lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Thu, 26 Mar 2015 11:25:51 +0100 From: Borislav Petkov <bp@...en8.de> To: Denys Vlasenko <vda.linux@...glemail.com> Cc: Ingo Molnar <mingo@...nel.org>, Linus Torvalds <torvalds@...ux-foundation.org>, "H. Peter Anvin" <hpa@...or.com>, Denys Vlasenko <dvlasenk@...hat.com>, Steven Rostedt <rostedt@...dmis.org>, Andy Lutomirski <luto@...capital.net>, Oleg Nesterov <oleg@...hat.com>, Frederic Weisbecker <fweisbec@...il.com>, Alexei Starovoitov <ast@...mgrid.com>, Will Drewry <wad@...omium.org>, Kees Cook <keescook@...omium.org>, the arch/x86 maintainers <x86@...nel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org> Subject: Re: [PATCH 3/4] x86/asm/entry/64: use smaller insns On Thu, Mar 26, 2015 at 11:07:42AM +0100, Denys Vlasenko wrote: > In my experiment, GAS uses 10-byte insn only for constants which > won't work with 7-byte encoding; or if I explicitly ask for "movabs": > > _start: .globl _start > mov $0x12345678,%edi # 5 bytes > mov $0x12345678,%rdi # 7 bytes > movq $0x12345678,%rdi # 7 bytes > mov $0x80000000,%rdi # 10 bytes Right, and since they're signed immediates, the AUDIT_ARCH_X86_64 thing is 0xc000003e and does not fit in an s32, thus the 64-bit immediate with bf opcode: mov $0x80000000-1,%rdi mov $0x80000000,%rdi mov $0xc000003e,%rdi mov $0xc000003e,%edi ... 21: 48 c7 c7 ff ff ff 7f mov $0x7fffffff,%rdi 28: 48 bf 00 00 00 80 00 movabs $0x80000000,%rdi 2f: 00 00 00 32: 48 bf 3e 00 00 c0 00 movabs $0xc000003e,%rdi 39: 00 00 00 3c: bf 3e 00 00 c0 mov $0xc000003e,%edi Makes sense to me. -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply. -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists