[PATCH v2] efi: vars: commonize the 512-byte name buffer quirk

[Jonggeun Park]

Some old UEFI implementations reject GetNextVariableName() calls with
a name buffer size larger than 512 bytes. Both efivar_init() and
efi_pstore_read() open-code the same workaround of resetting the size
to 512 on every iteration.

Move this workaround into efivar_get_next_variable(), which keeps this
quirk in one place, resolving the TODO in efi-pstore.c.

No functional change intended.

Signed-off-by: Jonggeun Park <jakejgpark@xxxxxxxxx>
---
v2:
- Move the workaround into the existing efivar_get_next_variable().
---
 drivers/firmware/efi/efi-pstore.c | 10 ----------
 drivers/firmware/efi/vars.c       |  7 +++++++
 fs/efivarfs/vars.c                | 12 +-----------
 3 files changed, 8 insertions(+), 21 deletions(-)

diff --git a/drivers/firmware/efi/efi-pstore.c b/drivers/firmware/efi/efi-pstore.c
index a5db3534f..4f2594d08 100644
--- a/drivers/firmware/efi/efi-pstore.c
+++ b/drivers/firmware/efi/efi-pstore.c
@@ -164,16 +164,6 @@ static ssize_t efi_pstore_read(struct pstore_record *record)
 	efi_status_t status;
 
 	for (;;) {
-		/*
-		 * A small set of old UEFI implementations reject sizes
-		 * above a certain threshold, the lowest seen in the wild
-		 * is 512.
-		 *
-		 * TODO: Commonize with the iteration implementation in
-		 *       fs/efivarfs to keep all the quirks in one place.
-		 */
-		varname_size = 512;
-
 		/*
 		 * If this is the first read() call in the pstore enumeration,
 		 * varname will be the empty string, and the GetNextVariable()
diff --git a/drivers/firmware/efi/vars.c b/drivers/firmware/efi/vars.c
index 3700e9869..0f95fc60d 100644
--- a/drivers/firmware/efi/vars.c
+++ b/drivers/firmware/efi/vars.c
@@ -191,11 +191,18 @@ EXPORT_SYMBOL_NS_GPL(efivar_get_variable, "EFIVAR");
 /*
  * efivar_get_next_variable() - enumerate the next name/vendor pair
  *
+ * A small set of old UEFI implementations reject sizes above a certain
+ * threshold, the lowest seen in the wild is 512. Set the name buffer size
+ * to 512 on each call.
+ *
  * Must be called with efivars_lock held.
  */
 efi_status_t efivar_get_next_variable(unsigned long *name_size,
 				      efi_char16_t *name, efi_guid_t *vendor)
 {
+	BUILD_BUG_ON(EFI_VAR_NAME_LEN < 512);
+	*name_size = 512;
+
 	return __efivars->ops->get_next_variable(name_size, name, vendor);
 }
 EXPORT_SYMBOL_NS_GPL(efivar_get_next_variable, "EFIVAR");
diff --git a/fs/efivarfs/vars.c b/fs/efivarfs/vars.c
index 6833c3d24..5a01833a6 100644
--- a/fs/efivarfs/vars.c
+++ b/fs/efivarfs/vars.c
@@ -391,18 +391,8 @@ int efivar_init(int (*func)(efi_char16_t *, efi_guid_t, unsigned long, void *),
 	if (err)
 		goto free;
 
-	/*
-	 * A small set of old UEFI implementations reject sizes
-	 * above a certain threshold, the lowest seen in the wild
-	 * is 512.
-	 */
-
 	do {
-		variable_name_size = 512;
-		BUILD_BUG_ON(EFI_VAR_NAME_LEN < 512);
-
-		status = efivar_get_next_variable(&variable_name_size,
-						  variable_name,
+		status = efivar_get_next_variable(&variable_name_size, variable_name,
 						  &vendor_guid);
 		switch (status) {
 		case EFI_SUCCESS:
-- 
2.43.0