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.
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.
code
Clone this repository
https://tangled.org/tjh.dev/kernel
git@gordian.tjh.dev:tjh.dev/kernel
For self-hosted knots, clone URLs may differ based on your setup.
Pull x86 fixes from Thomas Gleixner:
"Another set of x86 related updates:
- Fix the long broken x32 version of the IPC user space headers which
was noticed by Arnd Bergman in course of his ongoing y2038 work.
GLIBC seems to have non broken private copies of these headers so
this went unnoticed.
- Two microcode fixlets which address some more fallout from the
recent modifications in that area:
- Unconditionally save the microcode patch, which was only saved
when CPU_HOTPLUG was enabled causing failures in the late
loading mechanism
- Make the later loader synchronization finally work under all
circumstances. It was exiting early and causing timeout failures
due to a missing synchronization point.
- Do not use mwait_play_dead() on AMD systems to prevent excessive
power consumption as the CPU cannot go into deep power states from
there.
- Address an annoying sparse warning due to lost type qualifiers of
the vmemmap and vmalloc base address constants.
- Prevent reserving crash kernel region on Xen PV as this leads to
the wrong perception that crash kernels actually work there which
is not the case. Xen PV has its own crash mechanism handled by the
hypervisor.
- Add missing TLB cpuid values to the table to make the printout on
certain machines correct.
- Enumerate the new CLDEMOTE instruction
- Fix an incorrect SPDX identifier
- Remove stale macros"
* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/ipc: Fix x32 version of shmid64_ds and msqid64_ds
x86/setup: Do not reserve a crash kernel region if booted on Xen PV
x86/cpu/intel: Add missing TLB cpuid values
x86/smpboot: Don't use mwait_play_dead() on AMD systems
x86/mm: Make vmemmap and vmalloc base address constants unsigned long
x86/vector: Remove the unused macro FPU_IRQ
x86/vector: Remove the macro VECTOR_OFFSET_START
x86/cpufeatures: Enumerate cldemote instruction
x86/microcode: Do not exit early from __reload_late()
x86/microcode/intel: Save microcode patch unconditionally
x86/jailhouse: Fix incorrect SPDX identifier
Pull x86 pti fixes from Thomas Gleixner:
"A set of updates for the x86/pti related code:
- Preserve r8-r11 in int $0x80. r8-r11 need to be preserved, but the
int$80 entry code removed that quite some time ago. Make it correct
again.
- A set of fixes for the Global Bit work which went into 4.17 and
caused a bunch of interesting regressions:
- Triggering a BUG in the page attribute code due to a missing
check for early boot stage
- Warnings in the page attribute code about holes in the kernel
text mapping which are caused by the freeing of the init code.
Handle such holes gracefully.
- Reduce the amount of kernel memory which is set global to the
actual text and do not incidentally overlap with data.
- Disable the global bit when RANDSTRUCT is enabled as it
partially defeats the hardening.
- Make the page protection setup correct for vma->page_prot
population again. The adjustment of the protections fell through
the crack during the Global bit rework and triggers warnings on
machines which do not support certain features, e.g. NX"
* 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/entry/64/compat: Preserve r8-r11 in int $0x80
x86/pti: Filter at vma->vm_page_prot population
x86/pti: Disallow global kernel text with RANDSTRUCT
x86/pti: Reduce amount of kernel text allowed to be Global
x86/pti: Fix boot warning from Global-bit setting
x86/pti: Fix boot problems from Global-bit setting
A bugfix broke the x32 shmid64_ds and msqid64_ds data structure layout
(as seen from user space) a few years ago: Originally, __BITS_PER_LONG
was defined as 64 on x32, so we did not have padding after the 64-bit
__kernel_time_t fields, After __BITS_PER_LONG got changed to 32,
applications would observe extra padding.
In other parts of the uapi headers we seem to have a mix of those
expecting either 32 or 64 on x32 applications, so we can't easily revert
the path that broke these two structures.
Instead, this patch decouples x32 from the other architectures and moves
it back into arch specific headers, partially reverting the even older
commit 73a2d096fdf2 ("x86: remove all now-duplicate header files").
It's not clear whether this ever made any difference, since at least
glibc carries its own (correct) copy of both of these header files,
so possibly no application has ever observed the definitions here.
Based on a suggestion from H.J. Lu, I tried out the tool from
https://github.com/hjl-tools/linux-header to find other such
bugs, which pointed out the same bug in statfs(), which also has
a separate (correct) copy in glibc.
Fixes: f4b4aae18288 ("x86/headers/uapi: Fix __BITS_PER_LONG value for x32 builds")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: "H . J . Lu" <hjl.tools@gmail.com>
Cc: Jeffrey Walton <noloader@gmail.com>
Cc: stable@vger.kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>
Link: https://lkml.kernel.org/r/20180424212013.3967461-1-arnd@arndb.de
Pull timer fixes from Thomas Gleixner:
"Two fixes from the timer departement:
- Fix a long standing issue in the NOHZ tick code which causes RB
tree corruption, delayed timers and other malfunctions. The cause
for this is code which modifies the expiry time of an enqueued
hrtimer.
- Revert the CLOCK_MONOTONIC/CLOCK_BOOTTIME unification due to
regression reports. Seems userspace _is_ relying on the documented
behaviour despite our hope that it wont"
* 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
Revert: Unify CLOCK_MONOTONIC and CLOCK_BOOTTIME
tick/sched: Do not mess with an enqueued hrtimer
32-bit user code that uses int $80 doesn't care about r8-r11. There is,
however, some 64-bit user code that intentionally uses int $0x80 to invoke
32-bit system calls. From what I've seen, basically all such code assumes
that r8-r15 are all preserved, but the kernel clobbers r8-r11. Since I
doubt that there's any code that depends on int $0x80 zeroing r8-r11,
change the kernel to preserve them.
I suspect that very little user code is broken by the old clobber, since
r8-r11 are only rarely allocated by gcc, and they're clobbered by function
calls, so they only way we'd see a problem is if the same function that
invokes int $0x80 also spills something important to one of these
registers.
The current behavior seems to date back to the historical commit
"[PATCH] x86-64 merge for 2.6.4". Before that, all regs were
preserved. I can't find any explanation of why this change was made.
Update the test_syscall_vdso_32 testcase as well to verify the new
behavior, and it strengthens the test to make sure that the kernel doesn't
accidentally permute r8..r15.
Suggested-by: Denys Vlasenko <dvlasenk@redhat.com>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dominik Brodowski <linux@dominikbrodowski.net>
Link: https://lkml.kernel.org/r/d4c4d9985fbe64f8c9e19291886453914b48caee.1523975710.git.luto@kernel.org
Xen PV domains cannot shut down and start a crash kernel. Instead,
the crashing kernel makes a SCHEDOP_shutdown hypercall with the
reason code SHUTDOWN_crash, cf. xen_crash_shutdown() machine op in
arch/x86/xen/enlighten_pv.c.
A crash kernel reservation is merely a waste of RAM in this case. It
may also confuse users of kexec_load(2) and/or kexec_file_load(2).
When flags include KEXEC_ON_CRASH or KEXEC_FILE_ON_CRASH,
respectively, these syscalls return success, which is technically
correct, but the crash kexec image will never be actually used.
Signed-off-by: Petr Tesarik <ptesarik@suse.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Juergen Gross <jgross@suse.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Dou Liyang <douly.fnst@cn.fujitsu.com>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: xen-devel@lists.xenproject.org
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Jean Delvare <jdelvare@suse.de>
Link: https://lkml.kernel.org/r/20180425120835.23cef60c@ezekiel.suse.cz
Pull perf fixes from Thomas Gleixner:
"The perf update contains the following bits:
x86:
- Prevent setting freeze_on_smi on PerfMon V1 CPUs to avoid #GP
perf stat:
- Keep the '/' event modifier separator in fallback, for example when
fallbacking from 'cpu/cpu-cycles/' to user level only, where it
should become 'cpu/cpu-cycles/u' and not 'cpu/cpu-cycles/:u' (Jiri
Olsa)
- Fix PMU events parsing rule, improving error reporting for invalid
events (Jiri Olsa)
- Disable write_backward and other event attributes for !group events
in a group, fixing, for instance this group: '{cycles,msr/aperf/}:S'
that has leader sampling (:S) and where just the 'cycles', the
leader event, should have the write_backward attribute set, in this
case it all fails because the PMU where 'msr/aperf/' lives doesn't
accepts write_backward style sampling (Jiri Olsa)
- Only fall back group read for leader (Kan Liang)
- Fix core PMU alias list for x86 platform (Kan Liang)
- Print out hint for mixed PMU group error (Kan Liang)
- Fix duplicate PMU name for interval print (Kan Liang)
Core:
- Set main kernel end address properly when reading kernel and module
maps (Namhyung Kim)
perf mem:
- Fix incorrect entries and add missing man options (Sangwon Hong)
s/390:
- Remove s390 specific strcmp_cpuid_cmp function (Thomas Richter)
- Adapt 'perf test' case record+probe_libc_inet_pton.sh for s390
- Fix s390 undefined record__auxtrace_init() return value in 'perf
record' (Thomas Richter)"
* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
perf/x86/intel: Don't enable freeze-on-smi for PerfMon V1
perf stat: Fix duplicate PMU name for interval print
perf evsel: Only fall back group read for leader
perf stat: Print out hint for mixed PMU group error
perf pmu: Fix core PMU alias list for X86 platform
perf record: Fix s390 undefined record__auxtrace_init() return value
perf mem: Document incorrect and missing options
perf evsel: Disable write_backward for leader sampling group events
perf pmu: Fix pmu events parsing rule
perf stat: Keep the / modifier separator in fallback
perf test: Adapt test case record+probe_libc_inet_pton.sh for s390
perf list: Remove s390 specific strcmp_cpuid_cmp function
perf machine: Set main kernel end address properly
Revert commits
92af4dcb4e1c ("tracing: Unify the "boot" and "mono" tracing clocks")
127bfa5f4342 ("hrtimer: Unify MONOTONIC and BOOTTIME clock behavior")
7250a4047aa6 ("posix-timers: Unify MONOTONIC and BOOTTIME clock behavior")
d6c7270e913d ("timekeeping: Remove boot time specific code")
f2d6fdbfd238 ("Input: Evdev - unify MONOTONIC and BOOTTIME clock behavior")
d6ed449afdb3 ("timekeeping: Make the MONOTONIC clock behave like the BOOTTIME clock")
72199320d49d ("timekeeping: Add the new CLOCK_MONOTONIC_ACTIVE clock")
As stated in the pull request for the unification of CLOCK_MONOTONIC and
CLOCK_BOOTTIME, it was clear that we might have to revert the change.
As reported by several folks systemd and other applications rely on the
documented behaviour of CLOCK_MONOTONIC on Linux and break with the above
changes. After resume daemons time out and other timeout related issues are
observed. Rafael compiled this list:
* systemd kills daemons on resume, after >WatchdogSec seconds
of suspending (Genki Sky). [Verified that that's because systemd uses
CLOCK_MONOTONIC and expects it to not include the suspend time.]
* systemd-journald misbehaves after resume:
systemd-journald[7266]: File /var/log/journal/016627c3c4784cd4812d4b7e96a34226/system.journal
corrupted or uncleanly shut down, renaming and replacing.
(Mike Galbraith).
* NetworkManager reports "networking disabled" and networking is broken
after resume 50% of the time (Pavel). [May be because of systemd.]
* MATE desktop dims the display and starts the screensaver right after
system resume (Pavel).
* Full system hang during resume (me). [May be due to systemd or NM or both.]
That happens on debian and open suse systems.
It's sad, that these problems were neither catched in -next nor by those
folks who expressed interest in this change.
Reported-by: Rafael J. Wysocki <rjw@rjwysocki.net>
Reported-by: Genki Sky <sky@genki.is>,
Reported-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kevin Easton <kevin@guarana.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mark Salyzyn <salyzyn@android.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
commit ce9962bf7e22bb3891655c349faff618922d4a73
0day reported warnings at boot on 32-bit systems without NX support:
attempted to set unsupported pgprot: 8000000000000025 bits: 8000000000000000 supported: 7fffffffffffffff
WARNING: CPU: 0 PID: 1 at
arch/x86/include/asm/pgtable.h:540 handle_mm_fault+0xfc1/0xfe0:
check_pgprot at arch/x86/include/asm/pgtable.h:535
(inlined by) pfn_pte at arch/x86/include/asm/pgtable.h:549
(inlined by) do_anonymous_page at mm/memory.c:3169
(inlined by) handle_pte_fault at mm/memory.c:3961
(inlined by) __handle_mm_fault at mm/memory.c:4087
(inlined by) handle_mm_fault at mm/memory.c:4124
The problem is that due to the recent commit which removed auto-massaging
of page protections, filtering page permissions at PTE creation time is not
longer done, so vma->vm_page_prot is passed unfiltered to PTE creation.
Filter the page protections before they are installed in vma->vm_page_prot.
Fixes: fb43d6cb91 ("x86/mm: Do not auto-massage page protections")
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Kees Cook <keescook@google.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: linux-mm@kvack.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Nadav Amit <namit@vmware.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Link: https://lkml.kernel.org/r/20180420222028.99D72858@viggo.jf.intel.com
Make kernel print the correct number of TLB entries on Intel Xeon Phi 7210
(and others)
Before:
[ 0.320005] Last level dTLB entries: 4KB 0, 2MB 0, 4MB 0, 1GB 0
After:
[ 0.320005] Last level dTLB entries: 4KB 256, 2MB 128, 4MB 128, 1GB 16
The entries do exist in the official Intel SMD but the type column there is
incorrect (states "Cache" where it should read "TLB"), but the entries for
the values 0x6B, 0x6C and 0x6D are correctly described as 'Data TLB'.
Signed-off-by: Jacek Tomaka <jacek.tomaka@poczta.fm>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20180423161425.24366-1-jacekt@dugeo.com
Pull ext4 fixes from Ted Ts'o:
"Fix misc bugs and a regression for ext4"
* tag 'for_linus_stable' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4:
ext4: add MODULE_SOFTDEP to ensure crc32c is included in the initramfs
ext4: fix bitmap position validation
ext4: set h_journal if there is a failure starting a reserved handle
ext4: prevent right-shifting extents beyond EXT_MAX_BLOCKS
Pull perf/urgent fixes from Arnaldo Carvalho de Melo:
perf stat:
- Keep the '/' event modifier separator in fallback, for example when
fallbacking from 'cpu/cpu-cycles/' to user level only, where it should
become 'cpu/cpu-cycles/u' and not 'cpu/cpu-cycles/:u' (Jiri Olsa)
- Fix PMU events parsing rule, improving error reporting for
invalid events (Jiri Olsa)
- Disable write_backward and other event attributes for !group
events in a group, fixing, for instance this group: '{cycles,msr/aperf/}:S'
that has leader sampling (:S) and where just the 'cycles',
the leader event, should have the write_backward attribute
set, in this case it all fails because the PMU where 'msr/aperf/'
lives doesn't accepts write_backward style sampling (Jiri Olsa)
- Only fall back group read for leader (Kan Liang)
- Fix core PMU alias list for x86 platform (Kan Liang)
- Print out hint for mixed PMU group error (Kan Liang)
- Fix duplicate PMU name for interval print (Kan Liang)
Core:
- Set main kernel end address properly when reading kernel and
module maps (Namhyung Kim)
perf mem:
- Fix incorrect entries and add missing man options (Sangwon Hong)
s/390:
- Remove s390 specific strcmp_cpuid_cmp function (Thomas Richter)
- Adapt 'perf test' case record+probe_libc_inet_pton.sh for s390
- Fix s390 undefined record__auxtrace_init() return value in
'perf record' (Thomas Richter)
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Kaike reported that in tests rdma hrtimers occasionaly stopped working. He
did great debugging, which provided enough context to decode the problem.
CPU 3 CPU 2
idle
start sched_timer expires = 712171000000
queue->next = sched_timer
start rdmavt timer. expires = 712172915662
lock(baseof(CPU3))
tick_nohz_stop_tick()
tick = 716767000000 timerqueue_add(tmr)
hrtimer_set_expires(sched_timer, tick);
sched_timer->expires = 716767000000 <---- FAIL
if (tmr->expires < queue->next->expires)
hrtimer_start(sched_timer) queue->next = tmr;
lock(baseof(CPU3))
unlock(baseof(CPU3))
timerqueue_remove()
timerqueue_add()
ts->sched_timer is queued and queue->next is pointing to it, but then
ts->sched_timer.expires is modified.
This not only corrupts the ordering of the timerqueue RB tree, it also
makes CPU2 see the new expiry time of timerqueue->next->expires when
checking whether timerqueue->next needs to be updated. So CPU2 sees that
the rdma timer is earlier than timerqueue->next and sets the rdma timer as
new next.
Depending on whether it had also seen the new time at RB tree enqueue, it
might have queued the rdma timer at the wrong place and then after removing
the sched_timer the RB tree is completely hosed.
The problem was introduced with a commit which tried to solve inconsistency
between the hrtimer in the tick_sched data and the underlying hardware
clockevent. It split out hrtimer_set_expires() to store the new tick time
in both the NOHZ and the NOHZ + HIGHRES case, but missed the fact that in
the NOHZ + HIGHRES case the hrtimer might still be queued.
Use hrtimer_start(timer, tick...) for the NOHZ + HIGHRES case which sets
timer->expires after canceling the timer and move the hrtimer_set_expires()
invocation into the NOHZ only code path which is not affected as it merily
uses the hrtimer as next event storage so code pathes can be shared with
the NOHZ + HIGHRES case.
Fixes: d4af6d933ccf ("nohz: Fix spurious warning when hrtimer and clockevent get out of sync")
Reported-by: "Wan Kaike" <kaike.wan@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Cc: "Marciniszyn Mike" <mike.marciniszyn@intel.com>
Cc: Anna-Maria Gleixner <anna-maria@linutronix.de>
Cc: linux-rdma@vger.kernel.org
Cc: "Dalessandro Dennis" <dennis.dalessandro@intel.com>
Cc: "Fleck John" <john.fleck@intel.com>
Cc: stable@vger.kernel.org
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: "Weiny Ira" <ira.weiny@intel.com>
Cc: "linux-rdma@vger.kernel.org"
Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1804241637390.1679@nanos.tec.linutronix.de
Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1804242119210.1597@nanos.tec.linutronix.de
commit 26d35ca6c3776784f8156e1d6f80cc60d9a2a915
RANDSTRUCT derives its hardening benefits from the attacker's lack of
knowledge about the layout of kernel data structures. Keep the kernel
image non-global in cases where RANDSTRUCT is in use to help keep the
layout a secret.
Fixes: 8c06c7740 (x86/pti: Leave kernel text global for !PCID)
Reported-by: Kees Cook <keescook@google.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: linux-mm@kvack.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Nadav Amit <namit@vmware.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Link: https://lkml.kernel.org/r/20180420222026.D0B4AAC9@viggo.jf.intel.com