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Diffstat (limited to 'arch/powerpc/kernel/signal_64.c')
-rw-r--r--arch/powerpc/kernel/signal_64.c71
1 files changed, 50 insertions, 21 deletions
diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
index 83d51bf586c7..0935fe6c282a 100644
--- a/arch/powerpc/kernel/signal_64.c
+++ b/arch/powerpc/kernel/signal_64.c
@@ -467,20 +467,6 @@ static long restore_tm_sigcontexts(struct task_struct *tsk,
if (MSR_TM_RESV(msr))
return -EINVAL;
- /* pull in MSR TS bits from user context */
- regs->msr = (regs->msr & ~MSR_TS_MASK) | (msr & MSR_TS_MASK);
-
- /*
- * Ensure that TM is enabled in regs->msr before we leave the signal
- * handler. It could be the case that (a) user disabled the TM bit
- * through the manipulation of the MSR bits in uc_mcontext or (b) the
- * TM bit was disabled because a sufficient number of context switches
- * happened whilst in the signal handler and load_tm overflowed,
- * disabling the TM bit. In either case we can end up with an illegal
- * TM state leading to a TM Bad Thing when we return to userspace.
- */
- regs->msr |= MSR_TM;
-
/* pull in MSR LE from user context */
regs->msr = (regs->msr & ~MSR_LE) | (msr & MSR_LE);
@@ -572,6 +558,34 @@ static long restore_tm_sigcontexts(struct task_struct *tsk,
tm_enable();
/* Make sure the transaction is marked as failed */
tsk->thread.tm_texasr |= TEXASR_FS;
+
+ /*
+ * Disabling preemption, since it is unsafe to be preempted
+ * with MSR[TS] set without recheckpointing.
+ */
+ preempt_disable();
+
+ /* pull in MSR TS bits from user context */
+ regs->msr = (regs->msr & ~MSR_TS_MASK) | (msr & MSR_TS_MASK);
+
+ /*
+ * Ensure that TM is enabled in regs->msr before we leave the signal
+ * handler. It could be the case that (a) user disabled the TM bit
+ * through the manipulation of the MSR bits in uc_mcontext or (b) the
+ * TM bit was disabled because a sufficient number of context switches
+ * happened whilst in the signal handler and load_tm overflowed,
+ * disabling the TM bit. In either case we can end up with an illegal
+ * TM state leading to a TM Bad Thing when we return to userspace.
+ *
+ * CAUTION:
+ * After regs->MSR[TS] being updated, make sure that get_user(),
+ * put_user() or similar functions are *not* called. These
+ * functions can generate page faults which will cause the process
+ * to be de-scheduled with MSR[TS] set but without calling
+ * tm_recheckpoint(). This can cause a bug.
+ */
+ regs->msr |= MSR_TM;
+
/* This loads the checkpointed FP/VEC state, if used */
tm_recheckpoint(&tsk->thread);
@@ -585,6 +599,8 @@ static long restore_tm_sigcontexts(struct task_struct *tsk,
regs->msr |= MSR_VEC;
}
+ preempt_enable();
+
return err;
}
#endif
@@ -598,11 +614,12 @@ static long setup_trampoline(unsigned int syscall, unsigned int __user *tramp)
long err = 0;
/* addi r1, r1, __SIGNAL_FRAMESIZE # Pop the dummy stackframe */
- err |= __put_user(0x38210000UL | (__SIGNAL_FRAMESIZE & 0xffff), &tramp[0]);
+ err |= __put_user(PPC_INST_ADDI | __PPC_RT(R1) | __PPC_RA(R1) |
+ (__SIGNAL_FRAMESIZE & 0xffff), &tramp[0]);
/* li r0, __NR_[rt_]sigreturn| */
- err |= __put_user(0x38000000UL | (syscall & 0xffff), &tramp[1]);
+ err |= __put_user(PPC_INST_ADDI | (syscall & 0xffff), &tramp[1]);
/* sc */
- err |= __put_user(0x44000002UL, &tramp[2]);
+ err |= __put_user(PPC_INST_SC, &tramp[2]);
/* Minimal traceback info */
for (i=TRAMP_TRACEBACK; i < TRAMP_SIZE ;i++)
@@ -740,11 +757,23 @@ SYSCALL_DEFINE0(rt_sigreturn)
&uc_transact->uc_mcontext))
goto badframe;
}
- else
- /* Fall through, for non-TM restore */
#endif
- if (restore_sigcontext(current, NULL, 1, &uc->uc_mcontext))
- goto badframe;
+ /* Fall through, for non-TM restore */
+ if (!MSR_TM_ACTIVE(msr)) {
+ /*
+ * Unset MSR[TS] on the thread regs since MSR from user
+ * context does not have MSR active, and recheckpoint was
+ * not called since restore_tm_sigcontexts() was not called
+ * also.
+ *
+ * If not unsetting it, the code can RFID to userspace with
+ * MSR[TS] set, but without CPU in the proper state,
+ * causing a TM bad thing.
+ */
+ current->thread.regs->msr &= ~MSR_TS_MASK;
+ if (restore_sigcontext(current, NULL, 1, &uc->uc_mcontext))
+ goto badframe;
+ }
if (restore_altstack(&uc->uc_stack))
goto badframe;