Modules: handle symbols that have a zero value

The module subsystem cannot handle symbols that are zero.  If symbols are
present that have a zero value then the module resolver prints out a
message that these symbols are unresolved.

[akinobu.mita@gmail.com: fix __find_symbl() error checks]
Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: Kay Sievers <kay.sievers@vrfy.org
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 14 insertions, 9 deletions

diff --git a/kernel/module.c b/kernel/module.c
index bd60278ee703..dc04d4d88d02 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -290,7 +290,7 @@ static unsigned long __find_symbol(const char *name,
                 }
         }
         DEBUGP("Failed to find symbol %s\n", name);
-        return 0;
+        return -ENOENT;
 }
 
 /* Search for module by name: must hold module_mutex. */
@@ -783,7 +783,7 @@ void __symbol_put(const char *symbol)
         const unsigned long *crc;
 
         preempt_disable();
-        if (!__find_symbol(symbol, &owner, &crc, 1))
+        if (IS_ERR_VALUE(__find_symbol(symbol, &owner, &crc, 1)))
                 BUG();
         module_put(owner);
         preempt_enable();
@@ -929,7 +929,8 @@ static inline int check_modstruct_version(Elf_Shdr *sechdrs,
         const unsigned long *crc;
         struct module *owner;
 
-        if (!__find_symbol("struct_module", &owner, &crc, 1))
+        if (IS_ERR_VALUE(__find_symbol("struct_module",
+                                                &owner, &crc, 1)))
                 BUG();
         return check_version(sechdrs, versindex, "struct_module", mod,
                              crc);
@@ -978,12 +979,12 @@ static unsigned long resolve_symbol(Elf_Shdr *sechdrs,
 
         ret = __find_symbol(name, &owner, &crc,
                         !(mod->taints & TAINT_PROPRIETARY_MODULE));
-        if (ret) {
+        if (!IS_ERR_VALUE(ret)) {
                 /* use_module can fail due to OOM,
                    or module initialization or unloading */
                 if (!check_version(sechdrs, versindex, name, mod, crc) ||
                     !use_module(mod, owner))
-                        ret = 0;
+                        ret = -EINVAL;
         }
         return ret;
 }
@@ -1371,7 +1372,9 @@ void *__symbol_get(const char *symbol)
 
         preempt_disable();
         value = __find_symbol(symbol, &owner, &crc, 1);
-        if (value && strong_try_module_get(owner) != 0)
+        if (IS_ERR_VALUE(value))
+                value = 0;
+        else if (strong_try_module_get(owner))
                 value = 0;
         preempt_enable();
 
@@ -1391,14 +1394,16 @@ static int verify_export_symbols(struct module *mod)
         const unsigned long *crc;
 
         for (i = 0; i < mod->num_syms; i++)
-                if (__find_symbol(mod->syms[i].name, &owner, &crc, 1)) {
+                if (!IS_ERR_VALUE(__find_symbol(mod->syms[i].name,
+                                                        &owner, &crc, 1))) {
                         name = mod->syms[i].name;
                         ret = -ENOEXEC;
                         goto dup;
                 }
 
         for (i = 0; i < mod->num_gpl_syms; i++)
-                if (__find_symbol(mod->gpl_syms[i].name, &owner, &crc, 1)) {
+                if (!IS_ERR_VALUE(__find_symbol(mod->gpl_syms[i].name,
+                                                        &owner, &crc, 1))) {
                         name = mod->gpl_syms[i].name;
                         ret = -ENOEXEC;
                         goto dup;
@@ -1448,7 +1453,7 @@ static int simplify_symbols(Elf_Shdr *sechdrs,
                                            strtab + sym[i].st_name, mod);
 
                         /* Ok if resolved.  */
-                        if (sym[i].st_value != 0)
+                        if (!IS_ERR_VALUE(sym[i].st_value))
                                 break;
                         /* Ok if weak.  */
                         if (ELF_ST_BIND(sym[i].st_info) == STB_WEAK)