From 172f7aaa75d0eaae167edde25c08aae9059e80fc Mon Sep 17 00:00:00 2001 From: Cyril Bur Date: Wed, 14 Sep 2016 18:02:15 +1000 Subject: [PATCH] powerpc/tm: Add TM Unavailable Exception If the kernel disables transactional memory (TM) and userspace still tries TM related actions (TM instructions or TM SPR accesses) TM aware hardware will cause the kernel to take a facility unavailable exception. Add checks for the exception being caused by illegal TM access in userspace. Signed-off-by: Cyril Bur [mpe: Rewrite comment entirely, bugs in it are mine] Signed-off-by: Michael Ellerman --- arch/powerpc/kernel/traps.c | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+) diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c index 487e1b442473..2f5ef5a80353 100644 --- a/arch/powerpc/kernel/traps.c +++ b/arch/powerpc/kernel/traps.c @@ -1390,6 +1390,13 @@ void vsx_unavailable_exception(struct pt_regs *regs) } #ifdef CONFIG_PPC64 +static void tm_unavailable(struct pt_regs *regs) +{ + pr_emerg("Unrecoverable TM Unavailable Exception " + "%lx at %lx\n", regs->trap, regs->nip); + die("Unrecoverable TM Unavailable Exception", regs, SIGABRT); +} + void facility_unavailable_exception(struct pt_regs *regs) { static char *facility_strings[] = { @@ -1469,6 +1476,27 @@ void facility_unavailable_exception(struct pt_regs *regs) return; } + if (status == FSCR_TM_LG) { + /* + * If we're here then the hardware is TM aware because it + * generated an exception with FSRM_TM set. + * + * If cpu_has_feature(CPU_FTR_TM) is false, then either firmware + * told us not to do TM, or the kernel is not built with TM + * support. + * + * If both of those things are true, then userspace can spam the + * console by triggering the printk() below just by continually + * doing tbegin (or any TM instruction). So in that case just + * send the process a SIGILL immediately. + */ + if (!cpu_has_feature(CPU_FTR_TM)) + goto out; + + tm_unavailable(regs); + return; + } + if ((status < ARRAY_SIZE(facility_strings)) && facility_strings[status]) facility = facility_strings[status]; @@ -1481,6 +1509,7 @@ void facility_unavailable_exception(struct pt_regs *regs) "%sFacility '%s' unavailable, exception at 0x%lx, MSR=%lx\n", hv ? "Hypervisor " : "", facility, regs->nip, regs->msr); +out: if (user_mode(regs)) { _exception(SIGILL, regs, ILL_ILLOPC, regs->nip); return; -- 2.39.5