Thomas, Ingo or Peter.
Any of you willing to take this patch, or send me an ack and I'll take it and push it to Linus?
-- Steve
On Wed, 9 May 2018 14:46:05 -0400 Steven Rostedt rostedt@goodmis.org wrote:
From: "Steven Rostedt (VMware)" rostedt@goodmis.org
Doing an audit of trace events, I discovered two trace events in the xen subsystem that use a hack to create zero data size trace events. This is not what trace events are for. Trace events add memory footprint overhead, and if all you need to do is see if a function is hit or not, simply make that function noinline and use function tracer filtering.
Worse yet, the hack used was:
__array(char, x, 0)
Which creates a static string of zero in length. There's assumptions about such constructs in ftrace that this is a dynamic string that is nul terminated. This is not the case with these tracepoints and can cause problems in various parts of ftrace.
Nuke the trace events!
Cc: stable@vger.kernel.org Fixes: 95a7d76897c1e ("xen/mmu: Use Xen specific TLB flush instead of the generic one.") Signed-off-by: Steven Rostedt (VMware) rostedt@goodmis.org
arch/x86/xen/mmu.c | 4 +--- arch/x86/xen/mmu_pv.c | 4 +--- include/trace/events/xen.h | 16 ---------------- 3 files changed, 2 insertions(+), 22 deletions(-)
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c index d33e7dbe3129..2d76106788a3 100644 --- a/arch/x86/xen/mmu.c +++ b/arch/x86/xen/mmu.c @@ -42,13 +42,11 @@ xmaddr_t arbitrary_virt_to_machine(void *vaddr) } EXPORT_SYMBOL_GPL(arbitrary_virt_to_machine); -static void xen_flush_tlb_all(void) +static noinline void xen_flush_tlb_all(void) { struct mmuext_op *op; struct multicall_space mcs;
- trace_xen_mmu_flush_tlb_all(0);
- preempt_disable();
mcs = xen_mc_entry(sizeof(*op)); diff --git a/arch/x86/xen/mmu_pv.c b/arch/x86/xen/mmu_pv.c index 486c0a34d00b..2c30cabfda90 100644 --- a/arch/x86/xen/mmu_pv.c +++ b/arch/x86/xen/mmu_pv.c @@ -1310,13 +1310,11 @@ unsigned long xen_read_cr2_direct(void) return this_cpu_read(xen_vcpu_info.arch.cr2); } -static void xen_flush_tlb(void) +static noinline void xen_flush_tlb(void) { struct mmuext_op *op; struct multicall_space mcs;
- trace_xen_mmu_flush_tlb(0);
- preempt_disable();
mcs = xen_mc_entry(sizeof(*op)); diff --git a/include/trace/events/xen.h b/include/trace/events/xen.h index 7dd8f34c37df..fdcf88bcf0ea 100644 --- a/include/trace/events/xen.h +++ b/include/trace/events/xen.h @@ -352,22 +352,6 @@ DECLARE_EVENT_CLASS(xen_mmu_pgd, DEFINE_XEN_MMU_PGD_EVENT(xen_mmu_pgd_pin); DEFINE_XEN_MMU_PGD_EVENT(xen_mmu_pgd_unpin); -TRACE_EVENT(xen_mmu_flush_tlb_all,
TP_PROTO(int x),TP_ARGS(x),TP_STRUCT__entry(__array(char, x, 0)),TP_fast_assign((void)x),TP_printk("%s", "")- );
-TRACE_EVENT(xen_mmu_flush_tlb,
TP_PROTO(int x),TP_ARGS(x),TP_STRUCT__entry(__array(char, x, 0)),TP_fast_assign((void)x),TP_printk("%s", "")- );
TRACE_EVENT(xen_mmu_flush_tlb_one_user, TP_PROTO(unsigned long addr), TP_ARGS(addr),