module: make it clearer when we're handling kallsyms symbols vs exported symbols

The module loader internally works with both exported symbols
represented as struct kernel_symbol, as well as Elf symbols from a
module's symbol table. It's hard to distinguish sometimes which type of
symbol we're handling given that some helper function names are not
consistent or helpful. Take get_ksymbol() for instance - are we
looking for an exported symbol or a kallsyms symbol here? Or symname()
and kernel_symbol_name() - which function handles an exported symbol and
which one an Elf symbol?

Clean up and unify the function naming scheme a bit to make it clear
which kind of symbol we're handling. This change only affects static
functions internal to the module loader.

Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Jessica Yu <jeyu@kernel.org>

diff --git a/kernel/module.c b/kernel/module.c
index 49a4058..1b5edf7 100644 (file)
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -495,9 +495,9 @@ struct find_symbol_arg {
        const struct kernel_symbol *sym;
 };
 
-static bool check_symbol(const struct symsearch *syms,
-                                struct module *owner,
-                                unsigned int symnum, void *data)
+static bool check_exported_symbol(const struct symsearch *syms,
+                                 struct module *owner,
+                                 unsigned int symnum, void *data)
 {
        struct find_symbol_arg *fsa = data;
 
@@ -555,9 +555,9 @@ static int cmp_name(const void *va, const void *vb)
        return strcmp(a, kernel_symbol_name(b));
 }
 
-static bool find_symbol_in_section(const struct symsearch *syms,
-                                  struct module *owner,
-                                  void *data)
+static bool find_exported_symbol_in_section(const struct symsearch *syms,
+                                           struct module *owner,
+                                           void *data)
 {
        struct find_symbol_arg *fsa = data;
        struct kernel_symbol *sym;
@@ -565,13 +565,14 @@ static bool find_symbol_in_section(const struct symsearch *syms,
        sym = bsearch(fsa->name, syms->start, syms->stop - syms->start,
                        sizeof(struct kernel_symbol), cmp_name);
 
-       if (sym != NULL && check_symbol(syms, owner, sym - syms->start, data))
+       if (sym != NULL && check_exported_symbol(syms, owner,
+                                                sym - syms->start, data))
                return true;
 
        return false;
 }
 
-/* Find a symbol and return it, along with, (optional) crc and
+/* Find an exported symbol and return it, along with, (optional) crc and
  * (optional) module which owns it.  Needs preempt disabled or module_mutex. */
 const struct kernel_symbol *find_symbol(const char *name,
                                        struct module **owner,
@@ -585,7 +586,7 @@ const struct kernel_symbol *find_symbol(const char *name,
        fsa.gplok = gplok;
        fsa.warn = warn;
 
-       if (each_symbol_section(find_symbol_in_section, &fsa)) {
+       if (each_symbol_section(find_exported_symbol_in_section, &fsa)) {
                if (owner)
                        *owner = fsa.owner;
                if (crc)
@@ -2198,7 +2199,7 @@ EXPORT_SYMBOL_GPL(__symbol_get);
  *
  * You must hold the module_mutex.
  */
-static int verify_export_symbols(struct module *mod)
+static int verify_exported_symbols(struct module *mod)
 {
        unsigned int i;
        struct module *owner;
@@ -2519,10 +2520,10 @@ static void free_modinfo(struct module *mod)
 
 #ifdef CONFIG_KALLSYMS
 
-/* 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)
+/* Lookup exported symbol in given range of kernel_symbols */
+static const struct kernel_symbol *lookup_exported_symbol(const char *name,
+                                                         const struct kernel_symbol *start,
+                                                         const struct kernel_symbol *stop)
 {
        return bsearch(name, start, stop - start,
                        sizeof(struct kernel_symbol), cmp_name);
@@ -2533,9 +2534,10 @@ static int is_exported(const char *name, unsigned long value,
 {
        const struct kernel_symbol *ks;
        if (!mod)
-               ks = lookup_symbol(name, __start___ksymtab, __stop___ksymtab);
+               ks = lookup_exported_symbol(name, __start___ksymtab, __stop___ksymtab);
        else
-               ks = lookup_symbol(name, mod->syms, mod->syms + mod->num_syms);
+               ks = lookup_exported_symbol(name, mod->syms, mod->syms + mod->num_syms);
+
        return ks != NULL && kernel_symbol_value(ks) == value;
 }
 
@@ -3592,7 +3594,7 @@ static int complete_formation(struct module *mod, struct load_info *info)
        mutex_lock(&module_mutex);
 
        /* Find duplicate symbols (must be called under lock). */
-       err = verify_export_symbols(mod);
+       err = verify_exported_symbols(mod);
        if (err < 0)
                goto out;
 
@@ -3911,15 +3913,19 @@ static inline int is_arm_mapping_symbol(const char *str)
               && (str[2] == '\0' || str[2] == '.');
 }
 
-static const char *symname(struct mod_kallsyms *kallsyms, unsigned int symnum)
+static const char *kallsyms_symbol_name(struct mod_kallsyms *kallsyms, unsigned int symnum)
 {
        return kallsyms->strtab + kallsyms->symtab[symnum].st_name;
 }
 
-static const char *get_ksymbol(struct module *mod,
-                              unsigned long addr,
-                              unsigned long *size,
-                              unsigned long *offset)
+/*
+ * Given a module and address, find the corresponding symbol and return its name
+ * while providing its size and offset if needed.
+ */
+static const char *find_kallsyms_symbol(struct module *mod,
+                                       unsigned long addr,
+                                       unsigned long *size,
+                                       unsigned long *offset)
 {
        unsigned int i, best = 0;
        unsigned long nextval;
@@ -3939,8 +3945,8 @@ static const char *get_ksymbol(struct module *mod,
 
                /* We ignore unnamed symbols: they're uninformative
                 * and inserted at a whim. */
-               if (*symname(kallsyms, i) == '\0'
-                   || is_arm_mapping_symbol(symname(kallsyms, i)))
+               if (*kallsyms_symbol_name(kallsyms, i) == '\0'
+                   || is_arm_mapping_symbol(kallsyms_symbol_name(kallsyms, i)))
                        continue;
 
                if (kallsyms->symtab[i].st_value <= addr
@@ -3958,7 +3964,8 @@ static const char *get_ksymbol(struct module *mod,
                *size = nextval - kallsyms->symtab[best].st_value;
        if (offset)
                *offset = addr - kallsyms->symtab[best].st_value;
-       return symname(kallsyms, best);
+
+       return kallsyms_symbol_name(kallsyms, best);
 }
 
 void * __weak dereference_module_function_descriptor(struct module *mod,
@@ -3983,7 +3990,8 @@ const char *module_address_lookup(unsigned long addr,
        if (mod) {
                if (modname)
                        *modname = mod->name;
-               ret = get_ksymbol(mod, addr, size, offset);
+
+               ret = find_kallsyms_symbol(mod, addr, size, offset);
        }
        /* Make a copy in here where it's safe */
        if (ret) {
@@ -4006,9 +4014,10 @@ int lookup_module_symbol_name(unsigned long addr, char *symname)
                if (within_module(addr, mod)) {
                        const char *sym;
 
-                       sym = get_ksymbol(mod, addr, NULL, NULL);
+                       sym = find_kallsyms_symbol(mod, addr, NULL, NULL);
                        if (!sym)
                                goto out;
+
                        strlcpy(symname, sym, KSYM_NAME_LEN);
                        preempt_enable();
                        return 0;
@@ -4031,7 +4040,7 @@ int lookup_module_symbol_attrs(unsigned long addr, unsigned long *size,
                if (within_module(addr, mod)) {
                        const char *sym;
 
-                       sym = get_ksymbol(mod, addr, size, offset);
+                       sym = find_kallsyms_symbol(mod, addr, size, offset);
                        if (!sym)
                                goto out;
                        if (modname)
@@ -4062,7 +4071,7 @@ int module_get_kallsym(unsigned int symnum, unsigned long *value, char *type,
                if (symnum < kallsyms->num_symtab) {
                        *value = kallsyms->symtab[symnum].st_value;
                        *type = kallsyms->symtab[symnum].st_info;
-                       strlcpy(name, symname(kallsyms, symnum), KSYM_NAME_LEN);
+                       strlcpy(name, kallsyms_symbol_name(kallsyms, symnum), KSYM_NAME_LEN);
                        strlcpy(module_name, mod->name, MODULE_NAME_LEN);
                        *exported = is_exported(name, *value, mod);
                        preempt_enable();
@@ -4074,13 +4083,14 @@ int module_get_kallsym(unsigned int symnum, unsigned long *value, char *type,
        return -ERANGE;
 }
 
-static unsigned long mod_find_symname(struct module *mod, const char *name)
+/* Given a module and name of symbol, find and return the symbol's value */
+static unsigned long find_kallsyms_symbol_value(struct module *mod, const char *name)
 {
        unsigned int i;
        struct mod_kallsyms *kallsyms = rcu_dereference_sched(mod->kallsyms);
 
        for (i = 0; i < kallsyms->num_symtab; i++)
-               if (strcmp(name, symname(kallsyms, i)) == 0 &&
+               if (strcmp(name, kallsyms_symbol_name(kallsyms, i)) == 0 &&
                    kallsyms->symtab[i].st_shndx != SHN_UNDEF)
                        return kallsyms->symtab[i].st_value;
        return 0;
@@ -4097,12 +4107,12 @@ unsigned long module_kallsyms_lookup_name(const char *name)
        preempt_disable();
        if ((colon = strnchr(name, MODULE_NAME_LEN, ':')) != NULL) {
                if ((mod = find_module_all(name, colon - name, false)) != NULL)
-                       ret = mod_find_symname(mod, colon+1);
+                       ret = find_kallsyms_symbol_value(mod, colon+1);
        } else {
                list_for_each_entry_rcu(mod, &modules, list) {
                        if (mod->state == MODULE_STATE_UNFORMED)
                                continue;
-                       if ((ret = mod_find_symname(mod, name)) != 0)
+                       if ((ret = find_kallsyms_symbol_value(mod, name)) != 0)
                                break;
                }
        }
@@ -4131,7 +4141,7 @@ int module_kallsyms_on_each_symbol(int (*fn)(void *, const char *,
                        if (kallsyms->symtab[i].st_shndx == SHN_UNDEF)
                                continue;
 
-                       ret = fn(data, symname(kallsyms, i),
+                       ret = fn(data, kallsyms_symbol_name(kallsyms, i),
                                 mod, kallsyms->symtab[i].st_value);
                        if (ret != 0)
                                return ret;