From nobody Fri Dec 19 18:43:47 2025 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 DD684C5479D for ; Mon, 9 Jan 2023 08:45:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236820AbjAIIpA (ORCPT ); Mon, 9 Jan 2023 03:45:00 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51026 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236812AbjAIIms (ORCPT ); Mon, 9 Jan 2023 03:42:48 -0500 Received: from 1wt.eu (wtarreau.pck.nerim.net [62.212.114.60]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 5C6F813F49 for ; Mon, 9 Jan 2023 00:42:36 -0800 (PST) Received: (from willy@localhost) by pcw.home.local (8.15.2/8.15.2/Submit) id 3098gE6N027433; Mon, 9 Jan 2023 09:42:14 +0100 From: Willy Tarreau To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, Willy Tarreau Subject: [PATCH 14/22] tools/nolibc: add auxiliary vector retrieval for x86_64 Date: Mon, 9 Jan 2023 09:42:00 +0100 Message-Id: <20230109084208.27355-15-w@1wt.eu> X-Mailer: git-send-email 2.17.5 In-Reply-To: <20230109084208.27355-1-w@1wt.eu> References: <20230109084208.27355-1-w@1wt.eu> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" In the _start block we now iterate over envp to find the auxiliary vector after the NULL. The pointer is saved into an _auxv variable that is marked as weak so that it's accessible from multiple units. Signed-off-by: Willy Tarreau --- tools/include/nolibc/arch-x86_64.h | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/tools/include/nolibc/arch-x86_64.h b/tools/include/nolibc/arch= -x86_64.h index 683702a16a61..17f6751208e7 100644 --- a/tools/include/nolibc/arch-x86_64.h +++ b/tools/include/nolibc/arch-x86_64.h @@ -179,6 +179,7 @@ struct sys_stat_struct { }) =20 char **environ __attribute__((weak)); +const unsigned long *_auxv __attribute__((weak)); =20 /* startup code */ /* @@ -195,6 +196,12 @@ void __attribute__((weak,noreturn,optimize("omit-frame= -pointer"))) _start(void) "lea 8(%rsi,%rdi,8),%rdx\n" // then a NULL then envp (third arg, %rdx) "mov %rdx, environ\n" // save environ "xor %ebp, %ebp\n" // zero the stack frame + "mov %rdx, %rax\n" // search for auxv (follows NULL after last = env) + "0:\n" + "add $8, %rax\n" // search for auxv using rax, it follows the + "cmp -8(%rax), %rbp\n" // ... NULL after last env (rbp is zero here) + "jnz 0b\n" + "mov %rax, _auxv\n" // save it into _auxv "and $-16, %rsp\n" // x86 ABI : esp must be 16-byte aligned bef= ore call "call main\n" // main() returns the status code, we'll exi= t with it. "mov %eax, %edi\n" // retrieve exit code (32 bit) --=20 2.17.5