From patchwork Mon Aug 7 16:27:04 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ard Biesheuvel X-Patchwork-Id: 711720 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 361F2C04A94 for ; Mon, 7 Aug 2023 16:28:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229870AbjHGQ2Q (ORCPT ); Mon, 7 Aug 2023 12:28:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34370 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231671AbjHGQ2D (ORCPT ); Mon, 7 Aug 2023 12:28:03 -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 9F62610DE; Mon, 7 Aug 2023 09:27:58 -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 C401161F1B; Mon, 7 Aug 2023 16:27:56 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A8331C433C9; Mon, 7 Aug 2023 16:27:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1691425676; bh=7D4HdiWvB51jf9PtMrHNY1LkXYyyjvNVJhuX8x8xGjA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=kuZyfxX//dsYMytxVlhyRFGkSFiSHw8cD/YABMCIzaJthJ4PmTpg3r4Ckl/hfzKgg uPZXOE9mzZ9G6GVn9R0FNcMPAgg/DcgYNlew/U/epCuRbJACj1PsIKLFbFxX/LVwlI 4P9lc8Mn8EBjoVodGB3TDduGNhjc6cGaMSAkaKLWcl0pGbyF4+q6DyYZ8v98lxpsOs 0fcqUUCc9+TaWDGdqXZpUnKRcmoGoRbalyD0Zv325W28JLi2SCPT4lR163de95G2YW H1Ie0857RU2pxIndOrKw558EXdZa/qZLKLZ4ZWdeYZSfDKKS1ilEZrH9RT6ps9zTmN uHs5fcwy5ggJA== 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 07/23] x86/decompressor: Store boot_params pointer in callee save register Date: Mon, 7 Aug 2023 18:27:04 +0200 Message-Id: <20230807162720.545787-8-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=4376; i=ardb@kernel.org; h=from:subject; bh=7D4HdiWvB51jf9PtMrHNY1LkXYyyjvNVJhuX8x8xGjA=; b=owGbwMvMwCFmkMcZplerG8N4Wi2JIeWidPAN9aiZd6cnXHTISvH1tfg8vehj0JkNF9P8L03/L nV5+ZRHHaUsDGIcDLJiiiwCs/++23l6olSt8yxZmDmsTCBDGLg4BWAiB/8xMhyd+aBbWOXKKZ+f 225NefmuXZuL1d31X8V/9ZS7htkfowMYGSbN3rl/GudmacVIhdd9jjtmPNjg0vXCWi08o9n+h8m LPnYA 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 pushing and popping %RSI several times to preserve the struct boot_params pointer across the execution of the startup code, move it into a callee save register before the first call into C, and copy it back when needed. Signed-off-by: Ard Biesheuvel --- arch/x86/boot/compressed/head_64.S | 42 ++++++++------------ 1 file changed, 16 insertions(+), 26 deletions(-) diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S index a3f764daf3a3adbc..19bf810409e2aa62 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -405,10 +405,14 @@ SYM_CODE_START(startup_64) lretq .Lon_kernel_cs: + /* + * RSI holds a pointer to a boot_params structure provided by the + * loader, and this needs to be preserved across C function calls. So + * move it into a callee saved register. + */ + movq %rsi, %r15 - pushq %rsi call load_stage1_idt - popq %rsi #ifdef CONFIG_AMD_MEM_ENCRYPT /* @@ -419,12 +423,10 @@ SYM_CODE_START(startup_64) * CPUID instructions being issued, so go ahead and do that now via * sev_enable(), which will also handle the rest of the SEV-related * detection/setup to ensure that has been done in advance of any dependent - * code. + * code. Pass the boot_params pointer as the first argument. */ - pushq %rsi - movq %rsi, %rdi /* real mode address */ + movq %r15, %rdi call sev_enable - popq %rsi #endif /* @@ -437,13 +439,10 @@ SYM_CODE_START(startup_64) * - Non zero RDX means trampoline needs to enable 5-level * paging. * - * RSI holds real mode data and needs to be preserved across - * this function call. + * Pass the boot_params pointer as the first argument. */ - pushq %rsi - movq %rsi, %rdi /* real mode address */ + movq %r15, %rdi call paging_prepare - popq %rsi /* Save the trampoline address in RCX */ movq %rax, %rcx @@ -456,9 +455,9 @@ SYM_CODE_START(startup_64) * because the architecture does not guarantee that GPRs will retain * their full 64-bit values across a 32-bit mode switch. */ + pushq %r15 pushq %rbp pushq %rbx - pushq %rsi /* * Push the 64-bit address of trampoline_return() onto the new stack. @@ -475,9 +474,9 @@ SYM_CODE_START(startup_64) lretq trampoline_return: /* Restore live 64-bit registers */ - popq %rsi popq %rbx popq %rbp + popq %r15 /* Restore the stack, the 32-bit trampoline uses its own stack */ leaq rva(boot_stack_end)(%rbx), %rsp @@ -487,14 +486,9 @@ trampoline_return: * * RDI is address of the page table to use instead of page table * in trampoline memory (if required). - * - * RSI holds real mode data and needs to be preserved across - * this function call. */ - pushq %rsi leaq rva(top_pgtable)(%rbx), %rdi call cleanup_trampoline - popq %rsi /* Zero EFLAGS */ pushq $0 @@ -504,7 +498,6 @@ trampoline_return: * Copy the compressed kernel to the end of our buffer * where decompression in place becomes safe. */ - pushq %rsi leaq (_bss-8)(%rip), %rsi leaq rva(_bss-8)(%rbx), %rdi movl $(_bss - startup_32), %ecx @@ -512,7 +505,6 @@ trampoline_return: std rep movsq cld - popq %rsi /* * The GDT may get overwritten either during the copy we just did or @@ -544,30 +536,28 @@ SYM_FUNC_START_LOCAL_NOALIGN(.Lrelocated) shrq $3, %rcx rep stosq - pushq %rsi call load_stage2_idt /* Pass boot_params to initialize_identity_maps() */ - movq (%rsp), %rdi + movq %r15, %rdi call initialize_identity_maps - popq %rsi /* * Do the extraction, and jump to the new kernel.. */ - pushq %rsi /* Save the real mode argument */ - movq %rsi, %rdi /* real mode address */ + /* pass struct boot_params pointer */ + movq %r15, %rdi leaq boot_heap(%rip), %rsi /* malloc area for uncompression */ leaq input_data(%rip), %rdx /* input_data */ movl input_len(%rip), %ecx /* input_len */ movq %rbp, %r8 /* output target address */ movl output_len(%rip), %r9d /* decompressed length, end of relocs */ call extract_kernel /* returns kernel entry point in %rax */ - popq %rsi /* * Jump to the decompressed kernel. */ + movq %r15, %rsi jmp *%rax SYM_FUNC_END(.Lrelocated)