Re: [PATCH 3/3] perf jvmti: Fix demangling Java symbols
From: Arnaldo Carvalho de Melo
Date: Wed May 27 2020 - 12:23:52 EST
Em Wed, May 27, 2020 at 11:20:57AM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Mon, Apr 27, 2020 at 02:15:16PM +0800, Nick Gasson escreveu:
> > 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.
> >
> > Also added a test case.
>
> So, I took this and split into a patch for the new 'perf test java' and
> then the fix, so that we can see the problem being detected and then
> apply the fix and see it fixed, the last patch in this series thus
> became:
This is in my tmp.perf/core branch pending a round of testing, after
that it'll move to perf/core on its way to 5.8, thanks.
- Arnaldo
>
> commit 341e11c1d445999932da3f5d626c9fe096949ae3
> Author: Nick Gasson <nick.gasson@xxxxxxx>
> Date: Mon Apr 27 14:15:16 2020 +0800
>
> 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@xxxxxxx>
> Reviewed-by: Ian Rogers <irogers@xxxxxxxxxx>
> Tested-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
> Tested-by: Ian Rogers <irogers@xxxxxxxxxx>
> Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
> Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
> Cc: Mark Rutland <mark.rutland@xxxxxxx>
> Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Link: http://lore.kernel.org/lkml/20200427061520.24905-4-nick.gasson@xxxxxxx
> Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
>
> diff --git a/tools/perf/util/demangle-java.c b/tools/perf/util/demangle-java.c
> index 6fb7f34c0814..39c05200ed65 100644
> --- 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;
--
- Arnaldo