From: Arjan van de Ven 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 Signed-off-by: Andrew Morton --- Documentation/feature-removal-schedule.txt | 10 ++ include/asm-generic/vmlinux.lds.h | 28 ++++++ include/linux/module.h | 20 ++++ kernel/module.c | 78 ++++++++++++++++++- lib/Kconfig.debug | 14 +++ 5 files changed, 148 insertions(+), 2 deletions(-) diff -puN Documentation/feature-removal-schedule.txt~add-export_unused_symbol-and-export_unused_symbol_gpl Documentation/feature-removal-schedule.txt --- devel/Documentation/feature-removal-schedule.txt~add-export_unused_symbol-and-export_unused_symbol_gpl 2006-05-18 00:16:17.000000000 -0700 +++ devel-akpm/Documentation/feature-removal-schedule.txt 2006-05-18 00:16:57.000000000 -0700 @@ -169,6 +169,16 @@ Who: Jean Delvare --------------------------- +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 + +--------------------------- + What: remove EXPORT_SYMBOL(tasklist_lock) When: August 2006 Files: kernel/fork.c diff -puN include/asm-generic/vmlinux.lds.h~add-export_unused_symbol-and-export_unused_symbol_gpl include/asm-generic/vmlinux.lds.h --- devel/include/asm-generic/vmlinux.lds.h~add-export_unused_symbol-and-export_unused_symbol_gpl 2006-05-18 00:16:17.000000000 -0700 +++ devel-akpm/include/asm-generic/vmlinux.lds.h 2006-05-18 00:16:17.000000000 -0700 @@ -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 -puN include/linux/module.h~add-export_unused_symbol-and-export_unused_symbol_gpl include/linux/module.h --- devel/include/linux/module.h~add-export_unused_symbol-and-export_unused_symbol_gpl 2006-05-18 00:16:17.000000000 -0700 +++ devel-akpm/include/linux/module.h 2006-05-18 00:16:17.000000000 -0700 @@ -203,6 +203,15 @@ 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 @@ -261,6 +270,15 @@ 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; @@ -453,6 +471,8 @@ 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 * diff -puN kernel/module.c~add-export_unused_symbol-and-export_unused_symbol_gpl kernel/module.c --- devel/kernel/module.c~add-export_unused_symbol-and-export_unused_symbol_gpl 2006-05-18 00:16:17.000000000 -0700 +++ devel-akpm/kernel/module.c 2006-05-18 00:18:04.000000000 -0700 @@ -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. @@ -121,9 +121,17 @@ 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 @@ -143,6 +151,17 @@ 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, @@ -185,6 +204,25 @@ 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; @@ -203,6 +241,23 @@ 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)); @@ -1428,6 +1483,8 @@ static struct module *load_module(void _ exportindex, modindex, obsparmindex, infoindex, gplindex, crcindex, gplcrcindex, versindex, pcpuindex[2], gplfutureindex, gplfuturecrcindex; + unsigned int unusedindex, unusedcrcindex, unusedgplindex, + unusedgplcrcindex; unsigned int pcpusize = 0, pcpuinitsize = 0; struct module *mod; long err = 0; @@ -1509,9 +1566,13 @@ 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"); @@ -1671,14 +1732,27 @@ 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); diff -puN lib/Kconfig.debug~add-export_unused_symbol-and-export_unused_symbol_gpl lib/Kconfig.debug --- devel/lib/Kconfig.debug~add-export_unused_symbol-and-export_unused_symbol_gpl 2006-05-18 00:16:17.000000000 -0700 +++ devel-akpm/lib/Kconfig.debug 2006-05-18 00:16:17.000000000 -0700 @@ -23,6 +23,20 @@ config MAGIC_SYSRQ keys are documented in . Don't say Y unless you really know what this hack does. +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 _