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

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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: 95a7d76897 ("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>
This commit is contained in:
Steven Rostedt (VMware) 2018-05-09 14:36:09 -04:00
parent dc432c3d7f
commit 45dd9b0666
3 changed files with 2 additions and 22 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
arch/x86/xen/mmu.c
View File

@ -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));

4
arch/x86/xen/mmu_pv.c
View File

@ -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));

16
include/trace/events/xen.h
View File

@ -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),