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Linux kernel source tree for SHARP Brain series (PW-SH1 or later)
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Ingo Molnar 1251201c0d sched/core: Fix uclamp ABI bug, clean up and robustify sched_read_attr() ABI logic and code 
Thadeu Lima de Souza Cascardo reported that 'chrt' broke on recent kernels:

  $ chrt -p $$
  chrt: failed to get pid 26306's policy: Argument list too long

and he has root-caused the bug to the following commit increasing sched_attr
size and breaking sched_read_attr() into returning -EFBIG:

  a509a7cd79 ("sched/uclamp: Extend sched_setattr() to support utilization clamping")

The other, bigger bug is that the whole sched_getattr() and sched_read_attr()
logic of checking non-zero bits in new ABI components is arguably broken,
and pretty much any extension of the ABI will spuriously break the ABI.
That's way too fragile.

Instead implement the perf syscall's extensible ABI instead, which we
already implement on the sched_setattr() side:

 - if user-attributes have the same size as kernel attributes then the
   logic is unchanged.

 - if user-attributes are larger than the kernel knows about then simply
   skip the extra bits, but set attr->size to the (smaller) kernel size
   so that tooling can (in principle) handle older kernel as well.

 - if user-attributes are smaller than the kernel knows about then just
   copy whatever user-space can accept.

Also clean up the whole logic:

 - Simplify the code flow - there's no need for 'ret' for example.

 - Standardize on 'kattr/uattr' and 'ksize/usize' naming to make sure we
   always know which side we are dealing with.

 - Why is it called 'read' when what it does is to copy to user? This
   code is so far away from VFS read() semantics that the naming is
   actively confusing. Name it sched_attr_copy_to_user() instead, which
   mirrors other copy_to_user() functionality.

 - Move the attr->size assignment from the head of sched_getattr() to the
   sched_attr_copy_to_user() function. Nothing else within the kernel
   should care about the size of the structure.

With these fixes the sched_getattr() syscall now nicely supports an
extensible ABI in both a forward and backward compatible fashion, and
will also fix the chrt bug.

As an added bonus the bogus -EFBIG return is removed as well, which as
Thadeu noted should have been -E2BIG to begin with.

Reported-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Tested-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Acked-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Patrick Bellasi <patrick.bellasi@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: a509a7cd79 ("sched/uclamp: Extend sched_setattr() to support utilization clamping")
Link: https://lkml.kernel.org/r/20190904075532.GA26751@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2019-09-04 19:51:30 +02:00
arch Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-09-01 11:21:57 -07:00
block block: remove REQ_NOWAIT_INLINE 2019-08-15 11:09:16 -06:00
certs Revert "Merge tag 'keys-acl-20190703' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs" 2019-07-10 18:43:43 -07:00
crypto USB / PHY patches for 5.3-rc1 2019-07-11 15:40:06 -07:00
Documentation Char/Misc driver fixes for 5.3-rc7 2019-09-02 09:30:34 -07:00
drivers Char/Misc driver fixes for 5.3-rc7 2019-09-02 09:30:34 -07:00
fs a few small SMB3 fixes, and a larger one to fix various older string handling functions 2019-08-29 17:51:23 -07:00
include Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2019-09-01 18:45:28 -07:00
init Merge branch 'work.mount0' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-07-19 10:42:02 -07:00
ipc Merge branch 'work.mount0' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-07-19 10:42:02 -07:00
kernel sched/core: Fix uclamp ABI bug, clean up and robustify sched_read_attr() ABI logic and code 2019-09-04 19:51:30 +02:00
lib Partially revert "kfifo: fix kfifo_alloc() and kfifo_init()" 2019-08-30 18:47:15 -07:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
mm mm: memcontrol: fix percpu vmstats and vmevents flush 2019-08-30 18:00:50 -07:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2019-09-01 18:45:28 -07:00
samples auxdisplay: Fix a typo in cfag12864b-example.c 2019-08-08 20:00:18 +02:00
scripts SPDX fixes for 5.3-rc5 2019-08-18 09:26:16 -07:00
security keys: ensure that ->match_free() is called in request_key_and_link() 2019-08-30 11:10:55 -07:00
sound sound fixes for 5.3-rc7 2019-08-27 10:42:03 -07:00
tools Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2019-09-01 18:45:28 -07:00
usr kbuild: enable arch/s390/include/uapi/asm/zcrypt.h for uapi header test 2019-07-23 10:45:46 +02:00
virt arm64 fixes for -rc7 2019-08-28 10:37:21 -07:00
.clang-format Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-04-17 11:26:25 -07:00
.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: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore .gitignore: Add compilation database file 2019-07-27 12:18:19 +09:00
.mailmap mailmap: add aliases for Dmitry Safonov 2019-08-30 18:00:50 -07:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS Remove references to dead website. 2019-07-19 12:22:04 -07:00
Kbuild Kbuild updates for v5.1 2019-03-10 17:48:21 -07:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS Char/Misc driver fixes for 5.3-rc7 2019-09-02 09:30:34 -07:00
Makefile Linux 5.3-rc7 2019-09-02 09:57:40 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

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.