From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Borkmann Subject: Re: [PATCH bpf 2/3] bpf: show real jited address in bpf_prog_info->jited_ksyms Date: Fri, 2 Nov 2018 11:09:52 +0100 Message-ID: References: <20181101070058.2760251-1-songliubraving@fb.com> <20181101070058.2760251-3-songliubraving@fb.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: kernel-team@fb.com, ast@kernel.org, sandipan@linux.vnet.ibm.com To: Song Liu , netdev@vger.kernel.org Return-path: Received: from www62.your-server.de ([213.133.104.62]:34314 "EHLO www62.your-server.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725987AbeKBTQc (ORCPT ); Fri, 2 Nov 2018 15:16:32 -0400 In-Reply-To: <20181101070058.2760251-3-songliubraving@fb.com> Content-Language: en-US Sender: netdev-owner@vger.kernel.org List-ID: On 11/01/2018 08:00 AM, Song Liu wrote: > Currently, jited_ksyms in bpf_prog_info shows page addresses of jited > bpf program. This is not ideal for detailed profiling (find hot > instructions from stack traces). This patch replaces the page address > with real prog start address. > > Signed-off-by: Song Liu > --- > kernel/bpf/syscall.c | 1 - > 1 file changed, 1 deletion(-) > > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c > index ccb93277aae2..34a9eef5992c 100644 > --- a/kernel/bpf/syscall.c > +++ b/kernel/bpf/syscall.c > @@ -2172,7 +2172,6 @@ static int bpf_prog_get_info_by_fd(struct bpf_prog *prog, > user_ksyms = u64_to_user_ptr(info.jited_ksyms); > for (i = 0; i < ulen; i++) { > ksym_addr = (ulong) prog->aux->func[i]->bpf_func; > - ksym_addr &= PAGE_MASK; Note that the masking was done on purpose here and in patch 1/3 in order to not expose randomized start address to kallsyms at least. I suppose it's okay to change it here and for kallsyms given bpf_prog_get_info_by_fd() dump is for root only, and in each of the two cases we additionally apply kallsyms_show_value() logic, so for unpriv this is zeroed out plus only root loaded programs are added under kallsyms (capable(CAP_SYS_ADMIN)) anyway. > if (put_user((u64) ksym_addr, &user_ksyms[i])) > return -EFAULT; > } >