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TL;DR; This turns the configure flag -no-feature-webengine-noexecstack to -feature-webengine-noexecstack to workaround a link issue on ARM 32-bit if chromium requests for an executable stack. And now, the long story... The configure flag -no-feature-webengine-noexecstack was introduced with commit675cbaf9aa(package/qt5/qt5webengine: bump to version 5.15.8). That configure flag controls the feature webengine-noexecstack[1][2]; the -no-feature-webengine-noexecstack causes qmake to **NOT** append the linker flags -Wl,-z,noexecstack[3] to QMAKE_LFLAGS. It results in the linkage issue below on ARM 32-bit at the creation of its Qt module, i.e. after qmake has built the chromium third party via gn: ulimit -n 4096 && /home/gportay/src/buildroot/output/host/bin/arm-buildroot-linux-gnueabihf-g++ --sysroot=/home/gportay/src/buildroot/output/host/arm-buildroot-linux-gnueabihf/sysroot @/home/gportay/src/buildroot/output/build/qt5webengine-5.15.14/src/core/release/QtWebEngineCore_o.rsp -Wl,--start-group @/home/gportay/src/buildroot/output/build/qt5webengine-5.15.14/src/core/release/QtWebEngineCore_a.rsp -Wl,--end-group -Wl,--fatal-warnings -Wl,--build-id=sha1 -fPIC -Wl,-z,relro -Wl,-z,now -Wl,-z,defs -Wl,-O2 -Wl,--gc-sections --sysroot=/home/gportay/src/buildroot/output/host/arm-buildroot-linux-gnueabihf/sysroot --sysroot=/home/gportay/src/buildroot/output/host/arm-buildroot-linux-gnueabihf/sysroot -Wl,-O1 -Wl,--enable-new-dtags -Wl,-whole-archive -lqtwebenginecoreapi -Wl,-no-whole-archive -Wl,--no-undefined -Wl,--version-script,QtWebEngineCore.version -Wl,-O1 -Wl,--enable-new-dtags -shared -Wl,-soname,libQt5WebEngineCore.so.5 -o libQt5WebEngineCore.so.5.15.14 -latomic /home/gportay/src/buildroot/output/host/arm-buildroot-linux-gnueabihf/sysroot/usr/lib/libQt5Quick.so /home/gportay/src/buildroot/output/host/arm-buildroot-linux-gnueabihf/sysroot/usr/lib/libQt5Gui.so /home/gportay/src/buildroot/output/host/arm-buildroot-linux-gnueabihf/sysroot/usr/lib/libQt5QmlModels.so /home/gportay/src/buildroot/output/host/arm-buildroot-linux-gnueabihf/sysroot/usr/lib/libQt5WebChannel.so /home/gportay/src/buildroot/output/host/arm-buildroot-linux-gnueabihf/sysroot/usr/lib/libQt5Qml.so /home/gportay/src/buildroot/output/host/arm-buildroot-linux-gnueabihf/sysroot/usr/lib/libQt5Network.so /home/gportay/src/buildroot/output/host/arm-buildroot-linux-gnueabihf/sysroot/usr/lib/libQt5Core.so -lpthread -L/home/gportay/src/buildroot/output/host/arm-buildroot-linux-gnueabihf/sysroot/usr/lib -latomic -lGLESv2 -lpthread -ldl -lrt -lnss3 -lnssutil3 -lsmime3 -lplds4 -lplc4 -lnspr4 -levent -lresolv -ljpeg -lopus -lm -lz -lvpx -lpng16 -lwebp -lwebpmux -lwebpdemux -lfreetype -lexpat -lfontconfig -lharfbuzz-subset -lharfbuzz -lsnappy -lxml2 -lxslt -ldbus-1 -L/home/gportay/src/buildroot/output/build/qt5webengine-5.15.14/src/core/api/release -lGLESv2 -lrt -lpthread -ldl /home/gportay/src/buildroot/output/host/lib/gcc/arm-buildroot-linux-gnueabihf/13.3.0/../../../../arm-buildroot-linux-gnueabihf/bin/ld: warning: /home/gportay/src/buildroot/output/build/qt5webengine-5.15.14/src/core/release/obj/third_party/blink/renderer/platform/heap/asm/asm/SaveRegisters_arm.o: missing .note.GNU-stack section implies executable stack /home/gportay/src/buildroot/output/host/lib/gcc/arm-buildroot-linux-gnueabihf/13.3.0/../../../../arm-buildroot-linux-gnueabihf/bin/ld: NOTE: This behaviour is deprecated and will be removed in a future version of the linker collect2: error: ld returned 1 exit status The link succeeds if the missing linker flags are appended manually to the command-line: ulimit -n 4096 && /home/gportay/src/buildroot/output/host/bin/arm-buildroot-linux-gnueabihf-g++ --sysroot=/home/gportay/src/buildroot/output/host/arm-buildroot-linux-gnueabihf/sysroot @/home/gportay/src/buildroot/output/build/qt5webengine-5.15.14/src/core/release/QtWebEngineCore_o.rsp -Wl,--start-group @/home/gportay/src/buildroot/output/build/qt5webengine-5.15.14/src/core/release/QtWebEngineCore_a.rsp -Wl,--end-group -Wl,--fatal-warnings -Wl,--build-id=sha1 -fPIC -Wl,-z,relro -Wl,-z,now -Wl,-z,defs -Wl,-O2 -Wl,--gc-sections --sysroot=/home/gportay/src/buildroot/output/host/arm-buildroot-linux-gnueabihf/sysroot --sysroot=/home/gportay/src/buildroot/output/host/arm-buildroot-linux-gnueabihf/sysroot -Wl,-O1 -Wl,--enable-new-dtags -Wl,-whole-archive -lqtwebenginecoreapi -Wl,-no-whole-archive -Wl,--no-undefined -Wl,--version-script,QtWebEngineCore.version -Wl,-O1 -Wl,--enable-new-dtags -shared -Wl,-soname,libQt5WebEngineCore.so.5 -o libQt5WebEngineCore.so.5.15.14 -latomic /home/gportay/src/buildroot/output/host/arm-buildroot-linux-gnueabihf/sysroot/usr/lib/libQt5Quick.so /home/gportay/src/buildroot/output/host/arm-buildroot-linux-gnueabihf/sysroot/usr/lib/libQt5Gui.so /home/gportay/src/buildroot/output/host/arm-buildroot-linux-gnueabihf/sysroot/usr/lib/libQt5QmlModels.so /home/gportay/src/buildroot/output/host/arm-buildroot-linux-gnueabihf/sysroot/usr/lib/libQt5WebChannel.so /home/gportay/src/buildroot/output/host/arm-buildroot-linux-gnueabihf/sysroot/usr/lib/libQt5Qml.so /home/gportay/src/buildroot/output/host/arm-buildroot-linux-gnueabihf/sysroot/usr/lib/libQt5Network.so /home/gportay/src/buildroot/output/host/arm-buildroot-linux-gnueabihf/sysroot/usr/lib/libQt5Core.so -lpthread -L/home/gportay/src/buildroot/output/host/arm-buildroot-linux-gnueabihf/sysroot/usr/lib -latomic -lGLESv2 -lpthread -ldl -lrt -lnss3 -lnssutil3 -lsmime3 -lplds4 -lplc4 -lnspr4 -levent -lresolv -ljpeg -lopus -lvpx -lm -lpng16 -lwebp -lwebpmux -lwebpdemux -lfreetype -lexpat -lfontconfig -lharfbuzz-subset -lharfbuzz -lsnappy -lxml2 -lxslt -ldbus-1 -L/home/gportay/src/buildroot/output/build/qt5webengine-5.15.14/src/core/api/release -lGLESv2 -lrt -lpthread -ldl -Wl,-z,noexecstack && echo completed completed Note: The configure flag is not forwarded to chromium in any manner; its scope is limited to the Qt WebEngine module. That configure flag appears to be a workaround if the does not assemble, compile and link the Elf object correctly[4][5]. The linker flag -z noexecstack is responsible for marking the object as not requiring an executable stack by adding the section .note.GNU-stack in the Elf object. The file SaveRegisters_arm.S is assembled from the command-line below; there is no noexecstack flag set: /home/gportay/src/buildroot/output/host/bin/arm-buildroot-linux-gnueabihf-gcc -MMD -MF obj/third_party/blink/renderer/platform/heap/asm/asm/SaveRegisters_arm.o.d -DARM=1 -DUSE_UDEV -DUSE_AURA=1 -DUSE_NSS_CERTS=1 -DUSE_OZONE=1 -DOFFICIAL_BUILD -DTOOLKIT_QT -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -DNO_UNWIND_TABLES -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -DCR_SYSROOT_HASH=c2e54f675b83a61301dcdb22e8e7a2b85c01d58c -DNDEBUG -DNVALGRIND -DDYNAMIC_ANNOTATIONS_ENABLED=0 -Igen -I../../3rdparty/chromium -fPIC -fno-strict-aliasing --param=ssp-buffer-size=4 -fstack-protector -fno-unwind-tables -fno-asynchronous-unwind-tables -fPIC -pipe -pthread -std=gnu11 -march=armv7-a -mfloat-abi=hard -mtune=generic-armv7-a -mfpu=vfpv3-d16 -marm -g0 --sysroot=/home/gportay/src/buildroot/output/host/arm-buildroot-linux-gnueabihf/sysroot -c ../../3rdparty/chromium/third_party/blink/renderer/platform/heap/asm/SaveRegisters_arm.S -o obj/third_party/blink/renderer/platform/heap/asm/asm/SaveRegisters_arm.o The GNU assembler supports the assembler flag -Wa,--{,no}execstack to require, or not, an executable stack for the object to assemble. The BUILD.gn does **NOT** set it for the assembler files of the blink third-party; but it does it for boringssl[6] (see also the project file CMakeLists.txt[7]). See below what readelf says if the file is assembled manually with the flag --noexecstack: $ /home/gportay/src/buildroot/output/host/bin/arm-buildroot-linux-gnueabihf-gcc -MMD -MF obj/third_party/blink/renderer/platform/heap/asm/asm/SaveRegisters_arm.o.d -DARM=1 -DUSE_UDEV -DUSE_AURA=1 -DUSE_NSS_CERTS=1 -DUSE_OZONE=1 -DOFFICIAL_BUILD -DTOOLKIT_QT -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -DNO_UNWIND_TABLES -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -DCR_SYSROOT_HASH=c2e54f675b83a61301dcdb22e8e7a2b85c01d58c -DNDEBUG -DNVALGRIND -DDYNAMIC_ANNOTATIONS_ENABLED=0 -Igen -I../../3rdparty/chromium -fPIC -fno-strict-aliasing --param=ssp-buffer-size=4 -fstack-protector -fno-unwind-tables -fno-asynchronous-unwind-tables -fPIC -pipe -pthread -std=gnu11 -march=armv7-a -mfloat-abi=hard -mtune=generic-armv7-a -mfpu=vfpv3-d16 -marm -g0 --sysroot=/home/gportay/src/buildroot/output/host/arm-buildroot-linux-gnueabihf/sysroot -c ../../3rdparty/chromium/third_party/blink/renderer/platform/heap/asm/SaveRegisters_arm.S -o obj/third_party/blink/renderer/platform/heap/asm/asm/SaveRegisters_arm.o -Wa,--noexecstack $ readelf -a /home/gportay/src/buildroot/output/build/qt5webengine-5.15.14/src/core/release/obj/third_party/blink/renderer/platform/heap/asm/asm/SaveRegisters_arm.o (...) Section Headers: [Nr] Name Type Addr Off Size ES Flg Lk Inf Al (...) [ 4] .note.GNU-stack PROGBITS 00000000 000058 000000 00 0 0 1 The section the linker claims for is now part of the Elf object; and qmake is now able to link its Qt WebEngine module. Note: Alternatively, the patching the file SaveRegisters_arm.S to set explicitly the section in the source file works as well (this reduces the impact to the very single file causing the link issue): #if defined(__linux__) && defined(__ELF__) .section .note.GNU-stack,"",%progbits #endif Instead of fixing directly the origin of the issue and setting the missing assembler flag -Wa,--noexecstack to blink; this works around the link issue by turning on the feature noexecstack to qtwebengine to force qmake to link its module using the linker flag -Wl,-z,noexecstack. [1]: https://github.com/qt/qtwebengine/blob/5.15.14/src/buildtools/configure.json#L353-L357 [2]: https://github.com/qt/qtwebengine/blob/5.15.14/src/buildtools/configure.json#L720-L724 [3]: https://github.com/qt/qtwebengine/blob/5.15.14/src/buildtools/config/linking.pri#L61-L62 [4]:597359a16a[5]: https://codereview.qt-project.org/c/qt/qtwebengine/+/263545 [6]: https://github.com/qt/qtwebengine-chromium/blob/87-based/chromium/third_party/boringssl/src/util/BUILD.toplevel#L64 [7]: https://github.com/qt/qtwebengine-chromium/blob/87-based/chromium/third_party/boringssl/src/crypto/CMakeLists.txt#L33 Signed-off-by: Gaël PORTAY <gael.portay@rtone.fr> Signed-off-by: Arnout Vandecappelle <arnout@rnout.be>
Buildroot is a simple, efficient and easy-to-use tool to generate embedded Linux systems through cross-compilation. The documentation can be found in docs/manual. You can generate a text document with 'make manual-text' and read output/docs/manual/manual.text. Online documentation can be found at http://buildroot.org/docs.html To build and use the buildroot stuff, do the following: 1) run 'make menuconfig' 2) select the target architecture and the packages you wish to compile 3) run 'make' 4) wait while it compiles 5) find the kernel, bootloader, root filesystem, etc. in output/images You do not need to be root to build or run buildroot. Have fun! Buildroot comes with a basic configuration for a number of boards. Run 'make list-defconfigs' to view the list of provided configurations. Please feed suggestions, bug reports, insults, and bribes back to the buildroot mailing list: buildroot@buildroot.org You can also find us on #buildroot on OFTC IRC. If you would like to contribute patches, please read https://buildroot.org/manual.html#submitting-patches