177 lines
5.0 KiB
Diff
177 lines
5.0 KiB
Diff
From: Seiji Aguchi <seiji.aguchi@hds.com>
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Date: Tue, 12 Feb 2013 13:04:41 -0800
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Subject: efi_pstore: Introducing workqueue updating sysfs
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commit a93bc0c6e07ed9bac44700280e65e2945d864fd4 upstream.
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[Problem]
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efi_pstore creates sysfs entries, which enable users to access to NVRAM,
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in a write callback. If a kernel panic happens in an interrupt context,
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it may fail because it could sleep due to dynamic memory allocations during
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creating sysfs entries.
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[Patch Description]
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This patch removes sysfs operations from a write callback by introducing
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a workqueue updating sysfs entries which is scheduled after the write
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callback is called.
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Also, the workqueue is kicked in a just oops case.
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A system will go down in other cases such as panic, clean shutdown and emergency
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restart. And we don't need to create sysfs entries because there is no chance for
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users to access to them.
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efi_pstore will be robust against a kernel panic in an interrupt context with this patch.
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Signed-off-by: Seiji Aguchi <seiji.aguchi@hds.com>
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Acked-by: Matt Fleming <matt.fleming@intel.com>
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Signed-off-by: Tony Luck <tony.luck@intel.com>
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[bwh: Backported to 3.2:
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- Adjust contest
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- Don't check reason in efi_pstore_write(), as it is not given as a
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parameter
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- Move up declaration of __efivars]
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---
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--- a/drivers/firmware/efivars.c
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+++ b/drivers/firmware/efivars.c
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@@ -128,6 +128,8 @@ struct efivar_attribute {
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ssize_t (*store)(struct efivar_entry *entry, const char *buf, size_t count);
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};
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+static struct efivars __efivars;
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+
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#define PSTORE_EFI_ATTRIBUTES \
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(EFI_VARIABLE_NON_VOLATILE | \
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EFI_VARIABLE_BOOTSERVICE_ACCESS | \
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@@ -152,6 +154,13 @@ efivar_create_sysfs_entry(struct efivars
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efi_char16_t *variable_name,
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efi_guid_t *vendor_guid);
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+/*
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+ * Prototype for workqueue functions updating sysfs entry
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+ */
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+
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+static void efivar_update_sysfs_entries(struct work_struct *);
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+static DECLARE_WORK(efivar_work, efivar_update_sysfs_entries);
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+
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/* Return the number of unicode characters in data */
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static unsigned long
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utf16_strnlen(efi_char16_t *s, size_t maxlength)
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@@ -834,11 +843,7 @@ static int efi_pstore_write(enum pstore_
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if (found)
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efivar_unregister(found);
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- if (size)
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- ret = efivar_create_sysfs_entry(efivars,
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- utf16_strsize(efi_name,
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- DUMP_NAME_LEN * 2),
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- efi_name, &vendor);
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+ schedule_work(&efivar_work);
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*id = part;
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return ret;
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@@ -1017,6 +1022,75 @@ static ssize_t efivar_delete(struct file
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return count;
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}
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+static bool variable_is_present(efi_char16_t *variable_name, efi_guid_t *vendor)
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+{
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+ struct efivar_entry *entry, *n;
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+ struct efivars *efivars = &__efivars;
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+ unsigned long strsize1, strsize2;
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+ bool found = false;
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+
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+ strsize1 = utf16_strsize(variable_name, 1024);
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+ list_for_each_entry_safe(entry, n, &efivars->list, list) {
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+ strsize2 = utf16_strsize(entry->var.VariableName, 1024);
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+ if (strsize1 == strsize2 &&
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+ !memcmp(variable_name, &(entry->var.VariableName),
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+ strsize2) &&
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+ !efi_guidcmp(entry->var.VendorGuid,
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+ *vendor)) {
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+ found = true;
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+ break;
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+ }
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+ }
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+ return found;
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+}
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+
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+static void efivar_update_sysfs_entries(struct work_struct *work)
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+{
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+ struct efivars *efivars = &__efivars;
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+ efi_guid_t vendor;
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+ efi_char16_t *variable_name;
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+ unsigned long variable_name_size = 1024;
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+ efi_status_t status = EFI_NOT_FOUND;
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+ bool found;
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+
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+ /* Add new sysfs entries */
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+ while (1) {
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+ variable_name = kzalloc(variable_name_size, GFP_KERNEL);
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+ if (!variable_name) {
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+ pr_err("efivars: Memory allocation failed.\n");
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+ return;
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+ }
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+
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+ spin_lock_irq(&efivars->lock);
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+ found = false;
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+ while (1) {
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+ variable_name_size = 1024;
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+ status = efivars->ops->get_next_variable(
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+ &variable_name_size,
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+ variable_name,
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+ &vendor);
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+ if (status != EFI_SUCCESS) {
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+ break;
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+ } else {
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+ if (!variable_is_present(variable_name,
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+ &vendor)) {
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+ found = true;
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+ break;
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+ }
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+ }
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+ }
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+ spin_unlock_irq(&efivars->lock);
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+
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+ if (!found) {
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+ kfree(variable_name);
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+ break;
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+ } else
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+ efivar_create_sysfs_entry(efivars,
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+ variable_name_size,
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+ variable_name, &vendor);
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+ }
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+}
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+
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/*
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* Let's not leave out systab information that snuck into
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* the efivars driver
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@@ -1273,7 +1347,6 @@ out:
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}
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EXPORT_SYMBOL_GPL(register_efivars);
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-static struct efivars __efivars;
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static struct efivar_operations ops;
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/*
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@@ -1331,6 +1404,8 @@ err_put:
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static void __exit
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efivars_exit(void)
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{
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+ cancel_work_sync(&efivar_work);
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+
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if (efi_enabled(EFI_RUNTIME_SERVICES)) {
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unregister_efivars(&__efivars);
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kobject_put(efi_kobj);
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--- a/include/linux/efi.h
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+++ b/include/linux/efi.h
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@@ -620,7 +620,8 @@ struct efivars {
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* 1) ->list - adds, removals, reads, writes
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* 2) ops.[gs]et_variable() calls.
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* It must not be held when creating sysfs entries or calling kmalloc.
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- * ops.get_next_variable() is only called from register_efivars(),
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+ * ops.get_next_variable() is only called from register_efivars()
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+ * or efivar_update_sysfs_entries(),
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* which is protected by the BKL, so that path is safe.
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*/
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spinlock_t lock;
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