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Ard Biesheuvel 50596b7559 ARM: smp: Store current pointer in TPIDRURO register if available
Now that the user space TLS register is assigned on every return to user
space, we can use it to keep the 'current' pointer while running in the
kernel. This removes the need to access it via thread_info, which is
located at the base of the stack, but will be moved out of there in a
subsequent patch.

Use the __builtin_thread_pointer() helper when available - this will
help GCC understand that reloading the value within the same function is
not necessary, even when using the per-task stack protector (which also
generates accesses via the TLS register). For example, the generated
code below loads TPIDRURO only once, and uses it to access both the
stack canary and the preempt_count fields.

<do_one_initcall>:
       e92d 41f0       stmdb   sp!, {r4, r5, r6, r7, r8, lr}
       ee1d 4f70       mrc     15, 0, r4, cr13, cr0, {3}
       4606            mov     r6, r0
       b094            sub     sp, #80 ; 0x50
       f8d4 34e8       ldr.w   r3, [r4, #1256] ; 0x4e8  <- stack canary
       9313            str     r3, [sp, #76]   ; 0x4c
       f8d4 8004       ldr.w   r8, [r4, #4]             <- preempt count

Co-developed-by: Keith Packard <keithpac@amazon.com>
Signed-off-by: Keith Packard <keithpac@amazon.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
History 2021-09-27 16:54:02 +02:00
arch ARM: smp: Store current pointer in TPIDRURO register if available 2021-09-27 16:54:02 +02:00
block block-5.15-2021-09-11 2021-09-11 10:19:51 -07:00
certs certs: Add support for using elliptic curve keys for signing modules 2021-08-23 19:55:42 +03:00
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2021-08-30 12:57:10 -07:00
Documentation An assortment of improvements for auxdisplay: 2021-09-12 16:00:49 -07:00
drivers An assortment of improvements for auxdisplay: 2021-09-12 16:00:49 -07:00
fs Merge branch 'misc.namei' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2021-09-12 10:43:51 -07:00
include Compiler Attributes improvements: 2021-09-12 16:09:26 -07:00
init More tracing updates for 5.15: 2021-09-09 13:11:15 -07:00
ipc ARM development updates for 5.15: 2021-09-09 13:25:49 -07:00
kernel - Make sure the idle timer expires in hardirq context, on PREEMPT_RT 2021-09-12 11:37:41 -07:00
lib Minor fixes to the processing of the bootconfig tree. 2021-09-11 10:16:30 -07:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm ARM development updates for 5.15: 2021-09-09 13:25:49 -07:00
net virtio,vdpa,vhost: features, fixes 2021-09-11 14:48:42 -07:00
samples kgdb patches for 5.15 2021-09-07 12:08:04 -07:00
scripts gcc-plugins: arm-ssp: Prepare for THREAD_INFO_IN_TASK support 2021-09-27 16:54:01 +02:00
security Kbuild updates for v5.15 2021-09-03 15:33:47 -07:00
sound sound fixes for 5.15-rc1 2021-09-09 16:05:10 -07:00
tools perf tools changes for v5.15: 2nd batch 2021-09-12 16:18:15 -07:00
usr .gitignore: prefix local generated files with a slash 2021-05-02 00:43:35 +09:00
virt KVM: Drop unused kvm_dirty_gfn_invalid() 2021-09-06 08:23:46 -04:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap mailmap: update email address of Matthias Fuchs and Thomas Körper 2021-08-19 09:39:44 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: move Murali Karicheri to credits 2021-04-29 15:47:30 -07:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Compiler Attributes improvements: 2021-09-12 16:09:26 -07:00
Makefile Linux 5.15-rc1 2021-09-12 16:28:37 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

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.