module: neaten __find_symbol, rename to find_symbol

__find_symbol() has grown over time: there are now 5 different arrays
of symbols it traverses.  It also shouldn't print out a warning on
some calls (ie. verify_symbol which simply checks for name clashes,
and __symbol_put which checks for bugs).

1) Rename to find_symbol: no need for underscores.
2) Use bool and add "warn" parameter to suppress warnings.
3) Make table-driven rather than open coded.

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

1 files changed, 125 insertions, 121 deletions

diff --git a/kernel/module.c b/kernel/module.c
index 031bf26af8ea..679e4c88ed9e 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -164,131 +164,140 @@ static const struct kernel_symbol *lookup_symbol(const char *name,
         return NULL;
 }
 
-static void printk_unused_warning(const char *name)
+static bool always_ok(bool gplok, bool warn, const char *name)
 {
-        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;
 }
 
-/* Find a symbol, return value, crc and module which owns it */
-static unsigned long __find_symbol(const char *name,
-                                   struct module **owner,
-                                   const unsigned long **crc,
-                                   int gplok)
+static bool printk_unused_warning(bool gplok, bool warn, const char *name)
 {
-        struct module *mod;
-        const struct kernel_symbol *ks;
-
-        /* Core kernel first. */
-        *owner = NULL;
-        ks = lookup_symbol(name, __start___ksymtab, __stop___ksymtab);
-        if (ks) {
-                *crc = symversion(__start___kcrctab, (ks - __start___ksymtab));
-                return ks->value;
+        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");
         }
-        if (gplok) {
-                ks = lookup_symbol(name, __start___ksymtab_gpl,
-                                         __stop___ksymtab_gpl);
-                if (ks) {
-                        *crc = symversion(__start___kcrctab_gpl,
-                                          (ks - __start___ksymtab_gpl));
-                        return ks->value;
-                }
-        }
-        ks = lookup_symbol(name, __start___ksymtab_gpl_future,
-                                 __stop___ksymtab_gpl_future);
-        if (ks) {
-                if (!gplok) {
-                        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");
-                }
-                *crc = symversion(__start___kcrctab_gpl_future,
-                                  (ks - __start___ksymtab_gpl_future));
-                return ks->value;
+        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;
+}
 
-        ks = lookup_symbol(name, __start___ksymtab_unused,
-                                 __stop___ksymtab_unused);
-        if (ks) {
-                printk_unused_warning(name);
-                *crc = symversion(__start___kcrctab_unused,
-                                  (ks - __start___ksymtab_unused));
-                return ks->value;
+struct symsearch {
+        const struct kernel_symbol *start, *stop;
+        const unsigned long *crcs;
+        bool (*check)(bool gplok, bool warn, const char *name);
+};
+
+/* 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)
+{
+        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;
+
+                if (crc)
+                        *crc = symversion(arr[i].crcs, ks - arr[i].start);
+                return ks;
         }
+        return NULL;
+}
 
-        if (gplok)
-                ks = lookup_symbol(name, __start___ksymtab_unused_gpl,
-                                 __stop___ksymtab_unused_gpl);
+/* 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 module *mod;
+        const struct kernel_symbol *ks;
+        const struct symsearch arr[] = {
+                { __start___ksymtab, __stop___ksymtab, __start___kcrctab,
+                  always_ok },
+                { __start___ksymtab_gpl, __stop___ksymtab_gpl,
+                  __start___kcrctab_gpl, gpl_only },
+                { __start___ksymtab_gpl_future, __stop___ksymtab_gpl_future,
+                  __start___kcrctab_gpl_future, warn_if_not_gpl },
+                { __start___ksymtab_unused, __stop___ksymtab_unused,
+                  __start___kcrctab_unused, printk_unused_warning },
+                { __start___ksymtab_unused_gpl, __stop___ksymtab_unused_gpl,
+                  __start___kcrctab_unused_gpl, gpl_only_unused_warning },
+        };
+
+        /* Core kernel first. */
+        ks = search_symarrays(arr, ARRAY_SIZE(arr), name, gplok, warn, crc);
         if (ks) {
-                printk_unused_warning(name);
-                *crc = symversion(__start___kcrctab_unused_gpl,
-                                  (ks - __start___ksymtab_unused_gpl));
+                if (owner)
+                        *owner = NULL;
                 return ks->value;
         }
 
         /* Now try modules. */
         list_for_each_entry(mod, &modules, list) {
-                *owner = mod;
-                ks = lookup_symbol(name, mod->syms, mod->syms + mod->num_syms);
+                struct symsearch arr[] = {
+                        { mod->syms, mod->syms + mod->num_syms, mod->crcs,
+                          always_ok },
+                        { mod->gpl_syms, mod->gpl_syms + mod->num_gpl_syms,
+                          mod->gpl_crcs, gpl_only },
+                        { mod->gpl_future_syms,
+                          mod->gpl_future_syms + mod->num_gpl_future_syms,
+                          mod->gpl_future_crcs, warn_if_not_gpl },
+                        { mod->unused_syms,
+                          mod->unused_syms + mod->num_unused_syms,
+                          mod->unused_crcs, printk_unused_warning },
+                        { mod->unused_gpl_syms,
+                          mod->unused_gpl_syms + mod->num_unused_gpl_syms,
+                          mod->unused_gpl_crcs, gpl_only_unused_warning },
+                };
+
+                ks = search_symarrays(arr, ARRAY_SIZE(arr),
+                                      name, gplok, warn, crc);
                 if (ks) {
-                        *crc = symversion(mod->crcs, (ks - mod->syms));
-                        return ks->value;
-                }
-
-                if (gplok) {
-                        ks = lookup_symbol(name, mod->gpl_syms,
-                                           mod->gpl_syms + mod->num_gpl_syms);
-                        if (ks) {
-                                *crc = symversion(mod->gpl_crcs,
-                                                  (ks - mod->gpl_syms));
-                                return ks->value;
-                        }
-                }
-                ks = lookup_symbol(name, mod->unused_syms, mod->unused_syms + mod->num_unused_syms);
-                if (ks) {
-                        printk_unused_warning(name);
-                        *crc = symversion(mod->unused_crcs, (ks - mod->unused_syms));
-                        return ks->value;
-                }
-
-                if (gplok) {
-                        ks = lookup_symbol(name, mod->unused_gpl_syms,
-                                           mod->unused_gpl_syms + mod->num_unused_gpl_syms);
-                        if (ks) {
-                                printk_unused_warning(name);
-                                *crc = symversion(mod->unused_gpl_crcs,
-                                                  (ks - mod->unused_gpl_syms));
-                                return ks->value;
-                        }
-                }
-                ks = lookup_symbol(name, mod->gpl_future_syms,
-                                   (mod->gpl_future_syms +
-                                    mod->num_gpl_future_syms));
-                if (ks) {
-                        if (!gplok) {
-                                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");
-                        }
-                        *crc = symversion(mod->gpl_future_crcs,
-                                          (ks - mod->gpl_future_syms));
+                        if (owner)
+                                *owner = mod;
                         return ks->value;
                 }
         }
+
         DEBUGP("Failed to find symbol %s\n", name);
         return -ENOENT;
 }
@@ -777,10 +786,9 @@ static void print_unload_info(struct seq_file *m, struct module *mod)
 void __symbol_put(const char *symbol)
 {
         struct module *owner;
-        const unsigned long *crc;
 
         preempt_disable();
-        if (IS_ERR_VALUE(__find_symbol(symbol, &owner, &crc, 1)))
+        if (IS_ERR_VALUE(find_symbol(symbol, &owner, NULL, true, false)))
                 BUG();
         module_put(owner);
         preempt_enable();
@@ -924,13 +932,10 @@ static inline int check_modstruct_version(Elf_Shdr *sechdrs,
                                           struct module *mod)
 {
         const unsigned long *crc;
-        struct module *owner;
 
-        if (IS_ERR_VALUE(__find_symbol("struct_module",
-                                                &owner, &crc, 1)))
+        if (IS_ERR_VALUE(find_symbol("struct_module", NULL, &crc, true, false)))
                 BUG();
-        return check_version(sechdrs, versindex, "struct_module", mod,
-                             crc);
+        return check_version(sechdrs, versindex, "struct_module", mod, crc);
 }
 
 /* First part is kernel version, which we ignore. */
@@ -974,8 +979,8 @@ static unsigned long resolve_symbol(Elf_Shdr *sechdrs,
         unsigned long ret;
         const unsigned long *crc;
 
-        ret = __find_symbol(name, &owner, &crc,
-                        !(mod->taints & TAINT_PROPRIETARY_MODULE));
+        ret = find_symbol(name, &owner, &crc,
+                          !(mod->taints & TAINT_PROPRIETARY_MODULE), true);
         if (!IS_ERR_VALUE(ret)) {
                 /* use_module can fail due to OOM,
                    or module initialization or unloading */
@@ -1376,10 +1381,9 @@ void *__symbol_get(const char *symbol)
 {
         struct module *owner;
         unsigned long value;
-        const unsigned long *crc;
 
         preempt_disable();
-        value = __find_symbol(symbol, &owner, &crc, 1);
+        value = find_symbol(symbol, &owner, NULL, true, true);
         if (IS_ERR_VALUE(value))
                 value = 0;
         else if (strong_try_module_get(owner))
@@ -1402,16 +1406,16 @@ static int verify_export_symbols(struct module *mod)
         const unsigned long *crc;
 
         for (i = 0; i < mod->num_syms; i++)
-                if (!IS_ERR_VALUE(__find_symbol(mod->syms[i].name,
-                                                        &owner, &crc, 1))) {
+                if (!IS_ERR_VALUE(find_symbol(mod->syms[i].name,
+                                              &owner, &crc, true, false))) {
                         name = mod->syms[i].name;
                         ret = -ENOEXEC;
                         goto dup;
                 }
 
         for (i = 0; i < mod->num_gpl_syms; i++)
-                if (!IS_ERR_VALUE(__find_symbol(mod->gpl_syms[i].name,
-                                                        &owner, &crc, 1))) {
+                if (!IS_ERR_VALUE(find_symbol(mod->gpl_syms[i].name,
+                                              &owner, &crc, true, false))) {
                         name = mod->gpl_syms[i].name;
                         ret = -ENOEXEC;
                         goto dup;