firmware: enable to force disable the fallback mechanism at run time

You currently need four different kernel builds to test the firmware
API fully. By adding a proc knob to force disable the fallback mechanism
completely we are able to reduce the amount of kernels you need built
to test the firmware API down to two.

Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/base/firmware_loader/fallback.c b/drivers/base/firmware_loader/fallback.c
index 45cc409..d6838e7 100644 (file)
--- a/drivers/base/firmware_loader/fallback.c
+++ b/drivers/base/firmware_loader/fallback.c
@@ -643,6 +643,11 @@ static bool fw_force_sysfs_fallback(unsigned int opt_flags)
 
 static bool fw_run_sysfs_fallback(unsigned int opt_flags)
 {
+       if (fw_fallback_config.ignore_sysfs_fallback) {
+               pr_info_once("Ignoring firmware sysfs fallback due to debugfs knob\n");
+               return false;
+       }
+
        if ((opt_flags & FW_OPT_NOFALLBACK))
                return false;
 

diff --git a/drivers/base/firmware_loader/fallback.h b/drivers/base/firmware_loader/fallback.h
index ca7e69a..dfebc64 100644 (file)
--- a/drivers/base/firmware_loader/fallback.h
+++ b/drivers/base/firmware_loader/fallback.h
@@ -14,12 +14,16 @@
  *     as if one had enabled CONFIG_FW_LOADER_USER_HELPER_FALLBACK=y.
  *     Useful to help debug a CONFIG_FW_LOADER_USER_HELPER_FALLBACK=y
  *     functionality on a kernel where that config entry has been disabled.
+ * @ignore_sysfs_fallback: force to disable the sysfs fallback mechanism.
+ *     This emulates the behaviour as if we had set the kernel
+ *     config CONFIG_FW_LOADER_USER_HELPER=n.
  * @old_timeout: for internal use
  * @loading_timeout: the timeout to wait for the fallback mechanism before
  *     giving up, in seconds.
  */
 struct firmware_fallback_config {
        unsigned int force_sysfs_fallback;
+       unsigned int ignore_sysfs_fallback;
        int old_timeout;
        int loading_timeout;
 };

diff --git a/drivers/base/firmware_loader/fallback_table.c b/drivers/base/firmware_loader/fallback_table.c
index 92365e0..7428659 100644 (file)
--- a/drivers/base/firmware_loader/fallback_table.c
+++ b/drivers/base/firmware_loader/fallback_table.c
@@ -39,6 +39,15 @@ struct ctl_table firmware_config_table[] = {
                .extra1         = &zero,
                .extra2         = &one,
        },
+       {
+               .procname       = "ignore_sysfs_fallback",
+               .data           = &fw_fallback_config.ignore_sysfs_fallback,
+               .maxlen         = sizeof(unsigned int),
+               .mode           = 0644,
+               .proc_handler   = proc_douintvec_minmax,
+               .extra1         = &zero,
+               .extra2         = &one,
+       },
        { }
 };
 EXPORT_SYMBOL_GPL(firmware_config_table);