dt_module.c

Sun Solaris 10 中的 DTrace 组件的源代码。请参看: http://www.sun.com/software/solaris/observability.jsp

dt_module_t *
dt_module_lookup_by_name(dtrace_hdl_t *dtp, const char *name)
{
	uint_t h = dt_strtab_hash(name, NULL) % dtp->dt_modbuckets;
	dt_module_t *dmp;

	for (dmp = dtp->dt_mods[h]; dmp != NULL; dmp = dmp->dm_next) {
		if (strcmp(dmp->dm_name, name) == 0)
			return (dmp);
	}

	return (NULL);
}

dt_module_t *
dt_module_lookup_by_ctf(dtrace_hdl_t *dtp, ctf_file_t *ctfp)
{
	dt_module_t *dmp;

	for (dmp = dt_list_next(&dtp->dt_modlist); dmp != NULL;
	    dmp = dt_list_next(dmp)) {
		if (dmp->dm_ctfp == ctfp)
			return (dmp);
	}

	return (NULL);
}

static int
dt_module_load_sect(dtrace_hdl_t *dtp, dt_module_t *dmp, ctf_sect_t *ctsp)
{
	const char *s;
	size_t shstrs;
	GElf_Shdr sh;
	Elf_Data *dp;
	Elf_Scn *sp;

	if (elf_getshstrndx(dmp->dm_elf, &shstrs) == 0)
		return (dt_set_errno(dtp, EDT_NOTLOADED));

	for (sp = NULL; (sp = elf_nextscn(dmp->dm_elf, sp)) != NULL; ) {
		if (gelf_getshdr(sp, &sh) == NULL || sh.sh_type == SHT_NULL ||
		    (s = elf_strptr(dmp->dm_elf, shstrs, sh.sh_name)) == NULL)
			continue; /* skip any malformed sections */

		if (sh.sh_type == ctsp->cts_type &&
		    sh.sh_entsize == ctsp->cts_entsize &&
		    strcmp(s, ctsp->cts_name) == 0)
			break; /* section matches specification */
	}

	/*
	 * If the section isn't found, return success but leave cts_data set
	 * to NULL and cts_size set to zero for our caller.
	 */
	if (sp == NULL || (dp = elf_getdata(sp, NULL)) == NULL)
		return (0);

	ctsp->cts_data = dp->d_buf;
	ctsp->cts_size = dp->d_size;

	dt_dprintf("loaded %s [%s] (%lu bytes)\n",
	    dmp->dm_name, ctsp->cts_name, (ulong_t)ctsp->cts_size);

	return (0);
}

int
dt_module_load(dtrace_hdl_t *dtp, dt_module_t *dmp)
{
	if (dmp->dm_flags & DT_DM_LOADED)
		return (0); /* module is already loaded */

	dmp->dm_ctdata.cts_name = ".SUNW_ctf";
	dmp->dm_ctdata.cts_type = SHT_PROGBITS;
	dmp->dm_ctdata.cts_flags = 0;
	dmp->dm_ctdata.cts_data = NULL;
	dmp->dm_ctdata.cts_size = 0;
	dmp->dm_ctdata.cts_entsize = 0;
	dmp->dm_ctdata.cts_offset = 0;

	dmp->dm_symtab.cts_name = ".symtab";
	dmp->dm_symtab.cts_type = SHT_SYMTAB;
	dmp->dm_symtab.cts_flags = 0;
	dmp->dm_symtab.cts_data = NULL;
	dmp->dm_symtab.cts_size = 0;
	dmp->dm_symtab.cts_entsize = dmp->dm_ops == &dt_modops_64 ?
	    sizeof (Elf64_Sym) : sizeof (Elf32_Sym);
	dmp->dm_symtab.cts_offset = 0;

	dmp->dm_strtab.cts_name = ".strtab";
	dmp->dm_strtab.cts_type = SHT_STRTAB;
	dmp->dm_strtab.cts_flags = 0;
	dmp->dm_strtab.cts_data = NULL;
	dmp->dm_strtab.cts_size = 0;
	dmp->dm_strtab.cts_entsize = 0;
	dmp->dm_strtab.cts_offset = 0;

	/*
	 * Attempt to load the module's CTF section, symbol table section, and
	 * string table section.  Note that modules may not contain CTF data:
	 * this will result in a successful load_sect but data of size zero.
	 * We will then fail if dt_module_getctf() is called, as shown below.
	 */
	if (dt_module_load_sect(dtp, dmp, &dmp->dm_ctdata) == -1 ||
	    dt_module_load_sect(dtp, dmp, &dmp->dm_symtab) == -1 ||
	    dt_module_load_sect(dtp, dmp, &dmp->dm_strtab) == -1) {
		dt_module_unload(dtp, dmp);
		return (-1); /* dt_errno is set for us */
	}

	/*
	 * Allocate the hash chains and hash buckets for symbol name lookup.
	 * This is relatively simple since the symbol table is of fixed size
	 * and is known in advance.  We allocate one extra element since we
	 * use element indices instead of pointers and zero is our sentinel.
	 */
	dmp->dm_nsymelems =
	    dmp->dm_symtab.cts_size / dmp->dm_symtab.cts_entsize;

	dmp->dm_nsymbuckets = _dtrace_strbuckets;
	dmp->dm_symfree = 1;		/* first free element is index 1 */

	dmp->dm_symbuckets = malloc(sizeof (uint_t) * dmp->dm_nsymbuckets);
	dmp->dm_symchains = malloc(sizeof (dt_sym_t) * dmp->dm_nsymelems + 1);

	if (dmp->dm_symbuckets == NULL || dmp->dm_symchains == NULL) {
		dt_module_unload(dtp, dmp);
		return (dt_set_errno(dtp, EDT_NOMEM));
	}

	bzero(dmp->dm_symbuckets, sizeof (uint_t) * dmp->dm_nsymbuckets);
	bzero(dmp->dm_symchains, sizeof (dt_sym_t) * dmp->dm_nsymelems + 1);

	/*
	 * Iterate over the symbol table data buffer and insert each symbol
	 * name into the name hash if the name and type are valid.  Then
	 * allocate the address map, fill it in, and sort it.
	 */
	dmp->dm_asrsv = dmp->dm_ops->do_syminit(dmp);

	dt_dprintf("hashed %s [%s] (%u symbols)\n",
	    dmp->dm_name, dmp->dm_symtab.cts_name, dmp->dm_symfree - 1);

	if ((dmp->dm_asmap = malloc(sizeof (void *) * dmp->dm_asrsv)) == NULL) {
		dt_module_unload(dtp, dmp);
		return (dt_set_errno(dtp, EDT_NOMEM));
	}

	dmp->dm_ops->do_symsort(dmp);

	dt_dprintf("sorted %s [%s] (%u symbols)\n",
	    dmp->dm_name, dmp->dm_symtab.cts_name, dmp->dm_aslen);

	dmp->dm_flags |= DT_DM_LOADED;
	return (0);
}

ctf_file_t *
dt_module_getctf(dtrace_hdl_t *dtp, dt_module_t *dmp)
{
	const char *parent;
	dt_module_t *pmp;
	ctf_file_t *pfp;
	int model;

	if (dmp->dm_ctfp != NULL || dt_module_load(dtp, dmp) != 0)
		return (dmp->dm_ctfp);

	if (dmp->dm_ops == &dt_modops_64)
		model = CTF_MODEL_LP64;
	else
		model = CTF_MODEL_ILP32;

	/*
	 * If the data model of the module does not match our program data
	 * model, then do not permit CTF from this module to be opened and
	 * returned to the compiler.  If we support mixed data models in the
	 * future for combined kernel/user tracing, this can be removed.
	 */
	if (dtp->dt_conf.dtc_ctfmodel != model) {
		(void) dt_set_errno(dtp, EDT_DATAMODEL);
		return (NULL);
	}

	if (dmp->dm_ctdata.cts_size == 0) {
		(void) dt_set_errno(dtp, EDT_NOCTF);
		return (NULL);
	}

	dmp->dm_ctfp = ctf_bufopen(&dmp->dm_ctdata,
	    &dmp->dm_symtab, &dmp->dm_strtab, &dtp->dt_ctferr);

	if (dmp->dm_ctfp == NULL || ctf_setmodel(dmp->dm_ctfp, model) != 0) {
		(void) dt_set_errno(dtp, EDT_CTF);
		return (NULL);
	}

	if ((parent = ctf_parent_name(dmp->dm_ctfp)) != NULL) {
		if ((pmp = dt_module_create(dtp, parent)) == NULL ||
		    (pfp = dt_module_getctf(dtp, pmp)) == NULL) {
			if (pmp == NULL)
				(void) dt_set_errno(dtp, EDT_NOMEM);
			goto err;
		}

		if (ctf_import(dmp->dm_ctfp, pfp) == CTF_ERR) {
			dtp->dt_ctferr = ctf_errno(dmp->dm_ctfp);
			(void) dt_set_errno(dtp, EDT_CTF);
			goto err;
		}
	}

	dt_dprintf("loaded CTF container for %s (%p)\n",
	    dmp->dm_name, (void *)dmp->dm_ctfp);

	return (dmp->dm_ctfp);

err:
	ctf_close(dmp->dm_ctfp);
	dmp->dm_ctfp = NULL;
	return (NULL);
}

/*ARGSUSED*/
void
dt_module_unload(dtrace_hdl_t *dtp, dt_module_t *dmp)
{
	ctf_close(dmp->dm_ctfp);
	dmp->dm_ctfp = NULL;

	bzero(&dmp->dm_ctdata, sizeof (ctf_sect_t));
	bzero(&dmp->dm_symtab, sizeof (ctf_sect_t));
	bzero(&dmp->dm_strtab, sizeof (ctf_sect_t));

	if (dmp->dm_symbuckets != NULL) {
		free(dmp->dm_symbuckets);
		dmp->dm_symbuckets = NULL;
	}

	if (dmp->dm_symchains != NULL) {
		free(dmp->dm_symchains);
		dmp->dm_symchains = NULL;
	}

	if (dmp->dm_asmap != NULL) {
		free(dmp->dm_asmap);
		dmp->dm_asmap = NULL;
	}

	dmp->dm_symfree = 0;
	dmp->dm_nsymbuckets = 0;
	dmp->dm_nsymelems = 0;
	dmp->dm_asrsv = 0;
	dmp->dm_aslen = 0;

	dmp->dm_text_va = NULL;
	dmp->dm_text_size = 0;
	dmp->dm_data_va = NULL;
	dmp->dm_data_size = 0;
	dmp->dm_bss_va = NULL;
	dmp->dm_bss_size = 0;

	if (dmp->dm_extern != NULL) {
		dt_idhash_destroy(dmp->dm_extern);
		dmp->dm_extern = NULL;
	}

	(void) elf_end(dmp->dm_elf);
	dmp->dm_elf = NULL;

	dmp->dm_flags &= ~DT_DM_LOADED;
}

void
dt_module_destroy(dtrace_hdl_t *dtp, dt_module_t *dmp)
{
	dt_list_delete(&dtp->dt_modlist, dmp);
	assert(dtp->dt_nmods != 0);
	dtp->dt_nmods--;

	dt_module_unload(dtp, dmp);
	free(dmp);
}

/*
 * Insert a new external symbol reference into the specified module.  The new
 * symbol will be marked as undefined and is assigned a symbol index beyond
 * any existing cached symbols from this module.  We use the ident's di_data
 * field to store a pointer to a copy of the dtrace_syminfo_t for this symbol.
 */
dt_ident_t *
dt_module_extern(dtrace_hdl_t *dtp, dt_module_t *dmp,
    const char *name, const dtrace_typeinfo_t *tip)
{
	dtrace_syminfo_t *sip;
	dt_ident_t *idp;
	uint_t id;

	if (dmp->dm_extern == NULL && (dmp->dm_extern = dt_idhash_create(
	    "extern", NULL, dmp->dm_nsymelems, UINT_MAX)) == NULL) {
		(void) dt_set_errno(dtp, EDT_NOMEM);
		return (NULL);
	}

	if (dt_idhash_nextid(dmp->dm_extern, &id) == -1) {
		(void) dt_set_errno(dtp, EDT_SYMOFLOW);
		return (NULL);
	}

	if ((sip = malloc(sizeof (dtrace_syminfo_t))) == NULL) {
		(void) dt_set_errno(dtp, EDT_NOMEM);
		return (NULL);
	}

	idp = dt_idhash_insert(dmp->dm_extern, name, DT_IDENT_SYMBOL, 0, id,
	    _dtrace_symattr, 0, &dt_idops_thaw, NULL, dtp->dt_gen);

	if (idp == NULL) {
		(void) dt_set_errno(dtp, EDT_NOMEM);
		free(sip);
		return (NULL);
	}

	sip->dts_object = dmp->dm_name;
	sip->dts_name = idp->di_name;
	sip->dts_id = idp->di_id;

	idp->di_data = sip;
	idp->di_ctfp = tip->dtt_ctfp;
	idp->di_type = tip->dtt_type;

	return (idp);
}

const char *
dt_module_modelname(dt_module_t *dmp)
{
	if (dmp->dm_ops == &dt_modops_64)
		return ("64-bit");
	else
		return ("32-bit");
}

/*
 * Update our module cache by adding an entry for the specified module 'name'.
 * We create the dt_module_t and populate it using /system/object/<name>/.
 */
static void
dt_module_update(dtrace_hdl_t *dtp, const char *name)
{
	char fname[MAXPATHLEN];
	struct stat64 st;
	int fd, err, bits;

	dt_module_t *dmp;
	const char *s;
	size_t shstrs;
	GElf_Shdr sh;
	Elf_Data *dp;
	Elf_Scn *sp;

	(void) snprintf(fname, sizeof (fname),
	    "%s/%s/object", OBJFS_ROOT, name);

	if ((fd = open(fname, O_RDONLY)) == -1 || fstat64(fd, &st) == -1 ||
	    (dmp = dt_module_create(dtp, name)) == NULL) {
		dt_dprintf("failed to open %s: %s\n", fname, strerror(errno));
		(void) close(fd);
		return;
	}

	/*
	 * Since the module can unload out from under us (and /system/object
	 * will return ENOENT), tell libelf to cook the entire file now and
	 * then close the underlying file descriptor immediately.  If this
	 * succeeds, we know that we can continue safely using dmp->dm_elf.
	 */
	dmp->dm_elf = elf_begin(fd, ELF_C_READ, NULL);
	err = elf_cntl(dmp->dm_elf, ELF_C_FDREAD);
	(void) close(fd);

	if (dmp->dm_elf == NULL || err == -1 ||
	    elf_getshstrndx(dmp->dm_elf, &shstrs) == 0) {
		dt_dprintf("failed to load %s: %s\n",
		    fname, elf_errmsg(elf_errno()));
		dt_module_destroy(dtp, dmp);
		return;
	}

	switch (gelf_getclass(dmp->dm_elf)) {
	case ELFCLASS32:
		dmp->dm_ops = &dt_modops_32;
		bits = 32;
		break;
	case ELFCLASS64:
		dmp->dm_ops = &dt_modops_64;
		bits = 64;
		break;
	default:
		dt_dprintf("failed to load %s: unknown ELF class\n", fname);
		dt_module_destroy(dtp, dmp);
		return;
	}

	/*
	 * Iterate over the section headers locating various sections of
	 * interest and use their attributes to flesh out the dt_module_t.
	 */
	for (sp = NULL; (sp = elf_nextscn(dmp->dm_elf, sp)) != NULL; ) {
		if (gelf_getshdr(sp, &sh) == NULL || sh.sh_type == SHT_NULL ||
		    (s = elf_strptr(dmp->dm_elf, shstrs, sh.sh_name)) == NULL)
			continue; /* skip any malformed sections */

		if (strcmp(s, ".text") == 0) {
			dmp->dm_text_size = sh.sh_size;
			dmp->dm_text_va = sh.sh_addr;
		} else if (strcmp(s, ".data") == 0) {
			dmp->dm_data_size = sh.sh_size;
			dmp->dm_data_va = sh.sh_addr;
		} else if (strcmp(s, ".bss") == 0) {
			dmp->dm_bss_size = sh.sh_size;
			dmp->dm_bss_va = sh.sh_addr;
		} else if (strcmp(s, ".info") == 0 &&
		    (dp = elf_getdata(sp, NULL)) != NULL) {
			bcopy(dp->d_buf, &dmp->dm_info,
			    MIN(sh.sh_size, sizeof (dmp->dm_info)));
		} else if (strcmp(s, ".filename") == 0 &&