From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 5B93D309EFA; Wed, 5 Nov 2025 12:59:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762347577; cv=none; b=dPaS4OsYQLVoXpKAxJWyaNxN173fxJvV4C4NTeuBIWCMRn4YuNlgMcnYHBWyldKquNB+uXbiz+d6OdlrXqFvIx/dkGst+zgZZjo9bHZzYWWSsG86kred0lJJKhSi4xAQdI8uH/aiMSCTX7etOHABdAp97joDqU/vGOEfhuAo4qE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762347577; c=relaxed/simple; bh=jpnJ48qhdCzZWVaUVk/6Kd9usKKrMZGpmnLRffFITaM=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=YyE6UACT20t9FxCAiNKoy/hyvD2O6vzd4rOLjOWrZnn0LMkFN+a8cbk+mISl5rFvLy98wti4PjXffi3Q+veod04jSeJQO7Vb2Nmlblho8RJbaYcJGQwAcSNXdTVXdrmbnhlymPiRdQrIr3ImJdWnbSPCdcLxUkkhugT1vJJuhT8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=dh8V1Jzx; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="dh8V1Jzx" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 96201C4CEFB; Wed, 5 Nov 2025 12:59:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1762347576; bh=jpnJ48qhdCzZWVaUVk/6Kd9usKKrMZGpmnLRffFITaM=; h=From:To:Cc:Subject:Date:From; b=dh8V1JzxYunjByCIMP+bNdUc23uJ97cuIrGZSn9GTuEHit1ac7nDZMSTF0o7nLDyT zi5k+dp6JSjiZ5z/Fym3Abmcx/xTrMR5h+ztIPXGpdwWS8Ni5/KhQ7Q1mZkjn0xdQN VMn7yqnBYIJXnN7jIyE+fq1hx/tSADE9h7nAbMBgyknti7l7ST/JaQHsvIu8eEQ1aV FUhy1bnP11BOdizIZWdnrXJ+WHWjqtjw7CaOZ9p1y7SyJtlfMU6dpG/WzLRGBSIu6v BN3ge8M+q5I/7QempGWXqY1/qAwkRpWkkp72J8Axv1SRI/0IT0jQ6CDTQTb5Gkvbkl YflHEy4uz4Sww== From: Jiri Olsa To: Masami Hiramatsu , Steven Rostedt , Will Deacon Cc: Peter Zijlstra , bpf@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, x86@kernel.org, Yonghong Song , Song Liu , Andrii Nakryiko , Mark Rutland , Mahe Tardy Subject: [BUG/RFC 1/2] arm64/ftrace,bpf: Fix partial regs after bpf_prog_run Date: Wed, 5 Nov 2025 13:59:23 +0100 Message-ID: <20251105125924.365205-1-jolsa@kernel.org> X-Mailer: git-send-email 2.51.1 Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit hi, Mahe reported issue with bpf_override_return helper not working when executed from kprobe.multi bpf program on arm. The problem seems to be that on arm we use alternate storage for pt_regs object that is passed to bpf_prog_run and if any register is changed (which is the case of bpf_override_return) it's not propagated back to actual pt_regs object. The change below seems to fix the issue, but I have no idea if that's proper fix for arm, thoughts? I'm attaching selftest to actually test bpf_override_return helper functionality, because currently we only test that we are able to attach a program with it, but not the override itself. thanks, jirka --- arch/arm64/include/asm/ftrace.h | 11 +++++++++++ include/linux/ftrace.h | 3 +++ kernel/trace/bpf_trace.c | 1 + 3 files changed, 15 insertions(+) diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h index ba7cf7fec5e9..ad6cf587885c 100644 --- a/arch/arm64/include/asm/ftrace.h +++ b/arch/arm64/include/asm/ftrace.h @@ -157,6 +157,17 @@ ftrace_partial_regs(const struct ftrace_regs *fregs, struct pt_regs *regs) return regs; } +static __always_inline void +ftrace_partial_regs_fix(const struct ftrace_regs *fregs, struct pt_regs *regs) +{ + struct __arch_ftrace_regs *afregs = arch_ftrace_regs(fregs); + + if (afregs->pc != regs->pc) { + afregs->pc = regs->pc; + afregs->regs[0] = regs->regs[0]; + } +} + #define arch_ftrace_fill_perf_regs(fregs, _regs) do { \ (_regs)->pc = arch_ftrace_regs(fregs)->pc; \ (_regs)->regs[29] = arch_ftrace_regs(fregs)->fp; \ diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h index 7ded7df6e9b5..4cb1315522bb 100644 --- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h @@ -205,6 +205,9 @@ ftrace_partial_regs(struct ftrace_regs *fregs, struct pt_regs *regs) return &arch_ftrace_regs(fregs)->regs; } +static __always_inline void +ftrace_partial_regs_fix(struct ftrace_regs *fregs, struct pt_regs *regs) { } + #endif /* !CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS || CONFIG_HAVE_FTRACE_REGS_HAVING_PT_REGS */ #ifdef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index a795f7afbf3d..7b5768ced9b3 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -2564,6 +2564,7 @@ kprobe_multi_link_prog_run(struct bpf_kprobe_multi_link *link, old_run_ctx = bpf_set_run_ctx(&run_ctx.session_ctx.run_ctx); err = bpf_prog_run(link->link.prog, regs); bpf_reset_run_ctx(old_run_ctx); + ftrace_partial_regs_fix(fregs, bpf_kprobe_multi_pt_regs_ptr()); rcu_read_unlock(); out: -- 2.51.1