From f3bdb6da9af1d55c9a8db95d0427708b5e4fc078 Mon Sep 17 00:00:00 2001 From: "H.J. Lu" Date: Tue, 28 Apr 2020 06:21:05 -0700 Subject: [PATCH] Discard .note.gnu.property sections in generic NOTES 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 | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index 7ad6f51b3..7d4e4c46c 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -930,10 +930,16 @@ #endif /* + * Discard .note.gnu.property sections which are unused and have + * different alignment requirement from kernel note sections. + * * Discard .note.GNU-stack, which is emitted as PROGBITS by the compiler. * Otherwise, the type of .notes section would become PROGBITS instead of NOTES. */ #define NOTES \ + /DISCARD/ : { \ + *(.note.gnu.property) \ + } \ /DISCARD/ : { *(.note.GNU-stack) } \ .notes : AT(ADDR(.notes) - LOAD_OFFSET) { \ __start_notes = .; \ -- 2.23.1