[PATCH v2 04/19] perf, tools: Tighten detection of BPF events

Andi Kleen
2017-08-11T23:26:43Z

From: Andi Kleen <ak@linux.intel.com>

perf stat -e cpu/uops_executed.core,cmask=1/

would be detected as a BPF source event because the .c matches the .c
source BPF pattern.

v2:

Originally I tried to use lex lookahead, but it doesn't seem to work.

This now extends the BPF pattern to match longer events, but then
does an extra check in the C code to reject BPF matches that
do not end with .c/.o/.obj

This uses REJECT, which makes the flex scanner slower, but
that shouldn't be a big problem for the perf events.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
tools/perf/util/parse-events.l | 23 +++++++++++++++++++----
1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/tools/perf/util/parse-events.l b/tools/perf/util/parse-events.l
index 660fca05bc93..c42edeac451f 100644
--- a/tools/perf/util/parse-events.l
+++ b/tools/perf/util/parse-events.l
@@ -53,6 +53,21 @@ static int str(yyscan_t scanner, int token)
return token;
}

+static bool isbpf(yyscan_t scanner)
+{
+ char *text = parse_events_get_text(scanner);
+ int len = strlen(text);
+
+ if (len < 2)
+ return false;
+ if ((text[len - 1] == 'c' || text[len - 1] == 'o') &&
+ text[len - 2] == '.')
+ return true;
+ if (len > 4 && !strcmp(text + len - 4, ".obj"))
+ return true;
+ return false;
+}
+
/*
* This function is called when the parser gets two kind of input:
*
@@ -136,8 +151,8 @@ do { \
group [^,{}/]*[{][^}]*[}][^,{}/]*
event_pmu [^,{}/]+[/][^/]*[/][^,{}/]*
event [^,{}/]+
-bpf_object [^,{}]+\.(o|bpf)
-bpf_source [^,{}]+\.c
+bpf_object [^,{}]+\.(o|bpf)[a-zA-Z0-9._]*
+bpf_source [^,{}]+\.c[a-zA-Z0-9._]*

num_dec [0-9]+
num_hex 0x[a-fA-F0-9]+
@@ -307,8 +322,8 @@ r{num_raw_hex} { return raw(yyscanner); }
{num_hex} { return value(yyscanner, 16); }

{modifier_event} { return str(yyscanner, PE_MODIFIER_EVENT); }
-{bpf_object} { return str(yyscanner, PE_BPF_OBJECT); }
-{bpf_source} { return str(yyscanner, PE_BPF_SOURCE); }
+{bpf_object} { if (!isbpf(yyscanner)) REJECT; return str(yyscanner, PE_BPF_OBJECT); }
+{bpf_source} { if (!isbpf(yyscanner)) REJECT; return str(yyscanner, PE_BPF_SOURCE); }
{name} { return pmu_str_check(yyscanner); }
"/" { BEGIN(config); return '/'; }
- { return '-'; }
--
2.9.4