[src/trunk]: src/sys/kern obey the executable's ELF alignment constraints for...

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

details:   https://anonhg.NetBSD.org/src/rev/7d959bd82473
branches:  trunk
changeset: 351569:7d959bd82473
user:      chs <chs%NetBSD.org@localhost>
date:      Sat Feb 18 01:29:09 2017 +0000

description:
obey the executable's ELF alignment constraints for PIE.
this fixes gdb of PIE binaries on mac68k (and other platforms
which use an ELF alignment that is larger than PAGE_SIZE).

diffstat:

 sys/kern/exec_elf.c |   8 +++++---
 sys/kern/kern_pax.c |  13 +++++++------
 2 files changed, 12 insertions(+), 9 deletions(-)

diffs (78 lines):

diff -r cab7d7720d0f -r 7d959bd82473 sys/kern/exec_elf.c
--- a/sys/kern/exec_elf.c       Sat Feb 18 00:26:16 2017 +0000
+++ b/sys/kern/exec_elf.c       Sat Feb 18 01:29:09 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: exec_elf.c,v 1.88 2017/02/12 21:52:46 uwe Exp $        */
+/*     $NetBSD: exec_elf.c,v 1.89 2017/02/18 01:29:09 chs Exp $        */
 
 /*-
  * Copyright (c) 1994, 2000, 2005, 2015 The NetBSD Foundation, Inc.
@@ -57,7 +57,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(1, "$NetBSD: exec_elf.c,v 1.88 2017/02/12 21:52:46 uwe Exp $");
+__KERNEL_RCSID(1, "$NetBSD: exec_elf.c,v 1.89 2017/02/18 01:29:09 chs Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_pax.h"
@@ -134,7 +134,9 @@
                        align = ph[i].p_align;
 
        offset = (Elf_Addr)pax_aslr_exec_offset(epp, align);
-       offset += epp->ep_vm_minaddr;
+       if (offset < epp->ep_vm_minaddr)
+               offset = roundup(epp->ep_vm_minaddr, align);
+       KASSERT((offset & (align - 1)) == 0);
 
        for (i = 0; i < eh->e_phnum; i++)
                ph[i].p_vaddr += offset;
diff -r cab7d7720d0f -r 7d959bd82473 sys/kern/kern_pax.c
--- a/sys/kern/kern_pax.c       Sat Feb 18 00:26:16 2017 +0000
+++ b/sys/kern/kern_pax.c       Sat Feb 18 01:29:09 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_pax.c,v 1.57 2016/09/17 02:29:11 christos Exp $   */
+/*     $NetBSD: kern_pax.c,v 1.58 2017/02/18 01:29:09 chs Exp $        */
 
 /*
  * Copyright (c) 2015 The NetBSD Foundation, Inc.
@@ -57,7 +57,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_pax.c,v 1.57 2016/09/17 02:29:11 christos Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_pax.c,v 1.58 2017/02/18 01:29:09 chs Exp $");
 
 #include "opt_pax.h"
 
@@ -578,7 +578,7 @@
        uint32_t rand;
        vaddr_t offset;
 
-       pax_align = align == 0 ? PGSHIFT : align;
+       pax_align = align == 0 ? PAGE_SIZE : align;
        l2 = ilog2(pax_align);
 
        rand = cprng_fast32();
@@ -590,7 +590,8 @@
 #define        PAX_TRUNC(a, b) ((a) & ~((b) - 1))
 
        delta = PAX_ASLR_DELTA(rand, l2, PAX_ASLR_DELTA_EXEC_LEN);
-       offset = PAX_TRUNC(delta, pax_align) + PAGE_SIZE;
+       offset = PAX_TRUNC(delta, pax_align);
+       offset = MAX(offset, pax_align);
 
        PAX_DPRINTF("rand=%#x l2=%#zx pax_align=%#zx delta=%#zx offset=%#jx",
            rand, l2, pax_align, delta, (uintmax_t)offset);
@@ -608,9 +609,9 @@
        if (pax_aslr_flags & PAX_ASLR_EXEC_OFFSET)
                goto out;
 #endif
-       return pax_aslr_offset(align) + PAGE_SIZE;
+       return pax_aslr_offset(align);
 out:
-       return MAX(align, PAGE_SIZE);
+       return 0;
 }
 
 voff_t