From patchwork Mon Aug 7 16:27:00 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ard Biesheuvel X-Patchwork-Id: 711721 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 AA828C001DB for ; Mon, 7 Aug 2023 16:28:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231534AbjHGQ2P (ORCPT ); Mon, 7 Aug 2023 12:28:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34042 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231543AbjHGQ1u (ORCPT ); Mon, 7 Aug 2023 12:27:50 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 581CD100; Mon, 7 Aug 2023 09:27:49 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id E0F4A61EDB; Mon, 7 Aug 2023 16:27:48 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id CA225C433C8; Mon, 7 Aug 2023 16:27:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1691425668; bh=rZ4dagtCLM4Dd3aSWI/Kh+e/QUOV/FZ3MiPjfd5ziT8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=LpTz8LQNGrHo8uBSp/y4FC08ohdbzFusdoGs0IUbWK8E76h7WUsmMgmakcJwxb5vW YnryQKrUKtX+9A8yV2LIg0tNEHOhnwQfpBy8HW9ozC+bcKR/78fCLLBoH1FkkYvWaE uMb0CWjp5rpwvsZx/P1eIiV6xCvClnbggHVhuSeHeanGvAuUsAZmswxp5BGB+DalbA Suwx2t4v6v3VHygkjj2FyWNkkVdhGgQk+ch4t6l9PYekEsyTu4VM3dxjcTtHJ40lI6 3WoBxIu3kiz9pyI74jb5mj9EOCFsSL9BryzQH+fttEPmcp02QTiiqpoLoiXexf0/vt 2rgBrLYyeY66w== From: Ard Biesheuvel To: linux-efi@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Ard Biesheuvel , Borislav Petkov , Dave Hansen , Ingo Molnar , Thomas Gleixner Subject: [PATCH v9 03/23] x86/efistub: Branch straight to kernel entry point from C code Date: Mon, 7 Aug 2023 18:27:00 +0200 Message-Id: <20230807162720.545787-4-ardb@kernel.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230807162720.545787-1-ardb@kernel.org> References: <20230807162720.545787-1-ardb@kernel.org> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2314; i=ardb@kernel.org; h=from:subject; bh=rZ4dagtCLM4Dd3aSWI/Kh+e/QUOV/FZ3MiPjfd5ziT8=; b=owGbwMvMwCFmkMcZplerG8N4Wi2JIeWitJ8K17FjYUl3J6zaKBFfPW+pmv80l6sqQimN0sdnz EzTMzvYUcrCIMbBICumyCIw+++7nacnStU6z5KFmcPKBDKEgYtTACYyQZ3hn9Jm9aeTVu++HtP7 cKeiz9wPixNj9O3Wi/kve7mFpdVbU5Xhr1Ch/24vDaejW7g3JoUXhBh0LSl+xMMSp+at/M/3WuN 7TgA= X-Developer-Key: i=ardb@kernel.org; a=openpgp; fpr=F43D03328115A198C90016883D200E9CA6329909 Precedence: bulk List-ID: X-Mailing-List: linux-efi@vger.kernel.org Instead of returning to the calling code in assembler that does nothing more than perform an indirect call with the boot_params pointer in register ESI/RSI, perform the jump directly from the EFI stub C code. This will allow the asm entrypoint code to be dropped entirely in subsequent patches. Signed-off-by: Ard Biesheuvel --- drivers/firmware/efi/libstub/x86-stub.c | 22 +++++++++++++++----- 1 file changed, 17 insertions(+), 5 deletions(-) diff --git a/drivers/firmware/efi/libstub/x86-stub.c b/drivers/firmware/efi/libstub/x86-stub.c index 220be75a5cdc1f4c..40a10db2d85e7942 100644 --- a/drivers/firmware/efi/libstub/x86-stub.c +++ b/drivers/firmware/efi/libstub/x86-stub.c @@ -290,7 +290,7 @@ adjust_memory_range_protection(unsigned long start, unsigned long size) #define TRAMPOLINE_PLACEMENT_BASE ((128 - 8)*1024) #define TRAMPOLINE_PLACEMENT_SIZE (640*1024 - (128 - 8)*1024) -void startup_32(struct boot_params *boot_params); +extern const u8 startup_32[], startup_64[]; static void setup_memory_protection(unsigned long image_base, unsigned long image_size) @@ -803,10 +803,19 @@ static efi_status_t exit_boot(struct boot_params *boot_params, void *handle) return EFI_SUCCESS; } +static void __noreturn enter_kernel(unsigned long kernel_addr, + struct boot_params *boot_params) +{ + /* enter decompressed kernel with boot_params pointer in RSI/ESI */ + asm("jmp *%0"::"r"(kernel_addr), "S"(boot_params)); + + unreachable(); +} + /* - * On success, we return the address of startup_32, which has potentially been - * relocated by efi_relocate_kernel. - * On failure, we exit to the firmware via efi_exit instead of returning. + * On success, this routine will jump to the relocated image directly and never + * return. On failure, it will exit to the firmware via efi_exit() instead of + * returning. */ asmlinkage unsigned long efi_main(efi_handle_t handle, efi_system_table_t *sys_table_arg, @@ -950,7 +959,10 @@ asmlinkage unsigned long efi_main(efi_handle_t handle, goto fail; } - return bzimage_addr; + if (IS_ENABLED(CONFIG_X86_64)) + bzimage_addr += startup_64 - startup_32; + + enter_kernel(bzimage_addr, boot_params); fail: efi_err("efi_main() failed!\n");