[PATCH] Add EXPORT_UNUSED_SYMBOL and EXPORT_UNUSED_SYMBOL_GPL
Temporarily add EXPORT_UNUSED_SYMBOL and EXPORT_UNUSED_SYMBOL_GPL. These
will be used as a transition measure for symbols that aren't used in the
kernel and are on the way out. When a module uses such a symbol, a warning
is printk'd at modprobe time.
The main reason for removing unused exports is size: eacho export takes
roughly between 100 and 150 bytes of kernel space in the binary. This
patch gives users the option to immediately get this size gain via a config
option.
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt
index 027285d..033ac91 100644
--- a/Documentation/feature-removal-schedule.txt
+++ b/Documentation/feature-removal-schedule.txt
@@ -177,6 +177,16 @@
---------------------------
+What: Unused EXPORT_SYMBOL/EXPORT_SYMBOL_GPL exports
+ (temporary transition config option provided until then)
+ The transition config option will also be removed at the same time.
+When: before 2.6.19
+Why: Unused symbols are both increasing the size of the kernel binary
+ and are often a sign of "wrong API"
+Who: Arjan van de Ven <arjan@linux.intel.com>
+
+---------------------------
+
What: remove EXPORT_SYMBOL(tasklist_lock)
When: August 2006
Files: kernel/fork.c
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 9d11550..db5a373 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -58,6 +58,20 @@
VMLINUX_SYMBOL(__stop___ksymtab_gpl) = .; \
} \
\
+ /* Kernel symbol table: Normal unused symbols */ \
+ __ksymtab_unused : AT(ADDR(__ksymtab_unused) - LOAD_OFFSET) { \
+ VMLINUX_SYMBOL(__start___ksymtab_unused) = .; \
+ *(__ksymtab_unused) \
+ VMLINUX_SYMBOL(__stop___ksymtab_unused) = .; \
+ } \
+ \
+ /* Kernel symbol table: GPL-only unused symbols */ \
+ __ksymtab_unused_gpl : AT(ADDR(__ksymtab_unused_gpl) - LOAD_OFFSET) { \
+ VMLINUX_SYMBOL(__start___ksymtab_unused_gpl) = .; \
+ *(__ksymtab_unused_gpl) \
+ VMLINUX_SYMBOL(__stop___ksymtab_unused_gpl) = .; \
+ } \
+ \
/* Kernel symbol table: GPL-future-only symbols */ \
__ksymtab_gpl_future : AT(ADDR(__ksymtab_gpl_future) - LOAD_OFFSET) { \
VMLINUX_SYMBOL(__start___ksymtab_gpl_future) = .; \
@@ -79,6 +93,20 @@
VMLINUX_SYMBOL(__stop___kcrctab_gpl) = .; \
} \
\
+ /* Kernel symbol table: Normal unused symbols */ \
+ __kcrctab_unused : AT(ADDR(__kcrctab_unused) - LOAD_OFFSET) { \
+ VMLINUX_SYMBOL(__start___kcrctab_unused) = .; \
+ *(__kcrctab_unused) \
+ VMLINUX_SYMBOL(__stop___kcrctab_unused) = .; \
+ } \
+ \
+ /* Kernel symbol table: GPL-only unused symbols */ \
+ __kcrctab_unused_gpl : AT(ADDR(__kcrctab_unused_gpl) - LOAD_OFFSET) { \
+ VMLINUX_SYMBOL(__start___kcrctab_unused_gpl) = .; \
+ *(__kcrctab_unused_gpl) \
+ VMLINUX_SYMBOL(__stop___kcrctab_unused_gpl) = .; \
+ } \
+ \
/* Kernel symbol table: GPL-future-only symbols */ \
__kcrctab_gpl_future : AT(ADDR(__kcrctab_gpl_future) - LOAD_OFFSET) { \
VMLINUX_SYMBOL(__start___kcrctab_gpl_future) = .; \
diff --git a/include/linux/module.h b/include/linux/module.h
index 9ebbb74..9e9dc7c 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -203,6 +203,15 @@
#define EXPORT_SYMBOL_GPL_FUTURE(sym) \
__EXPORT_SYMBOL(sym, "_gpl_future")
+
+#ifdef CONFIG_UNUSED_SYMBOLS
+#define EXPORT_UNUSED_SYMBOL(sym) __EXPORT_SYMBOL(sym, "_unused")
+#define EXPORT_UNUSED_SYMBOL_GPL(sym) __EXPORT_SYMBOL(sym, "_unused_gpl")
+#else
+#define EXPORT_UNUSED_SYMBOL(sym)
+#define EXPORT_UNUSED_SYMBOL_GPL(sym)
+#endif
+
#endif
struct module_ref
@@ -261,6 +270,15 @@
unsigned int num_gpl_syms;
const unsigned long *gpl_crcs;
+ /* unused exported symbols. */
+ const struct kernel_symbol *unused_syms;
+ unsigned int num_unused_syms;
+ const unsigned long *unused_crcs;
+ /* GPL-only, unused exported symbols. */
+ const struct kernel_symbol *unused_gpl_syms;
+ unsigned int num_unused_gpl_syms;
+ const unsigned long *unused_gpl_crcs;
+
/* symbols that will be GPL-only in the near future. */
const struct kernel_symbol *gpl_future_syms;
unsigned int num_gpl_future_syms;
@@ -456,6 +474,8 @@
#define EXPORT_SYMBOL(sym)
#define EXPORT_SYMBOL_GPL(sym)
#define EXPORT_SYMBOL_GPL_FUTURE(sym)
+#define EXPORT_UNUSED_SYMBOL(sym)
+#define EXPORT_UNUSED_SYMBOL_GPL(sym)
/* Given an address, look for it in the exception tables. */
static inline const struct exception_table_entry *
diff --git a/kernel/module.c b/kernel/module.c
index 10e5b87..03b7381 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -1,4 +1,4 @@
-/* Rewritten by Rusty Russell, on the backs of many others...
+/*
Copyright (C) 2002 Richard Henderson
Copyright (C) 2001 Rusty Russell, 2002 Rusty Russell IBM.
@@ -122,9 +122,17 @@
extern const struct kernel_symbol __stop___ksymtab_gpl[];
extern const struct kernel_symbol __start___ksymtab_gpl_future[];
extern const struct kernel_symbol __stop___ksymtab_gpl_future[];
+extern const struct kernel_symbol __start___ksymtab_unused[];
+extern const struct kernel_symbol __stop___ksymtab_unused[];
+extern const struct kernel_symbol __start___ksymtab_unused_gpl[];
+extern const struct kernel_symbol __stop___ksymtab_unused_gpl[];
+extern const struct kernel_symbol __start___ksymtab_gpl_future[];
+extern const struct kernel_symbol __stop___ksymtab_gpl_future[];
extern const unsigned long __start___kcrctab[];
extern const unsigned long __start___kcrctab_gpl[];
extern const unsigned long __start___kcrctab_gpl_future[];
+extern const unsigned long __start___kcrctab_unused[];
+extern const unsigned long __start___kcrctab_unused_gpl[];
#ifndef CONFIG_MODVERSIONS
#define symversion(base, idx) NULL
@@ -144,6 +152,17 @@
return NULL;
}
+static void printk_unused_warning(const char *name)
+{
+ printk(KERN_WARNING "Symbol %s is marked as UNUSED, "
+ "however this module is using it.\n", name);
+ printk(KERN_WARNING "This symbol will go away in the future.\n");
+ printk(KERN_WARNING "Please evalute if this is the right api to use, "
+ "and if it really is, submit a report the linux kernel "
+ "mailinglist together with submitting your code for "
+ "inclusion.\n");
+}
+
/* Find a symbol, return value, crc and module which owns it */
static unsigned long __find_symbol(const char *name,
struct module **owner,
@@ -186,6 +205,25 @@
return ks->value;
}
+ ks = lookup_symbol(name, __start___ksymtab_unused,
+ __stop___ksymtab_unused);
+ if (ks) {
+ printk_unused_warning(name);
+ *crc = symversion(__start___kcrctab_unused,
+ (ks - __start___ksymtab_unused));
+ return ks->value;
+ }
+
+ if (gplok)
+ ks = lookup_symbol(name, __start___ksymtab_unused_gpl,
+ __stop___ksymtab_unused_gpl);
+ if (ks) {
+ printk_unused_warning(name);
+ *crc = symversion(__start___kcrctab_unused_gpl,
+ (ks - __start___ksymtab_unused_gpl));
+ return ks->value;
+ }
+
/* Now try modules. */
list_for_each_entry(mod, &modules, list) {
*owner = mod;
@@ -204,6 +242,23 @@
return ks->value;
}
}
+ ks = lookup_symbol(name, mod->unused_syms, mod->unused_syms + mod->num_unused_syms);
+ if (ks) {
+ printk_unused_warning(name);
+ *crc = symversion(mod->unused_crcs, (ks - mod->unused_syms));
+ return ks->value;
+ }
+
+ if (gplok) {
+ ks = lookup_symbol(name, mod->unused_gpl_syms,
+ mod->unused_gpl_syms + mod->num_unused_gpl_syms);
+ if (ks) {
+ printk_unused_warning(name);
+ *crc = symversion(mod->unused_gpl_crcs,
+ (ks - mod->unused_gpl_syms));
+ return ks->value;
+ }
+ }
ks = lookup_symbol(name, mod->gpl_future_syms,
(mod->gpl_future_syms +
mod->num_gpl_future_syms));
@@ -1407,6 +1462,8 @@
exportindex, modindex, obsparmindex, infoindex, gplindex,
crcindex, gplcrcindex, versindex, pcpuindex, gplfutureindex,
gplfuturecrcindex, unwindex = 0;
+ unsigned int unusedindex, unusedcrcindex, unusedgplindex,
+ unusedgplcrcindex;
struct module *mod;
long err = 0;
void *percpu = NULL, *ptr = NULL; /* Stops spurious gcc warning */
@@ -1487,9 +1544,13 @@
exportindex = find_sec(hdr, sechdrs, secstrings, "__ksymtab");
gplindex = find_sec(hdr, sechdrs, secstrings, "__ksymtab_gpl");
gplfutureindex = find_sec(hdr, sechdrs, secstrings, "__ksymtab_gpl_future");
+ unusedindex = find_sec(hdr, sechdrs, secstrings, "__ksymtab_unused");
+ unusedgplindex = find_sec(hdr, sechdrs, secstrings, "__ksymtab_unused_gpl");
crcindex = find_sec(hdr, sechdrs, secstrings, "__kcrctab");
gplcrcindex = find_sec(hdr, sechdrs, secstrings, "__kcrctab_gpl");
gplfuturecrcindex = find_sec(hdr, sechdrs, secstrings, "__kcrctab_gpl_future");
+ unusedcrcindex = find_sec(hdr, sechdrs, secstrings, "__kcrctab_unused");
+ unusedgplcrcindex = find_sec(hdr, sechdrs, secstrings, "__kcrctab_unused_gpl");
setupindex = find_sec(hdr, sechdrs, secstrings, "__param");
exindex = find_sec(hdr, sechdrs, secstrings, "__ex_table");
obsparmindex = find_sec(hdr, sechdrs, secstrings, "__obsparm");
@@ -1638,14 +1699,27 @@
mod->gpl_crcs = (void *)sechdrs[gplcrcindex].sh_addr;
mod->num_gpl_future_syms = sechdrs[gplfutureindex].sh_size /
sizeof(*mod->gpl_future_syms);
+ mod->num_unused_syms = sechdrs[unusedindex].sh_size /
+ sizeof(*mod->unused_syms);
+ mod->num_unused_gpl_syms = sechdrs[unusedgplindex].sh_size /
+ sizeof(*mod->unused_gpl_syms);
mod->gpl_future_syms = (void *)sechdrs[gplfutureindex].sh_addr;
if (gplfuturecrcindex)
mod->gpl_future_crcs = (void *)sechdrs[gplfuturecrcindex].sh_addr;
+ mod->unused_syms = (void *)sechdrs[unusedindex].sh_addr;
+ if (unusedcrcindex)
+ mod->unused_crcs = (void *)sechdrs[unusedcrcindex].sh_addr;
+ mod->unused_gpl_syms = (void *)sechdrs[unusedgplindex].sh_addr;
+ if (unusedgplcrcindex)
+ mod->unused_crcs = (void *)sechdrs[unusedgplcrcindex].sh_addr;
+
#ifdef CONFIG_MODVERSIONS
if ((mod->num_syms && !crcindex) ||
(mod->num_gpl_syms && !gplcrcindex) ||
- (mod->num_gpl_future_syms && !gplfuturecrcindex)) {
+ (mod->num_gpl_future_syms && !gplfuturecrcindex) ||
+ (mod->num_unused_syms && !unusedcrcindex) ||
+ (mod->num_unused_gpl_syms && !unusedgplcrcindex)) {
printk(KERN_WARNING "%s: No versions for exported symbols."
" Tainting kernel.\n", mod->name);
add_taint(TAINT_FORCED_MODULE);
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 5330911..e4fcbd1 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -23,6 +23,22 @@
keys are documented in <file:Documentation/sysrq.txt>. Don't say Y
unless you really know what this hack does.
+config UNUSED_SYMBOLS
+ bool "Enable unused/obsolete exported symbols"
+ default y if X86
+ help
+ Unused but exported symbols make the kernel needlessly bigger. For
+ that reason most of these unused exports will soon be removed. This
+ option is provided temporarily to provide a transition period in case
+ some external kernel module needs one of these symbols anyway. If you
+ encounter such a case in your module, consider if you are actually
+ using the right API. (rationale: since nobody in the kernel is using
+ this in a module, there is a pretty good chance it's actually the
+ wrong interface to use). If you really need the symbol, please send a
+ mail to the linux kernel mailing list mentioning the symbol and why
+ you really need it, and what the merge plan to the mainline kernel for
+ your module is.
+
config DEBUG_KERNEL
bool "Kernel debugging"
help