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

BugLink: http://bugs.launchpad.net/bugs/1782846
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>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index d33e7dbe3129fc327fe7f24fb0fb84c802b11edf..2d76106788a31c5638459bc35306445e59f2c02d 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 aae88fec9941a6dd4183ff2e85f43036e0c2aa88..ac17c206afd18f8b3117560951b3caff59073e48 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 7dd8f34c37dfea26f8ec460d3937a46c8f109f4d..fdcf88bcf0ea3dec3df105aa7e7d40fe2aaaaf0c 100644 (file)
--- 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),