linux_dsm_epyc7002/arch/powerpc
Michael Neuling 7f821fc9c7 powerpc/tm: Check for already reclaimed tasks
Currently we can hit a scenario where we'll tm_reclaim() twice.  This
results in a TM bad thing exception because the second reclaim occurs
when not in suspend mode.

The scenario in which this can happen is the following.  We attempt to
deliver a signal to userspace.  To do this we need obtain the stack
pointer to write the signal context.  To get this stack pointer we
must tm_reclaim() in case we need to use the checkpointed stack
pointer (see get_tm_stackpointer()).  Normally we'd then return
directly to userspace to deliver the signal without going through
__switch_to().

Unfortunatley, if at this point we get an error (such as a bad
userspace stack pointer), we need to exit the process.  The exit will
result in a __switch_to().  __switch_to() will attempt to save the
process state which results in another tm_reclaim().  This
tm_reclaim() now causes a TM Bad Thing exception as this state has
already been saved and the processor is no longer in TM suspend mode.
Whee!

This patch checks the state of the MSR to ensure we are TM suspended
before we attempt the tm_reclaim().  If we've already saved the state
away, we should no longer be in TM suspend mode.  This has the
additional advantage of checking for a potential TM Bad Thing
exception.

Found using syscall fuzzer.

Fixes: fb09692e71 ("powerpc: Add reclaim and recheckpoint functions for context switching transactional memory processes")
Cc: stable@vger.kernel.org # v3.9+
Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
2015-11-23 20:18:03 +11:00
..
boot powerpc updates for 4.4 2015-11-05 23:38:43 -08:00
configs powerpc updates for 4.4 2015-11-05 23:38:43 -08:00
crypto
include powerpc/tm: Block signal return setting invalid MSR state 2015-11-23 20:06:31 +11:00
kernel powerpc/tm: Check for already reclaimed tasks 2015-11-23 20:18:03 +11:00
kvm Four changes: 2015-11-12 14:34:06 -08:00
lib
math-emu
mm powerpc updates for 4.4 2015-11-05 23:38:43 -08:00
net
oprofile
perf powerpc updates for 4.4 2015-11-05 23:38:43 -08:00
platforms PCI changes for the v4.4 merge window: 2015-11-06 11:29:53 -08:00
sysdev Merge branch 'for-4.4/io-poll' of git://git.kernel.dk/linux-block 2015-11-10 17:23:49 -08:00
xmon powerpc/xmon: Add some more elements to the existing PACA dump list 2015-10-15 20:32:02 +11:00
Kconfig powerpc/book3e-64: Enable kexec 2015-10-27 18:13:30 -05:00
Kconfig.debug
Makefile powerpc/cell: Drop CONFIG_TUNE_CELL in favour of CONFIG_CELL_CPU 2015-10-19 19:51:18 +11:00
relocs_check.sh