linux-kernel - Re: [PATCH v2 13/17] x86/tsc: Rename native_read_tsc() to rdtsc

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:	Sat, 13 Jun 2015 10:57:59 +0200
From:	Borislav Petkov <bp@...e.de>
To:	Andy Lutomirski <luto@...nel.org>
Cc:	x86@...nel.org, Peter Zijlstra <peterz@...radead.org>,
	John Stultz <john.stultz@...aro.org>,
	linux-kernel@...r.kernel.org, Len Brown <lenb@...nel.org>,
	Huang Rui <ray.huang@....com>,
	Denys Vlasenko <dvlasenk@...hat.com>
Subject: Re: [PATCH v2 13/17] x86/tsc: Rename native_read_tsc() to
 rdtsc_unordered()

On Fri, Jun 12, 2015 at 04:44:53PM -0700, Andy Lutomirski wrote:
> Now that there is no paravirt TSC, the "native" is inappropriate.
> The fact that rdtsc is not ordered can catch people by surprise, so
> call it rdtsc_unordered().
> 
> Signed-off-by: Andy Lutomirski <luto@...nel.org>

...

> @@ -109,7 +109,16 @@ notrace static inline int native_write_msr_safe(unsigned int msr,
>  extern int rdmsr_safe_regs(u32 regs[8]);
>  extern int wrmsr_safe_regs(u32 regs[8]);
>  
> -static __always_inline unsigned long long native_read_tsc(void)
> +/**
> + * rdtsc_unordered() - returns the current TSC without ordering constraints
> + *
> + * rdtsc_unordered() returns the result of RDTSC as a 64-bit integer.  The
> + * only ordering constraint it supplies is the ordering implied by
> + * "asm volatile": it will put the RDTSC in the place you expect.  The
> + * CPU can and will speculatively execute that RDTSC, though, so the
> + * results can be non-monotonic if compared on different CPUs.
> + */
> +static __always_inline unsigned long long rdtsc_unordered(void)

I like the rdtsc_ordered() thing because it wraps the barrier and people
cannot just forget it. But let's call this not rdtsc_unordered() but
simply

	rdtsc()

The "_unordered" suffix is unnecessary IMO since this function is a
simple wrapper around the hw insn and we do that naming scheme with all
such wrappers.

-- 
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/