From mboxrd@z Thu Jan 1 00:00:00 1970 From: "H.J. Lu" Subject: [PATCH 2/2] Discard .note.gnu.property sections in generic NOTES Date: Thu, 26 Mar 2020 12:30:21 -0700 Message-ID: <20200326193021.255002-2-hjl.tools@gmail.com> References: <20200326193021.255002-1-hjl.tools@gmail.com> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: Received: from mga11.intel.com ([192.55.52.93]:38363 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726340AbgCZTa0 (ORCPT ); Thu, 26 Mar 2020 15:30:26 -0400 In-Reply-To: <20200326193021.255002-1-hjl.tools@gmail.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: linux-kernel@vger.kernel.org Cc: Andy Lutomirski , Thomas Gleixner , Kees Cook , Thomas Lendacky , Sami Tolvanen , Heiko Carstens , Ingo Molnar , Borislav Petkov , "H . Peter Anvin" , x86@kernel.org, Arnd Bergmann , linux-arch@vger.kernel.org, Yu-cheng Yu With the command-line option, -mx86-used-note=yes, the x86 assembler in binutils 2.32 and above generates a program property note in a note section, .note.gnu.property, to encode used x86 ISAs and features. But kernel linker script only contains a single NOTE segment: PHDRS { text PT_LOAD FLAGS(5); data PT_LOAD FLAGS(6); percpu PT_LOAD FLAGS(6); init PT_LOAD FLAGS(7); note PT_NOTE FLAGS(0); } SECTIONS { ... .notes : AT(ADDR(.notes) - 0xffffffff80000000) { __start_notes = .; KEEP(*(.not e.*)) __stop_notes = .; } :text :note ... } The NOTE segment generated by kernel linker script is aligned to 4 bytes. But .note.gnu.property section must be aligned to 8 bytes on x86-64 and we get [hjl@gnu-skx-1 linux]$ readelf -n vmlinux Displaying notes found in: .notes Owner Data size Description Xen 0x00000006 Unknown note type: (0x00000006) description data: 6c 69 6e 75 78 00 Xen 0x00000004 Unknown note type: (0x00000007) description data: 32 2e 36 00 xen-3.0 0x00000005 Unknown note type: (0x006e6558) description data: 08 00 00 00 03 readelf: Warning: note with invalid namesz and/or descsz found at offset 0x50 readelf: Warning: type: 0xffffffff, namesize: 0x006e6558, descsize: 0x80000000, alignment: 8 [hjl@gnu-skx-1 linux]$ Since note.gnu.property section in kernel image is never used, this patch discards .note.gnu.property sections in kernel linker script by adding /DISCARD/ : { *(.note.gnu.property) } before kernel NOTE segment in generic NOTES. Signed-off-by: H.J. Lu Reviewed-by: Kees Cook --- include/asm-generic/vmlinux.lds.h | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index 6b943fb8c5fd..6659a7c07c84 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -818,7 +818,14 @@ #define TRACEDATA #endif +/* + * Discard .note.gnu.property sections which are unused and have + * different alignment requirement from kernel note sections. + */ #define NOTES \ + /DISCARD/ : { \ + *(.note.gnu.property) \ + } \ .notes : AT(ADDR(.notes) - LOAD_OFFSET) { \ __start_notes = .; \ KEEP(*(.note.*)) \ -- 2.25.1