From 31ba334836c0ac0039084859f14a5b96858493dc Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Mon, 4 Feb 2013 17:11:58 +0100 Subject: [PATCH] uprobes/perf: Teach trace_uprobe/perf code to pre-filter Finally implement uprobe_perf_filter() which checks ->nr_systemwide or ->perf_events to figure out whether we need to insert the breakpoint. uprobe_perf_open/close are changed to do uprobe_apply(true/false) when the new perf event comes or goes away. Note that currently this is very suboptimal: - uprobe_register() called by TRACE_REG_PERF_REGISTER becomes a heavy nop, consumer->filter() always returns F at this stage. As it was already discussed we need uprobe_register_only() to avoid the costly register_for_each_vma() when possible. - uprobe_apply() is oftenly overkill. Unless "nr_systemwide != 0" changes we need uprobe_apply_mm(), unapply_uprobe() is almost what we need. - uprobe_apply() can be simply avoided sometimes, see the next changes. Testing: # perf probe -x /lib/libc.so.6 syscall # perl -e 'syscall -1 while 1' & [1] 530 # perf record -e probe_libc:syscall perl -e 'syscall -1 for 1..10; sleep 1' # perf report --show-total-period 100.00% 10 perl libc-2.8.so [.] syscall Before this patch: # cat /sys/kernel/debug/tracing/uprobe_profile /lib/libc.so.6 syscall 79291 A huge ->nrhit == 79291 reflects the fact that the background process 530 constantly hits this breakpoint too, even if doesn't contribute to the output. After the patch: # cat /sys/kernel/debug/tracing/uprobe_profile /lib/libc.so.6 syscall 10 This shows that only the target process was punished by int3. Signed-off-by: Oleg Nesterov --- kernel/trace/trace_uprobe.c | 46 ++++++++++++++++++++++++++++++++++--- 1 file changed, 43 insertions(+), 3 deletions(-) diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c index 2a74a93afdae..b7850f535acf 100644 --- a/kernel/trace/trace_uprobe.c +++ b/kernel/trace/trace_uprobe.c @@ -557,7 +557,12 @@ static inline bool is_trace_uprobe_enabled(struct trace_uprobe *tu) return tu->flags & (TP_FLAG_TRACE | TP_FLAG_PROFILE); } -static int probe_event_enable(struct trace_uprobe *tu, int flag) +typedef bool (*filter_func_t)(struct uprobe_consumer *self, + enum uprobe_filter_ctx ctx, + struct mm_struct *mm); + +static int +probe_event_enable(struct trace_uprobe *tu, int flag, filter_func_t filter) { int ret = 0; @@ -567,6 +572,7 @@ static int probe_event_enable(struct trace_uprobe *tu, int flag) WARN_ON(!uprobe_filter_is_empty(&tu->filter)); tu->flags |= flag; + tu->consumer.filter = filter; ret = uprobe_register(tu->inode, tu->offset, &tu->consumer); if (ret) tu->flags &= ~flag; @@ -656,6 +662,22 @@ static int set_print_fmt(struct trace_uprobe *tu) } #ifdef CONFIG_PERF_EVENTS +static bool +__uprobe_perf_filter(struct trace_uprobe_filter *filter, struct mm_struct *mm) +{ + struct perf_event *event; + + if (filter->nr_systemwide) + return true; + + list_for_each_entry(event, &filter->perf_events, hw.tp_list) { + if (event->hw.tp_target->mm == mm) + return true; + } + + return false; +} + static int uprobe_perf_open(struct trace_uprobe *tu, struct perf_event *event) { write_lock(&tu->filter.rwlock); @@ -665,6 +687,8 @@ static int uprobe_perf_open(struct trace_uprobe *tu, struct perf_event *event) tu->filter.nr_systemwide++; write_unlock(&tu->filter.rwlock); + uprobe_apply(tu->inode, tu->offset, &tu->consumer, true); + return 0; } @@ -677,9 +701,25 @@ static int uprobe_perf_close(struct trace_uprobe *tu, struct perf_event *event) tu->filter.nr_systemwide--; write_unlock(&tu->filter.rwlock); + uprobe_apply(tu->inode, tu->offset, &tu->consumer, false); + return 0; } +static bool uprobe_perf_filter(struct uprobe_consumer *uc, + enum uprobe_filter_ctx ctx, struct mm_struct *mm) +{ + struct trace_uprobe *tu; + int ret; + + tu = container_of(uc, struct trace_uprobe, consumer); + read_lock(&tu->filter.rwlock); + ret = __uprobe_perf_filter(&tu->filter, mm); + read_unlock(&tu->filter.rwlock); + + return ret; +} + /* uprobe profile handler */ static void uprobe_perf_func(struct trace_uprobe *tu, struct pt_regs *regs) { @@ -722,7 +762,7 @@ int trace_uprobe_register(struct ftrace_event_call *event, enum trace_reg type, switch (type) { case TRACE_REG_REGISTER: - return probe_event_enable(tu, TP_FLAG_TRACE); + return probe_event_enable(tu, TP_FLAG_TRACE, NULL); case TRACE_REG_UNREGISTER: probe_event_disable(tu, TP_FLAG_TRACE); @@ -730,7 +770,7 @@ int trace_uprobe_register(struct ftrace_event_call *event, enum trace_reg type, #ifdef CONFIG_PERF_EVENTS case TRACE_REG_PERF_REGISTER: - return probe_event_enable(tu, TP_FLAG_PROFILE); + return probe_event_enable(tu, TP_FLAG_PROFILE, uprobe_perf_filter); case TRACE_REG_PERF_UNREGISTER: probe_event_disable(tu, TP_FLAG_PROFILE); -- 2.30.2