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modpost: Create modalias for builtin modules

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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.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Alexey Gladkov <legion@kernel.org>
Tested-by: Stephen Rothwell <sfr@canb.auug.org.au>
Reviewed-by: Nicolas Schier <nsc@kernel.org>
Link: https://patch.msgid.link/28d4da3b0e3fc8474142746bcf469e03752c3208.1758182101.git.legion@kernel.org
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
This commit is contained in:
Alexey Gladkov
2025-09-18 10:05:51 +02:00
committed by Nathan Chancellor
parent 83fb49389b
commit 5ab23c7923
6 changed files with 41 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files

15
scripts/mod/modpost.c
View File

@@ -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);
}