[uml-devel] [PATCH]Modules support in 2.6: reaching the complete fix

[BlaisorBlade <blaisorblade_spam@yahoo.it>]

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I've applied the various modules patches(i.e. apply_alternatives + some 
exports), have added some others, but still make modules complains: no 
unresolved symbols, but CRC are missing(at least with MODVERSIONS enabled; 
I'll try disabling it), and the kernel still panics(I guess that without 
MODVERSION this panic can't at all happen). I'm attaching the patch I built.

I've analized this, and got to the point that:

1) user_ksyms.c bundles a copy of the EXPORT_SYMBOL definition, but it's 
outdated; I've inserted the new one(with appropriate changes, i.e. 
s/CONFIG_/UML_CONFIG/) and it works. This is attached.

Still, the CRC are missing. The CRC symbol are defined, but we need also #2:

2) then, the UML build system is broken for USER_OBJS. The UML Makefiles 
define their own rule for such files. But the needed rule which would be 
needed is much more complex; this means that:
a) the terse output of 2.6 make doesn't appear(we have the complete command 
line)
b) a part of the post-processing needed for modules doesn't work.
Instead of specifying the rule each time, wouldn't it be good something 
such(in pseudo-code, I know there is only foreach in make-language)?

for i in USER_OBJS; do
  CFLAGS_$i+=USER_CFLAGS
done

If you accept, I volunteer to do it(i.e. find how to write this with make and 
do it).

3) When running the kernel, it panics this way:
Kernel panic: kernel BUG at kernel/module.c:1021!
The offending code is:

       if (!__find_symbol("struct_module", &owner, &crc, 1))
                BUG();
        return check_version(sechdrs, versindex, "struct_module", mod,
                             crc);

Though, this symbol is defined. Here the problem is probably that the link 
script is not up-to-date. I've given a look and verified this, but I didn't 
found THE actual error. And for this, I cannot help because I've not enough 
experience with link scripts(I've been able to learn the syntax, but I don't 
know the reason why some section missing in the i386 appear in the UML 
script; some are from libc, but I don't know which ones).

Bye
-- 
cat <<EOSIGN
Paolo Giarrusso, aka Blaisorblade
Linux Kernel 2.4.21/2.6.0-test on an i686; Linux registered user n. 292729
EOSIGN

[-- Attachment #2: Module_support.patch --]
[-- Type: text/x-diff, Size: 3417 bytes --]

--- ./arch/um/kernel/mem.c.modfix	2003-12-02 17:20:43.000000000 +0100
+++ ./arch/um/kernel/mem.c	2003-12-12 18:56:29.000000000 +0100
@@ -119,6 +119,7 @@
 		kmem_top = CHOOSE_MODE(kmem_end_tt, kmem_end_skas);
 	return(kmem_top);
 }
+EXPORT_SYMBOL(get_kmem_end);
 
 #ifdef CONFIG_HIGHMEM
 /* Changed during early boot */
@@ -715,6 +716,7 @@
 
 	return(&mem_map[pfn - region->start_pfn]);
 }
+EXPORT_SYMBOL(pfn_to_page);
 
 unsigned long phys_to_pfn(unsigned long p)
 {
--- ./arch/um/kernel/user_syms.c.modfix	2003-12-02 17:20:43.000000000 +0100
+++ ./arch/um/kernel/user_syms.c	2003-12-13 12:05:17.000000000 +0100
@@ -16,6 +16,62 @@
  * since this includes various user-level headers.
  */
 
+/* Had to update this: this changed in late 2.5 to add CRC and other beasts
+ * and was never updated here- 13 Dec 2003-Blaisorblade*/
+
+/* v850 toolchain uses a `_' prefix for all user symbols */
+#ifndef MODULE_SYMBOL_PREFIX
+#define MODULE_SYMBOL_PREFIX ""
+#endif
+
+struct kernel_symbol
+{
+	unsigned long value;
+	const char *name;
+};
+
+#if !defined(UML_CONFIG_MODULES)
+#define EXPORT_SYMBOL(sym)
+#define EXPORT_SYMBOL_GPL(sym)
+#define EXPORT_SYMBOL_NOVERS(sym)
+
+#else /*UML_CONFIG_MODULES*/
+#ifndef __GENKSYMS__
+#ifdef UML_CONFIG_MODVERSIONS
+/* Mark the CRC weak since genksyms apparently decides not to
+ * generate a checksums for some symbols */
+#define __CRC_SYMBOL(sym, sec)					\
+	extern void *__crc_##sym __attribute__((weak));		\
+	static const unsigned long __kcrctab_##sym		\
+	__attribute__((section("__kcrctab" sec), unused))	\
+	= (unsigned long) &__crc_##sym;
+#else
+#define __CRC_SYMBOL(sym, sec)
+#endif
+
+/* For every exported symbol, place a struct in the __ksymtab section */
+#define __EXPORT_SYMBOL(sym, sec)				\
+	__CRC_SYMBOL(sym, sec)					\
+	static const char __kstrtab_##sym[]			\
+	__attribute__((section("__ksymtab_strings")))		\
+	= MODULE_SYMBOL_PREFIX #sym;                    	\
+	static const struct kernel_symbol __ksymtab_##sym	\
+	__attribute__((section("__ksymtab" sec), unused))	\
+	= { (unsigned long)&sym, __kstrtab_##sym }
+
+#define EXPORT_SYMBOL(sym)					\
+	__EXPORT_SYMBOL(sym, "")
+
+#define EXPORT_SYMBOL_GPL(sym)					\
+	__EXPORT_SYMBOL(sym, "_gpl")
+
+#endif
+
+/* We don't mangle the actual symbol anymore, so no need for
+ * special casing EXPORT_SYMBOL_NOVERS.  FIXME: Deprecated */
+#define EXPORT_SYMBOL_NOVERS(sym) EXPORT_SYMBOL(sym)
+#endif
+#if 0
 struct module_symbol
 {
 	unsigned long value;
@@ -57,6 +113,7 @@
 #define EXPORT_SYMBOL_NOVERS(var)  __EXPORT_SYMBOL(var, __MODULE_STRING(var))
 
 #endif
+#endif
 
 EXPORT_SYMBOL(__errno_location);
 
@@ -109,5 +166,7 @@
 
 EXPORT_SYMBOL(memset);
 EXPORT_SYMBOL(strstr);
+EXPORT_SYMBOL(printf);
+EXPORT_SYMBOL(strlen);
 
 EXPORT_SYMBOL(find_iomem);
--- ./include/asm-um/common.lds.S.modfix	2003-12-02 17:20:44.000000000 +0100
+++ ./include/asm-um/common.lds.S	2003-12-13 17:53:09.000000000 +0100
@@ -15,18 +15,6 @@
 
   RODATA
 
-  __start___ksymtab = .;	/* Kernel symbol table */
-  __ksymtab : { *(__ksymtab) }
-  __stop___ksymtab = .;
-
-  __start___gpl_ksymtab = .;	/* Kernel symbol table:	GPL-only symbols */
-  __gpl_ksymtab : { *(__gpl_ksymtab) }
-  __stop___gpl_ksymtab = .;
-
-  __start___kallsyms = .;       /* All kernel symbols */
-  __kallsyms : { *(__kallsyms) }
-  __stop___kallsyms = .;
-
   .unprotected : { *(.unprotected) }
   . = ALIGN(4096);
   PROVIDE (_unprotected_end = .);