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Date: Sat, 23 Nov 2019 15:42:45 +0900
From: Masahiro Yamada <yamada.masahiro@...ionext.com>
To: Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>
Cc: Michal Marek <michal.lkml@...kovi.net>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/6] modpost: stop symbol preloading for modversion CRC
On Fri, Nov 15, 2019 at 2:42 AM Masahiro Yamada
<yamada.masahiro@...ionext.com> wrote:
>
> It is complicated to add mocked-up symbols to pre-handle CRC.
> Handle CRC after all the export symbols in the relevant module
> are registered.
>
> Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
> ---
>
> scripts/mod/modpost.c | 64 +++++++++++++++++++++++--------------------
> 1 file changed, 35 insertions(+), 29 deletions(-)
>
> diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> index 6735ae3da4c2..73bdf27c41fe 100644
> --- a/scripts/mod/modpost.c
> +++ b/scripts/mod/modpost.c
> @@ -169,7 +169,7 @@ struct symbol {
> 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) **/
> - unsigned int preloaded:1; /* 1 if symbol from Module.symvers, or crc */
> + unsigned int preloaded:1; /* 1 if symbol from Module.symvers */
> unsigned int is_static:1; /* 1 if symbol is not global */
> enum export export; /* Type of export */
> char name[0];
> @@ -410,15 +410,15 @@ static struct symbol *sym_add_exported(const char *name, struct module *mod,
> return s;
> }
>
> -static void sym_update_crc(const char *name, struct module *mod,
> - unsigned int crc, enum export export)
> +static void sym_set_crc(const char *name, const struct module *mod,
> + unsigned int crc)
> {
> struct symbol *s = find_symbol(name);
>
> if (!s) {
> - s = new_symbol(name, mod, export);
> - /* Don't complain when we find it later. */
> - s->preloaded = 1;
> + warn("%s: '__crc_%s' is invalid use. __crc_* is reserved for modversion\n",
> + mod->name, name);
I notice this can produce false positive warnings.
ARCH=arm allyesconfig produces the following:
WARNING: vmlinux: '__crc_ccitt_veneer' is invalid use. __crc_* is
reserved for modversion
WARNING: vmlinux: '__crc_ccitt_veneer' is invalid use. __crc_* is
reserved for modversion
WARNING: vmlinux: '__crc_ccitt_veneer' is invalid use. __crc_* is
reserved for modversion
WARNING: vmlinux: '__crc_itu_t_veneer' is invalid use. __crc_* is
reserved for modversion
WARNING: vmlinux: '__crc_itu_t_veneer' is invalid use. __crc_* is
reserved for modversion
WARNING: vmlinux: '__crc_itu_t_veneer' is invalid use. __crc_* is
reserved for modversion
The ARM compiler inserts veneers automatically.
I will remove this warn(), and add commit messages as follows:
In some cases, I see atand-alone __crc_* without __ksymtab_*.
For example, ARCH=arm allyesconfig produces __crc_ccitt_veneer and
__crc_itu_t_veneer. I guess they come from crc_ccitt, crc_itu_t,
respectively. Since __*_veneer are auto-generated symbols, just
ignore them.
> + return;
> }
> s->crc = crc;
> s->crc_valid = 1;
> @@ -683,12 +683,34 @@ 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",
> + symname, mod->name, is_vmlinux(mod->name) ? "":".ko");
> + 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, mod, crc);
> +}
> +
> static void handle_symbol(struct module *mod, struct elf_info *info,
> const Elf_Sym *sym, const char *symname)
> {
> - unsigned int crc;
> enum export export;
> - bool is_crc = false;
> const char *name;
>
> if ((!is_vmlinux(mod->name) || mod->is_dot_o) &&
> @@ -697,21 +719,6 @@ static void handle_symbol(struct module *mod, struct elf_info *info,
> else
> export = export_from_sec(info, get_secindex(info, sym));
>
> - /* CRC'd symbol */
> - if (strstarts(symname, "__crc_")) {
> - is_crc = true;
> - crc = (unsigned int) sym->st_value;
> - if (sym->st_shndx != SHN_UNDEF && sym->st_shndx != SHN_ABS) {
> - unsigned int *crcp;
> -
> - /* symbol points to the CRC in the ELF object */
> - crcp = sym_get_data(info, sym);
> - crc = TO_NATIVE(*crcp);
> - }
> - sym_update_crc(symname + strlen("__crc_"), mod, crc,
> - export);
> - }
> -
> switch (sym->st_shndx) {
> case SHN_COMMON:
> if (strstarts(symname, "__gnu_lto_")) {
> @@ -746,11 +753,6 @@ static void handle_symbol(struct module *mod, struct elf_info *info,
> }
> #endif
>
> - if (is_crc) {
> - const char *e = is_vmlinux(mod->name) ?"":".ko";
> - warn("EXPORT symbol \"%s\" [%s%s] version generation failed, symbol will not be versioned.\n",
> - symname + strlen("__crc_"), mod->name, e);
> - }
> mod->unres = alloc_symbol(symname,
> ELF_ST_BIND(sym->st_info) == STB_WEAK,
> mod->unres);
> @@ -2063,6 +2065,10 @@ static void read_symbols(const char *modname)
> sym_update_namespace(symname + strlen("__kstrtabns_"),
> namespace_from_kstrtabns(&info,
> sym));
> +
> + if (strstarts(symname, "__crc_"))
> + handle_modversion(mod, &info, sym,
> + symname + strlen("__crc_"));
> }
>
> // check for static EXPORT_SYMBOL_* functions && global vars
> @@ -2476,7 +2482,7 @@ static void read_dump(const char *fname, unsigned int kernel)
> s->kernel = kernel;
> s->preloaded = 1;
> s->is_static = 0;
> - sym_update_crc(symname, mod, crc, export_no(export));
> + sym_set_crc(symname, mod, crc);
> sym_update_namespace(symname, namespace);
> }
> release_file(file, size);
> --
> 2.17.1
>
--
Best Regards
Masahiro Yamada
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