[src/trunk]: src/sys/arch/aarch64 set kernel rodata/data non-executable.

[ryo <ryo%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/1bba1623cc34
branches:  trunk
changeset: 834295:1bba1623cc34
user:      ryo <ryo%NetBSD.org@localhost>
date:      Mon Aug 06 20:05:26 2018 +0000

description:
set kernel rodata/data non-executable.
set rodata section on 2Mbytes aligned. (kernel image is mapped with 2Mbytes L2 block)

diffstat:

 sys/arch/aarch64/aarch64/locore.S   |  36 ++++++++++++++++++++++++++++++++++--
 sys/arch/aarch64/conf/kern.ldscript |   3 +++
 2 files changed, 37 insertions(+), 2 deletions(-)

diffs (70 lines):

diff -r 828e45ab0a89 -r 1bba1623cc34 sys/arch/aarch64/aarch64/locore.S
--- a/sys/arch/aarch64/aarch64/locore.S Mon Aug 06 12:50:56 2018 +0000
+++ b/sys/arch/aarch64/aarch64/locore.S Mon Aug 06 20:05:26 2018 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: locore.S,v 1.15 2018/08/06 12:50:56 ryo Exp $  */
+/*     $NetBSD: locore.S,v 1.16 2018/08/06 20:05:26 ryo Exp $  */
 
 /*
  * Copyright (c) 2017 Ryo Shimizu <ryo%nerv.org@localhost>
@@ -35,7 +35,7 @@
 #include <aarch64/hypervisor.h>
 #include "assym.h"
 
-RCSID("$NetBSD: locore.S,v 1.15 2018/08/06 12:50:56 ryo Exp $")
+RCSID("$NetBSD: locore.S,v 1.16 2018/08/06 20:05:26 ryo Exp $")
 
 /* #define DEBUG_LOCORE */
 /* #define DEBUG_MMU */
@@ -684,6 +684,38 @@
        cmp     x2, x3
        blo     1b
 
+
+       /* add eXecute Never bit from _rodata to _end */
+       VERBOSE("Set kernel rodata/data non-Executable\r\n")
+       ldr     x0, =__rodata_start
+       ands    x0, x0, #(L2_SIZE - 1)
+       beq     1f
+       PRINT("Warning: rodata section not aligned on size of L2 block\r\n")
+1:
+       /* x2 = l2pde_index(__rodata_start) */
+       ldr     x2, =__rodata_start
+       mov     x0, #(L2_SIZE - 1)
+       add     x2, x2, x0              /* round block */
+       and     x2, x2, #L2_ADDR_BITS
+       lsr     x2, x2, #L2_SHIFT
+
+       /* x3 = l2pde_inex(_end) */
+       ldr     x3, =_end
+       and     x3, x3, #L2_ADDR_BITS
+       lsr     x3, x3, #L2_SHIFT
+
+       ADDR    x1, ttbr1_l2table_kva
+       b       9f
+1:
+       ldr     x0, [x1, x2, lsl #3]    /* x0 = l2table[x2] */
+       orr     x0, x0, #(LX_BLKPAG_UXN|LX_BLKPAG_PXN)
+       str     x0, [x1, x2, lsl #3]    /* l2table[x2] = x0 */
+       add     x2, x2, #1
+9:
+       cmp     x2, x3                  /* including the L2 block of _end[] */
+       bls     1b
+
+
        VERBOSE("Creating devmap tables\r\n")
        /* devmap=PA table for L1 */
        ADDR    x0, ttbr1_l1table_kva
diff -r 828e45ab0a89 -r 1bba1623cc34 sys/arch/aarch64/conf/kern.ldscript
--- a/sys/arch/aarch64/conf/kern.ldscript       Mon Aug 06 12:50:56 2018 +0000
+++ b/sys/arch/aarch64/conf/kern.ldscript       Mon Aug 06 20:05:26 2018 +0000
@@ -20,6 +20,9 @@
     *(.stub .text.* .gnu.linkonce.t.*)
     /* .gnu.warning sections are handled specially by elf32.em.  */
   } =0
+  /* Move .rodata to the next L2 block to set unexecutable */
+  . = ALIGN (L2_SIZE);
+  PROVIDE (__rodata_start = .);
   .rodata         : { *(.rodata .rodata.* .gnu.linkonce.r.*) }
   .rodata1        : { *(.rodata1) }
   .eh_frame_hdr : { *(.eh_frame_hdr) }