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Arnd Bergmann 0763f0418b mtd: cfi: convert inline functions to macros 
commit 9e343e87d2 upstream.

The map_word_() functions, dating back to linux-2.6.8, try to perform
bitwise operations on a 'map_word' structure. This may have worked
with compilers that were current then (gcc-3.4 or earlier), but end
up being rather inefficient on any version I could try now (gcc-4.4 or
higher). Specifically we hit a problem analyzed in gcc PR81715 where we
fail to reuse the stack space for local variables.

This can be seen immediately in the stack consumption for
cfi_staa_erase_varsize() and other functions that (with CONFIG_KASAN)
can be up to 2200 bytes. Changing the inline functions into macros brings
this down to 1280 bytes.  Without KASAN, the same problem exists, but
the stack consumption is lower to start with, my patch shrinks it from
920 to 496 bytes on with arm-linux-gnueabi-gcc-5.4, and saves around
1KB in .text size for cfi_cmdset_0020.c, as it avoids copying map_word
structures for each call to one of these helpers.

With the latest gcc-8 snapshot, the problem is fixed in upstream gcc,
but nobody uses that yet, so we should still work around it in mainline
kernels and probably backport the workaround to stable kernels as well.
We had a couple of other functions that suffered from the same gcc bug,
and all of those had a simpler workaround involving dummy variables
in the inline function. Unfortunately that did not work here, the
macro hack was the best I could come up with.

It would also be helpful to have someone to a little performance testing
on the patch, to see how much it helps in terms of CPU utilitzation.

Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81715
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2018-02-16 20:22:56 +01:00
arch arm64: Kill PSCI_GET_VERSION as a variant-2 workaround 2018-02-16 20:22:56 +01:00
block block: don't let passthrough IO go into .make_request_fn() 2018-01-02 20:31:05 +01:00
certs License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
crypto crypto: tcrypt - fix S/G table for test_aead_speed() 2018-02-13 10:19:49 +01:00
Documentation arm64: cpu_errata: Add Kryo to Falkor 1003 errata 2018-02-16 20:22:48 +01:00
drivers firmware/psci: Expose SMCCC version through psci_ops 2018-02-16 20:22:56 +01:00
firmware License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
fs CIFS: zero sensitive data when freeing 2018-02-16 20:22:43 +01:00
include mtd: cfi: convert inline functions to macros 2018-02-16 20:22:56 +01:00
init bpf: introduce BPF_JIT_ALWAYS_ON config 2018-01-31 14:03:49 +01:00
ipc License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
kernel sched/rt: Up the root domain ref count when passing it around via IPIs 2018-02-16 20:22:44 +01:00
lib test_firmware: fix missing unlock on error in config_num_requests_store() 2018-02-03 17:39:24 +01:00
mm Revert "defer call to mem_cgroup_sk_alloc()" 2018-02-13 10:19:48 +01:00
net dccp: CVE-2017-8824: use-after-free in DCCP code 2018-02-16 20:22:45 +01:00
samples samples/bpf: adjust rlimit RLIMIT_MEMLOCK for xdp1 2017-12-20 10:10:31 +01:00
scripts kbuild: rpm-pkg: keep spec file until make mrproper 2018-02-13 10:19:46 +01:00
security ima/policy: fix parsing of fsuuid 2018-02-03 17:38:53 +01:00
sound ASoC: pcm512x: add missing MODULE_DESCRIPTION/AUTHOR/LICENSE 2018-02-07 11:12:20 -08:00
tools objtool: Warn on stripped section symbol 2018-02-07 11:12:21 -08:00
usr initramfs: fix initramfs rebuilds w/ compression after disabling 2017-11-03 07:39:19 -07:00
virt arm64: KVM: Report SMCCC_ARCH_WORKAROUND_1 BP hardening support 2018-02-16 20:22:55 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Add hch to .get_maintainer.ignore 2015-08-21 14:30:10 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore kbuild: rpm-pkg: keep spec file until make mrproper 2018-02-13 10:19:46 +01:00
.mailmap .mailmap: Add Maciej W. Rozycki's Imagination e-mail address 2017-11-10 12:16:15 -08:00
COPYING [PATCH] update FSF address in COPYING 2005-09-10 10:06:29 -07:00
CREDITS MAINTAINERS: update TPM driver infrastructure changes 2017-11-09 17:58:40 -08:00
Kbuild License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
Kconfig License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
MAINTAINERS Merge branch 'akpm' (patches from Andrew) 2017-11-09 18:26:51 -08:00
Makefile Linux 4.14.19 2018-02-13 10:19:50 +01:00
README README: add a new README file, pointing to the Documentation/ 2016-10-24 08:12:35 -02:00

README 

Linux kernel
============

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.