|author||Michael Neuling <email@example.com>||2013-05-26 18:09:41 +0000|
|committer||Benjamin Herrenschmidt <firstname.lastname@example.org>||2013-06-01 08:29:23 +1000|
powerpc/tm: Fix userspace stack corruption on signal delivery for active 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 <email@example.com> Cc: <firstname.lastname@example.org> # v3.9 Signed-off-by: Benjamin Herrenschmidt <email@example.com>
Diffstat (limited to 'arch/powerpc/kernel/signal_64.c')
1 files changed, 7 insertions, 16 deletions
diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
index c1794286098..345947367ec 100644
@@ -154,11 +154,12 @@ static long setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs,
* As above, but Transactional Memory is in use, so deliver sigcontexts
* containing checkpointed and transactional register states.
- * To do this, we treclaim to gather both sets of registers and set up the
- * 'normal' sigcontext registers with rolled-back register values such that a
- * simple signal handler sees a correct checkpointed register state.
- * If interested, a TM-aware sighandler can examine the transactional registers
- * in the 2nd sigcontext to determine the real origin of the signal.
+ * To do this, we treclaim (done before entering here) to gather both sets of
+ * registers and set up the 'normal' sigcontext registers with rolled-back
+ * register values such that a simple signal handler sees a correct
+ * checkpointed register state. If interested, a TM-aware sighandler can
+ * examine the transactional registers in the 2nd sigcontext to determine the
+ * real origin of the signal.
static long setup_tm_sigcontexts(struct sigcontext __user *sc,
struct sigcontext __user *tm_sc,
@@ -184,16 +185,6 @@ static long setup_tm_sigcontexts(struct sigcontext __user *sc,
- /* tm_reclaim rolls back all reg states, saving checkpointed (older)
- * GPRs to thread.ckpt_regs and (if used) FPRs to (newer)
- * thread.transact_fp and/or VRs to (newer) thread.transact_vr.
- * THEN we save out FP/VRs, if necessary, to the checkpointed (older)
- * thread.fr/vrs. The transactional (newer) GPRs are on the
- * stack, in *regs.
- tm_reclaim(¤t->thread, msr, TM_CAUSE_SIGNAL);
@@ -711,7 +702,7 @@ int handle_rt_signal64(int signr, struct k_sigaction *ka, siginfo_t *info,
unsigned long newsp = 0;
long err = 0;
- frame = get_sigframe(ka, regs, sizeof(*frame), 0);
+ frame = get_sigframe(ka, get_tm_stackpointer(regs), sizeof(*frame), 0);
if (unlikely(frame == NULL))