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2013-06-01powerpc/tm: Fix userspace stack corruption on signal delivery for active ↵Michael Neuling1-0/+19
transactions When in an active transaction that takes a signal, we need to be careful with the stack. It's possible that the stack has moved back up after the tbegin. The obvious case here is when the tbegin is called inside a function that returns before a tend. In this case, the stack is part of the checkpointed transactional memory state. If we write over this non transactionally or in suspend, we are in trouble because if we get a tm abort, the program counter and stack pointer will be back at the tbegin but our in memory stack won't be valid anymore. To avoid this, when taking a signal in an active transaction, we need to use the stack pointer from the checkpointed state, rather than the speculated state. This ensures that the signal context (written tm suspended) will be written below the stack required for the rollback. The transaction is aborted becuase of the treclaim, so any memory written between the tbegin and the signal will be rolled back anyway. For signals taken in non-TM or suspended mode, we use the normal/non-checkpointed stack pointer. Tested with 64 and 32 bit signals Signed-off-by: Michael Neuling <mikey@neuling.org> Cc: <stable@vger.kernel.org> # v3.9 Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2013-06-01powerpc/tm: Abort on emulation and alignment faultsMichael Neuling1-2/+5
If we are emulating an instruction inside an active user transaction that touches memory, the kernel can't emulate it as it operates in transactional suspend context. We need to abort these transactions and send them back to userspace for the hardware to rollback. We can service these if the user transaction is in suspend mode, since the kernel will operate in the same suspend context. This adds a check to all alignment faults and to specific instruction emulations (only string instructions for now). If the user process is in an active (non-suspended) transaction, we abort the transaction go back to userspace allowing the HW to roll back the transaction and tell the user of the failure. This also adds new tm abort cause codes to report the reason of the persistent error to the user. Crappy test case here http://neuling.org/devel/junkcode/aligntm.c Signed-off-by: Michael Neuling <mikey@neuling.org> Cc: <stable@vger.kernel.org> # v3.9 Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2013-06-01powerpc/tm: Update cause codes documentationMichael Neuling1-0/+1
Signed-off-by: Michael Neuling <mikey@neuling.org> Cc: <stable@vger.kernel.org> # 3.9 only Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2013-02-15powerpc: Documentation for transactional memory on powerpcMichael Neuling1-0/+175
Signed-off-by: Matt Evans <matt@ozlabs.org> Signed-off-by: Michael Neuling <mikey@neuling.org> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>