modpost: Create modalias for builtin modules

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>

1 files changed, 18 insertions, 1 deletions

diff --git a/scripts/mod/file2alias.c b/scripts/mod/file2alias.c
index 1260bc2287fb..7da9735e7ab3 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);
 }