From patchwork Wed Jun 17 08:25:05 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ard Biesheuvel X-Patchwork-Id: 11609391 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 9713C60D for ; Wed, 17 Jun 2020 08:25:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 768A921527 for ; Wed, 17 Jun 2020 08:25:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592382313; bh=WE28cH+mnd/5QSfDhggdio7ufTc6leSAfR4Hjh8Tn1s=; h=From:To:Cc:Subject:Date:List-ID:From; b=DAsiF3MKW0/oCjDF3eTs09TDiwG9Ekt4PWSePJC2/VF7hV7GyCHO88bKMGnZAd8Lo ORkQCKxHlj+rXWuofojnvJaiPlF+DRjP2Q4Wh4JmPas5AA64lQlrimVKh3Mcr50l1c XNxMX3TsUZTmR9q4yjK8DBN9Cp0CiyyHtNlvjdds= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725964AbgFQIZN (ORCPT ); Wed, 17 Jun 2020 04:25:13 -0400 Received: from mail.kernel.org ([198.145.29.99]:46314 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725901AbgFQIZM (ORCPT ); Wed, 17 Jun 2020 04:25:12 -0400 Received: from localhost.localdomain (lfbn-nic-1-188-42.w2-15.abo.wanadoo.fr [2.15.37.42]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2EF642100A; Wed, 17 Jun 2020 08:25:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592382312; bh=WE28cH+mnd/5QSfDhggdio7ufTc6leSAfR4Hjh8Tn1s=; h=From:To:Cc:Subject:Date:From; b=0bc/kx5HTLQkQkU30PmG/f7Is5rojzFBguZQoSq+KzGrH/Y2vGr/sVgCE2PNY2t8X lSLzZ/4wuZEKLmmv3t/PxChdkfo76chUxCN8hlq7aIYaqkNKisbKkZS0VbpAjkLh+M piit97Z6H5W7/dtjeRswAOj64rOiai+npqqjtNbg= From: Ard Biesheuvel To: linux-kernel@vger.kernel.org Cc: linux-acpi@vger.kernel.org, lenb@kernel.org, rjw@rjwysocki.net, Ard Biesheuvel Subject: [PATCH] ACPI: avoid relocations for table signature array Date: Wed, 17 Jun 2020 10:25:05 +0200 Message-Id: <20200617082505.1159131-1-ardb@kernel.org> X-Mailer: git-send-email 2.27.0 MIME-Version: 1.0 Sender: linux-acpi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org On architectures that implement KASLR using the ELF native RELA relocation format (such as arm64), every absolute reference in the code incurs an overhead of 24 bytes in the .rela section. So storing a 41 element array of 4 character signature strings using an array of pointer-to-char incurs an 8x overhead (32 bytes per entry => ~1500 bytes), and given the fixed length of the entries, and the fact that the array is only used locally, it is much better to use an array of arrays here, which gets rid of the overhead entirely. While at it, make it __initconst, as it is never referenced except from __init code. Signed-off-by: Ard Biesheuvel --- drivers/acpi/tables.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/drivers/acpi/tables.c b/drivers/acpi/tables.c index 0e905c3d1645..ada36bc40c2b 100644 --- a/drivers/acpi/tables.c +++ b/drivers/acpi/tables.c @@ -490,7 +490,7 @@ static u8 __init acpi_table_checksum(u8 *buffer, u32 length) } /* All but ACPI_SIG_RSDP and ACPI_SIG_FACS: */ -static const char * const table_sigs[] = { +static const char table_sigs[][ACPI_NAMESEG_SIZE] __initconst = { ACPI_SIG_BERT, ACPI_SIG_BGRT, ACPI_SIG_CPEP, ACPI_SIG_ECDT, ACPI_SIG_EINJ, ACPI_SIG_ERST, ACPI_SIG_HEST, ACPI_SIG_MADT, ACPI_SIG_MSCT, ACPI_SIG_SBST, ACPI_SIG_SLIT, ACPI_SIG_SRAT, @@ -501,7 +501,7 @@ static const char * const table_sigs[] = { ACPI_SIG_WDDT, ACPI_SIG_WDRT, ACPI_SIG_DSDT, ACPI_SIG_FADT, ACPI_SIG_PSDT, ACPI_SIG_RSDT, ACPI_SIG_XSDT, ACPI_SIG_SSDT, ACPI_SIG_IORT, ACPI_SIG_NFIT, ACPI_SIG_HMAT, ACPI_SIG_PPTT, - ACPI_SIG_NHLT, NULL }; + ACPI_SIG_NHLT }; #define ACPI_HEADER_SIZE sizeof(struct acpi_table_header) @@ -548,11 +548,11 @@ void __init acpi_table_upgrade(void) table = file.data; - for (sig = 0; table_sigs[sig]; sig++) + for (sig = 0; sig < ARRAY_SIZE(table_sigs); sig++) if (!memcmp(table->signature, table_sigs[sig], 4)) break; - if (!table_sigs[sig]) { + if (sig >= ARRAY_SIZE(table_sigs)) { pr_err("ACPI OVERRIDE: Unknown signature [%s%s]\n", cpio_path, file.name); continue;