[rfc 45/45] Modules: Hack to handle symbols that have a zero value

[clameter@sgi.com]

[-- Attachment #1: weaky --]
[-- Type: text/plain, Size: 3090 bytes --]

The module subsystem cannot handle symbols that are zero. It prints out
a message that these symbols are unresolved. Define a constant

UNRESOLVED

that is used to hold the value used for unresolved symbols. Set it to 1
(its hopefully unlikely that a symbol will have the value 1). This is necessary
so that the pda variable which is placed at offset 0 of the per cpu
segment is handled correctly.

Signed-off-by: Christoph Lameter <clameter@sgi.com>

---
 kernel/module.c |   15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

Index: linux-2.6/kernel/module.c
===================================================================
--- linux-2.6.orig/kernel/module.c	2007-11-19 17:08:40.563625526 -0800
+++ linux-2.6/kernel/module.c	2007-11-19 17:08:40.855625732 -0800
@@ -62,6 +62,7 @@ extern int module_sysfs_initialized;
 /* If this is set, the section belongs in the init part of the module */
 #define INIT_OFFSET_MASK (1UL << (BITS_PER_LONG-1))
 
+#define UNRESOLVED 1
 /* List of modules, protected by module_mutex or preempt_disable
  * (add/delete uses stop_machine). */
 static DEFINE_MUTEX(module_mutex);
@@ -285,7 +286,7 @@ static unsigned long __find_symbol(const
 		}
 	}
 	DEBUGP("Failed to find symbol %s\n", name);
-	return 0;
+	return UNRESOLVED;
 }
 
 /* Search for module by name: must hold module_mutex. */
@@ -755,7 +756,7 @@ void __symbol_put(const char *symbol)
 	const unsigned long *crc;
 
 	preempt_disable();
-	if (!__find_symbol(symbol, &owner, &crc, 1))
+	if (__find_symbol(symbol, &owner, &crc, 1) == UNRESOLVED)
 		BUG();
 	module_put(owner);
 	preempt_enable();
@@ -899,7 +900,7 @@ static inline int check_modstruct_versio
 	const unsigned long *crc;
 	struct module *owner;
 
-	if (!__find_symbol("struct_module", &owner, &crc, 1))
+	if (__find_symbol("struct_module", &owner, &crc, 1) == UNRESOLVED)
 		BUG();
 	return check_version(sechdrs, versindex, "struct_module", mod,
 			     crc);
@@ -952,7 +953,7 @@ static unsigned long resolve_symbol(Elf_
 		/* use_module can fail due to OOM, or module unloading */
 		if (!check_version(sechdrs, versindex, name, mod, crc) ||
 		    !use_module(mod, owner))
-			ret = 0;
+			ret = UNRESOLVED;
 	}
 	return ret;
 }
@@ -1345,14 +1346,14 @@ static int verify_export_symbols(struct 
 	const unsigned long *crc;
 
 	for (i = 0; i < mod->num_syms; i++)
-		if (__find_symbol(mod->syms[i].name, &owner, &crc, 1)) {
+		if (__find_symbol(mod->syms[i].name, &owner, &crc, 1) != UNRESOLVED) {
 			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 (__find_symbol(mod->gpl_syms[i].name, &owner, &crc, 1)!= UNRESOLVED) {
 			name = mod->gpl_syms[i].name;
 			ret = -ENOEXEC;
 			goto dup;
@@ -1402,7 +1403,7 @@ static int simplify_symbols(Elf_Shdr *se
 					   strtab + sym[i].st_name, mod);
 
 			/* Ok if resolved.  */
-			if (sym[i].st_value != 0)
+			if (sym[i].st_value != UNRESOLVED)
 				break;
 			/* Ok if weak.  */
 			if (ELF_ST_BIND(sym[i].st_info) == STB_WEAK)

--