From nobody Fri Oct 2 11:42:56 2026 Received: from dggsgout12.his.huawei.com (dggsgout12.his.huawei.com [45.249.212.56]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8748E489882; Sun, 2 Aug 2026 09:44:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.56 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785663901; cv=none; b=Qga+IzQZ3XfzhK+5FX9K5QA1yYruN3aldymGFRx7M8/hTGdRJUXPUbouN0wU/73MxQE6AIi+umEOCOpTuOltEFqN/D0if4YTme1ImiIEyPEbOJ+kwxJCUG1Fbp9D6avKaKSp+3lgyOraO4IdDPOFqtwtKk0rwOoNF/ALPHNNzGU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785663901; c=relaxed/simple; bh=Ww/YiWup2i15UucCBJ3OoekI3XS9iRZ0GCoteRPBGjg=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=S75GXmJjfo7a0RocGYS6i2uSWg7PDmr9a33jGA5aCia8OPLd3dIIXRciJPuA7BpooMz0iKjL1V/vdQvSo3o3SOHo3fhyw6eNj7/T6LgZ6orXYWAuTEHF6P506xreUrxpvWsltG44SUO6Pfy3NmGrzAt1FNFzJyFf86oZeza/EnU= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com; spf=pass smtp.mailfrom=huaweicloud.com; arc=none smtp.client-ip=45.249.212.56 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huaweicloud.com Received: from mail.maildlp.com (unknown [172.19.163.170]) by dggsgout12.his.huawei.com (SkyGuard) with ESMTPS id 4hCZf82C0kzKHMbX; Sun, 2 Aug 2026 17:44:48 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.252]) by mail.maildlp.com (Postfix) with ESMTP id 75FD34056E; Sun, 2 Aug 2026 17:44:49 +0800 (CST) Received: from ultra.huawei.com (unknown [10.90.53.71]) by APP3 (Coremail) with UTF8SMTPA id _Ch0CgBHN0aQEW9qkilYAw--.4417S2; Sun, 02 Aug 2026 17:44:49 +0800 (CST) From: Pu Lehui To: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Cc: Paul Walmsley , Palmer Dabbelt , Alexandre Ghiti , Andy Chiu , =?UTF-8?q?Bj=C3=B6rn=20T=C3=B6pel?= , Steven Rostedt , Masami Hiramatsu , bpf@vger.kernel.org, Pu Lehui , Pu Lehui Subject: [PATCH] riscv: ftrace: Fix ftrace_modify_call failure on kprobed functions Date: Sun, 2 Aug 2026 09:49:29 +0000 Message-Id: <20260802094929.3978390-1-pulehui@huaweicloud.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-CM-TRANSID: _Ch0CgBHN0aQEW9qkilYAw--.4417S2 X-Coremail-Antispam: 1UD129KBjvJXoWxZw4kAF4DArW5CF45Wr1fXrb_yoW5trW5pF yakw1qkr4rAanrKFZrKwn8urs7t3yDA34UAF93Ja4rAa4qkr15Jw4Ikr4ktr98ArZ8Jryf Z34qyr4UGryUAw7anT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUU9Y14x267AKxVW8JVW5JwAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2ocxC64kIII0Yj41l84x0c7CEw4AK67xGY2AK02 1l84ACjcxK6xIIjxv20xvE14v26r1j6r1xM28EF7xvwVC0I7IYx2IY6xkF7I0E14v26r4j 6F4UM28EF7xvwVC2z280aVAFwI0_Gr1j6F4UJwA2z4x0Y4vEx4A2jsIEc7CjxVAFwI0_Gc CE3s1le2I262IYc4CY6c8Ij28IcVAaY2xG8wAqx4xG64xvF2IEw4CE5I8CrVC2j2WlYx0E 2Ix0cI8IcVAFwI0_Jr0_Jr4lYx0Ex4A2jsIE14v26r1j6r4UMcvjeVCFs4IE7xkEbVWUJV W8JwACjcxG0xvY0x0EwIxGrwACjI8F5VA0II8E6IAqYI8I648v4I1lFIxGxcIEc7CjxVA2 Y2ka0xkIwI1lc7CjxVAaw2AFwI0_Jw0_GFyl42xK82IYc2Ij64vIr41l4I8I3I0E4IkC6x 0Yz7v_Jr0_Gr1lx2IqxVAqx4xG67AKxVWUJVWUGwC20s026x8GjcxK67AKxVWUGVWUWwC2 zVAF1VAY17CE14v26r1q6r43MIIYrxkI7VAKI48JMIIF0xvE2Ix0cI8IcVAFwI0_Jr0_JF 4lIxAIcVC0I7IYx2IY6xkF7I0E14v26r4j6F4UMIIF0xvE42xK8VAvwI8IcIk0rVWUJVWU CwCI42IY6I8E87Iv67AKxVWUJVW8JwCI42IY6I8E87Iv6xkF7I0E14v26r4j6r4UJbIYCT nIWIevJa73UjIFyTuYvjfUonmRUUUUU X-CM-SenderInfo: psxovxtxl6x35dzhxuhorxvhhfrp/ Content-Type: text/plain; charset="utf-8" From: Pu Lehui We are frequently hitting the following splat during the riscv bpf selftests: 00000000026dc75a: expected (7c3ff297) but got (00100073) ------------[ ftrace bug ]------------ ftrace failed to modify [] bpf_kfunc_common_test+0x4/0x20 [bpf_testmod] actual: e7:82:c2:ce Updating ftrace call site to call a different ftrace function ftrace record flags: 80100002 (2) expected tramp: ffffffff80043904 ------------[ cut here ]------------ WARNING: kernel/trace/ftrace.c:2278 at ftrace_bug+0x46e/0x4b0, CPU#1: test_= progs/98 ... [] ftrace_bug+0x46e/0x4b0 [] ftrace_replace_code+0x16e/0x170 [] ftrace_modify_all_code+0x12e/0x1b8 [] arch_ftrace_update_code+0x14/0x28 [] ftrace_startup+0x14c/0x2a0 [] ftrace_startup_subops+0x584/0x1050 [] register_ftrace_graph+0x4e6/0x1018 [] register_fprobe_ips+0xc66/0x12f8 [] bpf_kprobe_multi_link_attach+0x5d8/0xe68 [] __sys_bpf+0x3d5a/0x47f0 [] __riscv_sys_bpf+0xae/0x168 [] syscall_handler+0x60/0x100 [] do_trap_ecall_u+0x174/0x208 [] handle_exception+0x16c/0x178 After debugging, it can be triggered by similar commands below: ``` echo do_nanosleep > set_ftrace_filter echo function > current_tracer echo 'p do_nanosleep' > kprobe_events echo 1 > events/kprobes/enable echo 'f do_nanosleep' > dynamic_events echo 1 > events/fprobes/enable ``` The reason is that attaching a kprobe to an ftrace-traced function entry replaces its initial auipc insn with ebreak. When ftrace_modify_call later runs, it expects auipc insn, so verification fails and triggers ftrace_bug. The expected auipc logic remains conceptually unchanged, and kprobe single-stepping ensures normal execution. Therefore, if the first insn is ebreak, bypassing the check to continue patching the jalr insn is safe and avoids ftrace failures. Fixes: b2137c3b6d7a ("riscv: ftrace: prepare ftrace for atomic code patchin= g") Signed-off-by: Pu Lehui --- arch/riscv/kernel/ftrace.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/arch/riscv/kernel/ftrace.c b/arch/riscv/kernel/ftrace.c index b430edfb83f4..be8b68514417 100644 --- a/arch/riscv/kernel/ftrace.c +++ b/arch/riscv/kernel/ftrace.c @@ -12,6 +12,7 @@ #include #include #include +#include =20 #ifdef CONFIG_DYNAMIC_FTRACE void ftrace_arch_code_modify_prepare(void) @@ -63,7 +64,9 @@ static int __ftrace_modify_call(unsigned long source, uns= igned long target, bool if (copy_from_kernel_nofault(replaced, (void *)source, 2 * MCOUNT_INSN_S= IZE)) return -EFAULT; =20 - if (replaced[0] !=3D call[0]) { + /* Bypass the check if the auipc insn is a kprobe breakpoint */ + if (replaced[0] !=3D call[0] && + !(riscv_insn_is_ebreak(replaced[0]) || riscv_insn_is_c_ebreak(replac= ed[0]))) { pr_err("%p: expected (%08x) but got (%08x)\n", (void *)source, call[0], replaced[0]); return -EINVAL; --=20 2.34.1