Hello! We see this warning on x86 (real machine and Qemu) with Clang: -----8<----- [ 1.364590] ------------[ cut here ]------------ [ 1.364685] missing return thunk: __ret+0x5/0x7e-__ret+0x0/0x7e: e9 f6 ff ff ff [ 1.364691] WARNING: CPU: 0 PID: 0 at arch/x86/kernel/alternative.c:630 apply_returns+0x2c9/0x420 [ 1.366684] Modules linked in: [ 1.367685] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 6.4.11-rc1 #1 [ 1.368684] Hardware name: Supermicro SYS-5019S-ML/X11SSH-F, BIOS 2.0b 07/27/2017 [ 1.369685] RIP: 0010:apply_returns+0x2c9/0x420 [ 1.370685] Code: ff ff 0f 0b e9 b5 fd ff ff c6 05 a8 97 fa 01 01 48 c7 c7 e6 b5 9f a7 4c 89 ee 4c 89 e2 b9 05 00 00 00 4d 89 e8 e8 57 c2 11 00 <0f> 0b e9 8d fd ff ff 4d 85 e4 0f 84 1f ff ff ff 48 c7 c7 bf 44 98 [ 1.371684] RSP: 0000:ffffffffa7c03e00 EFLAGS: 00010246 [ 1.372684] RAX: 8bcba40230adee00 RBX: ffffffffa8150ba4 RCX: ffffffffa7c72440 [ 1.373684] RDX: ffffffffa7c03c88 RSI: 00000000ffffdfff RDI: 0000000000000001 [ 1.374684] RBP: ffffffffa7c03ed8 R08: 0000000000001fff R09: ffffffffa7c726d0 [ 1.375684] R10: 0000000000005ffd R11: 0000000000000004 R12: ffffffffa7182140 [ 1.376684] R13: ffffffffa7182145 R14: ffffffffa8150b9c R15: ffffffffa71821f0 [ 1.377684] FS: 0000000000000000(0000) GS:ffff8adb1fc00000(0000) knlGS:0000000000000000 [ 1.378684] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 1.379684] CR2: ffff8ad8b7001000 CR3: 00000001f6640001 CR4: 00000000003706f0 [ 1.380684] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 1.381684] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 1.382684] Call Trace: [ 1.383685] <TASK> [ 1.384685] ? show_regs+0x61/0x70 [ 1.385685] ? __warn+0xce/0x1d0 [ 1.386684] ? apply_returns+0x2c9/0x420 [ 1.387685] ? report_bug+0x160/0x210 [ 1.388685] ? handle_bug+0x41/0x70 [ 1.389684] ? exc_invalid_op+0x1f/0x50 [ 1.390685] ? asm_exc_invalid_op+0x1f/0x30 [ 1.391684] ? srso_safe_ret+0x30/0x30 [ 1.392685] ? __ret+0x5/0x7e [ 1.393684] ? zen_untrain_ret+0x1/0x1 [ 1.394685] ? apply_returns+0x2c9/0x420 [ 1.395685] ? __ret+0x5/0x7e [ 1.396684] ? __ret+0x14/0x7e [ 1.397684] ? __ret+0xa/0x7e [ 1.398685] alternative_instructions+0x50/0x120 [ 1.399685] arch_cpu_finalize_init+0x30/0x60 [ 1.400684] start_kernel+0x30e/0x3e0 [ 1.401685] x86_64_start_reservations+0x28/0x30 [ 1.402684] x86_64_start_kernel+0xaf/0xc0 [ 1.403685] secondary_startup_64_no_verify+0x107/0x10b [ 1.404685] </TASK> [ 1.405685] ---[ end trace 0000000000000000 ]--- -----8>----- Full log here of one of those instances: https://lkft.validation.linaro.org/scheduler/job/6664660#L671 There is a ClangBuiltLinux issue addressing this [1]. Nathan refers Peter's second patch [2] in his series fixes this problem. This was introduced in v6.4.9 (which we did not review). Clang builds failed for v6.4.10 [3][4] and are now fixed, so this is the first time we're seeing this warning. Rest of the report as follows: ## Build * kernel: 6.4.11-rc1 * git: https://gitlab.com/Linaro/lkft/mirrors/stable/linux-stable-rc * git branch: linux-6.4.y * git commit: 427a3a47257b870ef6dce995a40bb7aca1bfc6ec * git describe: v6.4.10-207-g427a3a47257b * test details: https://qa-reports.linaro.org/lkft/linux-stable-rc-linux-6.4.y/build/v6.4.10-207-g427a3a47257b ## Test Regressions (compared to v6.4.10) * x86, log-parser-boot - check-kernel-warning Reported-by: Linux Kernel Functional Testing <lkft@xxxxxxxxxx> ## No metric regressions (compared to v6.4.10) ## Test Fixes (compared to v6.4.10) * x86_64, build - clang-17-allmodconfig - clang-17-lkftconfig - clang-17-lkftconfig-compat - clang-17-lkftconfig-kcsan - clang-17-lkftconfig-no-kselftest-frag - clang-17-x86_64_defconfig - clang-lkftconfig - clang-nightly-lkftconfig - clang-nightly-lkftconfig-kselftest - clang-nightly-x86_64_defconfig ## No metric fixes (compared to v6.4.10) ## Test result summary total: 172870, pass: 149103, fail: 3038, skip: 20556, xfail: 173 ## Build Summary * arc: 5 total, 5 passed, 0 failed * arm: 145 total, 144 passed, 1 failed * arm64: 54 total, 52 passed, 2 failed * i386: 41 total, 40 passed, 1 failed * mips: 30 total, 28 passed, 2 failed * parisc: 4 total, 4 passed, 0 failed * powerpc: 38 total, 36 passed, 2 failed * riscv: 26 total, 24 passed, 2 failed * s390: 16 total, 14 passed, 2 failed * sh: 14 total, 12 passed, 2 failed * sparc: 8 total, 8 passed, 0 failed * x86_64: 46 total, 45 passed, 1 failed ## Test suites summary * boot * kselftest-android * kselftest-arm64 * kselftest-breakpoints * kselftest-capabilities * kselftest-cgroup * kselftest-clone3 * kselftest-core * kselftest-cpu-hotplug * kselftest-cpufreq * kselftest-drivers-dma-buf * kselftest-efivarfs * kselftest-exec * kselftest-filesystems * kselftest-filesystems-binderfs * kselftest-filesystems-epoll * kselftest-firmware * kselftest-fpu * kselftest-ftrace * kselftest-futex * kselftest-gpio * kselftest-intel_pstate * kselftest-ipc * kselftest-ir * kselftest-kcmp * kselftest-kexec * kselftest-kvm * kselftest-lib * kselftest-livepatch * kselftest-membarrier * kselftest-memfd * kselftest-memory-hotplug * kselftest-mincore * kselftest-mount * kselftest-mqueue * kselftest-net * kselftest-net-forwarding * kselftest-net-mptcp * kselftest-netfilter * kselftest-nsfs * kselftest-openat2 * kselftest-pid_namespace * kselftest-pidfd * kselftest-proc * kselftest-pstore * kselftest-ptrace * kselftest-rseq * kselftest-rtc * kselftest-seccomp * kselftest-sigaltstack * kselftest-size * kselftest-splice * kselftest-static_keys * kselftest-sync * kselftest-sysctl * kselftest-tc-testing * kselftest-timens * kselftest-timers * kselftest-tmpfs * kselftest-tpm2 * kselftest-user * kselftest-user_events * kselftest-vDSO * kselftest-vm * kselftest-watchdog * kselftest-x86 * kselftest-zram * kunit * kvm-unit-tests * libgpiod * libhugetlbfs * log-parser-boot * log-parser-test * ltp-cap_bounds * ltp-commands * ltp-containers * ltp-controllers * ltp-cpuhotplug * ltp-crypto * ltp-cve * ltp-dio * ltp-fcntl-locktests * ltp-filecaps * ltp-fs * ltp-fs_bind * ltp-fs_perms_simple * ltp-fsx * ltp-hugetlb * ltp-io * ltp-ipc * ltp-math * ltp-mm * ltp-nptl * ltp-pty * ltp-sched * ltp-securebits * ltp-smoke * ltp-syscalls * ltp-tracing * network-basic-tests * perf * rcutorture * v4l2-compliance Greetings! Daniel Díaz daniel.diaz@xxxxxxxxxx [1] https://github.com/ClangBuiltLinux/linux/issues/1911 [2] https://lore.kernel.org/20230809072200.543939260@xxxxxxxxxxxxx/ [3] https://lore.kernel.org/stable/CA+G9fYuoajK0n7RNhSqm-ycO6Md3W4ah_Sc=b_KVAQwY=Rt6YQ@xxxxxxxxxxxxxx/ [4] https://github.com/ClangBuiltLinux/linux/issues/1907 -- Linaro LKFT https://lkft.linaro.org
