| Message ID | 20220505072244.1155033-8-masahiroy@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | kbuild: yet another series of cleanups (modpost, LTO, MODULE_REL_CRCS) | expand |
On Thu, May 05, 2022 at 04:22:36PM +0900 Masahiro Yamada wrote: > Currently, CONFIG_MODVERSIONS needs extra link to embed the symbol > versions into ELF objects. Then, modpost extracts the version CRCs > from them. > > The following figures show how it currently works, and how I am trying > to change it. > > Current implementation > ====================== > |----------| > embed CRC -------------------------->| final | > $(CC) $(LD) / |---------| | link for | > *.c ------> *.o -------> *.o -->| modpost | | vmlinux | > / | |-- *.mod.c -->| or | > genksyms / |---------| | module | > *.c ------> *.symversions |----------| > > Genksyms outputs the calculated CRCs in the form of linker script > (*.symversions), which is used by $(LD) to update the object. > > If CONFIG_LTO_CLANG=y, the build process becomes much more complex. > Embedding the CRCs is postponed until the LLVM bitcode is converted > into ELF, creating another intermediate *.prelink.o. > > However, this complexity is unneeded. There is no reason why we must > embed version CRCs in objects so early. > > There is final link stage for vmlinux (scripts/link-vmlinux.sh) and > modules (scripts/Makefile.modfinal). We can link CRCs at the very last > moment. > > New implementation > ================== > |----------| > --------------------------------------->| final | > $(CC) / |---------| | link for | > *.c ------> *.o ---->| | | vmlinux | > | modpost |--- .vmlinux-symver.c -->| or | > genksyms | |--- *.mod.c ------------>| module | > *.c ------> *.cmd -->|---------| |----------| > > Pass the symbol versions to modpost as separate text data, which are > available in *.cmd files. > > This commit changes modpost to extract CRCs from *.cmd files instead of > from ELF objects. > > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> > --- > > (no changes since v2) > > Changes in v2: > - Simplify the implementation (parse .cmd files after ELF) > > scripts/mod/modpost.c | 177 ++++++++++++++++++++++++++++++------------ > 1 file changed, 129 insertions(+), 48 deletions(-) > > diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c > index 78a7107fcc40..92ee1f454e29 100644 > --- a/scripts/mod/modpost.c > +++ b/scripts/mod/modpost.c > @@ -383,19 +383,10 @@ static struct symbol *sym_add_exported(const char *name, struct module *mod, > return s; > } > > -static void sym_set_crc(const char *name, unsigned int crc) > +static void sym_set_crc(struct symbol *sym, unsigned int crc) > { > - struct symbol *s = find_symbol(name); > - > - /* > - * Ignore stand-alone __crc_*, which might be auto-generated symbols > - * such as __*_veneer in ARM ELF. > - */ > - if (!s) > - return; > - > - s->crc = crc; > - s->crc_valid = true; > + sym->crc = crc; > + sym->crc_valid = true; > } > > static void *grab_file(const char *filename, size_t *size) > @@ -618,33 +609,6 @@ static int ignore_undef_symbol(struct elf_info *info, const char *symname) > return 0; > } > > -static void handle_modversion(const struct module *mod, > - const struct elf_info *info, > - const Elf_Sym *sym, const char *symname) > -{ > - unsigned int crc; > - > - if (sym->st_shndx == SHN_UNDEF) { > - warn("EXPORT symbol \"%s\" [%s%s] version generation failed, symbol will not be versioned.\n" > - "Is \"%s\" prototyped in <asm/asm-prototypes.h>?\n", > - symname, mod->name, mod->is_vmlinux ? "" : ".ko", > - symname); > - > - return; > - } > - > - if (sym->st_shndx == SHN_ABS) { > - crc = sym->st_value; > - } else { > - unsigned int *crcp; > - > - /* symbol points to the CRC in the ELF object */ > - crcp = sym_get_data(info, sym); > - crc = TO_NATIVE(*crcp); > - } > - sym_set_crc(symname, crc); > -} > - > static void handle_symbol(struct module *mod, struct elf_info *info, > const Elf_Sym *sym, const char *symname) > { > @@ -1955,6 +1919,102 @@ static char *remove_dot(char *s) > return s; > } > > +/* > + * The CRCs are recorded in .*.cmd files in the form of: > + * #SYMVER <name> <crc> > + */ > +static void extract_crcs_for_object(const char *object, struct module *mod) > +{ > + char cmd_file[PATH_MAX]; > + char *buf, *p; > + const char *base; > + int dirlen, ret; > + > + base = strrchr(object, '/'); > + if (base) { > + base++; > + dirlen = base - object; > + } else { > + dirlen = 0; > + base = object; > + } > + > + ret = snprintf(cmd_file, sizeof(cmd_file), "%.*s.%s.cmd", > + dirlen, object, base); > + if (ret >= sizeof(cmd_file)) { > + error("%s: too long path was truncated\n", cmd_file); > + return; > + } > + > + buf = read_text_file(cmd_file); > + p = buf; > + > + while ((p = strstr(p, "\n#SYMVER "))) { > + char *name; > + size_t namelen; > + unsigned int crc; > + struct symbol *sym; > + > + name = p + strlen("\n#SYMVER "); > + > + p = strchr(name, ' '); > + if (!p) > + break; > + > + namelen = p - name; > + p++; > + > + if (!isdigit(*p)) > + continue; /* skip this line */ > + > + crc = strtol(p, &p, 0); > + if (*p != '\n') > + continue; /* skip this line */ > + > + name[namelen] = '\0'; > + > + sym = sym_find_with_module(name, mod); > + if (!sym) { > + warn("Skip the version for unexported symbol \"%s\" [%s%s]\n", > + name, mod->name, mod->is_vmlinux ? "" : ".ko"); > + continue; > + } > + sym_set_crc(sym, crc); > + } > + > + free(buf); > +} > + > +/* > + * The symbol versions (CRC) are recorded in the .*.cmd files. > + * Parse them to retrieve CRCs for the current module. > + */ > +static void mod_set_crcs(struct module *mod) > +{ > + char objlist[PATH_MAX]; > + char *buf, *p, *obj; > + int ret; > + > + if (mod->is_vmlinux) { > + strcpy(objlist, ".vmlinux.objs"); > + } else { > + /* objects for a module are listed in the *.mod file. */ > + ret = snprintf(objlist, sizeof(objlist), "%s.mod", mod->name); > + if (ret >= sizeof(objlist)) { > + error("%s: too long path was truncated\n", objlist); > + return; > + } > + } > + > + buf = read_text_file(objlist); > + p = buf; > + > + while ((obj = strsep(&p, "\n")) && obj[0]) > + extract_crcs_for_object(obj, mod); > + > + free(buf); > +} > + > static void read_symbols(const char *modname) > { > const char *symname; > @@ -2015,9 +2075,6 @@ static void read_symbols(const char *modname) > if (strstarts(symname, "__kstrtabns_")) > sym_update_namespace(symname + strlen("__kstrtabns_"), > sym_get_data(&info, sym)); > - if (strstarts(symname, "__crc_")) > - handle_modversion(mod, &info, sym, > - symname + strlen("__crc_")); > } > > // check for static EXPORT_SYMBOL_* functions && global vars > @@ -2046,12 +2103,17 @@ static void read_symbols(const char *modname) > > parse_elf_finish(&info); > > - /* Our trick to get versioning for module struct etc. - it's > - * never passed as an argument to an exported function, so > - * the automatic versioning doesn't pick it up, but it's really > - * important anyhow */ > - if (modversions) > + if (modversions) { > + /* > + * Our trick to get versioning for module struct etc. - it's > + * never passed as an argument to an exported function, so > + * the automatic versioning doesn't pick it up, but it's really > + * important anyhow > + */ > sym_add_unresolved("module_layout", mod, false); > + > + mod_set_crcs(mod); > + } > } > > static void read_symbols_from_files(const char *filename) > @@ -2214,6 +2276,23 @@ static void add_header(struct buffer *b, struct module *mod) > buf_printf(b, "\nMODULE_INFO(staging, \"Y\");\n"); > } > > +static void check_symversions(struct module *mod) > +{ > + struct symbol *sym; > + > + if (!modversions) > + return; > + > + list_for_each_entry(sym, &mod->exported_symbols, list) { > + if (!sym->crc_valid) { > + warn("EXPORT symbol \"%s\" [%s%s] version generation failed, symbol will not be versioned.\n" > + "Is \"%s\" prototyped in <asm/asm-prototypes.h>?\n", > + sym->name, mod->name, mod->is_vmlinux ? "" : ".ko", > + sym->name); > + } > + } > +} > + > /** > * Record CRCs for unresolved symbols > **/ > @@ -2429,7 +2508,7 @@ static void read_dump(const char *fname) > } > s = sym_add_exported(symname, mod, gpl_only); > s->is_static = false; > - sym_set_crc(symname, crc); > + sym_set_crc(s, crc); > sym_update_namespace(symname, namespace); > } > free(buf); > @@ -2554,6 +2633,8 @@ int main(int argc, char **argv) > if (mod->from_dump) > continue; > > + check_symversions(mod); > + > if (!mod->is_vmlinux) > write_mod_c_file(mod); > } > -- > 2.32.0 Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c index 78a7107fcc40..92ee1f454e29 100644 --- a/scripts/mod/modpost.c +++ b/scripts/mod/modpost.c @@ -383,19 +383,10 @@ static struct symbol *sym_add_exported(const char *name, struct module *mod, return s; } -static void sym_set_crc(const char *name, unsigned int crc) +static void sym_set_crc(struct symbol *sym, unsigned int crc) { - struct symbol *s = find_symbol(name); - - /* - * Ignore stand-alone __crc_*, which might be auto-generated symbols - * such as __*_veneer in ARM ELF. - */ - if (!s) - return; - - s->crc = crc; - s->crc_valid = true; + sym->crc = crc; + sym->crc_valid = true; } static void *grab_file(const char *filename, size_t *size) @@ -618,33 +609,6 @@ static int ignore_undef_symbol(struct elf_info *info, const char *symname) return 0; } -static void handle_modversion(const struct module *mod, - const struct elf_info *info, - const Elf_Sym *sym, const char *symname) -{ - unsigned int crc; - - if (sym->st_shndx == SHN_UNDEF) { - warn("EXPORT symbol \"%s\" [%s%s] version generation failed, symbol will not be versioned.\n" - "Is \"%s\" prototyped in <asm/asm-prototypes.h>?\n", - symname, mod->name, mod->is_vmlinux ? "" : ".ko", - symname); - - return; - } - - if (sym->st_shndx == SHN_ABS) { - crc = sym->st_value; - } else { - unsigned int *crcp; - - /* symbol points to the CRC in the ELF object */ - crcp = sym_get_data(info, sym); - crc = TO_NATIVE(*crcp); - } - sym_set_crc(symname, crc); -} - static void handle_symbol(struct module *mod, struct elf_info *info, const Elf_Sym *sym, const char *symname) { @@ -1955,6 +1919,102 @@ static char *remove_dot(char *s) return s; } +/* + * The CRCs are recorded in .*.cmd files in the form of: + * #SYMVER <name> <crc> + */ +static void extract_crcs_for_object(const char *object, struct module *mod) +{ + char cmd_file[PATH_MAX]; + char *buf, *p; + const char *base; + int dirlen, ret; + + base = strrchr(object, '/'); + if (base) { + base++; + dirlen = base - object; + } else { + dirlen = 0; + base = object; + } + + ret = snprintf(cmd_file, sizeof(cmd_file), "%.*s.%s.cmd", + dirlen, object, base); + if (ret >= sizeof(cmd_file)) { + error("%s: too long path was truncated\n", cmd_file); + return; + } + + buf = read_text_file(cmd_file); + p = buf; + + while ((p = strstr(p, "\n#SYMVER "))) { + char *name; + size_t namelen; + unsigned int crc; + struct symbol *sym; + + name = p + strlen("\n#SYMVER "); + + p = strchr(name, ' '); + if (!p) + break; + + namelen = p - name; + p++; + + if (!isdigit(*p)) + continue; /* skip this line */ + + crc = strtol(p, &p, 0); + if (*p != '\n') + continue; /* skip this line */ + + name[namelen] = '\0'; + + sym = sym_find_with_module(name, mod); + if (!sym) { + warn("Skip the version for unexported symbol \"%s\" [%s%s]\n", + name, mod->name, mod->is_vmlinux ? "" : ".ko"); + continue; + } + sym_set_crc(sym, crc); + } + + free(buf); +} + +/* + * The symbol versions (CRC) are recorded in the .*.cmd files. + * Parse them to retrieve CRCs for the current module. + */ +static void mod_set_crcs(struct module *mod) +{ + char objlist[PATH_MAX]; + char *buf, *p, *obj; + int ret; + + if (mod->is_vmlinux) { + strcpy(objlist, ".vmlinux.objs"); + } else { + /* objects for a module are listed in the *.mod file. */ + ret = snprintf(objlist, sizeof(objlist), "%s.mod", mod->name); + if (ret >= sizeof(objlist)) { + error("%s: too long path was truncated\n", objlist); + return; + } + } + + buf = read_text_file(objlist); + p = buf; + + while ((obj = strsep(&p, "\n")) && obj[0]) + extract_crcs_for_object(obj, mod); + + free(buf); +} + static void read_symbols(const char *modname) { const char *symname; @@ -2015,9 +2075,6 @@ static void read_symbols(const char *modname) if (strstarts(symname, "__kstrtabns_")) sym_update_namespace(symname + strlen("__kstrtabns_"), sym_get_data(&info, sym)); - if (strstarts(symname, "__crc_")) - handle_modversion(mod, &info, sym, - symname + strlen("__crc_")); } // check for static EXPORT_SYMBOL_* functions && global vars @@ -2046,12 +2103,17 @@ static void read_symbols(const char *modname) parse_elf_finish(&info); - /* Our trick to get versioning for module struct etc. - it's - * never passed as an argument to an exported function, so - * the automatic versioning doesn't pick it up, but it's really - * important anyhow */ - if (modversions) + if (modversions) { + /* + * Our trick to get versioning for module struct etc. - it's + * never passed as an argument to an exported function, so + * the automatic versioning doesn't pick it up, but it's really + * important anyhow + */ sym_add_unresolved("module_layout", mod, false); + + mod_set_crcs(mod); + } } static void read_symbols_from_files(const char *filename) @@ -2214,6 +2276,23 @@ static void add_header(struct buffer *b, struct module *mod) buf_printf(b, "\nMODULE_INFO(staging, \"Y\");\n"); } +static void check_symversions(struct module *mod) +{ + struct symbol *sym; + + if (!modversions) + return; + + list_for_each_entry(sym, &mod->exported_symbols, list) { + if (!sym->crc_valid) { + warn("EXPORT symbol \"%s\" [%s%s] version generation failed, symbol will not be versioned.\n" + "Is \"%s\" prototyped in <asm/asm-prototypes.h>?\n", + sym->name, mod->name, mod->is_vmlinux ? "" : ".ko", + sym->name); + } + } +} + /** * Record CRCs for unresolved symbols **/ @@ -2429,7 +2508,7 @@ static void read_dump(const char *fname) } s = sym_add_exported(symname, mod, gpl_only); s->is_static = false; - sym_set_crc(symname, crc); + sym_set_crc(s, crc); sym_update_namespace(symname, namespace); } free(buf); @@ -2554,6 +2633,8 @@ int main(int argc, char **argv) if (mod->from_dump) continue; + check_symversions(mod); + if (!mod->is_vmlinux) write_mod_c_file(mod); }
Currently, CONFIG_MODVERSIONS needs extra link to embed the symbol versions into ELF objects. Then, modpost extracts the version CRCs from them. The following figures show how it currently works, and how I am trying to change it. Current implementation ====================== |----------| embed CRC -------------------------->| final | $(CC) $(LD) / |---------| | link for | *.c ------> *.o -------> *.o -->| modpost | | vmlinux | / | |-- *.mod.c -->| or | genksyms / |---------| | module | *.c ------> *.symversions |----------| Genksyms outputs the calculated CRCs in the form of linker script (*.symversions), which is used by $(LD) to update the object. If CONFIG_LTO_CLANG=y, the build process becomes much more complex. Embedding the CRCs is postponed until the LLVM bitcode is converted into ELF, creating another intermediate *.prelink.o. However, this complexity is unneeded. There is no reason why we must embed version CRCs in objects so early. There is final link stage for vmlinux (scripts/link-vmlinux.sh) and modules (scripts/Makefile.modfinal). We can link CRCs at the very last moment. New implementation ================== |----------| --------------------------------------->| final | $(CC) / |---------| | link for | *.c ------> *.o ---->| | | vmlinux | | modpost |--- .vmlinux-symver.c -->| or | genksyms | |--- *.mod.c ------------>| module | *.c ------> *.cmd -->|---------| |----------| Pass the symbol versions to modpost as separate text data, which are available in *.cmd files. This commit changes modpost to extract CRCs from *.cmd files instead of from ELF objects. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> --- (no changes since v2) Changes in v2: - Simplify the implementation (parse .cmd files after ELF) scripts/mod/modpost.c | 177 ++++++++++++++++++++++++++++++------------ 1 file changed, 129 insertions(+), 48 deletions(-)