Ksplice: Add functions for walking kallsyms symbols

Impact: New API

kallsyms_lookup_name only returns the first match that it finds.  Ksplice
needs information about all symbols with a given name in order to correctly
resolve local symbols.

kallsyms_on_each_symbol provides a generic mechanism for iterating over the
kallsyms table.

Cc: Jeff Arnold <jbarnold@mit.edu>
Cc: Tim Abbott <tabbott@mit.edu>
Signed-off-by: Anders Kaseorg <andersk@mit.edu>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

4 files changed, 65 insertions, 0 deletions

diff --git a/include/linux/kallsyms.h b/include/linux/kallsyms.h
index f3fe34391d8e..792274269f2b 100644
--- a/include/linux/kallsyms.h
+++ b/include/linux/kallsyms.h
@@ -13,10 +13,17 @@
 #define KSYM_SYMBOL_LEN (sizeof("%s+%#lx/%#lx [%s]") + (KSYM_NAME_LEN - 1) + \
                          2*(BITS_PER_LONG*3/10) + (MODULE_NAME_LEN - 1) + 1)
 
+struct module;
+
 #ifdef CONFIG_KALLSYMS
 /* Lookup the address for a symbol. Returns 0 if not found. */
 unsigned long kallsyms_lookup_name(const char *name);
 
+/* Call a function on each kallsyms symbol in the core kernel */
+int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
+                                      unsigned long),
+                            void *data);
+
 extern int kallsyms_lookup_size_offset(unsigned long addr,
                                   unsigned long *symbolsize,
                                   unsigned long *offset);
@@ -43,6 +50,14 @@ static inline unsigned long kallsyms_lookup_name(const char *name)
         return 0;
 }
 
+static inline int kallsyms_on_each_symbol(int (*fn)(void *, const char *,
+                                                    struct module *,
+                                                    unsigned long),
+                                          void *data)
+{
+        return 0;
+}
+
 static inline int kallsyms_lookup_size_offset(unsigned long addr,
                                               unsigned long *symbolsize,
                                               unsigned long *offset)
diff --git a/include/linux/module.h b/include/linux/module.h
index 69761ce0dbf0..c3d3fc4ffb18 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -387,6 +387,10 @@ int module_get_kallsym(unsigned int symnum, unsigned long *value, char *type,
 /* Look for this name: can be of form module:name. */
 unsigned long module_kallsyms_lookup_name(const char *name);
 
+int module_kallsyms_on_each_symbol(int (*fn)(void *, const char *,
+                                             struct module *, unsigned long),
+                                   void *data);
+
 extern void __module_put_and_exit(struct module *mod, long code)
         __attribute__((noreturn));
 #define module_put_and_exit(code) __module_put_and_exit(THIS_MODULE, code);
@@ -566,6 +570,14 @@ static inline unsigned long module_kallsyms_lookup_name(const char *name)
         return 0;
 }
 
+static inline int module_kallsyms_on_each_symbol(int (*fn)(void *, const char *,
+                                                           struct module *,
+                                                           unsigned long),
+                                                 void *data)
+{
+        return 0;
+}
+
 static inline int register_module_notifier(struct notifier_block * nb)
 {
         /* no events will happen anyway, so this can always succeed */
diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index 7b8b0f21a5b1..374faf9bfdc7 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -161,6 +161,25 @@ unsigned long kallsyms_lookup_name(const char *name)
         return module_kallsyms_lookup_name(name);
 }
 
+int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
+                                      unsigned long),
+                            void *data)
+{
+        char namebuf[KSYM_NAME_LEN];
+        unsigned long i;
+        unsigned int off;
+        int ret;
+
+        for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
+                off = kallsyms_expand_symbol(off, namebuf);
+                ret = fn(data, namebuf, NULL, kallsyms_addresses[i]);
+                if (ret != 0)
+                        return ret;
+        }
+        return module_kallsyms_on_each_symbol(fn, data);
+}
+EXPORT_SYMBOL_GPL(kallsyms_on_each_symbol);
+
 static unsigned long get_symbol_pos(unsigned long addr,
                                     unsigned long *symbolsize,
                                     unsigned long *offset)
diff --git a/kernel/module.c b/kernel/module.c
index 8ddca629e079..dd4389be9152 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2612,6 +2612,25 @@ unsigned long module_kallsyms_lookup_name(const char *name)
         preempt_enable();
         return ret;
 }
+
+int module_kallsyms_on_each_symbol(int (*fn)(void *, const char *,
+                                             struct module *, unsigned long),
+                                   void *data)
+{
+        struct module *mod;
+        unsigned int i;
+        int ret;
+
+        list_for_each_entry(mod, &modules, list) {
+                for (i = 0; i < mod->num_symtab; i++) {
+                        ret = fn(data, mod->strtab + mod->symtab[i].st_name,
+                                 mod, mod->symtab[i].st_value);
+                        if (ret != 0)
+                                return ret;
+                }
+        }
+        return 0;
+}
 #endif /* CONFIG_KALLSYMS */
 
 static char *module_flags(struct module *mod, char *buf)