On Fri, 13 Oct 2023 at 09:47, Masahisa Kojima <masahisa.kojima@xxxxxxxxxx> wrote: > > efivar operation is updated when the tee_stmm_efi module is probed. > tee_stmm_efi module supports SetVariable runtime service, > but user needs to manually remount the efivarfs as RW to enable > the write access if the previous efivar operation does not support > SerVariable and efivarfs is mounted as read-only. > > This commit notifies the update of efivar operation to > efivarfs subsystem, then drops SB_RDONLY flag if the efivar > operation supports SetVariable. > > Signed-off-by: Masahisa Kojima <masahisa.kojima@xxxxxxxxxx> Unfortunately, I have identified a problem with this approach. There are cases where there are multiple instances of struct superblock are associated with the efivarfs file system [0]. So I reworked the patch a little - please take the time to double check that I did not make any mistakes here. [0] https://lore.kernel.org/linux-efi/20231208163925.3225018-8-ardb@xxxxxxxxxx/T/#u > --- > drivers/firmware/efi/efi.c | 6 ++++++ > drivers/firmware/efi/vars.c | 8 ++++++++ > fs/efivarfs/super.c | 33 +++++++++++++++++++++++++++++++++ > include/linux/efi.h | 8 ++++++++ > 4 files changed, 55 insertions(+) > > diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c > index 53ae25bbb6ac..d2eec5ed8e5e 100644 > --- a/drivers/firmware/efi/efi.c > +++ b/drivers/firmware/efi/efi.c > @@ -32,6 +32,7 @@ > #include <linux/ucs2_string.h> > #include <linux/memblock.h> > #include <linux/security.h> > +#include <linux/notifier.h> > > #include <asm/early_ioremap.h> > > @@ -187,6 +188,9 @@ static const struct attribute_group efi_subsys_attr_group = { > .is_visible = efi_attr_is_visible, > }; > > +struct blocking_notifier_head efivar_ops_nh; > +EXPORT_SYMBOL_GPL(efivar_ops_nh); > + > static struct efivars generic_efivars; > static struct efivar_operations generic_ops; > > @@ -427,6 +431,8 @@ static int __init efisubsys_init(void) > platform_device_register_simple("efivars", 0, NULL, 0); > } > > + BLOCKING_INIT_NOTIFIER_HEAD(&efivar_ops_nh); > + > error = sysfs_create_group(efi_kobj, &efi_subsys_attr_group); > if (error) { > pr_err("efi: Sysfs attribute export failed with error %d.\n", > diff --git a/drivers/firmware/efi/vars.c b/drivers/firmware/efi/vars.c > index e9dc7116daf1..f654e6f6af87 100644 > --- a/drivers/firmware/efi/vars.c > +++ b/drivers/firmware/efi/vars.c > @@ -63,6 +63,7 @@ int efivars_register(struct efivars *efivars, > const struct efivar_operations *ops) > { > int rv; > + int event; > > if (down_interruptible(&efivars_lock)) > return -EINTR; > @@ -77,6 +78,13 @@ int efivars_register(struct efivars *efivars, > > __efivars = efivars; > > + if (efivar_supports_writes()) > + event = EFIVAR_OPS_RDWR; > + else > + event = EFIVAR_OPS_RDONLY; > + > + blocking_notifier_call_chain(&efivar_ops_nh, event, NULL); > + > pr_info("Registered efivars operations\n"); > rv = 0; > out: > diff --git a/fs/efivarfs/super.c b/fs/efivarfs/super.c > index e028fafa04f3..0f6e4d223aea 100644 > --- a/fs/efivarfs/super.c > +++ b/fs/efivarfs/super.c > @@ -14,11 +14,36 @@ > #include <linux/slab.h> > #include <linux/magic.h> > #include <linux/statfs.h> > +#include <linux/notifier.h> > > #include "internal.h" > > LIST_HEAD(efivarfs_list); > > +struct efivarfs_info { > + struct super_block *sb; > + struct notifier_block nb; > +}; > + > +static struct efivarfs_info info; > + > +static int efivarfs_ops_notifier(struct notifier_block *nb, unsigned long event, > + void *data) > +{ > + switch (event) { > + case EFIVAR_OPS_RDONLY: > + info.sb->s_flags |= SB_RDONLY; > + break; > + case EFIVAR_OPS_RDWR: > + info.sb->s_flags &= ~SB_RDONLY; > + break; > + default: > + return NOTIFY_DONE; > + } > + > + return NOTIFY_OK; > +} > + > static void efivarfs_evict_inode(struct inode *inode) > { > clear_inode(inode); > @@ -255,6 +280,12 @@ static int efivarfs_fill_super(struct super_block *sb, struct fs_context *fc) > if (!root) > return -ENOMEM; > > + info.sb = sb; > + info.nb.notifier_call = efivarfs_ops_notifier; > + err = blocking_notifier_chain_register(&efivar_ops_nh, &info.nb); > + if (err) > + return err; > + > INIT_LIST_HEAD(&efivarfs_list); > > err = efivar_init(efivarfs_callback, (void *)sb, true, &efivarfs_list); > @@ -281,6 +312,8 @@ static int efivarfs_init_fs_context(struct fs_context *fc) > > static void efivarfs_kill_sb(struct super_block *sb) > { > + blocking_notifier_chain_unregister(&efivar_ops_nh, &info.nb); > + info.sb = NULL; > kill_litter_super(sb); > > if (!efivar_is_available()) > diff --git a/include/linux/efi.h b/include/linux/efi.h > index 4776a3dd9a72..489707b9b0b0 100644 > --- a/include/linux/efi.h > +++ b/include/linux/efi.h > @@ -1355,6 +1355,14 @@ bool efi_config_table_is_usable(const efi_guid_t *guid, unsigned long table) > > umode_t efi_attr_is_visible(struct kobject *kobj, struct attribute *attr, int n); > > +/* > + * efivar ops event type > + */ > +#define EFIVAR_OPS_RDONLY 0 > +#define EFIVAR_OPS_RDWR 1 > + > +extern struct blocking_notifier_head efivar_ops_nh; > + > void efivars_generic_ops_register(void); > void efivars_generic_ops_unregister(void); > > -- > 2.30.2 >
