[PATCH 3.17-rc4 v7 0/6] arm: Implement arch_trigger_all_cpu_backtrace

[Daniel Thompson]

This patchset implements arch_trigger_all_cpu_backtrace for arm.

Non-maskable signalling relies on the kernel being able to access FIQ
and therefore, for devices that implement TrustZone, it will work only on
systems that boot the kernel in secure mode.

Tested on Freescale iMX.6 (both via SysRq-l and by deliberately locking
up the kernel with CONFIG_DEBUG_SPINLOCK=y).

Changes since v6:

* Re-arranged code within the patch series to fix a regression introduced midway
  through the series and corrected by a later patch (testing by Olof's
  autobuilder). Tested offending patch in isolation using defconfig
  identified by the autobuilder.

Changes since v5:

* Renamed svc_entry's call_trace argument to just trace (example code
  from Russell King).

* Fixed mismatched ENDPROC() in __fiq_abt (example code from Russell
  King).

* Modified usr_entry to optionall avoid calling into the trace code and
  used this in FIQ entry from usr path. Modified corresponding exit code to
  avoid calling into trace code and the scheduler (example code from
  Russell King).

* Ensured the default FIQ register state is restored when the default
  FIQ handler is reinstalled (example code from Russell King).

* Renamed no_fiq_insn to dfl_fiq_insn to reflect the effect of adopting
  a default FIQ handler.

* Re-instated fiq_safe_migration_lock and associated logic in
  gic_raise_softirq(). gic_raise_softirq() is called by wake_up_klogd()
  in the console unlock logic.

Changes since v4:

* Rebased on 3.17-rc4.

* Removed a spurious line from the final "glue it together" patch
  that broke the build.

Changes since v3:

* Replaced push/pop with stmfd/ldmfd respectively (review of Nicolas
  Pitre).

* Really fix bad pt_regs pointer generation in __fiq_abt.

* Remove fiq_safe_migration_lock and associated logic in
  gic_raise_softirq() (review of Russell King)

* Restructured to introduce the default FIQ handler first, before the
  new features (review of Russell King).

Changes since v2:

* Removed redundant header guards from arch/arm64/include/asm/fiq.h
  (review of Catalin Marinas).

* Moved svc_exit_via_fiq macro to entry-header.S (review of Nicolas
  Pitre).

Changes since v1:

* Restructured to sit nicely on a similar FYI patchset from Russell
  King. It now effectively replaces the work in progress final patch
  with something much more complete.

* Implemented (and tested) a Thumb-2 implementation of svc_exit_via_fiq
  (review of Nicolas Pitre)

* Dropped the GIC group 0 workaround patch. The issue of FIQ interrupts
  being acknowledged by the IRQ handler does still exist but should be
  harmless because the IRQ handler will still wind up calling
  ipi_cpu_backtrace().

* Removed any dependency on CONFIG_FIQ; all cpu backtrace effectively
  becomes a platform feature (although the use of non-maskable
  interrupts to implement it is best effort rather than guaranteed).

* Better comments highlighting usage of RAZ/WI registers (and parts of
  registers) in the GIC code.

Changes *before* v1:

* This patchset is a hugely cut-down successor to "[PATCH v11 00/19]
  arm: KGDB NMI/FIQ support". Thanks to Thomas Gleixner for suggesting
  the new structure. For historic details see:
        https://lkml.org/lkml/2014/9/2/227

* Fix bug in __fiq_abt (no longer passes a bad struct pt_regs value).
  In fixing this we also remove the useless indirection previously
  found in the fiq_handler macro.

* Make default fiq handler "always on" by migrating from fiq.c to
  traps.c and replace do_unexp_fiq with the new handler (review
  of Russell King).

* Add arm64 version of fiq.h (review of Russell King)

* Removed conditional branching and code from irq-gic.c, this is
  replaced by much simpler code that relies on the GIC specification's
  heavy use of read-as-zero/write-ignored (review of Russell King)


Daniel Thompson (5):
  arm: fiq: Replace default FIQ handler
  arm64: Introduce dummy version of asm/fiq.h
  irqchip: gic: Add support for IPI FIQ
  ARM: add basic support for on-demand backtrace of other CPUs
  arm: smp: Handle ipi_cpu_backtrace() using FIQ (if available)

Russell King (1):
  ARM: remove unused do_unexp_fiq() function

 arch/arm/include/asm/irq.h      |   5 ++
 arch/arm/include/asm/smp.h      |   3 +
 arch/arm/kernel/entry-armv.S    |  98 +++++++++++++++++++++---
 arch/arm/kernel/entry-header.S  |  47 ++++++++++++
 arch/arm/kernel/fiq.c           |  17 ++++-
 arch/arm/kernel/setup.c         |   8 +-
 arch/arm/kernel/smp.c           |  64 ++++++++++++++++
 arch/arm/kernel/traps.c         |  32 +++++++-
 arch/arm64/include/asm/fiq.h    |   8 ++
 drivers/irqchip/irq-gic.c       | 162 ++++++++++++++++++++++++++++++++++++++--
 include/linux/irqchip/arm-gic.h |   3 +
 11 files changed, 421 insertions(+), 26 deletions(-)
 create mode 100644 arch/arm64/include/asm/fiq.h

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1.9.3