module: simplify load_module.

Linus' recent catch of stack overflow in load_module lead me to look
at the code.  A couple of helpers to get a section address and get
objects from a section can help clean things up a little.

(And in case you're wondering, the stack size also dropped from 328 to
284 bytes).

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

diff --git a/include/linux/module.h b/include/linux/module.h
index 5d2970c..eddf27d 100644 (file)
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -277,7 +277,7 @@ struct module
 
        /* Exception table */
        unsigned int num_exentries;
-       const struct exception_table_entry *extable;
+       struct exception_table_entry *extable;
 
        /* Startup function. */
        int (*init)(void);

diff --git a/kernel/module.c b/kernel/module.c
index 0d8d21e..3d25668 100644 (file)
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -132,6 +132,29 @@ static unsigned int find_sec(Elf_Ehdr *hdr,
        return 0;
 }
 
+/* Find a module section, or NULL. */
+static void *section_addr(Elf_Ehdr *hdr, Elf_Shdr *shdrs,
+                         const char *secstrings, const char *name)
+{
+       /* Section 0 has sh_addr 0. */
+       return (void *)shdrs[find_sec(hdr, shdrs, secstrings, name)].sh_addr;
+}
+
+/* Find a module section, or NULL.  Fill in number of "objects" in section. */
+static void *section_objs(Elf_Ehdr *hdr,
+                         Elf_Shdr *sechdrs,
+                         const char *secstrings,
+                         const char *name,
+                         size_t object_size,
+                         unsigned int *num)
+{
+       unsigned int sec = find_sec(hdr, sechdrs, secstrings, name);
+
+       /* Section 0 has sh_addr 0 and sh_size 0. */
+       *num = sechdrs[sec].sh_size / object_size;
+       return (void *)sechdrs[sec].sh_addr;
+}
+
 /* Provided by the linker */
 extern const struct kernel_symbol __start___ksymtab[];
 extern const struct kernel_symbol __stop___ksymtab[];
@@ -1789,32 +1812,20 @@ static inline void add_kallsyms(struct module *mod,
 }
 #endif /* CONFIG_KALLSYMS */
 
-#ifdef CONFIG_DYNAMIC_PRINTK_DEBUG
-static void dynamic_printk_setup(Elf_Shdr *sechdrs, unsigned int verboseindex)
+static void dynamic_printk_setup(struct mod_debug *debug, unsigned int num)
 {
-       struct mod_debug *debug_info;
-       unsigned long pos, end;
-       unsigned int num_verbose;
-
-       pos = sechdrs[verboseindex].sh_addr;
-       num_verbose = sechdrs[verboseindex].sh_size /
-                               sizeof(struct mod_debug);
-       end = pos + (num_verbose * sizeof(struct mod_debug));
+#ifdef CONFIG_DYNAMIC_PRINTK_DEBUG
+       unsigned int i;
 
-       for (; pos < end; pos += sizeof(struct mod_debug)) {
-               debug_info = (struct mod_debug *)pos;
-               register_dynamic_debug_module(debug_info->modname,
-                       debug_info->type, debug_info->logical_modname,
-                       debug_info->flag_names, debug_info->hash,
-                       debug_info->hash2);
+       for (i = 0; i < num; i++) {
+               register_dynamic_debug_module(debug[i].modname,
+                                             debug[i].type,
+                                             debug[i].logical_modname,
+                                             debug[i].flag_names,
+                                             debug[i].hash, debug[i].hash2);
        }
-}
-#else
-static inline void dynamic_printk_setup(Elf_Shdr *sechdrs,
-                                       unsigned int verboseindex)
-{
-}
 #endif /* CONFIG_DYNAMIC_PRINTK_DEBUG */
+}
 
 static void *module_alloc_update_bounds(unsigned long size)
 {
@@ -1843,37 +1854,14 @@ static noinline struct module *load_module(void __user *umod,
        unsigned int i;
        unsigned int symindex = 0;
        unsigned int strindex = 0;
-       unsigned int setupindex;
-       unsigned int exindex;
-       unsigned int exportindex;
-       unsigned int modindex;
-       unsigned int obsparmindex;
-       unsigned int infoindex;
-       unsigned int gplindex;
-       unsigned int crcindex;
-       unsigned int gplcrcindex;
-       unsigned int versindex;
-       unsigned int pcpuindex;
-       unsigned int gplfutureindex;
-       unsigned int gplfuturecrcindex;
+       unsigned int modindex, versindex, infoindex, pcpuindex;
        unsigned int unwindex = 0;
-#ifdef CONFIG_UNUSED_SYMBOLS
-       unsigned int unusedindex;
-       unsigned int unusedcrcindex;
-       unsigned int unusedgplindex;
-       unsigned int unusedgplcrcindex;
-#endif
-       unsigned int markersindex;
-       unsigned int markersstringsindex;
-       unsigned int verboseindex;
-       unsigned int tracepointsindex;
-       unsigned int tracepointsstringsindex;
-       unsigned int mcountindex;
+       unsigned int num_kp, num_mcount;
+       struct kernel_param *kp;
        struct module *mod;
        long err = 0;
        void *percpu = NULL, *ptr = NULL; /* Stops spurious gcc warning */
-       void *mseg;
-       struct exception_table_entry *extable;
+       unsigned long *mseg;
        mm_segment_t old_fs;
 
        DEBUGP("load_module: umod=%p, len=%lu, uargs=%p\n",
@@ -1937,6 +1925,7 @@ static noinline struct module *load_module(void __user *umod,
                err = -ENOEXEC;
                goto free_hdr;
        }
+       /* This is temporary: point mod into copy of data. */
        mod = (void *)sechdrs[modindex].sh_addr;
 
        if (symindex == 0) {
@@ -1946,22 +1935,6 @@ static noinline struct module *load_module(void __user *umod,
                goto free_hdr;
        }
 
-       /* Optional sections */
-       exportindex = find_sec(hdr, sechdrs, secstrings, "__ksymtab");
-       gplindex = find_sec(hdr, sechdrs, secstrings, "__ksymtab_gpl");
-       gplfutureindex = find_sec(hdr, sechdrs, secstrings, "__ksymtab_gpl_future");
-       crcindex = find_sec(hdr, sechdrs, secstrings, "__kcrctab");
-       gplcrcindex = find_sec(hdr, sechdrs, secstrings, "__kcrctab_gpl");
-       gplfuturecrcindex = find_sec(hdr, sechdrs, secstrings, "__kcrctab_gpl_future");
-#ifdef CONFIG_UNUSED_SYMBOLS
-       unusedindex = find_sec(hdr, sechdrs, secstrings, "__ksymtab_unused");
-       unusedgplindex = find_sec(hdr, sechdrs, secstrings, "__ksymtab_unused_gpl");
-       unusedcrcindex = find_sec(hdr, sechdrs, secstrings, "__kcrctab_unused");
-       unusedgplcrcindex = find_sec(hdr, sechdrs, secstrings, "__kcrctab_unused_gpl");
-#endif
-       setupindex = find_sec(hdr, sechdrs, secstrings, "__param");
-       exindex = find_sec(hdr, sechdrs, secstrings, "__ex_table");
-       obsparmindex = find_sec(hdr, sechdrs, secstrings, "__obsparm");
        versindex = find_sec(hdr, sechdrs, secstrings, "__versions");
        infoindex = find_sec(hdr, sechdrs, secstrings, ".modinfo");
        pcpuindex = find_pcpusec(hdr, sechdrs, secstrings);
@@ -2117,42 +2090,57 @@ static noinline struct module *load_module(void __user *umod,
        if (err < 0)
                goto cleanup;
 
-       /* Set up EXPORTed & EXPORT_GPLed symbols (section 0 is 0 length) */
-       mod->num_syms = sechdrs[exportindex].sh_size / sizeof(*mod->syms);
-       mod->syms = (void *)sechdrs[exportindex].sh_addr;
-       if (crcindex)
-               mod->crcs = (void *)sechdrs[crcindex].sh_addr;
-       mod->num_gpl_syms = sechdrs[gplindex].sh_size / sizeof(*mod->gpl_syms);
-       mod->gpl_syms = (void *)sechdrs[gplindex].sh_addr;
-       if (gplcrcindex)
-               mod->gpl_crcs = (void *)sechdrs[gplcrcindex].sh_addr;
-       mod->num_gpl_future_syms = sechdrs[gplfutureindex].sh_size /
-                                       sizeof(*mod->gpl_future_syms);
-       mod->gpl_future_syms = (void *)sechdrs[gplfutureindex].sh_addr;
-       if (gplfuturecrcindex)
-               mod->gpl_future_crcs = (void *)sechdrs[gplfuturecrcindex].sh_addr;
+       /* Now we've got everything in the final locations, we can
+        * find optional sections. */
+       kp = section_objs(hdr, sechdrs, secstrings, "__param", sizeof(*kp),
+                         &num_kp);
+       mod->syms = section_objs(hdr, sechdrs, secstrings, "__ksymtab",
+                                sizeof(*mod->syms), &mod->num_syms);
+       mod->crcs = section_addr(hdr, sechdrs, secstrings, "__kcrctab");
+       mod->gpl_syms = section_objs(hdr, sechdrs, secstrings, "__ksymtab_gpl",
+                                    sizeof(*mod->gpl_syms),
+                                    &mod->num_gpl_syms);
+       mod->gpl_crcs = section_addr(hdr, sechdrs, secstrings, "__kcrctab_gpl");
+       mod->gpl_future_syms = section_objs(hdr, sechdrs, secstrings,
+                                           "__ksymtab_gpl_future",
+                                           sizeof(*mod->gpl_future_syms),
+                                           &mod->num_gpl_future_syms);
+       mod->gpl_future_crcs = section_addr(hdr, sechdrs, secstrings,
+                                           "__kcrctab_gpl_future");
 
 #ifdef CONFIG_UNUSED_SYMBOLS
-       mod->num_unused_syms = sechdrs[unusedindex].sh_size /
-                                       sizeof(*mod->unused_syms);
-       mod->num_unused_gpl_syms = sechdrs[unusedgplindex].sh_size /
-                                       sizeof(*mod->unused_gpl_syms);
-       mod->unused_syms = (void *)sechdrs[unusedindex].sh_addr;
-       if (unusedcrcindex)
-               mod->unused_crcs = (void *)sechdrs[unusedcrcindex].sh_addr;
-       mod->unused_gpl_syms = (void *)sechdrs[unusedgplindex].sh_addr;
-       if (unusedgplcrcindex)
-               mod->unused_gpl_crcs
-                       = (void *)sechdrs[unusedgplcrcindex].sh_addr;
+       mod->unused_syms = section_objs(hdr, sechdrs, secstrings,
+                                       "__ksymtab_unused",
+                                       sizeof(*mod->unused_syms),
+                                       &mod->num_unused_syms);
+       mod->unused_crcs = section_addr(hdr, sechdrs, secstrings,
+                                       "__kcrctab_unused");
+       mod->unused_gpl_syms = section_objs(hdr, sechdrs, secstrings,
+                                           "__ksymtab_unused_gpl",
+                                           sizeof(*mod->unused_gpl_syms),
+                                           &mod->num_unused_gpl_syms);
+       mod->unused_gpl_crcs = section_addr(hdr, sechdrs, secstrings,
+                                           "__kcrctab_unused_gpl");
+#endif
+
+#ifdef CONFIG_MARKERS
+       mod->markers = section_objs(hdr, sechdrs, secstrings, "__markers",
+                                   sizeof(*mod->markers), &mod->num_markers);
+#endif
+#ifdef CONFIG_TRACEPOINTS
+       mod->tracepoints = section_objs(hdr, sechdrs, secstrings,
+                                       "__tracepoints",
+                                       sizeof(*mod->tracepoints),
+                                       &mod->num_tracepoints);
 #endif
 
 #ifdef CONFIG_MODVERSIONS
-       if ((mod->num_syms && !crcindex)
-           || (mod->num_gpl_syms && !gplcrcindex)
-           || (mod->num_gpl_future_syms && !gplfuturecrcindex)
+       if ((mod->num_syms && !mod->crcs)
+           || (mod->num_gpl_syms && !mod->gpl_crcs)
+           || (mod->num_gpl_future_syms && !mod->gpl_future_crcs)
 #ifdef CONFIG_UNUSED_SYMBOLS
-           || (mod->num_unused_syms && !unusedcrcindex)
-           || (mod->num_unused_gpl_syms && !unusedgplcrcindex)
+           || (mod->num_unused_syms && !mod->unused_crcs)
+           || (mod->num_unused_gpl_syms && !mod->unused_gpl_crcs)
 #endif
                ) {
                printk(KERN_WARNING "%s: No versions for exported symbols.\n", mod->name);
@@ -2161,16 +2149,6 @@ static noinline struct module *load_module(void __user *umod,
                        goto cleanup;
        }
 #endif
-       markersindex = find_sec(hdr, sechdrs, secstrings, "__markers");
-       markersstringsindex = find_sec(hdr, sechdrs, secstrings,
-                                       "__markers_strings");
-       verboseindex = find_sec(hdr, sechdrs, secstrings, "__verbose");
-       tracepointsindex = find_sec(hdr, sechdrs, secstrings, "__tracepoints");
-       tracepointsstringsindex = find_sec(hdr, sechdrs, secstrings,
-                                       "__tracepoints_strings");
-
-       mcountindex = find_sec(hdr, sechdrs, secstrings,
-                              "__mcount_loc");
 
        /* Now do relocations. */
        for (i = 1; i < hdr->e_shnum; i++) {
@@ -2193,28 +2171,16 @@ static noinline struct module *load_module(void __user *umod,
                if (err < 0)
                        goto cleanup;
        }
-#ifdef CONFIG_MARKERS
-       mod->markers = (void *)sechdrs[markersindex].sh_addr;
-       mod->num_markers =
-               sechdrs[markersindex].sh_size / sizeof(*mod->markers);
-#endif
-#ifdef CONFIG_TRACEPOINTS
-       mod->tracepoints = (void *)sechdrs[tracepointsindex].sh_addr;
-       mod->num_tracepoints =
-               sechdrs[tracepointsindex].sh_size / sizeof(*mod->tracepoints);
-#endif
-
 
         /* Find duplicate symbols */
        err = verify_export_symbols(mod);
-
        if (err < 0)
                goto cleanup;
 
        /* Set up and sort exception table */
-       mod->num_exentries = sechdrs[exindex].sh_size / sizeof(*mod->extable);
-       mod->extable = extable = (void *)sechdrs[exindex].sh_addr;
-       sort_extable(extable, extable + mod->num_exentries);
+       mod->extable = section_objs(hdr, sechdrs, secstrings, "__ex_table",
+                                   sizeof(*mod->extable), &mod->num_exentries);
+       sort_extable(mod->extable, mod->extable + mod->num_exentries);
 
        /* Finally, copy percpu area over. */
        percpu_modcopy(mod->percpu, (void *)sechdrs[pcpuindex].sh_addr,
@@ -2223,11 +2189,17 @@ static noinline struct module *load_module(void __user *umod,
        add_kallsyms(mod, sechdrs, symindex, strindex, secstrings);
 
        if (!mod->taints) {
+               struct mod_debug *debug;
+               unsigned int num_debug;
+
 #ifdef CONFIG_MARKERS
                marker_update_probe_range(mod->markers,
                        mod->markers + mod->num_markers);
 #endif
-       dynamic_printk_setup(sechdrs, verboseindex);
+               debug = section_objs(hdr, sechdrs, secstrings, "__verbose",
+                                    sizeof(*debug), &num_debug);
+               dynamic_printk_setup(debug, num_debug);
+
 #ifdef CONFIG_TRACEPOINTS
                tracepoint_update_probe_range(mod->tracepoints,
                        mod->tracepoints + mod->num_tracepoints);
@@ -2235,8 +2207,9 @@ static noinline struct module *load_module(void __user *umod,
        }
 
        /* sechdrs[0].sh_size is always zero */
-       mseg = (void *)sechdrs[mcountindex].sh_addr;
-       ftrace_init_module(mseg, mseg + sechdrs[mcountindex].sh_size);
+       mseg = section_objs(hdr, sechdrs, secstrings, "__mcount_loc",
+                           sizeof(*mseg), &num_mcount);
+       ftrace_init_module(mseg, mseg + num_mcount);
 
        err = module_finalize(hdr, sechdrs, mod);
        if (err < 0)
@@ -2261,7 +2234,7 @@ static noinline struct module *load_module(void __user *umod,
        set_fs(old_fs);
 
        mod->args = args;
-       if (obsparmindex)
+       if (section_addr(hdr, sechdrs, secstrings, "__obsparm"))
                printk(KERN_WARNING "%s: Ignoring obsolete parameters\n",
                       mod->name);
 
@@ -2270,21 +2243,11 @@ static noinline struct module *load_module(void __user *umod,
          * strong_try_module_get() will fail. */
        stop_machine(__link_module, mod, NULL);
 
-       /* Size of section 0 is 0, so this works well if no params */
-       err = parse_args(mod->name, mod->args,
-                        (struct kernel_param *)
-                        sechdrs[setupindex].sh_addr,
-                        sechdrs[setupindex].sh_size
-                        / sizeof(struct kernel_param),
-                        NULL);
+       err = parse_args(mod->name, mod->args, kp, num_kp, NULL);
        if (err < 0)
                goto unlink;
 
-       err = mod_sysfs_setup(mod,
-                             (struct kernel_param *)
-                             sechdrs[setupindex].sh_addr,
-                             sechdrs[setupindex].sh_size
-                             / sizeof(struct kernel_param));
+       err = mod_sysfs_setup(mod, kp, num_kp);
        if (err < 0)
                goto unlink;
        add_sect_attrs(mod, hdr->e_shnum, secstrings, sechdrs);