[ltt-dev] [PATCH] tracepoints: Generate Module.tracepoints file

[Jan Blunck]

This adds support to generate the Module.tracepoints file by modpost. This
can be read by tools like SystemTap very similar to the Module.markers file.

Signed-off-by: Jan Blunck <jblunck at suse.de>
---
 Makefile                 |    6 +
 scripts/Makefile.modpost |    5 +
 scripts/mod/modpost.c    |  173 +++++++++++++++++++++++++++++++++++++++++++++--
 scripts/mod/modpost.h    |    3 
 4 files changed, 178 insertions(+), 9 deletions(-)

Index: b/Makefile
===================================================================
--- a/Makefile
+++ b/Makefile
@@ -1178,7 +1178,8 @@ MRPROPER_FILES += .config .config.old in
                   include/linux/autoconf.h include/linux/version.h      \
                   include/linux/utsrelease.h                            \
                   include/linux/bounds.h include/asm*/asm-offsets.h     \
-		  Module.symvers Module.markers tags TAGS cscope*
+		  Module.symvers Module.markers Module.tracepoints	\
+		  tags TAGS cscope*
 
 # clean - Delete most, but leave enough to build external modules
 #
@@ -1197,7 +1198,8 @@ clean: archclean $(clean-dirs)
 		\( -name '*.[oas]' -o -name '*.ko' -o -name '.*.cmd' \
 		-o -name '.*.d' -o -name '.*.tmp' -o -name '*.mod.c' \
 		-o -name '*.symtypes' -o -name 'modules.order' \
-		-o -name 'Module.markers' -o -name '.tmp_*.o.*' \) \
+		-o -name 'Module.markers' -o -name 'Module.tracepoints' \
+		-o -name '.tmp_*.o.*' \) \
 		-type f -print | xargs rm -f
 
 # mrproper - Delete all generated files, including .config
Index: b/scripts/Makefile.modpost
===================================================================
--- a/scripts/Makefile.modpost
+++ b/scripts/Makefile.modpost
@@ -61,8 +61,11 @@ kernelsymfile := $(objtree)/Module.symve
 modulesymfile := $(firstword $(KBUILD_EXTMOD))/Module.symvers
 kernelmarkersfile := $(objtree)/Module.markers
 modulemarkersfile := $(firstword $(KBUILD_EXTMOD))/Module.markers
+kerneltracepointsfile := $(objtree)/Module.tracepoints
+moduletracepointsfile := $(firstword $(KBUILD_EXTMOD))/Module.tracepoints
 
 markersfile = $(if $(KBUILD_EXTMOD),$(modulemarkersfile),$(kernelmarkersfile))
+tracepointsfile = $(if $(KBUILD_EXTMOD),$(moduletracepointsfile),$(kerneltracepointsfile))
 
 # Step 1), find all modules listed in $(MODVERDIR)/
 __modules := $(sort $(shell grep -h '\.ko' /dev/null $(wildcard $(MODVERDIR)/*.mod)))
@@ -87,6 +90,8 @@ modpost = scripts/mod/modpost
  $(if $(CONFIG_DEBUG_SECTION_MISMATCH),,-S)      \
  $(if $(CONFIG_MARKERS),-K $(kernelmarkersfile)) \
  $(if $(CONFIG_MARKERS),-M $(markersfile))	 \
+ $(if $(CONFIG_TRACEPOINTS),-T $(kerneltracepointsfile)) \
+ $(if $(CONFIG_TRACEPOINTS),-t $(tracepointsfile))	 \
  $(if $(KBUILD_EXTMOD)$(KBUILD_MODPOST_WARN),-w) \
  $(if $(cross_build),-c)			 \
  -N $(firstword $(wildcard $(dir $(MODVERDIR))/Module.supported \
Index: b/scripts/mod/modpost.c
===================================================================
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -439,6 +439,8 @@ static int parse_elf(struct elf_info *in
 			info->export_gpl_future_sec = i;
 		else if (strcmp(secname, "__markers_strings") == 0)
 			info->markers_strings_sec = i;
+		else if (strcmp(secname, "__tracepoints_strings") == 0)
+			info->tracepoints_strings_sec = i;
 
 		if (sechdrs[i].sh_type != SHT_SYMTAB)
 			continue;
@@ -1545,6 +1547,63 @@ static void get_markers(struct elf_info
 		}
 }
 
+static void get_tracepoints(struct elf_info *info, struct module *mod)
+{
+	const Elf_Shdr *sh = &info->sechdrs[info->tracepoints_strings_sec];
+	const char *strings = (const char *) info->hdr + sh->sh_offset;
+	const Elf_Sym *sym, *first_sym, *last_sym;
+	size_t n;
+
+	if (!info->tracepoints_strings_sec)
+		return;
+
+	/*
+	 * First count the strings.  We look for all the symbols defined
+	 * in the __tracepoints_strings section named __tpstrtab_*.  For
+	 * these local names, the compiler puts a random .NNN suffix on,
+	 * so the names don't correspond exactly.
+	 */
+	first_sym = last_sym = NULL;
+	n = 0;
+	for (sym = info->symtab_start; sym < info->symtab_stop; sym++)
+		if (ELF_ST_TYPE(sym->st_info) == STT_OBJECT &&
+		    sym->st_shndx == info->tracepoints_strings_sec &&
+		    !strncmp(info->strtab + sym->st_name,
+			     "__tpstrtab_", sizeof "__tpstrtab_" - 1)) {
+			if (first_sym == NULL)
+				first_sym = sym;
+			last_sym = sym;
+			++n;
+		}
+
+	if (n == 0)
+		return;
+
+	/*
+	 * Now collect each name and format into a line for the output.
+	 * Lines look like:
+	 *	marker_name	vmlinux	marker %s format %d
+	 * The format string after the second \t can use whitespace.
+	 */
+	mod->tracepoints = NOFAIL(malloc(sizeof mod->tracepoints[0] * n));
+	mod->ntracepoints = n;
+
+	n = 0;
+	for (sym = first_sym; sym <= last_sym; sym++)
+		if (ELF_ST_TYPE(sym->st_info) == STT_OBJECT &&
+		    sym->st_shndx == info->tracepoints_strings_sec &&
+		    !strncmp(info->strtab + sym->st_name,
+			     "__tpstrtab_", sizeof "__tpstrtab_" - 1)) {
+			const char *name = strings + sym->st_value;
+			const char *fmt = strchr(name, ':') + 1;
+			char *line = NULL;
+			asprintf(&line, "%.*s\t%s\t%s\n", fmt - name - 1, name,
+				 mod->name, fmt);
+			NOFAIL(line);
+			mod->tracepoints[n++] = line;
+		}
+}
+
 void *supported_file;
 unsigned long supported_size;
 
@@ -1643,6 +1702,7 @@ static void read_symbols(char *modname)
 				sizeof(mod->srcversion)-1);
 
 	get_markers(&info, mod);
+	get_tracepoints(&info, mod);
 
 	parse_elf_finish(&info);
 
@@ -2091,6 +2151,91 @@ static void write_markers(const char *fn
 	write_if_changed(&buf, fname);
 }
 
+static void add_tracepoint(struct module *mod, const char *name,
+			   const char *fmt)
+{
+	char *line = NULL;
+	asprintf(&line, "%s\t%s\t%s\n", name, mod->name, fmt);
+	NOFAIL(line);
+
+	mod->tracepoints = NOFAIL(realloc(mod->tracepoints,
+					  ((mod->ntracepoints + 1) *
+					   sizeof mod->tracepoints[0])));
+	mod->tracepoints[mod->ntracepoints++] = line;
+}
+
+static void read_tracepoints(const char *fname)
+{
+	unsigned long size, pos = 0;
+	void *file = grab_file(fname, &size);
+	char *line;
+
+	if (!file)		/* No old tracepoints, silently ignore */
+		return;
+
+	while ((line = get_next_line(&pos, file, size))) {
+		char *tracepoint, *modname, *fmt;
+		struct module *mod;
+
+		tracepoint = line;
+		modname = strchr(tracepoint, '\t');
+		if (!modname)
+			goto fail;
+		*modname++ = '\0';
+		fmt = strchr(modname, '\t');
+		if (!fmt)
+			goto fail;
+		*fmt++ = '\0';
+		if (*tracepoint == '\0' || *modname == '\0')
+			goto fail;
+
+		mod = find_module(modname);
+		if (!mod) {
+			if (is_vmlinux(modname))
+				have_vmlinux = 1;
+			mod = new_module(NOFAIL(strdup(modname)));
+			mod->skip = 1;
+		}
+
+		if (!mod->skip)
+			add_tracepoint(mod, tracepoint, fmt);
+	}
+	return;
+fail:
+	fatal("parse error in tracepoints list file\n");
+}
+
+static void write_tracepoints(const char *fname)
+{
+	struct buffer buf = { };
+	struct module *mod;
+	size_t i;
+
+	for (mod = modules; mod; mod = mod->next)
+		if ((!external_module || !mod->skip) &&
+		    mod->tracepoints != NULL) {
+			/*
+			 * Sort the strings so we can skip duplicates when
+			 * we write them out.
+			 */
+			qsort(mod->tracepoints, mod->ntracepoints,
+			      sizeof mod->tracepoints[0], &compare_strings);
+			for (i = 0; i < mod->ntracepoints; ++i) {
+				char *line = mod->tracepoints[i];
+				buf_write(&buf, line, strlen(line));
+				while (i + 1 < mod->ntracepoints &&
+				       !strcmp(mod->tracepoints[i],
+					       mod->tracepoints[i + 1]))
+					free(mod->tracepoints[i++]);
+				free(mod->tracepoints[i]);
+			}
+			free(mod->tracepoints);
+			mod->tracepoints = NULL;
+		}
+
+	write_if_changed(&buf, fname);
+}
+
 struct ext_sym_list {
 	struct ext_sym_list *next;
 	const char *file;
@@ -2104,13 +2249,15 @@ int main(int argc, char **argv)
 	char *dump_write = NULL;
 	char *markers_read = NULL;
 	char *markers_write = NULL;
+	char *tracepoints_read = NULL;
+	char *tracepoints_write = NULL;
 	const char *supported = NULL;
 	int opt;
 	int err;
 	struct ext_sym_list *extsym_iter;
 	struct ext_sym_list *extsym_start = NULL;
 
-	while ((opt = getopt(argc, argv, "i:I:e:cmsSo:awM:K:N:")) != -1) {
+	while ((opt = getopt(argc, argv, "i:I:e:cmsSo:awM:K:N:t:T:")) != -1) {
 		switch (opt) {
 		case 'i':
 			kernel_read = optarg;
@@ -2148,12 +2295,18 @@ int main(int argc, char **argv)
 		case 'w':
 			warn_unresolved = 1;
 			break;
-			case 'M':
-				markers_write = optarg;
-				break;
-			case 'K':
-				markers_read = optarg;
-				break;
+		case 'M':
+			markers_write = optarg;
+			break;
+		case 'K':
+			markers_read = optarg;
+			break;
+		case 't':
+			tracepoints_write = optarg;
+			break;
+		case 'T':
+			tracepoints_read = optarg;
+			break;
 		case 'N':
 			supported = optarg;
 			break;
@@ -2219,5 +2372,11 @@ int main(int argc, char **argv)
 	if (markers_write)
 		write_markers(markers_write);
 
+	if (tracepoints_read)
+		read_tracepoints(tracepoints_read);
+
+	if (tracepoints_write)
+		write_tracepoints(tracepoints_write);
+
 	return err;
 }
Index: b/scripts/mod/modpost.h
===================================================================
--- a/scripts/mod/modpost.h
+++ b/scripts/mod/modpost.h
@@ -114,6 +114,8 @@ struct module {
 	struct buffer dev_table_buf;
 	char **markers;
 	size_t nmarkers;
+	char **tracepoints;
+	size_t ntracepoints;
 	char	     srcversion[25];
 };
 
@@ -129,6 +131,7 @@ struct elf_info {
 	Elf_Section  export_unused_gpl_sec;
 	Elf_Section  export_gpl_future_sec;
 	Elf_Section  markers_strings_sec;
+	Elf_Section  tracepoints_strings_sec;
 	const char   *strtab;
 	char	     *modinfo;
 	unsigned int modinfo_len;