From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 88608C001DE for ; Fri, 28 Jul 2023 03:52:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232167AbjG1Dwj (ORCPT ); Thu, 27 Jul 2023 23:52:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60518 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231573AbjG1Dwg (ORCPT ); Thu, 27 Jul 2023 23:52:36 -0400 Received: from out-117.mta0.migadu.com (out-117.mta0.migadu.com [91.218.175.117]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 008C32D42 for ; Thu, 27 Jul 2023 20:52:34 -0700 (PDT) Message-ID: <8a7a1960-1678-6949-b4e0-b3621d31ea9c@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1690516352; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=xca0fbgynp4YpJaFG42+C3Unmv24xUnm5jqMs1cBm6w=; b=LYdWv563hDZrLdby8OHTM5QHEQmjOD/RWvRdZDmjqcpaD6ZOLSF+tRrqoMQluZ8orDYG+q 5wyXyc6GlUAV6nEvUZ8/m+nmW4HQYgWCWxXhaqKWE8wI2YTxyMeR3Pfkgag6xVkXPe2zVa +Ly0IEXTX4DSRu88z6M7P4Y0OHH4G5Y= Date: Thu, 27 Jul 2023 20:52:25 -0700 MIME-Version: 1.0 Reply-To: yonghong.song@linux.dev Subject: Re: [PATCH] [v4] bpf: fix bpf_probe_read_kernel prototype mismatch Content-Language: en-US To: Arnd Bergmann , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Song Liu , Steven Rostedt , Masami Hiramatsu Cc: Arnd Bergmann , stable@vger.kernel.org, John Fastabend , Martin KaFai Lau , Yonghong Song , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Kumar Kartikeya Dwivedi , Dave Marchevsky , David Vernet , Kees Cook , bpf@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org References: <20230725204149.3411961-1-arnd@kernel.org> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Yonghong Song In-Reply-To: <20230725204149.3411961-1-arnd@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/25/23 1:41 PM, Arnd Bergmann wrote: > From: Arnd Bergmann > > bpf_probe_read_kernel() has a __weak definition in core.c and another > definition with an incompatible prototype in kernel/trace/bpf_trace.c, > when CONFIG_BPF_EVENTS is enabled. > > Since the two are incompatible, there cannot be a shared declaration in > a header file, but the lack of a prototype causes a W=1 warning: > > kernel/bpf/core.c:1638:12: error: no previous prototype for 'bpf_probe_read_kernel' [-Werror=missing-prototypes] > > On 32-bit architectures, the local prototype > > u64 __weak bpf_probe_read_kernel(void *dst, u32 size, const void *unsafe_ptr) > > passes arguments in other registers as the one in bpf_trace.c > > BPF_CALL_3(bpf_probe_read_kernel, void *, dst, u32, size, > const void *, unsafe_ptr) > > which uses 64-bit arguments in pairs of registers. > > As both versions of the function are fairly simple and only really > differ in one line, just move them into a header file as an inline > function that does not add any overhead for the bpf_trace.c callers > and actually avoids a function call for the other one. > > Cc: stable@vger.kernel.org > Link: https://lore.kernel.org/all/ac25cb0f-b804-1649-3afb-1dc6138c2716@iogearbox.net/ > Signed-off-by: Arnd Bergmann LGTM but there are some additional changes in kernel so you need to rebase on top of master branch with the following additional change: @@ -2082,7 +2076,7 @@ static u64 ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn) DST = *(SIZE *)(unsigned long) (SRC + insn->off); \ CONT; \ LDX_PROBE_MEMSX_##SIZEOP: \ - bpf_probe_read_kernel(&DST, sizeof(SIZE), \ + bpf_probe_read_kernel_common(&DST, sizeof(SIZE), \ (const void *)(long) (SRC + insn->off)); \ DST = *((SIZE *)&DST); \ CONT; Thanks! > -- > v4: rewrite again to use a shared inline helper > v3: clarify changelog text further. > v2: rewrite completely to fix the mismatch. > --- > include/linux/bpf.h | 12 ++++++++++++ > kernel/bpf/core.c | 10 ++-------- > kernel/trace/bpf_trace.c | 11 ----------- > 3 files changed, 14 insertions(+), 19 deletions(-) > > diff --git a/include/linux/bpf.h b/include/linux/bpf.h > index ceaa8c23287fc..abe75063630b8 100644 > --- a/include/linux/bpf.h > +++ b/include/linux/bpf.h > @@ -2661,6 +2661,18 @@ static inline void bpf_dynptr_set_rdonly(struct bpf_dynptr_kern *ptr) > } > #endif /* CONFIG_BPF_SYSCALL */ > > +static __always_inline int > +bpf_probe_read_kernel_common(void *dst, u32 size, const void *unsafe_ptr) > +{ > + int ret = -EFAULT; > + > + if (IS_ENABLED(CONFIG_BPF_EVENTS)) > + ret = copy_from_kernel_nofault(dst, unsafe_ptr, size); > + if (unlikely(ret < 0)) > + memset(dst, 0, size); > + return ret; > +} > + > void __bpf_free_used_btfs(struct bpf_prog_aux *aux, > struct btf_mod_pair *used_btfs, u32 len); > > diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c > index dd70c58c9d3a3..9cdf53bfb8bd3 100644 > --- a/kernel/bpf/core.c > +++ b/kernel/bpf/core.c > @@ -1634,12 +1634,6 @@ bool bpf_opcode_in_insntable(u8 code) > } > > #ifndef CONFIG_BPF_JIT_ALWAYS_ON > -u64 __weak bpf_probe_read_kernel(void *dst, u32 size, const void *unsafe_ptr) > -{ > - memset(dst, 0, size); > - return -EFAULT; > -} > - > /** > * ___bpf_prog_run - run eBPF program on a given context > * @regs: is the array of MAX_BPF_EXT_REG eBPF pseudo-registers > @@ -1930,8 +1924,8 @@ static u64 ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn) > DST = *(SIZE *)(unsigned long) (SRC + insn->off); \ > CONT; \ > LDX_PROBE_MEM_##SIZEOP: \ > - bpf_probe_read_kernel(&DST, sizeof(SIZE), \ > - (const void *)(long) (SRC + insn->off)); \ > + bpf_probe_read_kernel_common(&DST, sizeof(SIZE), \ > + (const void *)(long) (SRC + insn->off)); \ > DST = *((SIZE *)&DST); \ > CONT; > > diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c > index c92eb8c6ff08d..83bde2475ae54 100644 > --- a/kernel/trace/bpf_trace.c > +++ b/kernel/trace/bpf_trace.c > @@ -223,17 +223,6 @@ const struct bpf_func_proto bpf_probe_read_user_str_proto = { > .arg3_type = ARG_ANYTHING, > }; > > -static __always_inline int > -bpf_probe_read_kernel_common(void *dst, u32 size, const void *unsafe_ptr) > -{ > - int ret; > - > - ret = copy_from_kernel_nofault(dst, unsafe_ptr, size); > - if (unlikely(ret < 0)) > - memset(dst, 0, size); > - return ret; > -} > - > BPF_CALL_3(bpf_probe_read_kernel, void *, dst, u32, size, > const void *, unsafe_ptr) > {