linux-kernel - Re: [v3, 3/3] MIPS: VDSO: Add implementations of gettimeofday() and clock

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

Date:	Thu, 22 Oct 2015 18:41:30 -0700
From:	Leonid Yegoshin <Leonid.Yegoshin@...tec.com>
To:	Markos Chandras <markos.chandras@...tec.com>,
	<linux-mips@...ux-mips.org>
CC:	Alex Smith <alex.smith@...tec.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [v3, 3/3] MIPS: VDSO: Add implementations of gettimeofday() and
 clock_gettime()

You can not use R4K CP0_count in SMP (multicore) without core-specific 
adjustment.
After first power-saving with core clock off or core down the values in 
CP0_count
in different cores are absolutely different.

Until you include in system a patch like 
http://patchwork.linux-mips.org/patch/10871/

     "MIPS: Setup an instruction emulation in VDSO protected page 
instead of user stack"

which creates a per-thread memory and put into that memory an adjustment 
value
(which can be changed during re-schedule to another core), the use of 
R4K counter is incorrect
in SMP environment.

Note: It is also possible to setup and maintain a per-core page with 
that value too as
an alternative variant for adjustment.
--
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/