Commit 609abcd0 authored Jun 07, 2016 by Heiko Carstens Committed by Sami Tolvanen Sep 23, 2016

UPSTREAM: vmlinux.lds.h: allow arch specific handling of ro_after_init data section



commit c74ba8b3480d ("arch: Introduce post-init read-only memory")
introduced the __ro_after_init attribute which allows to add variables
to the ro_after_init data section.

This new section was added to rodata, even though it contains writable
data. This in turn causes problems on architectures which mark the
page table entries read-only that point to rodata very early.

This patch allows architectures to implement an own handling of the
.data..ro_after_init section.
Usually that would be:
- mark the rodata section read-only very early
- mark the ro_after_init section read-only within mark_rodata_ro

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

Bug: 31660652
Change-Id: If68cb4d86f88678c9bac8c47072775ab85ef5770
(cherry picked from commit 32fb2fc5c357fb99616bbe100dbcb27bc7f5d045)
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>

parent 3cfedbe6

include/asm-generic/vmlinux.lds.h

+9 −1

Original line number	Diff line number	Diff line
		@@ -248,6 +248,14 @@
		. = ALIGN(align); \
		*(.data..init_task)

		/*
		* Allow architectures to handle ro_after_init data on their
		* own by defining an empty RO_AFTER_INIT_DATA.
		*/
		#ifndef RO_AFTER_INIT_DATA
		#define RO_AFTER_INIT_DATA *(.data..ro_after_init)
		#endif

		/*
		* Read only Data
		*/
		@@ -256,7 +264,7 @@
		.rodata : AT(ADDR(.rodata) - LOAD_OFFSET) { \
		VMLINUX_SYMBOL(__start_rodata) = .; \
		(.rodata) (.rodata.*) \
		(.data..ro_after_init) / Read only after init */ \
		RO_AFTER_INIT_DATA /* Read only after init */ \
		(__vermagic) / Kernel version magic */ \
		. = ALIGN(8); \
		VMLINUX_SYMBOL(__start___tracepoints_ptrs) = .; \