linux-kernel - range operation of outer cache when start >= end?

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]

Date:	Fri, 8 Jan 2016 11:54:30 +0900
From:	Masahiro Yamada <yamada.masahiro@...ionext.com>
To:	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Arnd Bergmann <arnd@...db.de>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: range operation of outer cache when start >= end?

Hi.


I know I am nitpicking.  Forgive me if I am asking a silly question.


How should the outer-cache handle such an insane case like  start >= end?

Assumed answers are:

[1] Do not care about that.  It should never happen.  If it does, fix
the caller.

[2]  Add   "if (start < end)" checking to
      outer_inv_range(), outer_clean_range(), outer_flush_range()
      in arch/arm/include/asm/outercache.h

[3] It should be cared in each of callbacks as needed



For example, l2c210_inv_range()
flushes the both ends of the range even if start >= end.

In this case, there is nothing to do, so should it have something like this?
    if (start >= end)
                 return;


static void l2c210_inv_range(unsigned long start, unsigned long end)
{
        void __iomem *base = l2x0_base;

        if (start & (CACHE_LINE_SIZE - 1)) {
                  start &= ~(CACHE_LINE_SIZE - 1);
                  writel_relaxed(start, base + L2X0_CLEAN_INV_LINE_PA);
                  start += CACHE_LINE_SIZE;
        }

        if (end & (CACHE_LINE_SIZE - 1)) {
                  end &= ~(CACHE_LINE_SIZE - 1);
                  writel_relaxed(end, base + L2X0_CLEAN_INV_LINE_PA);
        }

        __l2c210_op_pa_range(base + L2X0_INV_LINE_PA, start, end);
        __l2c210_cache_sync(base);
}





-- 
Best Regards
Masahiro Yamada