On Fri, Nov 17, 2017 at 9:29 PM, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > On Fri, Nov 17, 2017 at 9:14 PM, Kees Cook <keescook@xxxxxxxxxxxx> wrote: >> >> FWIW, myself doing a build at d9e12200852d with and without >> GCC_PLUGIN_RANDSTRUCT _appears_ to produce identical objdump output >> where I did spot-checks. > > That would probably be a good thing to check anyway - check the > difference between GCC_PLUGIN_RANDSTRUCT on and off at that commit. > > Just do > > objdump --disassemble vmlinux > file > > and compare the two files for where the differences start occurring. Yeah, I was just doing that now. Looks like there _is_ something getting changed just from having the plugin enabled, but it appears localized. For me, the first non-offset change happens in lookup_user_key and persists for a while. -ffffffff813893a7: 0f 85 55 03 00 00 jne ffffffff81389702 <lookup_user_key+0x3f2> -ffffffff813893ad: f0 41 ff 06 lock incl (%r14) -ffffffff813893b1: 83 fb 07 cmp $0x7,%ebx -ffffffff813893b4: 4c 89 b5 70 ff ff ff mov %r14,-0x90(%rbp) ... +ffffffff813893a7: 0f 85 35 03 00 00 jne ffffffff813896e2 <lookup_user_key+0x3d2> +ffffffff813893ad: 4d 89 f0 mov %r14,%r8 +ffffffff813893b0: f0 41 ff 06 lock incl (%r14) +ffffffff813893b4: 83 fb 07 cmp $0x7,%ebx +ffffffff813893b7: 4c 89 b5 70 ff ff ff mov %r14,-0x90(%rbp) And removing the TYPE_ATTRIBUTES() poking makes the register storage differences go away, but there's still a 0x40 byte offset delta. I'll continue looking at this tomorrow. -Kees -- Kees Cook Pixel Security -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
