linux-kernel - sort out the flush_icache

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Message-Id: <20200510075510.987823-1-hch@lst.de>
Date:   Sun, 10 May 2020 09:54:39 +0200
From:   Christoph Hellwig <hch@....de>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Arnd Bergmann <arnd@...db.de>,
        Roman Zippel <zippel@...ux-m68k.org>
Cc:     Jessica Yu <jeyu@...nel.org>, Michal Simek <monstr@...str.eu>,
        x86@...nel.org, linux-alpha@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-c6x-dev@...ux-c6x.org, linux-hexagon@...r.kernel.org,
        linux-ia64@...r.kernel.org, linux-m68k@...ts.linux-m68k.org,
        linux-mips@...r.kernel.org, openrisc@...ts.librecores.org,
        linuxppc-dev@...ts.ozlabs.org, linux-riscv@...ts.infradead.org,
        linux-sh@...r.kernel.org, sparclinux@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-mm@...ck.org,
        linux-um@...ts.infradead.org, linux-xtensa@...ux-xtensa.org,
        linux-fsdevel@...r.kernel.org
Subject: sort out the flush_icache_range mess

Hi all,

flush_icache_range is mostly used for kernel address, except for the following
cases:

 - the nommu brk and mmap implementations,
 - the read_code helper that is only used for binfmt_flat, binfmt_elf_fdpic,
   and binfmt_aout including the broken ia32 compat version
 - binfmt_flat itself,

none of which really are used by a typical MMU enabled kernel, as a.out can
only be build for alpha and m68k to start with.

But strangely enough commit ae92ef8a4424 ("PATCH] flush icache in correct
context") added a "set_fs(KERNEL_DS)" around the flush_icache_range call
in the module loader, because apparently m68k assumed user pointers.

This series first cleans up the cacheflush implementations, largely by
switching as much as possible to the asm-generic version after a few
preparations, then moves the misnamed current flush_icache_user_range to
a new name, to finally introduce a real flush_icache_user_range to be used
for the above use cases to flush the instruction cache for a userspace
address range.  The last patch then drops the set_fs in the module code
and moves it into the m68k implementation.

A git tree is available here:

    git://git.infradead.org/users/hch/misc.git flush_icache_range

Gitweb:

    http://git.infradead.org/users/hch/misc.git/shortlog/refs/heads/flush_icache_range