[Buildroot] [PATCH v2 1/2] package/libopenssl: disable atomic operations for m68k Coldfire

* [Buildroot] [PATCH v2 1/2] package/libopenssl: disable atomic operations for m68k Coldfire
@ 2026-09-03  6:39 Bernd Kuhls
  2026-09-03  6:39 ` [Buildroot] [PATCH v2 2/2] package/libcurl: security bump to version 8.22.0 Bernd Kuhls
  2026-09-04 11:51 ` [Buildroot] [PATCH v2 1/2] package/libopenssl: disable atomic operations for m68k Coldfire Peter Korsgaard
  0 siblings, 2 replies; 4+ messages in thread
From: Bernd Kuhls @ 2026-09-03  6:39 UTC (permalink / raw)
  To: buildroot

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
#define __ATOMIC_ACQ_REL 4
$

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@kuhls.net>
---
v2: fixed patch description (Baruch)

 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),)
-- 
2.47.3

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