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Linux kernel
============
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In order to build the documentation, use ``make htmldocs`` or
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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.
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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Pull Kbuild fixes from Masahiro Yamada:
- ignore compiler stubs for PPC to fix builds
- fix the usage of --target mentioned in the LLVM document
* tag 'kbuild-fixes-v5.9-4' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
Documentation/llvm: Fix clang target examples
scripts/kallsyms: skip ppc compiler stub *.long_branch.* / *.plt_branch.*
Pull x86 fixes from Thomas Gleixner:
"Two fixes for the x86 interrupt code:
- Unbreak the magic 'search the timer interrupt' logic in IO/APIC
code which got wreckaged when the core interrupt code made the
state tracking logic stricter.
That caused the interrupt line to stay masked after switching from
IO/APIC to PIC delivery mode, which obviously prevents interrupts
from being delivered.
- Make run_on_irqstack_code() typesafe. The function argument is a
void pointer which is then cast to 'void (*fun)(void *).
This breaks Control Flow Integrity checking in clang. Use proper
helper functions for the three variants reuqired"
* tag 'x86-urgent-2020-09-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/ioapic: Unbreak check_timer()
x86/irq: Make run_on_irqstack_cond() typesafe
clang --target=<triple> is how we can specify a particular toolchain
triple to be use, fix the two occurences in the documentation.
Fixes: fcf1b6a35c16 ("Documentation/llvm: add documentation on building w/ Clang/LLVM")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Pull timer updates from Thomas Gleixner:
"A set of clocksource/clockevents updates:
- Reset the TI/DM timer before enabling it instead of doing it the
other way round.
- Initialize the reload value for the GX6605s timer correctly so the
hardware counter starts at 0 again after overrun.
- Make error return value negative in the h8300 timer init function"
* tag 'timers-urgent-2020-09-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
clocksource/drivers/timer-gx6605s: Fixup counter reload
clocksource/drivers/timer-ti-dm: Do reset before enable
clocksource/drivers/h8300_timer8: Fix wrong return value in h8300_8timer_init()
Several people reported in the kernel bugzilla that between v4.12 and v4.13
the magic which works around broken hardware and BIOSes to find the proper
timer interrupt delivery mode stopped working for some older affected
platforms which need to fall back to ExtINT delivery mode.
The reason is that the core code changed to keep track of the masked and
disabled state of an interrupt line more accurately to avoid the expensive
hardware operations.
That broke an assumption in i8259_make_irq() which invokes
disable_irq_nosync();
irq_set_chip_and_handler();
enable_irq();
Up to v4.12 this worked because enable_irq() unconditionally unmasked the
interrupt line, but after the state tracking improvements this is not
longer the case because the IO/APIC uses lazy disabling. So the line state
is unmasked which means that enable_irq() does not call into the new irq
chip to unmask it.
In principle this is a shortcoming of the core code, but it's more than
unclear whether the core code should try to reset state. At least this
cannot be done unconditionally as that would break other existing use cases
where the chip type is changed, e.g. when changing the trigger type, but
the callers expect the state to be preserved.
As the way how check_timer() is switching the delivery modes is truly
unique, the obvious fix is to simply unmask the i8259 manually after
changing the mode to ExtINT delivery and switching the irq chip to the
legacy PIC.
Note, that the fixes tag is not really precise, but identifies the commit
which broke the assumptions in the IO/APIC and i8259 code and that's the
kernel version to which this needs to be backported.
Fixes: bf22ff45bed6 ("genirq: Avoid unnecessary low level irq function calls")
Reported-by: p_c_chan@hotmail.com
Reported-by: ecm4@mail.com
Reported-by: perdigao1@yahoo.com
Reported-by: matzes@users.sourceforge.net
Reported-by: rvelascog@gmail.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: p_c_chan@hotmail.com
Tested-by: matzes@users.sourceforge.net
Cc: stable@vger.kernel.org
Link: https://bugzilla.kernel.org/show_bug.cgi?id=197769
PowerPC allmodconfig often fails to build as follows:
LD .tmp_vmlinux.kallsyms1
KSYM .tmp_vmlinux.kallsyms1.o
LD .tmp_vmlinux.kallsyms2
KSYM .tmp_vmlinux.kallsyms2.o
LD .tmp_vmlinux.kallsyms3
KSYM .tmp_vmlinux.kallsyms3.o
LD vmlinux
SORTTAB vmlinux
SYSMAP System.map
Inconsistent kallsyms data
Try make KALLSYMS_EXTRA_PASS=1 as a workaround
make[2]: *** [../Makefile:1162: vmlinux] Error 1
Setting KALLSYMS_EXTRA_PASS=1 does not help.
This is caused by the compiler inserting stubs such as *.long_branch.*
and *.plt_branch.*
$ powerpc-linux-nm -n .tmp_vmlinux.kallsyms2
[ snip ]
c00000000210c010 t 00000075.plt_branch.da9:19
c00000000210c020 t 00000075.plt_branch.1677:5
c00000000210c030 t 00000075.long_branch.memmove
c00000000210c034 t 00000075.plt_branch.9e0:5
c00000000210c044 t 00000075.plt_branch.free_initrd_mem
...
Actually, the problem mentioned in scripts/link-vmlinux.sh comments;
"In theory it's possible this results in even more stubs, but unlikely"
is happening here, and ends up with another kallsyms step required.
scripts/kallsyms.c already ignores various compiler stubs. Let's do
similar to make kallsysms for PowerPC always succeed in 2 steps.
Reported-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Pinned pages shouldn't be write-protected when fork() happens, because
follow up copy-on-write on these pages could cause the pinned pages to
be replaced by random newly allocated pages.
For huge PMDs, we split the huge pmd if pinning is detected. So that
future handling will be done by the PTE level (with our latest changes,
each of the small pages will be copied). We can achieve this by let
copy_huge_pmd() return -EAGAIN for pinned pages, so that we'll
fallthrough in copy_pmd_range() and finally land the next
copy_pte_range() call.
Huge PUDs will be even more special - so far it does not support
anonymous pages. But it can actually be done the same as the huge PMDs
even if the split huge PUDs means to erase the PUD entries. It'll
guarantee the follow up fault ins will remap the same pages in either
parent/child later.
This might not be the most efficient way, but it should be easy and
clean enough. It should be fine, since we're tackling with a very rare
case just to make sure userspaces that pinned some thps will still work
even without MADV_DONTFORK and after they fork()ed.
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Merge tag 'timers-v5.9-rc4' of https://git.linaro.org/people/daniel.lezcano/linux into timers/urgent
Pull clocksource/clockevent fixes from Daniel Lezcano:
- Fix wrong signed return value when checking of_iomap in the probe
function for the h8300 timer (Tianjia Zhang)
- Fix reset sequence when setting up the timer on the dm_timer (Tony
Lindgren)
- Fix counter reload when the interrupt fires on gx6605s (Guo Ren)
Sami reported that run_on_irqstack_cond() requires the caller to cast
functions to mismatching types, which trips indirect call Control-Flow
Integrity (CFI) in Clang.
Instead of disabling CFI on that function, provide proper helpers for
the three call variants. The actual ASM code stays the same as that is
out of reach.
[ bp: Fix __run_on_irqstack() prototype to match. ]
Fixes: 931b94145981 ("x86/entry: Provide helpers for executing on the irqstack")
Reported-by: Nathan Chancellor <natechancellor@gmail.com>
Reported-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Tested-by: Sami Tolvanen <samitolvanen@google.com>
Cc: <stable@vger.kernel.org>
Link: https://github.com/ClangBuiltLinux/linux/issues/1052
Link: https://lkml.kernel.org/r/87pn6eb5tv.fsf@nanos.tec.linutronix.de
This allows copy_pte_range() to do early cow if the pages were pinned on
the source mm.
Currently we don't have an accurate way to know whether a page is pinned
or not. The only thing we have is page_maybe_dma_pinned(). However
that's good enough for now. Especially, with the newly added
mm->has_pinned flag to make sure we won't affect processes that never
pinned any pages.
It would be easier if we can do GFP_KERNEL allocation within
copy_one_pte(). Unluckily, we can't because we're with the page table
locks held for both the parent and child processes. So the page
allocation needs to be done outside copy_one_pte().
Some trick is there in copy_present_pte(), majorly the wrprotect trick
to block concurrent fast-gup. Comments in the function should explain
better in place.
Oleg Nesterov reported a (probably harmless) bug during review that we
didn't reset entry.val properly in copy_pte_range() so that potentially
there's chance to call add_swap_count_continuation() multiple times on
the same swp entry. However that should be harmless since even if it
happens, the same function (add_swap_count_continuation()) will return
directly noticing that there're enough space for the swp counter. So
instead of a standalone stable patch, it is touched up in this patch
directly.
Link: https://lore.kernel.org/lkml/20200914143829.GA1424636@nvidia.com/
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Drop repeated words in kernel/time/. {when, one, into}
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <john.stultz@linaro.org>
Link: https://lore.kernel.org/r/20200807033248.8452-1-rdunlap@infradead.org
When the timer counts to the upper limit, an overflow interrupt is
generated, and the count is reset with the value in the TIME_INI
register. But the software expects to start counting from 0 when
the count overflows, so it forces TIME_INI to 0 to solve the
potential interrupt storm problem.
Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Tested-by: Xu Kai <xukai@nationalchip.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/1597735877-71115-1-git-send-email-guoren@kernel.org
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