[Buildroot] [PATCH 1/2] package/libopenssl: disable atomic operations for m68k Coldfire

[Baruch Siach]

Hi Bernd,

On Wed, Sep 02 2026, Bernd Kuhls wrote:
> This patch fixes a build error with OpenSSL-enabled libcurl which was
> detected by the Gitlab pipelines:
>
> checking for openssl options with pkg-config... found
> configure: pkg-config: SSL_LIBS: "-lssl -lcrypto -pthread"
> configure: pkg-config: SSL_LDFLAGS:
> "-L/builds/bkuhls/buildroot/br-test-pkg/bootlin-m68k-5208-uclibc/host/bin/../m68k-buildroot-uclinux-uclibc/sysroot/usr/lib"
> configure: pkg-config: SSL_CPPFLAGS: ""
> checking for HMAC_Update in -lcrypto... no
> checking for HMAC_Init_ex in -lcrypto... no
> checking OpenSSL linking with -ldl... no
> checking OpenSSL linking with -ldl and -lpthread... no
> checking for SSL_set_quic_use_legacy_codepoint... no
> checking for SSL_set_quic_tls_cbs... no
> configure: OpenSSL version does not speak any known QUIC API
> configure: OPT_OPENSSL:
> /builds/bkuhls/buildroot/br-test-pkg/bootlin-m68k-5208-uclibc/host/m68k-buildroot-uclinux-uclibc/sysroot/usr
> configure: OPENSSL_ENABLED:
> configure: error: --with-openssl was given but OpenSSL could not be detected
> make[1]: *** [package/pkg-generic.mk:263:
> /builds/bkuhls/buildroot/br-test-pkg/bootlin-m68k-5208-uclibc/build/libcurl-8.21.0/.stamp_configured]
> Error 1
>
> Although OpenSSL was found using pkg-config the build tests fail.
>
> A local build shows the concrete error in config.log, for example:
>
> configure:27577: checking for HMAC_Update in -lcrypto
> configure:27599: /home/bernd/buildroot/output/host/bin/m68k-linux-gcc
>  -o conftest -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE
>  -D_FILE_OFFSET_BITS=64 -O2 -g0 -fno-dwarf2-cfi-asm -Wl,-elf2flt=-r
>  -static -Werror-implicit-function-declaration -Wno-system-headers
>  -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64
>  -D_GNU_SOURCE     -Wl,-elf2flt=-r -static
>  -L/home/bernd/buildroot/output/host/bin/../m68k-buildroot-uclinux-uclibc/sysroot/usr/lib
>  -L/home/bernd/buildroot/output/host/bin/../m68k-buildroot-uclinux-uclibc/sysroot/usr/lib
>  conftest.c -lcrypto  -lssl -lcrypto -lz -pthread -lz  >&5
> /home/bernd/buildroot/output/host/opt/ext-toolchain/m68k-buildroot-uclinux-uclibc/bin/ld.real:
>  /home/bernd/buildroot/output/host/bin/../m68k-buildroot-uclinux-uclibc/sysroot/usr/lib/libcrypto.a(libcrypto-lib-threads_pthread.o):
>  in function `ossl_rcu_read_lock':
> threads_pthread.c:(.text+0xa4): undefined reference to `__atomic_fetch_add_8'
>
> This error occurs many times for various atomic operations:
>
> $ grep "undefined reference to \`__atomic" output/build/libcurl-8.20.0/config.log | sort -u | grep -v real
> threads_pthread.c:(.text+0x28a): undefined reference to `__atomic_fetch_sub_8'
> threads_pthread.c:(.text+0x3b4): undefined reference to `__atomic_fetch_add_8'
> threads_pthread.c:(.text+0x9c8): undefined reference to `__atomic_is_lock_free'
> threads_pthread.c:(.text+0xa4): undefined reference to `__atomic_fetch_add_8'
> threads_pthread.c:(.text+0xa9c): undefined reference to `__atomic_is_lock_free'
> threads_pthread.c:(.text+0xb66): undefined reference to `__atomic_is_lock_free'
> threads_pthread.c:(.text+0xc30): undefined reference to `__atomic_is_lock_free'
> threads_pthread.c:(.text+0xcdc): undefined reference to `__atomic_is_lock_free'
>
> The build error can be reproduced with the current buildroot tree using
> this defconfig:
>
> BR2_m68k=y
> BR2_m68k_cf5208=y
> BR2_TOOLCHAIN_EXTERNAL=y
> BR2_TOOLCHAIN_EXTERNAL_BOOTLIN_M68K_COLDFIRE_UCLIBC_STABLE=y
> BR2_PACKAGE_OPENSSL=y
> BR2_PACKAGE_LIBCURL=y
>
> Although the toolchain lacks atomics support
>
> $ grep ATOMIC .config
> $
>
> it emits atomic-related defines, for example:
>
> $ echo | output/host/bin/m68k-linux-gcc -dM -E - | grep __ATOMIC_ACQ_REL
> $

git-commit strips lines starting with '#' from commit message. Try
committing with --cleanup=whitespace.

Thanks for the patch,
baruch

>
> This specific define __ATOMIC_ACQ_REL is used in OpenSSL to enable
> atomic support at various places:
> https://github.com/openssl/openssl/blob/openssl-3.6.3/crypto/threads_pthread.c
>
> causing the build errors we see with the mentioned defconfig.
>
> To fix the problem we use an OpenSSL-provided define to forcefully
> disable the usage of atomic intrinsics.
>
> The misdetection of atomic intrinsics for m68k coldfire is not a new
> problem:
> https://lists.buildroot.org/pipermail/buildroot/2017-May/180841.html
> https://lists.buildroot.org/pipermail/buildroot/2026-May/803110.html
>
> Signed-off-by: Bernd Kuhls <bernd at kuhls.net>
> ---
>  package/libopenssl/libopenssl.mk | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/package/libopenssl/libopenssl.mk b/package/libopenssl/libopenssl.mk
> index 9ddc85c197..9b3eec4baa 100644
> --- a/package/libopenssl/libopenssl.mk
> +++ b/package/libopenssl/libopenssl.mk
> @@ -23,6 +23,10 @@ ifeq ($(BR2_m68k_cf),y)
>  LIBOPENSSL_CFLAGS += -mxgot
>  # resolves an assembler "out of range error" with blake2 and sha512 algorithms
>  LIBOPENSSL_CFLAGS += -DOPENSSL_SMALL_FOOTPRINT
> +# disable atomic operations
> +ifeq ($(BR2_TOOLCHAIN_HAS_ATOMIC),)
> +LIBOPENSSL_CFLAGS += -DBROKEN_CLANG_ATOMICS
> +endif
>  endif
>  
>  ifeq ($(BR2_USE_MMU),)

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