diff options
| -rw-r--r-- | Documentation/kbuild/modules.txt | 87 | ||||
| -rw-r--r-- | scripts/Makefile.modpost | 7 | ||||
| -rw-r--r-- | scripts/mod/modpost.c | 123 |
3 files changed, 158 insertions, 59 deletions
diff --git a/Documentation/kbuild/modules.txt b/Documentation/kbuild/modules.txt index 87d858d..fcccf24 100644 --- a/Documentation/kbuild/modules.txt +++ b/Documentation/kbuild/modules.txt @@ -23,7 +23,10 @@ In this document you will find information about: === 6. Module installation --- 6.1 INSTALL_MOD_PATH --- 6.2 INSTALL_MOD_DIR - === 7. Module versioning + === 7. Module versioning & Module.symvers + --- 7.1 Symbols fron the kernel (vmlinux + modules) + --- 7.2 Symbols and external modules + --- 7.3 Symbols from another external module === 8. Tips & Tricks --- 8.1 Testing for CONFIG_FOO_BAR @@ -89,7 +92,8 @@ when building an external module. make -C $KDIR M=$PWD modules_install Install the external module(s). Installation default is in /lib/modules/<kernel-version>/extra, - but may be prefixed with INSTALL_MOD_PATH - see separate chapter. + but may be prefixed with INSTALL_MOD_PATH - see separate + chapter. make -C $KDIR M=$PWD clean Remove all generated files for the module - the kernel @@ -433,7 +437,7 @@ External modules are installed in the directory: => Install dir: /lib/modules/$(KERNELRELEASE)/gandalf -=== 7. Module versioning +=== 7. Module versioning & Module.symvers Module versioning is enabled by the CONFIG_MODVERSIONS tag. @@ -443,11 +447,80 @@ when a module is loaded/used then the CRC values contained in the kernel are compared with similar values in the module. If they are not equal then the kernel refuses to load the module. -During a kernel build a file named Module.symvers will be generated. This -file includes the symbol version of all symbols within the kernel. If the -Module.symvers file is saved from the last full kernel compile one does not -have to do a full kernel compile to build a module version's compatible module. +Module.symvers contains a list of all exported symbols from a kernel build. +--- 7.1 Symbols fron the kernel (vmlinux + modules) + + During a kernel build a file named Module.symvers will be generated. + Module.symvers contains all exported symbols from the kernel and + compiled modules. For each symbols the corresponding CRC value + is stored too. + + The syntax of the Module.symvers file is: + <CRC> <Symbol> <module> + Sample: + 0x2d036834 scsi_remove_host drivers/scsi/scsi_mod + + For a kernel build without CONFIG_MODVERSIONING enabled the crc + would read: 0x00000000 + + Module.symvers serve two purposes. + 1) It list all exported symbols both from vmlinux and all modules + 2) It list CRC if CONFIG_MODVERSION is enabled + +--- 7.2 Symbols and external modules + + When building an external module the build system needs access to + the symbols from the kernel to check if all external symbols are + defined. This is done in the MODPOST step and to obtain all + symbols modpost reads Module.symvers from the kernel. + If a Module.symvers file is present in the directory where + the external module is being build this file will be read too. + During the MODPOST step a new Module.symvers file will be written + containing all exported symbols that was not defined in the kernel. + +--- 7.3 Symbols from another external module + + Sometimes one external module uses exported symbols from another + external module. Kbuild needs to have full knowledge on all symbols + to avoid spitting out warnings about undefined symbols. + Two solutions exist to let kbuild know all symbols of more than + one external module. + The method with a top-level kbuild file is recommended but may be + impractical in certain situations. + + Use a top-level Kbuild file + If you have two modules: 'foo', 'bar' and 'foo' needs symbols + from 'bar' then one can use a common top-level kbuild file so + both modules are compiled in same build. + + Consider following directory layout: + ./foo/ <= contains the foo module + ./bar/ <= contains the bar module + The top-level Kbuild file would then look like: + + #./Kbuild: (this file may also be named Makefile) + obj-y := foo/ bar/ + + Executing: + make -C $KDIR M=`pwd` + + will then do the expected and compile both modules with full + knowledge on symbols from both modules. + + Use an extra Module.symvers file + When an external module is build a Module.symvers file is + generated containing all exported symbols which are not + defined in the kernel. + To get access to symbols from module 'bar' one can copy the + Module.symvers file from the compilation of the 'bar' module + to the directory where the 'foo' module is build. + During the module build kbuild will read the Module.symvers + file in the directory of the external module and when the + build is finished a new Module.symvers file is created + containing the sum of all symbols defined and not part of the + kernel. + === 8. Tips & Tricks --- 8.1 Testing for CONFIG_FOO_BAR diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost index bf96a61..563e3c5 100644 --- a/scripts/Makefile.modpost +++ b/scripts/Makefile.modpost @@ -39,7 +39,8 @@ include .config include scripts/Kbuild.include include scripts/Makefile.lib -symverfile := $(objtree)/Module.symvers +kernelsymfile := $(objtree)/Module.symvers +modulesymfile := $(KBUILD_EXTMOD)/Modules.symvers # Step 1), find all modules listed in $(MODVERDIR)/ __modules := $(sort $(shell grep -h '\.ko' /dev/null $(wildcard $(MODVERDIR)/*.mod))) @@ -54,7 +55,9 @@ quiet_cmd_modpost = MODPOST cmd_modpost = scripts/mod/modpost \ $(if $(CONFIG_MODVERSIONS),-m) \ $(if $(CONFIG_MODULE_SRCVERSION_ALL),-a,) \ - $(if $(KBUILD_EXTMOD),-i,-o) $(symverfile) \ + $(if $(KBUILD_EXTMOD),-i,-o) $(kernelsymfile) \ + $(if $(KBUILD_EXTMOD),-I $(modulesymfile)) \ + $(if $(KBUILD_EXTMOD),-o $(modulesymfile)) \ $(filter-out FORCE,$^) .PHONY: __modpost diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c index 4a2f2e3..976adf1 100644 --- a/scripts/mod/modpost.c +++ b/scripts/mod/modpost.c @@ -20,6 +20,8 @@ int modversions = 0; int have_vmlinux = 0; /* Is CONFIG_MODULE_SRCVERSION_ALL set? */ static int all_versions = 0; +/* If we are modposting external module set to 1 */ +static int external_module = 0; void fatal(const char *fmt, ...) { @@ -45,6 +47,18 @@ void warn(const char *fmt, ...) va_end(arglist); } +static int is_vmlinux(const char *modname) +{ + const char *myname; + + if ((myname = strrchr(modname, '/'))) + myname++; + else + myname = modname; + + return strcmp(myname, "vmlinux") == 0; +} + void *do_nofail(void *ptr, const char *expr) { if (!ptr) { @@ -100,6 +114,9 @@ struct symbol { unsigned int crc; int crc_valid; unsigned int weak:1; + unsigned int vmlinux:1; /* 1 if symbol is defined in vmlinux */ + unsigned int kernel:1; /* 1 if symbol is from kernel + * (only for external modules) **/ char name[0]; }; @@ -135,8 +152,7 @@ static struct symbol *alloc_symbol(const char *name, unsigned int weak, } /* For the hash of exported symbols */ -static void new_symbol(const char *name, struct module *module, - unsigned int *crc) +static struct symbol *new_symbol(const char *name, struct module *module) { unsigned int hash; struct symbol *new; @@ -144,10 +160,7 @@ static void new_symbol(const char *name, struct module *module, hash = tdb_hash(name) % SYMBOL_HASH_SIZE; new = symbolhash[hash] = alloc_symbol(name, 0, symbolhash[hash]); new->module = module; - if (crc) { - new->crc = *crc; - new->crc_valid = 1; - } + return new; } static struct symbol *find_symbol(const char *name) @@ -169,19 +182,27 @@ static struct symbol *find_symbol(const char *name) * Add an exported symbol - it may have already been added without a * CRC, in this case just update the CRC **/ -static void add_exported_symbol(const char *name, struct module *module, - unsigned int *crc) +static struct symbol *sym_add_exported(const char *name, struct module *mod) { struct symbol *s = find_symbol(name); - if (!s) { - new_symbol(name, module, crc); - return; - } - if (crc) { - s->crc = *crc; - s->crc_valid = 1; - } + if (!s) + s = new_symbol(name, mod); + + s->vmlinux = is_vmlinux(mod->name); + s->kernel = 0; + return s; +} + +static void sym_update_crc(const char *name, struct module *mod, + unsigned int crc) +{ + struct symbol *s = find_symbol(name); + + if (!s) + s = new_symbol(name, mod); + s->crc = crc; + s->crc_valid = 1; } void *grab_file(const char *filename, unsigned long *size) @@ -332,8 +353,7 @@ static void handle_modversions(struct module *mod, struct elf_info *info, /* CRC'd symbol */ if (memcmp(symname, CRC_PFX, strlen(CRC_PFX)) == 0) { crc = (unsigned int) sym->st_value; - add_exported_symbol(symname + strlen(CRC_PFX), - mod, &crc); + sym_update_crc(symname + strlen(CRC_PFX), mod, crc); } break; case SHN_UNDEF: @@ -377,8 +397,7 @@ static void handle_modversions(struct module *mod, struct elf_info *info, default: /* All exported symbols */ if (memcmp(symname, KSYMTAB_PFX, strlen(KSYMTAB_PFX)) == 0) { - add_exported_symbol(symname + strlen(KSYMTAB_PFX), - mod, NULL); + sym_add_exported(symname + strlen(KSYMTAB_PFX), mod); } if (strcmp(symname, MODULE_SYMBOL_PREFIX "init_module") == 0) mod->has_init = 1; @@ -388,18 +407,6 @@ static void handle_modversions(struct module *mod, struct elf_info *info, } } -static int is_vmlinux(const char *modname) -{ - const char *myname; - - if ((myname = strrchr(modname, '/'))) - myname++; - else - myname = modname; - - return strcmp(myname, "vmlinux") == 0; -} - /** * Parse tag=value strings from .modinfo section **/ @@ -450,9 +457,7 @@ static void read_symbols(char *modname) /* When there's no vmlinux, don't print warnings about * unresolved symbols (since there'll be too many ;) */ if (is_vmlinux(modname)) { - unsigned int fake_crc = 0; have_vmlinux = 1; - add_exported_symbol("struct_module", mod, &fake_crc); mod->skip = 1; } @@ -665,7 +670,7 @@ static void write_if_changed(struct buffer *b, const char *fname) fclose(file); } -static void read_dump(const char *fname) +static void read_dump(const char *fname, unsigned int kernel) { unsigned long size, pos = 0; void *file = grab_file(fname, &size); @@ -679,6 +684,7 @@ static void read_dump(const char *fname) char *symname, *modname, *d; unsigned int crc; struct module *mod; + struct symbol *s; if (!(symname = strchr(line, '\t'))) goto fail; @@ -699,13 +705,28 @@ static void read_dump(const char *fname) mod = new_module(NOFAIL(strdup(modname))); mod->skip = 1; } - add_exported_symbol(symname, mod, &crc); + s = sym_add_exported(symname, mod); + s->kernel = kernel; + sym_update_crc(symname, mod, crc); } return; fail: fatal("parse error in symbol dump file\n"); } +/* For normal builds always dump all symbols. + * For external modules only dump symbols + * that are not read from kernel Module.symvers. + **/ +static int dump_sym(struct symbol *sym) +{ + if (!external_module) + return 1; + if (sym->vmlinux || sym->kernel) + return 0; + return 1; +} + static void write_dump(const char *fname) { struct buffer buf = { }; @@ -715,15 +736,10 @@ static void write_dump(const char *fname) for (n = 0; n < SYMBOL_HASH_SIZE ; n++) { symbol = symbolhash[n]; while (symbol) { - symbol = symbol->next; - } - } - - for (n = 0; n < SYMBOL_HASH_SIZE ; n++) { - symbol = symbolhash[n]; - while (symbol) { - buf_printf(&buf, "0x%08x\t%s\t%s\n", symbol->crc, - symbol->name, symbol->module->name); + if (dump_sym(symbol)) + buf_printf(&buf, "0x%08x\t%s\t%s\n", + symbol->crc, symbol->name, + symbol->module->name); symbol = symbol->next; } } @@ -735,13 +751,18 @@ int main(int argc, char **argv) struct module *mod; struct buffer buf = { }; char fname[SZ]; - char *dump_read = NULL, *dump_write = NULL; + char *kernel_read = NULL, *module_read = NULL; + char *dump_write = NULL; int opt; - while ((opt = getopt(argc, argv, "i:mo:a")) != -1) { + while ((opt = getopt(argc, argv, "i:I:mo:a")) != -1) { switch(opt) { case 'i': - dump_read = optarg; + kernel_read = optarg; + break; + case 'I': + module_read = optarg; + external_module = 1; break; case 'm': modversions = 1; @@ -757,8 +778,10 @@ int main(int argc, char **argv) } } - if (dump_read) - read_dump(dump_read); + if (kernel_read) + read_dump(kernel_read, 1); + if (module_read) + read_dump(module_read, 0); while (optind < argc) { read_symbols(argv[optind++]); |