tracing/x86/xen: Remove zero data size trace events trace_xen_mmu_flush_tlb{_all}

commit 45dd9b0666a162f8e4be76096716670cf1741f0e upstream.

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!

Link: http://lkml.kernel.org/r/20180509144605.5a220327@gandalf.local.home
Cc: stable@vger.kernel.org
Fixes: 95a7d76897c1e ("xen/mmu: Use Xen specific TLB flush instead of the generic one.")
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 3e15345abfe70db670ba1d8376ca267915d0437a..de0263348f2d5149e015aa2def52c3a4619b2ca5 100644 (file)
--- 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 042e9c422b2112406e13f9b795f408bdfb9b568d..b3526a98a5a51151f95d26932fe612a79373af7c 100644 (file)
--- a/arch/x86/xen/mmu_pv.c
+++ b/arch/x86/xen/mmu_pv.c
@@ -1280,13 +1280,11 @@ 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 d791863b62fc361b0ce8ddfed40fa28962798983..2ec9064a2bb7373ef4f138cfc22404bd06538c0b 100644 (file)
--- a/include/trace/events/xen.h
+++ b/include/trace/events/xen.h
@@ -349,22 +349,6 @@ 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),