[src/trunk]: src/sys/arch/amd64/conf Split each kernel section into sub-block...

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

details:   https://anonhg.NetBSD.org/src/rev/4de0f41aa373
branches:  trunk
changeset: 827836:4de0f41aa373
user:      maxv <maxv%NetBSD.org@localhost>
date:      Tue Nov 14 10:15:40 2017 +0000

description:
Split each kernel section into sub-blocks of approximately 2MB. The newly
created sections are named .origname.i, for example:

        .text -> { .text .text.0 .text.1 .text.2 .text.3 .text.4 }

Each section is randomized independently by the prekern - and in a random
order obviously. As a result we can get intertwined mappings, of the type:

+-------+-----------+------+---------+-----------+-------+-------+------+-
| text1 | NOTMAPPED | bss0 | rodata1 | NOTMAPPED | data2 | text3 | bss1 |
+-------+-----------+------+---------+-----------+-------+-------+------+-

   ---------+-
    rodata0 | ...
   ---------+-

The CTF section is dropped completely, because (a) when split it becomes
enormous for some reason (that I don't quite understand, verily), and (b)
the kernel expects only one CTF and can't handle several of them.

diffstat:

 sys/arch/amd64/conf/Makefile.amd64      |  4 ++--
 sys/arch/amd64/conf/kern.ldscript.kaslr |  8 +++++++-
 2 files changed, 9 insertions(+), 3 deletions(-)

diffs (38 lines):

diff -r 873a39637223 -r 4de0f41aa373 sys/arch/amd64/conf/Makefile.amd64
--- a/sys/arch/amd64/conf/Makefile.amd64        Tue Nov 14 09:56:26 2017 +0000
+++ b/sys/arch/amd64/conf/Makefile.amd64        Tue Nov 14 10:15:40 2017 +0000
@@ -1,4 +1,4 @@
-#      $NetBSD: Makefile.amd64,v 1.62 2017/11/14 09:56:26 maxv Exp $
+#      $NetBSD: Makefile.amd64,v 1.63 2017/11/14 10:15:40 maxv Exp $
 
 # Makefile for NetBSD
 #
@@ -62,7 +62,7 @@
 ##
 TEXTADDR?=     0xffffffff80200000
 .if defined(KASLR)
-EXTRA_LINKFLAGS=       -r -d
+EXTRA_LINKFLAGS=       --split-by-file=0x200000 -r -d
 KERNLDSCRIPT?= ${AMD64}/conf/kern.ldscript.kaslr
 .else
 EXTRA_LINKFLAGS=       -z max-page-size=0x200000
diff -r 873a39637223 -r 4de0f41aa373 sys/arch/amd64/conf/kern.ldscript.kaslr
--- a/sys/arch/amd64/conf/kern.ldscript.kaslr   Tue Nov 14 09:56:26 2017 +0000
+++ b/sys/arch/amd64/conf/kern.ldscript.kaslr   Tue Nov 14 10:15:40 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern.ldscript.kaslr,v 1.2 2017/11/13 20:01:48 maxv Exp $       */
+/*     $NetBSD: kern.ldscript.kaslr,v 1.3 2017/11/14 10:15:40 maxv Exp $       */
 
 #include "assym.h"
 
@@ -57,4 +57,10 @@
        {
                KEEP(*(.note.netbsd.ident));
        }
+
+       /DISCARD/ :
+       {
+               *(.SUNW_ctf)
+               *(.SUNW_ctf.*)
+       }
 }