tracing/x86/xen: Remove zero data size trace events trace_xen_mmu_flush_tlb{_all} (45dd9b06) · Commits · 戴 / test

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: ("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>

arch/x86/xen/mmu.c

+1 −3

Original line number	Diff line number	Diff line
		@@ -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));

arch/x86/xen/mmu_pv.c

+1 −3

Original line number	Diff line number	Diff line
		@@ -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));

include/trace/events/xen.h

+0 −16

Original line number	Diff line number	Diff line
		@@ -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),

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