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Re: [PATCH v2 1/3] SDT markers listing by perf:

On 10/08/2013 05:09 PM, Masami Hiramatsu wrote:

(2013/10/07 15:47), Hemant Kumar wrote:

@@ -325,6 +326,7 @@ int cmd_probe(int argc, const char **argv, const char *prefix __maybe_unused)
  		     opt_set_filter),
  	OPT_CALLBACK('x', "exec", NULL, "executable|path",
  			"target executable name or path", opt_set_target),
+	OPT_BOOLEAN('S', "markers", &params.sdt, "Show probe-able sdt notes"),

BTW, "-S" for short of "--markers" option is a bit odd. Would we better use -M ? :)
I thought of -S as SDT. :) Anyways, on second thought, will change that to -M. 



[...]

@@ -355,6 +357,26 @@ int cmd_probe(int argc, const char **argv, const char *prefix __maybe_unused)
  	 */
  	symbol_conf.try_vmlinux_path = (symbol_conf.vmlinux_name == NULL);
+ if (params.sdt) { 
+		if (params.show_lines) {
+			pr_err("Error: Don't use --markers with --lines.\n");
+			usage_with_options(probe_usage, options);
+		}
+		if (params.show_vars) {
+			pr_err("Error: Don't use --markers with --vars.\n");
+			usage_with_options(probe_usage, options);
+		}
+		if (params.show_funcs) {
+			pr_err("Error: Don't use --markers with --funcs.\n");
+			usage_with_options(probe_usage, options);
+		}
+		ret = show_sdt_notes(params.target);

You have to ensure params.target is set before use it.


Yes, will do that.


+		if (ret < 0) {
+			pr_err("  Error : Failed to find SDT markers!"
+			       "(%d)\n", ret);
+		}
+		return ret;
+	}
  	if (params.list_events) {
  		if (params.mod_events) {
  			pr_err("  Error: Don't use --list with --add/--del.\n");

[...]

diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
index 4b12bf8..6b17260 100644
--- a/tools/perf/util/symbol-elf.c
+++ b/tools/perf/util/symbol-elf.c
@@ -846,6 +846,182 @@ out_elf_end:
  	return err;
  }
+/* 
+ * Populate the name, type, offset in the SDT note structure and
+ * ignore the argument fields (for now)
+ */
+static struct sdt_note *populate_sdt_note(Elf **elf, const char *data,
+					  size_t len, int type)
+{
+	const char *provider, *name;
+	struct sdt_note *note;
+
+	/*
+	 * Three addresses need to be obtained :
+	 * Marker location, address of base section and semaphore location
+	 */
+	union {
+		Elf64_Addr a64[3];
+		Elf32_Addr a32[3];
+	} buf;
+
+	/*
+	 * dst and src are required for translation from file to memory
+	 * representation
+	 */
+	Elf_Data dst = {
+		.d_buf = &buf, .d_type = ELF_T_ADDR, .d_version = EV_CURRENT,
+		.d_size = gelf_fsize((*elf), ELF_T_ADDR, 3, EV_CURRENT),
+		.d_off = 0, .d_align = 0
+	};
+
+	Elf_Data src = {
+		.d_buf = (void *) data, .d_type = ELF_T_ADDR,
+		.d_version = EV_CURRENT, .d_size = dst.d_size, .d_off = 0,
+		.d_align = 0
+	};
+
+	/* Check the type of each of the notes */
+	if (type != SDT_NOTE_TYPE)
+		goto out_ret;
+
+	note = (struct sdt_note *)zalloc(sizeof(struct sdt_note));
+	if (note == NULL) {
+		pr_err("Memory allocation error\n");

No need to state out of memory for each place...
If you hit an out of memory for such small piece, you'd better
abort execution. For that purpose, I recommend you to return
errno from each function, and caller must check it.


Yeah this will be better... will return errno from each function.


+		goto out_ret;
+	}
+	INIT_LIST_HEAD(&note->note_list);
+
+	if (len < dst.d_size + 3)
+		goto out_free;
+
+	/* Translation from file representation to memory representation */
+	if (gelf_xlatetom(*elf, &dst, &src,
+			  elf_getident(*elf, NULL)[EI_DATA]) == NULL)
+		pr_debug("gelf_xlatetom : %s", elf_errmsg(-1));
+
+	/* Populate the fields of sdt_note */
+	provider = data + dst.d_size;
+
+	name = (const char *)memchr(provider, '\0', data + len - provider);
+	if (name++ == NULL)
+		goto out_free;
+	note->provider = strdup(provider);
+	note->name = strdup(name);
+
+	/* Obtain the addresses and ignore notes with semaphores set*/
+	if (gelf_getclass(*elf) == ELFCLASS32) {
+		note->addr.a32[0] = buf.a32[0];
+		note->addr.a32[1] = buf.a32[1];
+		note->addr.a32[2] = buf.a32[2];
+		note->bit32 = true;
+		if (buf.a32[2] != 0)
+			goto out_free;
+	} else {
+		note->addr.a64[0] = buf.a64[0];
+		note->addr.a64[1] = buf.a64[1];
+		note->addr.a64[2] = buf.a64[2];
+		note->bit32 = false;
+		if (buf.a64[2] != 0)
+			goto out_free;
+	}
+	return note;
+
+out_free:
+	free(note);
+out_ret:
+	return NULL;
+}
+
+static struct list_head *construct_sdt_notes_list(Elf *elf)

This also would better return errno.


Ok.


+{
+	GElf_Ehdr ehdr;
+	Elf_Scn *scn = NULL;
+	Elf_Data *data;
+	GElf_Shdr shdr;
+	size_t shstrndx;
+	size_t next;
+	GElf_Nhdr nhdr;
+	size_t name_off, desc_off, offset;
+	struct sdt_note *tmp = NULL, *note = NULL;
+
+	if (gelf_getehdr(elf, &ehdr) == NULL) {
+		pr_debug("%s: Can't get elf header.\n", __func__);
+		goto out_err;
+	}
+	if (elf_getshdrstrndx(elf, &shstrndx) != 0) {
+		pr_debug("getshdrstrndx failed\n");
+		goto out_err;
+	}
+
+	/*
+	 * Look for section type = SHT_NOTE, flags = no SHF_ALLOC
+	 * and name = .note.stapsdt
+	 */
+	scn = elf_section_by_name(elf, &ehdr, &shdr, NOTE_SCN, NULL);
+	if (!scn) {
+		printf("SDT markers not present!\n");

Why you don't use pr_err() here ? :)
Because, I thought it isn't an error that SDT markers are not present. It won't make much of a difference though. :) 


And also, as I commented, I'd like to know which binary doesn't have SDT markers,
at least with -v (verbose) option.
Yes, I guess it would be better to show the binary name even without -v option. Will make the changes. 

--
Thanks
Hemant
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