efi_loader: re-enable GRUB workaround on 32bit ARM
GRUB on ARM 32bit prior to version 2.04 lacks proper handling of caches.
In U-Boot v2019.04 a workaround for this was inadvertently removed.
The workaround is currently also needed for booting on systems with caches
that cannot be managed via CP15 (e.g. with an i.MX6 CPU).
Re-enable the workaround and make it customizable.
Fixes: f69d63fae281 ("efi_loader: use efi_start_image() for bootefi")
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/lib/efi_loader/Kconfig b/lib/efi_loader/Kconfig
index a7f2c68..c7027a9 100644
--- a/lib/efi_loader/Kconfig
+++ b/lib/efi_loader/Kconfig
@@ -107,4 +107,12 @@
default y
depends on ARCH_BCM283X || FSL_LAYERSCAPE || PSCI_RESET || SYSRESET_X86
+config EFI_GRUB_ARM32_WORKAROUND
+ bool "Workaround for GRUB on 32bit ARM"
+ default y
+ depends on ARM && !ARM64
+ help
+ GRUB prior to version 2.04 requires U-Boot to disable caches. This
+ workaround currently is also needed on systems with caches that
+ cannot be managed via CP15.
endif
diff --git a/lib/efi_loader/efi_boottime.c b/lib/efi_loader/efi_boottime.c
index 4f6e8d1..f75ca1a 100644
--- a/lib/efi_loader/efi_boottime.c
+++ b/lib/efi_loader/efi_boottime.c
@@ -39,14 +39,6 @@
/* Handle of the currently executing image */
static efi_handle_t current_image;
-/*
- * If we're running on nasty systems (32bit ARM booting into non-EFI Linux)
- * we need to do trickery with caches. Since we don't want to break the EFI
- * aware boot path, only apply hacks when loading exiting directly (breaking
- * direct Linux EFI booting along the way - oh well).
- */
-static bool efi_is_direct_boot = true;
-
#ifdef CONFIG_ARM
/*
* The "gd" pointer lives in a register on ARM and AArch64 that we declare
@@ -1911,13 +1903,21 @@
*/
static void efi_exit_caches(void)
{
-#if defined(CONFIG_ARM) && !defined(CONFIG_ARM64)
+#if defined(CONFIG_EFI_GRUB_ARM32_WORKAROUND)
/*
- * Grub on 32bit ARM needs to have caches disabled before jumping into
- * a zImage, but does not know of all cache layers. Give it a hand.
+ * Boooting Linux via GRUB prior to version 2.04 fails on 32bit ARM if
+ * caches are enabled.
+ *
+ * TODO:
+ * According to the UEFI spec caches that can be managed via CP15
+ * operations should be enabled. Caches requiring platform information
+ * to manage should be disabled. This should not happen in
+ * ExitBootServices() but before invoking any UEFI binary is invoked.
+ *
+ * We want to keep the current workaround while GRUB prior to version
+ * 2.04 is still in use.
*/
- if (efi_is_direct_boot)
- cleanup_before_linux();
+ cleanup_before_linux();
#endif
}
@@ -2893,8 +2893,6 @@
if (ret != EFI_SUCCESS)
return EFI_EXIT(EFI_INVALID_PARAMETER);
- efi_is_direct_boot = false;
-
image_obj->exit_data_size = exit_data_size;
image_obj->exit_data = exit_data;