linux-kernel - x86: asm doubt

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

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <ce0170d90903150716t14033a9dr3b3bf028933dde7c@mail.gmail.com>
Date:	Sun, 15 Mar 2009 11:16:24 -0300
From:	Sergio Luis <eeeesti@...il.com>
To:	Ingo Molnar <mingo@...e.hu>, "Rafael J. Wysocki" <rjw@...k.pl>,
	Pavel Machek <pavel@...e.cz>,
	Linux-kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: x86: asm doubt

Hi there,

taking a look at arch/x86/power/cpu_(32|64).c, I saw the 32.c one
using the following macros

#define savesegment(seg, value)                         \
        asm("mov %%" #seg ",%0":"=r" (value) : : "memory")


#define loadsegment(seg, value)                 \
        asm volatile("\n"                       \
                     "1:\t"                     \
                     "movl %k0,%%" #seg "\n"    \
                     "2:\n"                     \
                     ".section .fixup,\"ax\"\n" \
                     "3:\t"                     \
                     "movl %k1, %%" #seg "\n\t" \
                     "jmp 2b\n"                 \
                     ".previous\n"              \
                     _ASM_EXTABLE(1b,3b)        \
                     : :"r" (value), "r" (0) : "memory")


saving and loading segment registers as in

savesegment(es, ctxt->es);
loadsegment(es, ctxt->es);

the code in cpu_64.c doesn't make use of such macros, doing the following:

saving:
 asm volatile ("movw %%es, %0" : "=m" (ctxt->es));

loading:
asm volatile ("movw %0, %%es" :: "r" (ctxt->es));

So, my question is... what's the actual difference between both
versions? Aren't the macros suitable for the 64 version as well?

Thanks,
Sergio.
--
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/