perf jvmti: Fix demangling Java symbols

For a Java method signature like:

    Ljava/lang/AbstractStringBuilder;appendChars(Ljava/lang/String;II)V

The demangler produces:

    void class java.lang.AbstractStringBuilder.appendChars(class java.lang., shorttring., int, int)

The arguments should be (java.lang.String, int, int) but the demangler
interprets the "S" in String as the type code for "short". Correct this
and two other minor things:

- There is no "bool" type in Java, should be "boolean".

- The demangler prepends "class" to every Java class name. This is not
  standard Java syntax and it wastes a lot of horizontal space if the
  signature is long. Remove this as there isn't any ambiguity between
  class names and primitives.

Committer notes:

This was split from a larger patch that also added a java demangler
'perf test' entry, that, before this patch shows the error being fixed
by it:

  $ perf test java
  65: Demangle Java                                         : FAILED!
  $ perf test -v java
  Couldn't bump rlimit(MEMLOCK), failures may take place when creating BPF maps, etc
  65: Demangle Java                                         :
  --- start ---
  test child forked, pid 307264
  FAILED: Ljava/lang/StringLatin1;equals([B[B)Z: bool class java.lang.StringLatin1.equals(byte[], byte[]) != boolean java.lang.StringLatin1.equals(byte[], byte[])
  FAILED: Ljava/util/zip/ZipUtils;CENSIZ([BI)J: long class java.util.zip.ZipUtils.CENSIZ(byte[], int) != long java.util.zip.ZipUtils.CENSIZ(byte[], int)
  FAILED: Ljava/util/regex/Pattern$BmpCharProperty;match(Ljava/util/regex/Matcher;ILjava/lang/CharSequence;)Z: bool class java.util.regex.Pattern$BmpCharProperty.match(class java.util.regex.Matcher., int, class java.lang., charhar, shortequence) != boolean java.util.regex.Pattern$BmpCharProperty.match(java.util.regex.Matcher, int, java.lang.CharSequence)
  FAILED: Ljava/lang/AbstractStringBuilder;appendChars(Ljava/lang/String;II)V: void class java.lang.AbstractStringBuilder.appendChars(class java.lang., shorttring., int, int) != void java.lang.AbstractStringBuilder.appendChars(java.lang.String, int, int)
  FAILED: Ljava/lang/Object;<init>()V: void class java.lang.Object<init>() != void java.lang.Object<init>()
  test child finished with -1
  ---- end ----
  Demangle Java: FAILED!
  $

After applying this patch:

  $ perf test  java
  65: Demangle Java                                         : Ok
  $

Signed-off-by: Nick Gasson <nick.gasson@arm.com>
Reviewed-by: Ian Rogers <irogers@google.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Tested-by: Ian Rogers <irogers@google.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20200427061520.24905-4-nick.gasson@arm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/demangle-java.c b/tools/perf/util/demangle-java.c
index 6fb7f34..39c0520 100644 (file)
--- a/tools/perf/util/demangle-java.c
+++ b/tools/perf/util/demangle-java.c
@@ -15,7 +15,7 @@ enum {
        MODE_CLASS  = 1,
        MODE_FUNC   = 2,
        MODE_TYPE   = 3,
-       MODE_CTYPE  = 3, /* class arg */
+       MODE_CTYPE  = 4, /* class arg */
 };
 
 #define BASE_ENT(c, n) [c - 'A']=n
@@ -27,7 +27,7 @@ static const char *base_types['Z' - 'A' + 1] = {
        BASE_ENT('I', "int" ),
        BASE_ENT('J', "long" ),
        BASE_ENT('S', "short" ),
-       BASE_ENT('Z', "bool" ),
+       BASE_ENT('Z', "boolean" ),
 };
 
 /*
@@ -59,15 +59,16 @@ __demangle_java_sym(const char *str, const char *end, char *buf, int maxlen, int
 
                switch (*q) {
                case 'L':
-                       if (mode == MODE_PREFIX || mode == MODE_CTYPE) {
-                               if (mode == MODE_CTYPE) {
+                       if (mode == MODE_PREFIX || mode == MODE_TYPE) {
+                               if (mode == MODE_TYPE) {
                                        if (narg)
                                                rlen += scnprintf(buf + rlen, maxlen - rlen, ", ");
                                        narg++;
                                }
-                               rlen += scnprintf(buf + rlen, maxlen - rlen, "class ");
                                if (mode == MODE_PREFIX)
                                        mode = MODE_CLASS;
+                               else
+                                       mode = MODE_CTYPE;
                        } else
                                buf[rlen++] = *q;
                        break;
@@ -120,7 +121,7 @@ __demangle_java_sym(const char *str, const char *end, char *buf, int maxlen, int
                        if (mode != MODE_CLASS && mode != MODE_CTYPE)
                                goto error;
                        /* safe because at least one other char to process */
-                       if (isalpha(*(q + 1)))
+                       if (isalpha(*(q + 1)) && mode == MODE_CLASS)
                                rlen += scnprintf(buf + rlen, maxlen - rlen, ".");
                        if (mode == MODE_CLASS)
                                mode = MODE_FUNC;