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Message-ID: <20251007011637.2512413-1-cmirabil@redhat.com>
Date: Mon, 6 Oct 2025 21:16:37 -0400
From: Charles Mirabile <cmirabil@...hat.com>
To: legion@...nel.org
Cc: da.gomez@...sung.com,
linux-kbuild@...r.kernel.org,
linux-kernel@...r.kernel.org,
linux-modules@...r.kernel.org,
masahiroy@...nel.org,
mcgrof@...nel.org,
nathan@...nel.org,
nicolas.schier@...ux.dev,
petr.pavlu@...e.com,
samitolvanen@...gle.com,
sfr@...b.auug.org.au
Subject: Re: [PATCH v8 7/8] modpost: Create modalias for builtin modules
On Thu, Sep 18, 2025 at 10:05:51AM +0200, Alexey Gladkov wrote:
> For some modules, modalias is generated using the modpost utility and
> the section is added to the module file.
>
> When a module is added inside vmlinux, modpost does not generate
> modalias for such modules and the information is lost.
>
> As a result kmod (which uses modules.builtin.modinfo in userspace)
> cannot determine that modalias is handled by a builtin kernel module.
>
> $ cat /sys/devices/pci0000:00/0000:00:14.0/modalias
> pci:v00008086d0000A36Dsv00001043sd00008694bc0Csc03i30
>
> $ modinfo xhci_pci
> name: xhci_pci
> filename: (builtin)
> license: GPL
> file: drivers/usb/host/xhci-pci
> description: xHCI PCI Host Controller Driver
>
> Missing modalias "pci:v*d*sv*sd*bc0Csc03i30*" which will be generated by
> modpost if the module is built separately.
>
> To fix this it is necessary to generate the same modalias for vmlinux as
> for the individual modules. Fortunately '.vmlinux.export.o' is already
> generated from which '.modinfo' can be extracted in the same way as for
> vmlinux.o.
Hi -
This patch broke RISC-V builds for me. During the final objcopy where the new
symbols are supposed to be stripped, an error occurs producing lots of error
messages similar to this one:
riscv64-linux-gnu-objcopy: not stripping symbol `__mod_device_table__...'
because it is named in a relocation
It does not occur using defconfig, but I was able to bisect my way to this
commit and then reduce my config delta w.r.t defconfig until I landed on:
cat > .config <<'EOF'
CONFIG_RELOCATABLE=y
CONFIG_KASAN=y
EOF
ARCH=riscv CROSS_COMPILE=riscv64-linux-gnu- make olddefconfig
ARCH=riscv CROSS_COMPILE=riscv64-linux-gnu- make -j $(nproc)
...
LD vmlinux.unstripped
NM System.map
SORTTAB vmlinux.unstripped
CHKREL vmlinux.unstripped
OBJCOPY vmlinux
OBJCOPY modules.builtin.modinfo
GEN modules.builtin
riscv64-linux-gnu-objcopy: not stripping symbol `<long symbol name>'
because it is named in a relocation
<repeats with different symbol names about a dozen times>
make[3]: *** [scripts/Makefile.vmlinux:97: vmlinux] Error 1
make[3]: *** Deleting file 'vmlinux'
make[2]: *** [Makefile:1242: vmlinux] Error 2
make[1]: *** [/tmp/linux/Makefile:369: __build_one_by_one] Error 2
make: *** [Makefile:248: __sub-make] Error 2
I confirmed that reverting this commit fixes the issue.
>
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> Signed-off-by: Alexey Gladkov <legion@...nel.org>
> Tested-by: Stephen Rothwell <sfr@...b.auug.org.au>
> ---
> include/linux/module.h | 4 ----
> scripts/Makefile.vmlinux | 4 +++-
> scripts/mksysmap | 3 +++
> scripts/mod/file2alias.c | 19 ++++++++++++++++++-
> scripts/mod/modpost.c | 15 +++++++++++++++
> scripts/mod/modpost.h | 2 ++
> 6 files changed, 41 insertions(+), 6 deletions(-)
>
> diff --git a/include/linux/module.h b/include/linux/module.h
> index e31ee29fac6b7..e135cc79aceea 100644
> --- a/include/linux/module.h
> +++ b/include/linux/module.h
> @@ -256,14 +256,10 @@ struct module_kobject *lookup_or_create_module_kobject(const char *name);
> __PASTE(type, \
> __PASTE(__, name)))))
>
> -#ifdef MODULE
> /* Creates an alias so file2alias.c can find device table. */
> #define MODULE_DEVICE_TABLE(type, name) \
> static typeof(name) __mod_device_table(type, name) \
> __attribute__ ((used, alias(__stringify(name))))
> -#else /* !MODULE */
> -#define MODULE_DEVICE_TABLE(type, name)
> -#endif
>
> /* Version of form [<epoch>:]<version>[-<extra-version>].
> * Or for CVS/RCS ID version, everything but the number is stripped.
> diff --git a/scripts/Makefile.vmlinux b/scripts/Makefile.vmlinux
> index ce79461714979..1e5e37aadcd05 100644
> --- a/scripts/Makefile.vmlinux
> +++ b/scripts/Makefile.vmlinux
> @@ -89,11 +89,13 @@ endif
> remove-section-y := .modinfo
> remove-section-$(CONFIG_ARCH_VMLINUX_NEEDS_RELOCS) += '.rel*'
>
> +remove-symbols := -w --strip-symbol='__mod_device_table__*'
> +
> # To avoid warnings: "empty loadable segment detected at ..." from GNU objcopy,
> # it is necessary to remove the PT_LOAD flag from the segment.
> quiet_cmd_strip_relocs = OBJCOPY $@
> cmd_strip_relocs = $(OBJCOPY) $(patsubst %,--set-section-flags %=noload,$(remove-section-y)) $< $@; \
> - $(OBJCOPY) $(addprefix --remove-section=,$(remove-section-y)) $@
> + $(OBJCOPY) $(addprefix --remove-section=,$(remove-section-y)) $(remove-symbols) $@
>
> targets += vmlinux
> vmlinux: vmlinux.unstripped FORCE
> diff --git a/scripts/mksysmap b/scripts/mksysmap
> index a607a0059d119..c4531eacde202 100755
> --- a/scripts/mksysmap
> +++ b/scripts/mksysmap
> @@ -59,6 +59,9 @@
> # EXPORT_SYMBOL (namespace)
> / __kstrtabns_/d
>
> +# MODULE_DEVICE_TABLE (symbol name)
> +/ __mod_device_table__/d
> +
> # ---------------------------------------------------------------------------
> # Ignored suffixes
> # (do not forget '$' after each pattern)
> diff --git a/scripts/mod/file2alias.c b/scripts/mod/file2alias.c
> index 1260bc2287fba..7da9735e7ab3e 100644
> --- a/scripts/mod/file2alias.c
> +++ b/scripts/mod/file2alias.c
> @@ -1477,7 +1477,7 @@ void handle_moddevtable(struct module *mod, struct elf_info *info,
> void *symval;
> char *zeros = NULL;
> const char *type, *name, *modname;
> - size_t typelen;
> + size_t typelen, modnamelen;
> static const char *prefix = "__mod_device_table__";
>
> /* We're looking for a section relative symbol */
> @@ -1500,6 +1500,7 @@ void handle_moddevtable(struct module *mod, struct elf_info *info,
> type = strstr(modname, "__");
> if (!type)
> return;
> + modnamelen = type - modname;
> type += strlen("__");
>
> name = strstr(type, "__");
> @@ -1526,5 +1527,21 @@ void handle_moddevtable(struct module *mod, struct elf_info *info,
> }
> }
>
> + if (mod->is_vmlinux) {
> + struct module_alias *alias;
> +
> + /*
> + * If this is vmlinux, record the name of the builtin module.
> + * Traverse the linked list in the reverse order, and set the
> + * builtin_modname unless it has already been set in the
> + * previous call.
> + */
> + list_for_each_entry_reverse(alias, &mod->aliases, node) {
> + if (alias->builtin_modname)
> + break;
> + alias->builtin_modname = xstrndup(modname, modnamelen);
> + }
> + }
> +
> free(zeros);
> }
> diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> index 5ca7c268294eb..47c8aa2a69392 100644
> --- a/scripts/mod/modpost.c
> +++ b/scripts/mod/modpost.c
> @@ -2067,11 +2067,26 @@ static void write_if_changed(struct buffer *b, const char *fname)
> static void write_vmlinux_export_c_file(struct module *mod)
> {
> struct buffer buf = { };
> + struct module_alias *alias, *next;
>
> buf_printf(&buf,
> "#include <linux/export-internal.h>\n");
>
> add_exported_symbols(&buf, mod);
> +
> + buf_printf(&buf,
> + "#include <linux/module.h>\n"
> + "#undef __MODULE_INFO_PREFIX\n"
> + "#define __MODULE_INFO_PREFIX\n");
> +
> + list_for_each_entry_safe(alias, next, &mod->aliases, node) {
> + buf_printf(&buf, "MODULE_INFO(%s.alias, \"%s\");\n",
> + alias->builtin_modname, alias->str);
> + list_del(&alias->node);
> + free(alias->builtin_modname);
> + free(alias);
> + }
> +
> write_if_changed(&buf, ".vmlinux.export.c");
> free(buf.p);
> }
> diff --git a/scripts/mod/modpost.h b/scripts/mod/modpost.h
> index 9133e4c3803f0..2aecb8f25c87e 100644
> --- a/scripts/mod/modpost.h
> +++ b/scripts/mod/modpost.h
> @@ -99,10 +99,12 @@ buf_write(struct buffer *buf, const char *s, int len);
> * struct module_alias - auto-generated MODULE_ALIAS()
> *
> * @node: linked to module::aliases
> + * @modname: name of the builtin module (only for vmlinux)
> * @str: a string for MODULE_ALIAS()
> */
> struct module_alias {
> struct list_head node;
> + char *builtin_modname;
> char str[];
> };
>
> --
> 2.51.0
>
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