talos-obmc-linux/arch/arm/kernel, branch dev-5.0-raptor-04-16-2019

ARM: avoid Cortex-A9 livelock on tight dmb loops

2019-04-05T20:34:45+00:00

[ Upstream commit 5388a5b82199facacd3d7ac0d05aca6e8f902fed ] machine_crash_nonpanic_core() does this: while (1) cpu_relax(); because the kernel has crashed, and we have no known safe way to deal with the CPU. So, we place the CPU into an infinite loop which we expect it to never exit - at least not until the system as a whole is reset by some method. In the absence of erratum 754327, this code assembles to: b . In other words, an infinite loop. When erratum 754327 is enabled, this becomes: 1: dmb b 1b It has been observed that on some systems (eg, OMAP4) where, if a crash is triggered, the system tries to kexec into the panic kernel, but fails after taking the secondary CPU down - placing it into one of these loops. This causes the system to livelock, and the most noticable effect is the system stops after issuing: Loading crashdump kernel... to the system console. The tested as working solution I came up with was to add wfe() to these infinite loops thusly: while (1) { cpu_relax(); wfe(); } which, without 754327 builds to: 1: wfe b 1b or with 754327 is enabled: 1: dmb wfe b 1b Adding "wfe" does two things depending on the environment we're running under: - where we're running on bare metal, and the processor implements "wfe", it stops us spinning endlessly in a loop where we're never going to do any useful work. - if we're running in a VM, it allows the CPU to be given back to the hypervisor and rescheduled for other purposes (maybe a different VM) rather than wasting CPU cycles inside a crashed VM. However, in light of erratum 794072, Will Deacon wanted to see 10 nops as well - which is reasonable to cover the case where we have erratum 754327 enabled _and_ we have a processor that doesn't implement the wfe hint. So, we now end up with: 1: wfe b 1b when erratum 754327 is disabled, or: 1: dmb nop nop nop nop nop nop nop nop nop nop wfe b 1b when erratum 754327 is enabled. We also get the dmb + 10 nop sequence elsewhere in the kernel, in terminating loops. This is reasonable - it means we get the workaround for erratum 794072 when erratum 754327 is enabled, but still relinquish the dead processor - either by placing it in a lower power mode when wfe is implemented as such or by returning it to the hypervisior, or in the case where wfe is a no-op, we use the workaround specified in erratum 794072 to avoid the problem. These as two entirely orthogonal problems - the 10 nops addresses erratum 794072, and the wfe is an optimisation that makes the system more efficient when crashed either in terms of power consumption or by allowing the host/other VMs to make use of the CPU. I don't see any reason not to use kexec() inside a VM - it has the potential to provide automated recovery from a failure of the VMs kernel with the opportunity for saving a crashdump of the failure. A panic() with a reboot timeout won't do that, and reading the libvirt documentation, setting on_reboot to "preserve" won't either (the documentation states "The preserve action for an on_reboot event is treated as a destroy".) Surely it has to be a good thing to avoiding having CPUs spinning inside a VM that is doing no useful work. Acked-by: Will Deacon Signed-off-by: Russell King Signed-off-by: Sasha Levin

ARM: 8830/1: NOMMU: Toggle only bits in EXC_RETURN we are really care of

2019-04-05T20:34:45+00:00

[ Upstream commit 72cd4064fccaae15ab84d40d4be23667402df4ed ] ARMv8M introduces support for Security extension to M class, among other things it affects exception handling, especially, encoding of EXC_RETURN. The new bits have been added: Bit [6] Secure or Non-secure stack Bit [5] Default callee register stacking Bit [0] Exception Secure which conflicts with hard-coded value of EXC_RETURN: In fact, we only care of few bits: Bit [3] Mode (0 - Handler, 1 - Thread) Bit [2] Stack pointer selection (0 - Main, 1 - Process) We can toggle only those bits and left other bits as they were on exception entry. It is basically, what patch does - saves EXC_RETURN when we do transition form Thread to Handler mode (it is first svc), so later saved value is used instead of EXC_RET_THREADMODE_PROCESSSTACK. Signed-off-by: Vladimir Murzin Signed-off-by: Russell King Signed-off-by: Sasha Levin

ARM: 8840/1: use a raw_spinlock_t in unwind

2019-04-05T20:34:29+00:00

[ Upstream commit 74ffe79ae538283bbf7c155e62339f1e5c87b55a ] Mostly unwind is done with irqs enabled however SLUB may call it with irqs disabled while creating a new SLUB cache. I had system freeze while loading a module which called kmem_cache_create() on init. That means SLUB's __slab_alloc() disabled interrupts and then ->new_slab_objects() ->new_slab() ->setup_object() ->setup_object_debug() ->init_tracking() ->set_track() ->save_stack_trace() ->save_stack_trace_tsk() ->walk_stackframe() ->unwind_frame() ->unwind_find_idx() =>spin_lock_irqsave(&unwind_lock); Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Russell King Signed-off-by: Sasha Levin

ARM: 8824/1: fix a migrating irq bug when hotplug cpu

2019-02-01T21:54:49+00:00

Arm TC2 fails cpu hotplug stress test. This issue was tracked down to a missing copy of the new affinity cpumask for the vexpress-spc interrupt into struct irq_common_data.affinity when the interrupt is migrated in migrate_one_irq(). Fix it by replacing the arm specific hotplug cpu migration with the generic irq code. This is the counterpart implementation to commit 217d453d473c ("arm64: fix a migrating irq bug when hotplug cpu"). Tested with cpu hotplug stress test on Arm TC2 (multi_v7_defconfig plus CONFIG_ARM_BIG_LITTLE_CPUFREQ=y and CONFIG_ARM_VEXPRESS_SPC_CPUFREQ=y). The vexpress-spc interrupt (irq=22) on this board is affine to CPU0. Its affinity cpumask now changes correctly e.g. from 0 to 1-4 when CPU0 is hotplugged out. Suggested-by: Marc Zyngier Signed-off-by: Dietmar Eggemann Acked-by: Marc Zyngier Reviewed-by: Linus Walleij Signed-off-by: Russell King

jump_label: move 'asm goto' support test to Kconfig

2019-01-06T00:46:51+00:00

Currently, CONFIG_JUMP_LABEL just means "I _want_ to use jump label". The jump label is controlled by HAVE_JUMP_LABEL, which is defined like this: #if defined(CC_HAVE_ASM_GOTO) && defined(CONFIG_JUMP_LABEL) # define HAVE_JUMP_LABEL #endif We can improve this by testing 'asm goto' support in Kconfig, then make JUMP_LABEL depend on CC_HAS_ASM_GOTO. Ugly #ifdef HAVE_JUMP_LABEL will go away, and CONFIG_JUMP_LABEL will match to the real kernel capability. Signed-off-by: Masahiro Yamada Acked-by: Michael Ellerman (powerpc) Tested-by: Sedat Dilek

Merge branch 'mount.part1' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

2019-01-05T21:25:58+00:00

Pull vfs mount API prep from Al Viro: "Mount API prereqs. Mostly that's LSM mount options cleanups. There are several minor fixes in there, but nothing earth-shattering (leaks on failure exits, mostly)" * 'mount.part1' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (27 commits) mount_fs: suppress MAC on MS_SUBMOUNT as well as MS_KERNMOUNT smack: rewrite smack_sb_eat_lsm_opts() smack: get rid of match_token() smack: take the guts of smack_parse_opts_str() into a new helper LSM: new method: ->sb_add_mnt_opt() selinux: rewrite selinux_sb_eat_lsm_opts() selinux: regularize Opt_... names a bit selinux: switch away from match_token() selinux: new helper - selinux_add_opt() LSM: bury struct security_mnt_opts smack: switch to private smack_mnt_opts selinux: switch to private struct selinux_mnt_opts LSM: hide struct security_mnt_opts from any generic code selinux: kill selinux_sb_get_mnt_opts() LSM: turn sb_eat_lsm_opts() into a method nfs_remount(): don't leak, don't ignore LSM options quietly btrfs: sanitize security_mnt_opts use selinux; don't open-code a loop in sb_finish_set_opts() LSM: split ->sb_set_mnt_opts() out of ->sb_kern_mount() new helper: security_sb_eat_lsm_opts() ...

Merge tag 'for-4.21' of git://git.armlinux.org.uk/~rmk/linux-arm

2019-01-05T19:23:17+00:00

Pull ARM updates from Russell King: "Included in this update: - Florian Fainelli noticed that userspace segfaults caused by the lack of kernel-userspace helpers was hard to diagnose; we now issue a warning when userspace tries to use the helpers but the kernel has them disabled. - Ben Dooks wants compatibility for the old ATAG serial number with DT systems. - Some cleanup of assembly by Nicolas Pitre. - User accessors optimisation from Vincent Whitchurch. - More robust kdump on SMP systems from Yufen Wang. - Sebastian Andrzej Siewior noticed problems with the SMP "boot_lock" on RT kernels, and so we convert the Versatile series of platforms to use a raw spinlock instead, consolidating the Versatile implementation. We entirely remove the boot_lock on OMAP systems, where it's unnecessary. Further patches for other systems will be submitted for the following merge window. - Start switching old StrongARM-11x0 systems to use gpiolib rather than their private GPIO implementation - mostly PCMCIA bits. - ARM Kconfig cleanups. - Cleanup a mostly harmless mistake in the recent Spectre patch in 4.20 (which had the effect that data that can be placed into the init sections was incorrectly always placed in the rodata section)" * tag 'for-4.21' of git://git.armlinux.org.uk/~rmk/linux-arm: (25 commits) ARM: omap2: remove unnecessary boot_lock ARM: versatile: rename and comment SMP implementation ARM: versatile: convert boot_lock to raw ARM: vexpress/realview: consolidate immitation CPU hotplug ARM: fix the cockup in the previous patch ARM: sa1100/cerf: switch to using gpio_led_register_device() ARM: sa1100/assabet: switch to using gpio leds ARM: sa1100/assabet: add gpio keys support for right-hand two buttons ARM: sa1111: remove legacy GPIO interfaces pcmcia: sa1100*: remove redundant bvd1/bvd2 setting ARM: pxa/lubbock: switch PCMCIA to MAX1600 library ARM: pxa/mainstone: switch PCMCIA to MAX1600 library and gpiod APIs ARM: sa1100/neponset: switch PCMCIA to MAX1600 library and gpiod APIs ARM: sa1100/jornada720: switch PCMCIA to gpiod APIs pcmcia: add MAX1600 library ARM: sa1100: explicitly register sa11x0-pcmcia devices ARM: 8813/1: Make aligned 2-byte getuser()/putuser() atomic on ARMv6+ ARM: 8812/1: Optimise copy_{from/to}_user for !CPU_USE_DOMAINS ARM: 8811/1: always list both ldrd/strd registers explicitly ARM: 8808/1: kexec:offline panic_smp_self_stop CPU ...

Remove 'type' argument from access_ok() function

2019-01-04T02:57:57+00:00

Nobody has actually used the type (VERIFY_READ vs VERIFY_WRITE) argument of the user address range verification function since we got rid of the old racy i386-only code to walk page tables by hand. It existed because the original 80386 would not honor the write protect bit when in kernel mode, so you had to do COW by hand before doing any user access. But we haven't supported that in a long time, and these days the 'type' argument is a purely historical artifact. A discussion about extending 'user_access_begin()' to do the range checking resulted this patch, because there is no way we're going to move the old VERIFY_xyz interface to that model. And it's best done at the end of the merge window when I've done most of my merges, so let's just get this done once and for all. This patch was mostly done with a sed-script, with manual fix-ups for the cases that weren't of the trivial 'access_ok(VERIFY_xyz' form. There were a couple of notable cases: - csky still had the old "verify_area()" name as an alias. - the iter_iov code had magical hardcoded knowledge of the actual values of VERIFY_{READ,WRITE} (not that they mattered, since nothing really used it) - microblaze used the type argument for a debug printout but other than those oddities this should be a total no-op patch. I tried to fix up all architectures, did fairly extensive grepping for access_ok() uses, and the changes are trivial, but I may have missed something. Any missed conversion should be trivially fixable, though. Signed-off-by: Linus Torvalds

Merge branches 'misc', 'sa1100-for-next' and 'spectre' into for-linus

2019-01-02T10:37:05+00:00

Merge tag 'kgdb-4.21-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/danielt/linux

2019-01-01T23:38:14+00:00

Pull kgdb updates from Daniel Thompson: "Mostly clean ups although while Doug's was chasing down a odd lockdep warning he also did some work to improved debugger resilience when some CPUs fail to respond to the round up request. The main changes are: - Fixing a lockdep warning on architectures that cannot use an NMI for the round up plus related changes to make CPU round up and all CPU backtrace more resilient. - Constify the arch ops tables - A couple of other small clean ups Two of the three patchsets here include changes that spill over into arch/. Changes in the arch space are relatively narrow in scope (and directly related to kgdb). Didn't get comprehensive acks but all impacted maintainers were Cc:ed in good time" * tag 'kgdb-4.21-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/danielt/linux: kgdb/treewide: constify struct kgdb_arch arch_kgdb_ops mips/kgdb: prepare arch_kgdb_ops for constness kdb: use bool for binary state indicators kdb: Don't back trace on a cpu that didn't round up kgdb: Don't round up a CPU that failed rounding up before kgdb: Fix kgdb_roundup_cpus() for arches who used smp_call_function() kgdb: Remove irq flags from roundup