_DIR}/altservers.c
                             ${CMAKE_CURRENT_SOURCE_DIR}/uplink.c
                             ${CMAKE_CURRENT_SOURCE_DIR}/urldecode.c)
 target_include_directories(dnbd3-server PRIVATE ${JANSSON_INCLUDE_DIR})
-target_link_libraries(dnbd3-server dnbd3-version dnbd3-build dnbd3-shared ${CMAKE_THREAD_LIBS_INIT} ${JANSSON_LIBRARIES})
+target_link_libraries(dnbd3-server dnbd3-version dnbd3-build dnbd3-shared atomic ${CMAKE_THREAD_LIBS_INIT} ${JANSSON_LIBRARIES})
 
 if(DNBD3_SERVER_FUSE)
     find_package(Fuse REQUIRED)
-- 
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