| Message ID | 20220508190631.2386038-11-masahiroy@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | kbuild: yet another series of cleanups (modpost, LTO, MODULE_REL_CRCS, export.h) | expand |
On Sun, May 8, 2022 at 12:10 PM Masahiro Yamada <masahiroy@kernel.org> wrote: > > diff --git a/scripts/check-local-export b/scripts/check-local-export > new file mode 100755 > index 000000000000..d1721fa63057 > --- /dev/null > +++ b/scripts/check-local-export > @@ -0,0 +1,48 @@ > +#!/bin/bash > +# SPDX-License-Identifier: GPL-2.0-only > +# > +# Copyright (C) 2022 Masahiro Yamada > + > +set -e > +set -o pipefail > + > +declare -A symbol_types > +declare -a export_symbols > + > +exit_code=0 > + > +while read value type name > +do > + # to avoid error for clang LTO; $name may be empty > + if [[ $value = -* && -z $name ]]; then > + continue > + fi > + > + # The first field (value) may be empty. If so, fix it up. > + if [[ -z $name ]]; then > + name=${type} > + type=${value} > + fi Consider adding examples of output from NM as comments where you're handling special cases. Aren't BOTH from LTO? The first case is: ---------------- T strncpy while the second is U strncpy IIUC? Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
On Tue, May 10, 2022 at 3:05 AM 'Nick Desaulniers' via Clang Built Linux <clang-built-linux@googlegroups.com> wrote: > > On Sun, May 8, 2022 at 12:10 PM Masahiro Yamada <masahiroy@kernel.org> wrote: > > > > diff --git a/scripts/check-local-export b/scripts/check-local-export > > new file mode 100755 > > index 000000000000..d1721fa63057 > > --- /dev/null > > +++ b/scripts/check-local-export > > @@ -0,0 +1,48 @@ > > +#!/bin/bash > > +# SPDX-License-Identifier: GPL-2.0-only > > +# > > +# Copyright (C) 2022 Masahiro Yamada > > + > > +set -e > > +set -o pipefail > > + > > +declare -A symbol_types > > +declare -a export_symbols > > + > > +exit_code=0 > > + > > +while read value type name > > +do > > + # to avoid error for clang LTO; $name may be empty > > + if [[ $value = -* && -z $name ]]; then > > + continue > > + fi > > + > > + # The first field (value) may be empty. If so, fix it up. > > + if [[ -z $name ]]; then > > + name=${type} > > + type=${value} > > + fi > > Consider adding examples of output from NM as comments where you're > handling special cases. > > Aren't BOTH from LTO? The first case is: > > ---------------- T strncpy For LTO, I see ---------------- t in the llvm-nm output. > > while the second is > > U strncpy Right, this happens for all unresolved symbols. The address part is empty. I will add the output example in the comment block. > IIUC? > > Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> > -- > Thanks, > ~Nick Desaulniers > > -- > You received this message because you are subscribed to the Google Groups "Clang Built Linux" group. > To unsubscribe from this group and stop receiving emails from it, send an email to clang-built-linux+unsubscribe@googlegroups.com. > To view this discussion on the web visit https://groups.google.com/d/msgid/clang-built-linux/CAKwvOdkhcJB8Bnrt51siRefWe%2BZSvHagCs2G011PzkkrD3cxQw%40mail.gmail.com.
diff --git a/scripts/Makefile.build b/scripts/Makefile.build index 838ea5e83174..c2a173b3fd60 100644 --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -244,9 +244,12 @@ cmd_gen_ksymdeps = \ $(CONFIG_SHELL) $(srctree)/scripts/gen_ksymdeps.sh $@ >> $(dot-target).cmd endif +cmd_check_local_export = $(srctree)/scripts/check-local-export $@ + define rule_cc_o_c $(call cmd_and_fixdep,cc_o_c) $(call cmd,gen_ksymdeps) + $(call cmd,check_local_export) $(call cmd,checksrc) $(call cmd,checkdoc) $(call cmd,gen_objtooldep) @@ -257,6 +260,7 @@ endef define rule_as_o_S $(call cmd_and_fixdep,as_o_S) $(call cmd,gen_ksymdeps) + $(call cmd,check_local_export) $(call cmd,gen_objtooldep) $(call cmd,gen_symversions_S) endef diff --git a/scripts/check-local-export b/scripts/check-local-export new file mode 100755 index 000000000000..d1721fa63057 --- /dev/null +++ b/scripts/check-local-export @@ -0,0 +1,48 @@ +#!/bin/bash +# SPDX-License-Identifier: GPL-2.0-only +# +# Copyright (C) 2022 Masahiro Yamada + +set -e +set -o pipefail + +declare -A symbol_types +declare -a export_symbols + +exit_code=0 + +while read value type name +do + # to avoid error for clang LTO; $name may be empty + if [[ $value = -* && -z $name ]]; then + continue + fi + + # The first field (value) may be empty. If so, fix it up. + if [[ -z $name ]]; then + name=${type} + type=${value} + fi + + # save (name, type) in the associative array + symbol_types[$name]=$type + + # append the exported symbol to the array + if [[ $name == __ksymtab_* ]]; then + export_symbols+=(${name#__ksymtab_}) + fi +done < <(${NM} ${1} 2>/dev/null) + +# Catch error in the process substitution +wait $! + +for name in "${export_symbols[@]}" +do + # nm(3) says "If lowercase, the symbol is usually local" + if [[ ${symbol_types[$name]} =~ [a-z] ]]; then + echo "$@: error: local symbol '${name}' was exported" >&2 + exit_code=1 + fi +done + +exit ${exit_code} diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c index 018527d96680..fa73ddb6a6cf 100644 --- a/scripts/mod/modpost.c +++ b/scripts/mod/modpost.c @@ -212,7 +212,6 @@ struct symbol { unsigned int crc; bool crc_valid; bool weak; - bool is_static; /* true if symbol is not global */ bool is_gpl_only; /* exported by EXPORT_SYMBOL_GPL */ char name[]; }; @@ -242,7 +241,7 @@ static struct symbol *alloc_symbol(const char *name) memset(s, 0, sizeof(*s)); strcpy(s->name, name); - s->is_static = true; + return s; } @@ -875,20 +874,6 @@ static void read_symbols(const char *modname) sym_get_data(&info, sym)); } - // check for static EXPORT_SYMBOL_* functions && global vars - for (sym = info.symtab_start; sym < info.symtab_stop; sym++) { - unsigned char bind = ELF_ST_BIND(sym->st_info); - - if (bind == STB_GLOBAL || bind == STB_WEAK) { - struct symbol *s = - find_symbol(remove_dot(info.strtab + - sym->st_name)); - - if (s) - s->is_static = false; - } - } - check_sec_ref(mod, modname, &info); if (!mod->is_vmlinux) { @@ -1318,7 +1303,6 @@ static void read_dump(const char *fname) mod->from_dump = true; } s = sym_add_exported(symname, mod, gpl_only); - s->is_static = false; sym_set_crc(s, crc); sym_update_namespace(symname, namespace); } @@ -1383,7 +1367,6 @@ int main(int argc, char **argv) char *missing_namespace_deps = NULL; char *dump_write = NULL, *files_source = NULL; int opt; - int n; LIST_HEAD(dump_lists); struct dump_list *dl, *dl2; @@ -1459,15 +1442,6 @@ int main(int argc, char **argv) if (sec_mismatch_count && !sec_mismatch_warn_only) error("Section mismatches detected.\n" "Set CONFIG_SECTION_MISMATCH_WARN_ONLY=y to allow them.\n"); - for (n = 0; n < SYMBOL_HASH_SIZE; n++) { - struct symbol *s; - - for (s = symbolhash[n]; s; s = s->next) { - if (s->is_static) - error("\"%s\" [%s] is a static EXPORT_SYMBOL\n", - s->name, s->module->name); - } - } if (nr_unresolved > MAX_UNRESOLVED_REPORTS) warn("suppressed %u unresolved symbol warnings because there were too many)\n",
The 'static' specifier and EXPORT_SYMBOL() are an odd combination. Commit 15bfc2348d54 ("modpost: check for static EXPORT_SYMBOL* functions") tried to detect it, but this check has false negatives. Here is the sample code. Makefile: obj-y += foo1.o foo2.o foo1.c: #include <linux/export.h> static void foo(void) {} EXPORT_SYMBOL(foo); foo2.c: void foo(void) {} foo1.c exports the static symbol 'foo', but modpost cannot catch it because it is fooled by foo2.c, which has a global symbol with the same name. s->is_static is cleared if a global symbol with the same name is found somewhere, but EXPORT_SYMBOL() and the global symbol do not necessarily belong to the same compilation unit. This check should be done per compilation unit, but I do not know how to do it in modpost. modpost runs against vmlinux.o or modules, which merges multiple objects, then forgets their origin. It is true modpost gets access to the lists of all the member objects (.vmlinux.objs and *.mod), but it is impossible to parse individual objects in modpost; they might be LLVM IR instead of ELF when CONFIG_LTO_CLANG=y. Add a simple bash script to parse the output from ${NM}. This works for CONFIG_LTO_CLANG=y because llvm-nm can dump symbols of LLVM bitcode. Revert 15bfc2348d54. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> --- Changes in v4: - New patch scripts/Makefile.build | 4 ++++ scripts/check-local-export | 48 ++++++++++++++++++++++++++++++++++++++ scripts/mod/modpost.c | 28 +--------------------- 3 files changed, 53 insertions(+), 27 deletions(-) create mode 100755 scripts/check-local-export