Hi,
As discussed on lkml before; the patch with the infrastructure to deprecate unused symbols
This is patch one in a series of 17; to not overload lkml the other 16 will be mailed direct;
people who want to see them all can see them at http://www.fenrus.org/unused
This patch temporarily adds EXPORT_UNUSED_SYMBOL and EXPORT_UNUSED_SYMBOL_GPL.
These will be used as 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.
It would be nice to at least get this infrastructure into 2.6.17 even if
the rest of this series won't get there.
Signed-off-by: Arjan van de Ven <[email protected]>
---
Documentation/feature-removal-schedule.txt | 10 +++
include/asm-generic/vmlinux.lds.h | 28 ++++++++++
include/linux/module.h | 20 +++++++
kernel/module.c | 79 +++++++++++++++++++++++++++--
lib/Kconfig.debug | 14 +++++
5 files changed, 148 insertions(+), 3 deletions(-)
Index: linux-2.6.17-rc3-mm1-unused/Documentation/feature-removal-schedule.txt
===================================================================
--- linux-2.6.17-rc3-mm1-unused.orig/Documentation/feature-removal-schedule.txt
+++ linux-2.6.17-rc3-mm1-unused/Documentation/feature-removal-schedule.txt
@@ -22,6 +22,16 @@ Who: Adrian Bunk <[email protected]>
---------------------------
+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 <[email protected]>
+
+---------------------------
+
What: RCU API moves to EXPORT_SYMBOL_GPL
When: April 2006
Files: include/linux/rcupdate.h, kernel/rcupdate.c
Index: linux-2.6.17-rc3-mm1-unused/include/asm-generic/vmlinux.lds.h
===================================================================
--- linux-2.6.17-rc3-mm1-unused.orig/include/asm-generic/vmlinux.lds.h
+++ linux-2.6.17-rc3-mm1-unused/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) = .; \
Index: linux-2.6.17-rc3-mm1-unused/include/linux/module.h
===================================================================
--- linux-2.6.17-rc3-mm1-unused.orig/include/linux/module.h
+++ linux-2.6.17-rc3-mm1-unused/include/linux/module.h
@@ -204,6 +204,15 @@ void *__symbol_get_gpl(const char *symbo
#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
@@ -278,6 +287,15 @@ struct module
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;
@@ -470,6 +488,8 @@ void module_remove_driver(struct device_
#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 *
Index: linux-2.6.17-rc3-mm1-unused/kernel/module.c
===================================================================
--- linux-2.6.17-rc3-mm1-unused.orig/kernel/module.c
+++ linux-2.6.17-rc3-mm1-unused/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.
@@ -120,9 +120,17 @@ extern const struct kernel_symbol __star
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
@@ -142,6 +150,17 @@ static const struct kernel_symbol *looku
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,
@@ -184,6 +203,25 @@ static unsigned long __find_symbol(const
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;
@@ -202,6 +240,23 @@ static unsigned long __find_symbol(const
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));
@@ -1449,7 +1504,8 @@ static struct module *load_module(void _
unsigned int i, symindex = 0, strindex = 0, setupindex, exindex,
exportindex, modindex, obsparmindex, infoindex, gplindex,
crcindex, gplcrcindex, versindex, pcpuindex, gplfutureindex,
- gplfuturecrcindex;
+ gplfuturecrcindex, unusedindex, unusedcrcindex, unusedgplindex,
+ unusedgplcrcindex;
struct module *mod;
long err = 0;
void *percpu = NULL, *ptr = NULL; /* Stops spurious gcc warning */
@@ -1530,9 +1586,13 @@ static struct module *load_module(void _
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");
@@ -1676,14 +1736,27 @@ static struct module *load_module(void _
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);
Index: linux-2.6.17-rc3-mm1-unused/lib/Kconfig.debug
===================================================================
--- linux-2.6.17-rc3-mm1-unused.orig/lib/Kconfig.debug
+++ linux-2.6.17-rc3-mm1-unused/lib/Kconfig.debug
@@ -32,6 +32,20 @@ config DEBUG_SHIRQ
to be able to handle interrupts coming in at those points; some don't and
need to be caught.
+config UNUSED_SYMBOLS
+ bool "Enable unused/obsolete exported symbols"
+ 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
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
