use INT3 instead of NOP for x86 binary padding

We should never end up executing the inter-function padding, so we
are better off faulting than silently carrying on to whatever function
happens to be next.

Note that LLD will soon do this by default (although it currently pads
with zeros).

Reviewed by:	dim, kib
MFC after:	1 month
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D10047

contrib/binutils/ld/emulparams/elf_i386.sh

@@ -6,7 +6,7 @@ COMMONPAGESIZE="CONSTANT (COMMONPAGESIZE)"
 NONPAGED_TEXT_START_ADDR=0x08048000
 ARCH=i386
 MACHINE=
-NOP=0x90909090
+NOP=0xCCCCCCCC
 TEMPLATE_NAME=elf32
 GENERATE_SHLIB_SCRIPT=yes
 GENERATE_PIE_SCRIPT=yes

contrib/binutils/ld/emulparams/elf_x86_64.sh

@@ -7,7 +7,7 @@ COMMONPAGESIZE="CONSTANT (COMMONPAGESIZE)"
 NONPAGED_TEXT_START_ADDR=0x400000
 ARCH="i386:x86-64"
 MACHINE=
-NOP=0x90909090
+NOP=0xCCCCCCCC
 TEMPLATE_NAME=elf32
 GENERATE_SHLIB_SCRIPT=yes
 GENERATE_PIE_SCRIPT=yes

sys/conf/ldscript.amd64

@@ -56,7 +56,7 @@ SECTIONS
   .init           :
   {
     KEEP (*(.init))
-  } =0x90909090
+  } =0xCCCCCCCC
   .plt            : { *(.plt) }
   .text           :
   {
@@ -64,11 +64,11 @@ SECTIONS
     KEEP (*(.text.*personality*))
     /* .gnu.warning sections are handled specially by elf32.em.  */
     *(.gnu.warning)
-  } =0x90909090
+  } =0xCCCCCCCC
   .fini           :
   {
     KEEP (*(.fini))
-  } =0x90909090
+  } =0xCCCCCCCC
   PROVIDE (__etext = .);
   PROVIDE (_etext = .);
   PROVIDE (etext = .);

sys/conf/ldscript.i386

@@ -44,7 +44,7 @@ SECTIONS
   .init           :
   {
     KEEP (*(.init))
-  } =0x90909090
+  } =0xCCCCCCCC
   .plt            : { *(.plt) }
   .text           :
   {
@@ -52,11 +52,11 @@ SECTIONS
     KEEP (*(.text.*personality*))
     /* .gnu.warning sections are handled specially by elf32.em.  */
     *(.gnu.warning)
-  } =0x90909090
+  } =0xCCCCCCCC
   .fini           :
   {
     KEEP (*(.fini))
-  } =0x90909090
+  } =0xCCCCCCCC
   PROVIDE (__etext = .);
   PROVIDE (_etext = .);
   PROVIDE (etext = .);