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: Wed, 30 Sep 2009 20:14:47 +0400 From: Cyrill Gorcunov <gorcunov@...il.com> To: Eric Dumazet <eric.dumazet@...il.com> Cc: Arjan van de Ven <arjan@...radead.org>, Linus Torvalds <torvalds@...ux-foundation.org>, Martin Schwidefsky <schwidefsky@...ibm.com>, Thomas Gleixner <tglx@...utronix.de>, John Stultz <johnstul@...ibm.com>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Peter Zijlstra <a.p.zijlstra@...llo.nl>, Ingo Molnar <mingo@...e.hu> Subject: Re: Linux 2.6.32-rc1 [Eric Dumazet - Wed, Sep 30, 2009 at 05:57:25PM +0200] ... | | > +#define cmpxchg64(ptr, o, n) \ | > +({ \ | > + __typeof__(*(ptr)) __ret; \ | > + __typeof__(*(ptr)) __old = (o); \ | > + __typeof__(*(ptr)) __new = (n); \ | > + alternative_io("call cmpxchg8b_emu", \ | > + "lock; cmpxchg8b (%%esi)" , \ | > + X86_FEATURE_CX8, \ | > + "=A" (__ret), \ | > + "S" ((ptr)), "0" (__old), \ | > + "b" ((unsigned int)__new), \ | > + "c" ((unsigned int)(__new>>32))); \ | | | Note: | | lock; cmpxchg8b (%%esi) | | gives 4 bytes opcode : f0 0f c7 0e | Because alternative (call cmpxchg8b_emu) uses 5 bytes, a nop will be added. | | Choosing ".byte 0xf0, 0x0f, 0xc7, 0x4e, 0x00" aka "lock cmpxchg8b 0x0(%esi)" is a litle bit better ? | Just curious why not "nop; lock; cmpxchg8b (%esi)"? lock itself is destructive instruction with causes write buffers to flush data back and NOP itself will be discarded by cpu internals so I suppose this form should be better. Though I could miss something, and OTOH it's not a big deal. But still curious :) -- Cyrill -- 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