module: Make find_symbol return a struct kernel_symbol

Impact: Cleanup, internal API change

Ksplice needs access to the kernel_symbol structure in order to support
modifications to the exported symbol table.

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

1 files changed, 37 insertions, 38 deletions

diff --git a/kernel/module.c b/kernel/module.c
index 7af72bbe4cc0..2f0fddf3c114 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -283,7 +283,7 @@ struct find_symbol_arg {
         /* Output */
         struct module *owner;
         const unsigned long *crc;
-        unsigned long value;
+        const struct kernel_symbol *sym;
 };
 
 static bool find_symbol_in_section(const struct symsearch *syms,
@@ -324,17 +324,17 @@ static bool find_symbol_in_section(const struct symsearch *syms,
 
         fsa->owner = owner;
         fsa->crc = symversion(syms->crcs, symnum);
-        fsa->value = syms->start[symnum].value;
+        fsa->sym = &syms->start[symnum];
         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)
+/* Find a symbol and return it, along with, (optional) crc and
+ * (optional) module which owns it */
+static const struct kernel_symbol *find_symbol(const char *name,
+                                               struct module **owner,
+                                               const unsigned long **crc,
+                                               bool gplok,
+                                               bool warn)
 {
         struct find_symbol_arg fsa;
 
@@ -347,11 +347,11 @@ static unsigned long find_symbol(const char *name,
                         *owner = fsa.owner;
                 if (crc)
                         *crc = fsa.crc;
-                return fsa.value;
+                return fsa.sym;
         }
 
         DEBUGP("Failed to find symbol %s\n", name);
-        return -ENOENT;
+        return NULL;
 }
 
 /* Search for module by name: must hold module_mutex. */
@@ -894,7 +894,7 @@ void __symbol_put(const char *symbol)
         struct module *owner;
 
         preempt_disable();
-        if (IS_ERR_VALUE(find_symbol(symbol, &owner, NULL, true, false)))
+        if (!find_symbol(symbol, &owner, NULL, true, false))
                 BUG();
         module_put(owner);
         preempt_enable();
@@ -1057,7 +1057,7 @@ static inline int check_modstruct_version(Elf_Shdr *sechdrs,
 {
         const unsigned long *crc;
 
-        if (IS_ERR_VALUE(find_symbol("struct_module", NULL, &crc, true, false)))
+        if (!find_symbol("struct_module", NULL, &crc, true, false))
                 BUG();
         return check_version(sechdrs, versindex, "struct_module", mod, crc);
 }
@@ -1098,25 +1098,25 @@ static inline int same_magic(const char *amagic, const char *bmagic,
 
 /* Resolve a symbol for this module.  I.e. if we find one, record usage.
    Must be holding module_mutex. */
-static unsigned long resolve_symbol(Elf_Shdr *sechdrs,
-                                    unsigned int versindex,
-                                    const char *name,
-                                    struct module *mod)
+static const struct kernel_symbol *resolve_symbol(Elf_Shdr *sechdrs,
+                                                  unsigned int versindex,
+                                                  const char *name,
+                                                  struct module *mod)
 {
         struct module *owner;
-        unsigned long ret;
+        const struct kernel_symbol *sym;
         const unsigned long *crc;
 
-        ret = find_symbol(name, &owner, &crc,
+        sym = find_symbol(name, &owner, &crc,
                           !(mod->taints & (1 << TAINT_PROPRIETARY_MODULE)), true);
-        if (!IS_ERR_VALUE(ret)) {
-                /* use_module can fail due to OOM,
-                   or module initialization or unloading */
+        /* use_module can fail due to OOM,
+           or module initialization or unloading */
+        if (sym) {
                 if (!check_version(sechdrs, versindex, name, mod, crc) ||
                     !use_module(mod, owner))
-                        ret = -EINVAL;
+                        sym = NULL;
         }
-        return ret;
+        return sym;
 }
 
 /*
@@ -1516,17 +1516,15 @@ static void free_module(struct module *mod)
 void *__symbol_get(const char *symbol)
 {
         struct module *owner;
-        unsigned long value;
+        const struct kernel_symbol *sym;
 
         preempt_disable();
-        value = find_symbol(symbol, &owner, NULL, true, true);
-        if (IS_ERR_VALUE(value))
-                value = 0;
-        else if (strong_try_module_get(owner))
-                value = 0;
+        sym = find_symbol(symbol, &owner, NULL, true, true);
+        if (sym && strong_try_module_get(owner))
+                sym = NULL;
         preempt_enable();
 
-        return (void *)value;
+        return sym ? (void *)sym->value : NULL;
 }
 EXPORT_SYMBOL_GPL(__symbol_get);
 
@@ -1554,8 +1552,7 @@ static int verify_export_symbols(struct module *mod)
 
         for (i = 0; i < ARRAY_SIZE(arr); i++) {
                 for (s = arr[i].sym; s < arr[i].sym + arr[i].num; s++) {
-                        if (!IS_ERR_VALUE(find_symbol(s->name, &owner,
-                                                      NULL, true, false))) {
+                        if (find_symbol(s->name, &owner, NULL, true, false)) {
                                 printk(KERN_ERR
                                        "%s: exports duplicate symbol %s"
                                        " (owned by %s)\n",
@@ -1579,6 +1576,7 @@ static int simplify_symbols(Elf_Shdr *sechdrs,
         unsigned long secbase;
         unsigned int i, n = sechdrs[symindex].sh_size / sizeof(Elf_Sym);
         int ret = 0;
+        const struct kernel_symbol *ksym;
 
         for (i = 1; i < n; i++) {
                 switch (sym[i].st_shndx) {
@@ -1598,13 +1596,14 @@ static int simplify_symbols(Elf_Shdr *sechdrs,
                         break;
 
                 case SHN_UNDEF:
-                        sym[i].st_value
-                          = resolve_symbol(sechdrs, versindex,
-                                           strtab + sym[i].st_name, mod);
-
+                        ksym = resolve_symbol(sechdrs, versindex,
+                                              strtab + sym[i].st_name, mod);
                         /* Ok if resolved.  */
-                        if (!IS_ERR_VALUE(sym[i].st_value))
+                        if (ksym) {
+                                sym[i].st_value = ksym->value;
                                 break;
+                        }
+
                         /* Ok if weak.  */
                         if (ELF_ST_BIND(sym[i].st_info) == STB_WEAK)
                                 break;