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>

diff --git a/kernel/module.c b/kernel/module.c
index bd60278ee7035945d1db4dfaed0f26b3c4a457e8..dc04d4d88d02afffbe088fab748427adbb00c50b 100644 (file)
--- 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)