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)

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)
Tim Abbott · Rusty Russell
1 parent b10153fe31
Showing 1 changed file with 37 additions and 38 deletions Side-by-side Diff
kernel/module.c
@@ -283,7 +283,7 @@
 	/* 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 @@
  
 	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 @@
 			*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 @@
 	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 @@
 {
 	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 @@
  
 /* 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 @@
 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 @@
  
 	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 @@
 	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 @@
 			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;
...	...	@@ -283,7 +283,7 @@
283	283	/* Output */
284	284	struct module *owner;
285	285	const unsigned long *crc;
286		- unsigned long value;
	286	+ const struct kernel_symbol *sym;
287	287	};
288	288
289	289	static bool find_symbol_in_section(const struct symsearch *syms,
290	290
...	...	@@ -324,17 +324,17 @@
324	324
325	325	fsa->owner = owner;
326	326	fsa->crc = symversion(syms->crcs, symnum);
327		- fsa->value = syms->start[symnum].value;
	327	+ fsa->sym = &syms->start[symnum];
328	328	return true;
329	329	}
330	330
331		-/* Find a symbol, return value, (optional) crc and (optional) module
332		- * which owns it */
333		-static unsigned long find_symbol(const char *name,
334		- struct module **owner,
335		- const unsigned long **crc,
336		- bool gplok,
337		- bool warn)
	331	+/* Find a symbol and return it, along with, (optional) crc and
	332	+ * (optional) module which owns it */
	333	+static const struct kernel_symbol find_symbol(const char name,
	334	+ struct module **owner,
	335	+ const unsigned long **crc,
	336	+ bool gplok,
	337	+ bool warn)
338	338	{
339	339	struct find_symbol_arg fsa;
340	340
341	341
...	...	@@ -347,11 +347,11 @@
347	347	*owner = fsa.owner;
348	348	if (crc)
349	349	*crc = fsa.crc;
350		- return fsa.value;
	350	+ return fsa.sym;
351	351	}
352	352
353	353	DEBUGP("Failed to find symbol %s\n", name);
354		- return -ENOENT;
	354	+ return NULL;
355	355	}
356	356
357	357	/* Search for module by name: must hold module_mutex. */
...	...	@@ -894,7 +894,7 @@
894	894	struct module *owner;
895	895
896	896	preempt_disable();
897		- if (IS_ERR_VALUE(find_symbol(symbol, &owner, NULL, true, false)))
	897	+ if (!find_symbol(symbol, &owner, NULL, true, false))
898	898	BUG();
899	899	module_put(owner);
900	900	preempt_enable();
...	...	@@ -1057,7 +1057,7 @@
1057	1057	{
1058	1058	const unsigned long *crc;
1059	1059
1060		- if (IS_ERR_VALUE(find_symbol("struct_module", NULL, &crc, true, false)))
	1060	+ if (!find_symbol("struct_module", NULL, &crc, true, false))
1061	1061	BUG();
1062	1062	return check_version(sechdrs, versindex, "struct_module", mod, crc);
1063	1063	}
1064	1064
1065	1065
1066	1066
1067	1067
1068	1068
...	...	@@ -1098,25 +1098,25 @@
1098	1098
1099	1099	/* Resolve a symbol for this module. I.e. if we find one, record usage.
1100	1100	Must be holding module_mutex. */
1101		-static unsigned long resolve_symbol(Elf_Shdr *sechdrs,
1102		- unsigned int versindex,
1103		- const char *name,
1104		- struct module *mod)
	1101	+static const struct kernel_symbol resolve_symbol(Elf_Shdr sechdrs,
	1102	+ unsigned int versindex,
	1103	+ const char *name,
	1104	+ struct module *mod)
1105	1105	{
1106	1106	struct module *owner;
1107		- unsigned long ret;
	1107	+ const struct kernel_symbol *sym;
1108	1108	const unsigned long *crc;
1109	1109
1110		- ret = find_symbol(name, &owner, &crc,
	1110	+ sym = find_symbol(name, &owner, &crc,
1111	1111	!(mod->taints & (1 << TAINT_PROPRIETARY_MODULE)), true);
1112		- if (!IS_ERR_VALUE(ret)) {
1113		- /* use_module can fail due to OOM,
1114		- or module initialization or unloading */
	1112	+ /* use_module can fail due to OOM,
	1113	+ or module initialization or unloading */
	1114	+ if (sym) {
1115	1115	if (!check_version(sechdrs, versindex, name, mod, crc) \|\|
1116	1116	!use_module(mod, owner))
1117		- ret = -EINVAL;
	1117	+ sym = NULL;
1118	1118	}
1119		- return ret;
	1119	+ return sym;
1120	1120	}
1121	1121
1122	1122	/*
1123	1123
1124	1124
...	...	@@ -1516,17 +1516,15 @@
1516	1516	void __symbol_get(const char symbol)
1517	1517	{
1518	1518	struct module *owner;
1519		- unsigned long value;
	1519	+ const struct kernel_symbol *sym;
1520	1520
1521	1521	preempt_disable();
1522		- value = find_symbol(symbol, &owner, NULL, true, true);
1523		- if (IS_ERR_VALUE(value))
1524		- value = 0;
1525		- else if (strong_try_module_get(owner))
1526		- value = 0;
	1522	+ sym = find_symbol(symbol, &owner, NULL, true, true);
	1523	+ if (sym && strong_try_module_get(owner))
	1524	+ sym = NULL;
1527	1525	preempt_enable();
1528	1526
1529		- return (void *)value;
	1527	+ return sym ? (void *)sym->value : NULL;
1530	1528	}
1531	1529	EXPORT_SYMBOL_GPL(__symbol_get);
1532	1530
...	...	@@ -1554,8 +1552,7 @@
1554	1552
1555	1553	for (i = 0; i < ARRAY_SIZE(arr); i++) {
1556	1554	for (s = arr[i].sym; s < arr[i].sym + arr[i].num; s++) {
1557		- if (!IS_ERR_VALUE(find_symbol(s->name, &owner,
1558		- NULL, true, false))) {
	1555	+ if (find_symbol(s->name, &owner, NULL, true, false)) {
1559	1556	printk(KERN_ERR
1560	1557	"%s: exports duplicate symbol %s"
1561	1558	" (owned by %s)\n",
...	...	@@ -1579,6 +1576,7 @@
1579	1576	unsigned long secbase;
1580	1577	unsigned int i, n = sechdrs[symindex].sh_size / sizeof(Elf_Sym);
1581	1578	int ret = 0;
	1579	+ const struct kernel_symbol *ksym;
1582	1580
1583	1581	for (i = 1; i < n; i++) {
1584	1582	switch (sym[i].st_shndx) {
1585	1583
1586	1584
...	...	@@ -1598,13 +1596,14 @@
1598	1596	break;
1599	1597
1600	1598	case SHN_UNDEF:
1601		- sym[i].st_value
1602		- = resolve_symbol(sechdrs, versindex,
1603		- strtab + sym[i].st_name, mod);
1604		-
	1599	+ ksym = resolve_symbol(sechdrs, versindex,
	1600	+ strtab + sym[i].st_name, mod);
1605	1601	/* Ok if resolved. */
1606		- if (!IS_ERR_VALUE(sym[i].st_value))
	1602	+ if (ksym) {
	1603	+ sym[i].st_value = ksym->value;
1607	1604	break;
	1605	+ }
	1606	+
1608	1607	/* Ok if weak. */
1609	1608	if (ELF_ST_BIND(sym[i].st_info) == STB_WEAK)
1610	1609	break;