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 EF907ECAAA1 for ; Mon, 31 Oct 2022 15:16:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231736AbiJaPQr (ORCPT ); Mon, 31 Oct 2022 11:16:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45358 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229839AbiJaPQk (ORCPT ); Mon, 31 Oct 2022 11:16:40 -0400 Received: from mga07.intel.com (mga07.intel.com [134.134.136.100]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4BCBB11456 for ; Mon, 31 Oct 2022 08:16:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1667229399; x=1698765399; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=Ij2hEDRZG6EMb0z+MYknc0l1TIq/FCdvq5UymJFqZws=; b=J0oKhm7WSP4v0rmrn1h9MkfD3e9V98o2lEcImV8v9p5RGIRc/dTgc/CU td8mlL0EEx76eB4nXn0qEKX7X7BnY3poHKqL5bBDhvb6kf/HHZQaceVQj UIvDcc4DaUnBVby1TQFjqgyJgAGhJ88XRxefAopNdAYMidrHKbmnjjdBV rSa6cXqgw9Hj4ekEBEoB450kFT4TBscO/z1E2hiqrvkoo7FLwqUrne7RF Brch808ZFAsCtRR+ELLA3lgBMH7bwgApKioJg620SqaKBNqdD5aza6df5 1DmNNZBSSIk5DBMJABUz6tHIBe09YDMbt7T2TxDIvRw4YT7S5ENs7BDNR Q==; X-IronPort-AV: E=McAfee;i="6500,9779,10517"; a="373134131" X-IronPort-AV: E=Sophos;i="5.95,228,1661842800"; d="scan'208";a="373134131" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 31 Oct 2022 08:16:38 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6500,9779,10517"; a="697045598" X-IronPort-AV: E=Sophos;i="5.95,228,1661842800"; d="scan'208";a="697045598" Received: from irvmail001.ir.intel.com ([10.43.11.63]) by fmsmga008.fm.intel.com with ESMTP; 31 Oct 2022 08:16:35 -0700 Received: from newjersey.igk.intel.com (newjersey.igk.intel.com [10.102.20.203]) by irvmail001.ir.intel.com (8.14.3/8.13.6/MailSET/Hub) with ESMTP id 29VFGXGE008839; Mon, 31 Oct 2022 15:16:34 GMT From: Alexander Lobakin To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen Cc: Alexander Lobakin , "H. Peter Anvin" , "Peter Zijlstra (Intel)" , Tony Luck , Kees Cook , Masahiro Yamada , x86@kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH 1/2] x86/boot: robustify calling startup_{32,64}() from the decompressor code Date: Mon, 31 Oct 2022 16:10:46 +0100 Message-Id: <20221031151047.167288-2-alexandr.lobakin@intel.com> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221031151047.167288-1-alexandr.lobakin@intel.com> References: <20221031151047.167288-1-alexandr.lobakin@intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org After commit ce697ccee1a8 ("kbuild: remove head-y syntax"), I started digging whether x86 is ready from removing this old cruft. Removing its objects from the list makes the kernel unbootable. This applies only to bzImage, vmlinux still works correctly. The reason is that with no strict object order determined by the linker arguments, not the linker script, startup_64 can be placed not right at the beginning of the kernel. Here's vmlinux.map's beginning before removing: ffffffff81000000 vmlinux.o:(.head.text) ffffffff81000000 startup_64 ffffffff81000070 secondary_startup_64 ffffffff81000075 secondary_startup_64_no_verify ffffffff81000160 verify_cpu and after: ffffffff81000000 vmlinux.o:(.head.text) ffffffff81000000 pvh_start_xen ffffffff81000080 startup_64 ffffffff810000f0 secondary_startup_64 ffffffff810000f5 secondary_startup_64_no_verify Not a problem itself, but the self-extractor code has the address of that function hardcoded the beginning, not looking onto the ELF header, which always contains the address of startup_{32,64}(). So, instead of doing an "act of blind faith", just take the address from the ELF header and extract a relative offset to the entry point. The decompressor function already returns a pointer to the beginning of the kernel to the Asm code, which then jumps to it, so add that offset to the return value. This doesn't change anything for now, but allows to resign from the "head object list" for x86 and makes sure valid Kbuild or any other improvements won't break anything here in general. Signed-off-by: Alexander Lobakin --- arch/x86/boot/compressed/head_32.S | 2 +- arch/x86/boot/compressed/head_64.S | 2 +- arch/x86/boot/compressed/misc.c | 16 +++++++++++----- 3 files changed, 13 insertions(+), 7 deletions(-) diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S index 3b354eb9516d..56f9847e208b 100644 --- a/arch/x86/boot/compressed/head_32.S +++ b/arch/x86/boot/compressed/head_32.S @@ -187,7 +187,7 @@ SYM_FUNC_START_LOCAL_NOALIGN(.Lrelocated) leal boot_heap@GOTOFF(%ebx), %eax pushl %eax /* heap area */ pushl %esi /* real mode pointer */ - call extract_kernel /* returns kernel location in %eax */ + call extract_kernel /* returns kernel entry point in %eax */ addl $24, %esp /* diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S index d33f060900d2..aeba5aa3d26c 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -593,7 +593,7 @@ SYM_FUNC_START_LOCAL_NOALIGN(.Lrelocated) 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 location in %rax */ + call extract_kernel /* returns kernel entry point in %rax */ popq %rsi /* diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c index cf690d8712f4..96ae5af29f49 100644 --- a/arch/x86/boot/compressed/misc.c +++ b/arch/x86/boot/compressed/misc.c @@ -277,7 +277,7 @@ static inline void handle_relocations(void *output, unsigned long output_len, { } #endif -static void parse_elf(void *output) +static size_t parse_elf(void *output) { #ifdef CONFIG_X86_64 Elf64_Ehdr ehdr; @@ -287,6 +287,7 @@ static void parse_elf(void *output) Elf32_Phdr *phdrs, *phdr; #endif void *dest; + size_t off; int i; memcpy(&ehdr, output, sizeof(ehdr)); @@ -295,16 +296,19 @@ static void parse_elf(void *output) ehdr.e_ident[EI_MAG2] != ELFMAG2 || ehdr.e_ident[EI_MAG3] != ELFMAG3) { error("Kernel is not a valid ELF file"); - return; + return 0; } debug_putstr("Parsing ELF... "); phdrs = malloc(sizeof(*phdrs) * ehdr.e_phnum); - if (!phdrs) + if (!phdrs) { error("Failed to allocate space for phdrs"); + return 0; + } memcpy(phdrs, output + ehdr.e_phoff, sizeof(*phdrs) * ehdr.e_phnum); + off = ehdr.e_entry - phdrs->p_paddr; for (i = 0; i < ehdr.e_phnum; i++) { phdr = &phdrs[i]; @@ -328,6 +332,7 @@ static void parse_elf(void *output) } free(phdrs); + return off; } /* @@ -356,6 +361,7 @@ asmlinkage __visible void *extract_kernel(void *rmode, memptr heap, const unsigned long kernel_total_size = VO__end - VO__text; unsigned long virt_addr = LOAD_PHYSICAL_ADDR; unsigned long needed_size; + size_t off; /* Retain x86 boot parameters pointer passed from startup_32/64. */ boot_params = rmode; @@ -456,14 +462,14 @@ asmlinkage __visible void *extract_kernel(void *rmode, memptr heap, debug_putstr("\nDecompressing Linux... "); __decompress(input_data, input_len, NULL, NULL, output, output_len, NULL, error); - parse_elf(output); + off = parse_elf(output); handle_relocations(output, output_len, virt_addr); debug_putstr("done.\nBooting the kernel.\n"); /* Disable exception handling before booting the kernel */ cleanup_exception_handling(); - return output; + return output + off; } void fortify_panic(const char *name) -- 2.38.1