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@xxxxxxxxxxx> wrote:
> From: "Steven Rostedt (VMware)" <rostedt@xxxxxxxxxxx>
>
> 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@xxxxxxxxxxxxxxx
> Fixes: 95a7d76897c1e ("xen/mmu: Use Xen specific TLB flush instead of the generic one.")
> Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
> ---
> 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),
