diff options
Diffstat (limited to 'arch/powerpc/kernel/signal_64.c')
| -rw-r--r-- | arch/powerpc/kernel/signal_64.c | 27 |
1 files changed, 26 insertions, 1 deletions
diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c index 6794466f6420..06c299ef6132 100644 --- a/arch/powerpc/kernel/signal_64.c +++ b/arch/powerpc/kernel/signal_64.c @@ -565,7 +565,7 @@ static long restore_tm_sigcontexts(struct task_struct *tsk, preempt_disable(); /* pull in MSR TS bits from user context */ - regs->msr = (regs->msr & ~MSR_TS_MASK) | (msr & MSR_TS_MASK); + regs->msr |= msr & MSR_TS_MASK; /* * Ensure that TM is enabled in regs->msr before we leave the signal @@ -745,6 +745,31 @@ SYSCALL_DEFINE0(rt_sigreturn) if (MSR_TM_SUSPENDED(mfmsr())) tm_reclaim_current(0); + /* + * Disable MSR[TS] bit also, so, if there is an exception in the + * code below (as a page fault in copy_ckvsx_to_user()), it does + * not recheckpoint this task if there was a context switch inside + * the exception. + * + * A major page fault can indirectly call schedule(). A reschedule + * process in the middle of an exception can have a side effect + * (Changing the CPU MSR[TS] state), since schedule() is called + * with the CPU MSR[TS] disable and returns with MSR[TS]=Suspended + * (switch_to() calls tm_recheckpoint() for the 'new' process). In + * this case, the process continues to be the same in the CPU, but + * the CPU state just changed. + * + * This can cause a TM Bad Thing, since the MSR in the stack will + * have the MSR[TS]=0, and this is what will be used to RFID. + * + * Clearing MSR[TS] state here will avoid a recheckpoint if there + * is any process reschedule in kernel space. The MSR[TS] state + * does not need to be saved also, since it will be replaced with + * the MSR[TS] that came from user context later, at + * restore_tm_sigcontexts. + */ + regs->msr &= ~MSR_TS_MASK; + if (__get_user(msr, &uc->uc_mcontext.gp_regs[PT_MSR])) goto badframe; if (MSR_TM_ACTIVE(msr)) { |