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: Tue, 28 Apr 2020 06:21:05 -0700 Message-ID: <20200428132105.170886-2-hjl.tools@gmail.com> References: <20200428132105.170886-1-hjl.tools@gmail.com> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20200428132105.170886-1-hjl.tools@gmail.com> Sender: linux-kernel-owner@vger.kernel.org To: linux-kernel@vger.kernel.org Cc: Yu-cheng Yu , Arnd Bergmann , linux-arch@vger.kernel.org, Michael Ellerman , Benjamin Herrenschmidt , Paul Mackerras , Kees Cook , Borislav Petkov , "Naveen N . Rao" , linuxppc-dev@lists.ozlabs.org List-Id: linux-arch.vger.kernel.org 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 71e387a5fe90..95cd678428f4 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -833,7 +833,14 @@ #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.*)) \ -- 2.25.4 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51642 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727804AbgD1NVJ (ORCPT ); Tue, 28 Apr 2020 09:21:09 -0400 From: "H.J. Lu" Subject: [PATCH 2/2] Discard .note.gnu.property sections in generic NOTES Date: Tue, 28 Apr 2020 06:21:05 -0700 Message-ID: <20200428132105.170886-2-hjl.tools@gmail.com> In-Reply-To: <20200428132105.170886-1-hjl.tools@gmail.com> References: <20200428132105.170886-1-hjl.tools@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-arch-owner@vger.kernel.org List-ID: To: linux-kernel@vger.kernel.org Cc: Yu-cheng Yu , Arnd Bergmann , linux-arch@vger.kernel.org, Michael Ellerman , Benjamin Herrenschmidt , Paul Mackerras , Kees Cook , Borislav Petkov , "Naveen N . Rao" , linuxppc-dev@lists.ozlabs.org Message-ID: <20200428132105.AJi5co9SuNYxF9e0C7V1z_a00JwoZLLgdSp6aWXjl_8@z> 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 71e387a5fe90..95cd678428f4 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -833,7 +833,14 @@ #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.*)) \ -- 2.25.4