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 50EE9C5479D for ; Mon, 9 Jan 2023 08:47:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233854AbjAIIrk (ORCPT ); Mon, 9 Jan 2023 03:47:40 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54682 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237034AbjAIIqY (ORCPT ); Mon, 9 Jan 2023 03:46:24 -0500 Received: from 1wt.eu (wtarreau.pck.nerim.net [62.212.114.60]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 960851581D for ; Mon, 9 Jan 2023 00:43:03 -0800 (PST) Received: (from willy@localhost) by pcw.home.local (8.15.2/8.15.2/Submit) id 3098gFI5027435; Mon, 9 Jan 2023 09:42:15 +0100 From: Willy Tarreau To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, Willy Tarreau Subject: [PATCH 16/22] tools/nolibc: add auxiliary vector retrieval for arm Date: Mon, 9 Jan 2023 09:42:02 +0100 Message-Id: <20230109084208.27355-17-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 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 It was tested in arm, thumb1 and thumb2 modes. --- tools/include/nolibc/arch-arm.h | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/tools/include/nolibc/arch-arm.h b/tools/include/nolibc/arch-arm.h index 79666b590e87..42499f23e73c 100644 --- a/tools/include/nolibc/arch-arm.h +++ b/tools/include/nolibc/arch-arm.h @@ -197,6 +197,7 @@ struct sys_stat_struct { }) char **environ __attribute__((weak)); +const unsigned long *_auxv __attribute__((weak)); /* startup code */ void __attribute__((weak,noreturn,optimize("omit-frame-pointer"))) _start(void) @@ -211,6 +212,16 @@ void __attribute__((weak,noreturn,optimize("omit-frame-pointer"))) _start(void) "ldr %r3, 1f\n" // r3 = &environ (see below) "str %r2, [r3]\n" // store envp into environ + "mov r4, r2\n" // search for auxv (follows NULL after last env) + "0:\n" + "mov r5, r4\n" // r5 = r4 + "add r4, r4, #4\n" // r4 += 4 + "ldr r5,[r5]\n" // r5 = *r5 = *(r4-4) + "cmp r5, #0\n" // and stop at NULL after last env + "bne 0b\n" + "ldr %r3, 2f\n" // r3 = &_auxv (low bits) + "str r4, [r3]\n" // store r4 into _auxv + "mov %r3, $8\n" // AAPCS : sp must be 8-byte aligned in the "neg %r3, %r3\n" // callee, and bl doesn't push (lr=pc) "and %r3, %r3, %r1\n" // so we do sp = r1(=sp) & r3(=-8); @@ -222,6 +233,8 @@ void __attribute__((weak,noreturn,optimize("omit-frame-pointer"))) _start(void) ".align 2\n" // below are the pointers to a few variables "1:\n" ".word environ\n" + "2:\n" + ".word _auxv\n" ); __builtin_unreachable(); } -- 2.17.5