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authorHeiko Carstens <heiko.carstens@de.ibm.com>2016-06-07 10:12:55 +0200
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2016-06-13 15:58:23 +0200
commitd07a980c1b8d7ac18854bae94a4e7aeabce933b8 (patch)
tree80f32e86c81aa68b12944c0534938c758d7e405d /arch/s390/kernel
parent32fb2fc5c357fb99616bbe100dbcb27bc7f5d045 (diff)
s390: add proper __ro_after_init support
On s390 __ro_after_init is currently mapped to __read_mostly which means that data marked as __ro_after_init will not be protected. Reason for this is that the common code __ro_after_init implementation is x86 centric: the ro_after_init data section was added to rodata, since x86 enables write protection to kernel text and rodata very late. On s390 we have write protection for these sections enabled with the initial page tables. So adding the ro_after_init data section to rodata does not work on s390. In order to make __ro_after_init work properly on s390 move the ro_after_init data, right behind rodata. Unlike the rodata section it will be marked read-only later after all init calls happened. This s390 specific implementation adds new __start_ro_after_init and __end_ro_after_init labels. Everything in between will be marked read-only after the init calls happened. In addition to the __ro_after_init data move also the exception table there, since from a practical point of view it fits the __ro_after_init requirements. 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>
Diffstat (limited to 'arch/s390/kernel')
-rw-r--r--arch/s390/kernel/vmlinux.lds.S12
1 files changed, 11 insertions, 1 deletions
diff --git a/arch/s390/kernel/vmlinux.lds.S b/arch/s390/kernel/vmlinux.lds.S
index 0656f7cc7fb4..429bfd111961 100644
--- a/arch/s390/kernel/vmlinux.lds.S
+++ b/arch/s390/kernel/vmlinux.lds.S
@@ -11,6 +11,9 @@
*/
#define BSS_FIRST_SECTIONS *(.bss..swapper_pg_dir)
+/* Handle ro_after_init data on our own. */
+#define RO_AFTER_INIT_DATA
+
#include <asm-generic/vmlinux.lds.h>
OUTPUT_FORMAT("elf64-s390", "elf64-s390", "elf64-s390")
@@ -56,7 +59,14 @@ SECTIONS
_eshared = .; /* End of shareable data */
_sdata = .; /* Start of data section */
- EXCEPTION_TABLE(16) :data
+ . = ALIGN(PAGE_SIZE);
+ __start_ro_after_init = .;
+ .data..ro_after_init : {
+ *(.data..ro_after_init)
+ }
+ EXCEPTION_TABLE(16)
+ . = ALIGN(PAGE_SIZE);
+ __end_ro_after_init = .;
RW_DATA_SECTION(0x100, PAGE_SIZE, THREAD_SIZE)