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>

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 71581125e60402b26f217456f9638466181e19ca..a65eedc15e939fd5f4cbf729bfa2df5cf7ffc779 100644 (file)
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -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) = .;         \