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

[Mathieu Desnoyers <compudj at krystal dot dyndns dot org>]

Hrmmm, is there a real need for it ? I mean.. if the information is
available in the kernel headers found in include/trace/*.h, why would we
need another repository created at build time ?

Mathieu

* Jan Blunck (jblunck@suse.de) wrote:
> 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@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;
> 
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> 

-- 
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68