module: generic each_symbol iterator function

Introduce an each_symbol() iterator to avoid duplicating the knowledge
about the 5 different sections containing symbols.  Currently only
used by find_symbol(), but will be used by symbol_put_addr() too.

(Includes NULL ptr deref fix by Jiri Kosina <jkosina@suse.cz>)

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Jiri Kosina <jkosina@suse.cz>

1 files changed, 134 insertions, 110 deletions

diff --git a/kernel/module.c b/kernel/module.c
index 705e1d5d516c..c51c089c666e 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -152,156 +152,180 @@ extern const unsigned long __start___kcrctab_unused_gpl[];
 #define symversion(base, idx) ((base != NULL) ? ((base) + (idx)) : NULL)
 #endif
 
-/* lookup symbol in given range of kernel_symbols */
-static const struct kernel_symbol *lookup_symbol(const char *name,
-        const struct kernel_symbol *start,
-        const struct kernel_symbol *stop)
-{
-        const struct kernel_symbol *ks = start;
-        for (; ks < stop; ks++)
-                if (strcmp(ks->name, name) == 0)
-                        return ks;
-        return NULL;
-}
-
-static bool always_ok(bool gplok, bool warn, const char *name)
-{
-        return true;
-}
-
-static bool printk_unused_warning(bool gplok, bool warn, const char *name)
-{
-        if (warn) {
-                printk(KERN_WARNING "Symbol %s is marked as UNUSED, "
-                       "however this module is using it.\n", name);
-                printk(KERN_WARNING
-                       "This symbol will go away in the future.\n");
-                printk(KERN_WARNING
-                       "Please evalute if this is the right api to use and if "
-                       "it really is, submit a report the linux kernel "
-                       "mailinglist together with submitting your code for "
-                       "inclusion.\n");
-        }
-        return true;
-}
-
-static bool gpl_only_unused_warning(bool gplok, bool warn, const char *name)
-{
-        if (!gplok)
-                return false;
-        return printk_unused_warning(gplok, warn, name);
-}
-
-static bool gpl_only(bool gplok, bool warn, const char *name)
-{
-        return gplok;
-}
-
-static bool warn_if_not_gpl(bool gplok, bool warn, const char *name)
-{
-        if (!gplok && warn) {
-                printk(KERN_WARNING "Symbol %s is being used "
-                       "by a non-GPL module, which will not "
-                       "be allowed in the future\n", name);
-                printk(KERN_WARNING "Please see the file "
-                       "Documentation/feature-removal-schedule.txt "
-                       "in the kernel source tree for more details.\n");
-        }
-        return true;
-}
-
 struct symsearch {
         const struct kernel_symbol *start, *stop;
         const unsigned long *crcs;
-        bool (*check)(bool gplok, bool warn, const char *name);
+        enum {
+                NOT_GPL_ONLY,
+                GPL_ONLY,
+                WILL_BE_GPL_ONLY,
+        } licence;
+        bool unused;
 };
 
-/* Look through this array of symbol tables for a symbol match which
- * passes the check function. */
-static const struct kernel_symbol *search_symarrays(const struct symsearch *arr,
-                                                    unsigned int num,
-                                                    const char *name,
-                                                    bool gplok,
-                                                    bool warn,
-                                                    const unsigned long **crc)
+static bool each_symbol_in_section(const struct symsearch *arr,
+                                   unsigned int arrsize,
+                                   struct module *owner,
+                                   bool (*fn)(const struct symsearch *syms,
+                                              struct module *owner,
+                                              unsigned int symnum, void *data),
+                                   void *data)
 {
-        unsigned int i;
-        const struct kernel_symbol *ks;
-
-        for (i = 0; i < num; i++) {
-                ks = lookup_symbol(name, arr[i].start, arr[i].stop);
-                if (!ks || !arr[i].check(gplok, warn, name))
-                        continue;
+        unsigned int i, j;
 
-                if (crc)
-                        *crc = symversion(arr[i].crcs, ks - arr[i].start);
-                return ks;
+        for (j = 0; j < arrsize; j++) {
+                for (i = 0; i < arr[j].stop - arr[j].start; i++)
+                        if (fn(&arr[j], owner, i, data))
+                                return true;
         }
-        return NULL;
+
+        return false;
 }
 
-/* Find a symbol, return value, (optional) crc and (optional) module
- * which owns it */
-static unsigned long find_symbol(const char *name,
-                                 struct module **owner,
-                                 const unsigned long **crc,
-                                 bool gplok,
-                                 bool warn)
+/* Returns true as soon as fn returns true, otherwise false. */
+static bool each_symbol(bool (*fn)(const struct symsearch *arr,
+                                   struct module *owner,
+                                   unsigned int symnum, void *data),
+                        void *data)
 {
         struct module *mod;
-        const struct kernel_symbol *ks;
         const struct symsearch arr[] = {
                 { __start___ksymtab, __stop___ksymtab, __start___kcrctab,
-                  always_ok },
+                  NOT_GPL_ONLY, false },
                 { __start___ksymtab_gpl, __stop___ksymtab_gpl,
-                  __start___kcrctab_gpl, gpl_only },
+                  __start___kcrctab_gpl,
+                  GPL_ONLY, false },
                 { __start___ksymtab_gpl_future, __stop___ksymtab_gpl_future,
-                  __start___kcrctab_gpl_future, warn_if_not_gpl },
+                  __start___kcrctab_gpl_future,
+                  WILL_BE_GPL_ONLY, false },
                 { __start___ksymtab_unused, __stop___ksymtab_unused,
-                  __start___kcrctab_unused, printk_unused_warning },
+                  __start___kcrctab_unused,
+                  NOT_GPL_ONLY, true },
                 { __start___ksymtab_unused_gpl, __stop___ksymtab_unused_gpl,
-                  __start___kcrctab_unused_gpl, gpl_only_unused_warning },
+                  __start___kcrctab_unused_gpl,
+                  GPL_ONLY, true },
         };
 
-        /* Core kernel first. */
-        ks = search_symarrays(arr, ARRAY_SIZE(arr), name, gplok, warn, crc);
-        if (ks) {
-                if (owner)
-                        *owner = NULL;
-                return ks->value;
-        }
+        if (each_symbol_in_section(arr, ARRAY_SIZE(arr), NULL, fn, data))
+                return true;
 
-        /* Now try modules. */
         list_for_each_entry(mod, &modules, list) {
                 struct symsearch arr[] = {
                         { mod->syms, mod->syms + mod->num_syms, mod->crcs,
-                          always_ok },
+                          NOT_GPL_ONLY, false },
                         { mod->gpl_syms, mod->gpl_syms + mod->num_gpl_syms,
-                          mod->gpl_crcs, gpl_only },
+                          mod->gpl_crcs,
+                          GPL_ONLY, false },
                         { mod->gpl_future_syms,
                           mod->gpl_future_syms + mod->num_gpl_future_syms,
-                          mod->gpl_future_crcs, warn_if_not_gpl },
+                          mod->gpl_future_crcs,
+                          WILL_BE_GPL_ONLY, false },
                         { mod->unused_syms,
                           mod->unused_syms + mod->num_unused_syms,
-                          mod->unused_crcs, printk_unused_warning },
+                          mod->unused_crcs,
+                          NOT_GPL_ONLY, true },
                         { mod->unused_gpl_syms,
                           mod->unused_gpl_syms + mod->num_unused_gpl_syms,
-                          mod->unused_gpl_crcs, gpl_only_unused_warning },
+                          mod->unused_gpl_crcs,
+                          GPL_ONLY, true },
                 };
 
-                ks = search_symarrays(arr, ARRAY_SIZE(arr),
-                                      name, gplok, warn, crc);
-                if (ks) {
-                        if (owner)
-                                *owner = mod;
-                        return ks->value;
+                if (each_symbol_in_section(arr, ARRAY_SIZE(arr), mod, fn, data))
+                        return true;
+        }
+        return false;
+}
+
+struct find_symbol_arg {
+        /* Input */
+        const char *name;
+        bool gplok;
+        bool warn;
+
+        /* Output */
+        struct module *owner;
+        const unsigned long *crc;
+        unsigned long value;
+};
+
+static bool find_symbol_in_section(const struct symsearch *syms,
+                                   struct module *owner,
+                                   unsigned int symnum, void *data)
+{
+        struct find_symbol_arg *fsa = data;
+
+        if (strcmp(syms->start[symnum].name, fsa->name) != 0)
+                return false;
+
+        if (!fsa->gplok) {
+                if (syms->licence == GPL_ONLY)
+                        return false;
+                if (syms->licence == WILL_BE_GPL_ONLY && fsa->warn) {
+                        printk(KERN_WARNING "Symbol %s is being used "
+                               "by a non-GPL module, which will not "
+                               "be allowed in the future\n", fsa->name);
+                        printk(KERN_WARNING "Please see the file "
+                               "Documentation/feature-removal-schedule.txt "
+                               "in the kernel source tree for more details.\n");
                 }
         }
 
+        if (syms->unused && fsa->warn) {
+                printk(KERN_WARNING "Symbol %s is marked as UNUSED, "
+                       "however this module is using it.\n", fsa->name);
+                printk(KERN_WARNING
+                       "This symbol will go away in the future.\n");
+                printk(KERN_WARNING
+                       "Please evalute if this is the right api to use and if "
+                       "it really is, submit a report the linux kernel "
+                       "mailinglist together with submitting your code for "
+                       "inclusion.\n");
+        }
+
+        fsa->owner = owner;
+        fsa->crc = symversion(syms->crcs, symnum);
+        fsa->value = syms->start[symnum].value;
+        return true;
+}
+
+/* Find a symbol, return value, (optional) crc and (optional) module
+ * which owns it */
+static unsigned long find_symbol(const char *name,
+                                 struct module **owner,
+                                 const unsigned long **crc,
+                                 bool gplok,
+                                 bool warn)
+{
+        struct find_symbol_arg fsa;
+
+        fsa.name = name;
+        fsa.gplok = gplok;
+        fsa.warn = warn;
+
+        if (each_symbol(find_symbol_in_section, &fsa)) {
+                if (owner)
+                        *owner = fsa.owner;
+                if (crc)
+                        *crc = fsa.crc;
+                return fsa.value;
+        }
+
         DEBUGP("Failed to find symbol %s\n", name);
         return -ENOENT;
 }
 
+/* lookup symbol in given range of kernel_symbols */
+static const struct kernel_symbol *lookup_symbol(const char *name,
+        const struct kernel_symbol *start,
+        const struct kernel_symbol *stop)
+{
+        const struct kernel_symbol *ks = start;
+        for (; ks < stop; ks++)
+                if (strcmp(ks->name, name) == 0)
+                        return ks;
+        return NULL;
+}
+
 /* Search for module by name: must hold module_mutex. */
 static struct module *find_module(const char *name)
 {