[PATCH] efi_loader: Get rid of kaslr-seed

[Ilias Apalodimas]

Right now we unconditionally pass a 'kaslr-seed' property to the kernel
if the DTB we ended up in EFI includes the entry.  However the kernel
EFI stub completely ignores it and only relies on EFI_RNG_PROTOCOL.
So let's get rid of it unconditionally since it would mess up the
(upcoming) DTB TPM measuring as well.

Signed-off-by: Ilias Apalodimas <ilias.apalodimas at linaro.org>
---
 cmd/bootefi.c                 |  2 ++
 include/efi_loader.h          |  2 ++
 lib/efi_loader/efi_dt_fixup.c | 22 ++++++++++++++++++++++
 3 files changed, 26 insertions(+)

diff --git a/cmd/bootefi.c b/cmd/bootefi.c
index d77d3b6e943d..25f9bfce9b84 100644
--- a/cmd/bootefi.c
+++ b/cmd/bootefi.c
@@ -310,6 +310,8 @@ efi_status_t efi_install_fdt(void *fdt)
 	/* Create memory reservations as indicated by the device tree */
 	efi_carve_out_dt_rsv(fdt);
 
+	efi_purge_kaslr_seed(fdt);
+
 	/* Install device tree as UEFI table */
 	ret = efi_install_configuration_table(&efi_guid_fdt, fdt);
 	if (ret != EFI_SUCCESS) {
diff --git a/include/efi_loader.h b/include/efi_loader.h
index 9dd6c2033634..e560401ac54f 100644
--- a/include/efi_loader.h
+++ b/include/efi_loader.h
@@ -519,6 +519,8 @@ efi_status_t EFIAPI efi_convert_pointer(efi_uintn_t debug_disposition,
 					void **address);
 /* Carve out DT reserved memory ranges */
 void efi_carve_out_dt_rsv(void *fdt);
+/* Purge unused kaslr-seed */
+void efi_purge_kaslr_seed(void *fdt);
 /* Called by bootefi to make console interface available */
 efi_status_t efi_console_register(void);
 /* Called by bootefi to make all disk storage accessible as EFI objects */
diff --git a/lib/efi_loader/efi_dt_fixup.c b/lib/efi_loader/efi_dt_fixup.c
index b6fe5d2e5a34..02f7de73872e 100644
--- a/lib/efi_loader/efi_dt_fixup.c
+++ b/lib/efi_loader/efi_dt_fixup.c
@@ -40,6 +40,28 @@ static void efi_reserve_memory(u64 addr, u64 size, bool nomap)
 			addr, size);
 }
 
+/**
+ * efi_remove_kaslr_seed() - Removed unused kaslr-seed
+ *
+ * Kernel's EFI STUB only relies on EFI_RNG_PROTOCOL for randomization
+ * and completely ignores the kaslr-seed.  Weed it out from the DTB we
+ * hand over, which would mess up our DTB TPM measurements as well.
+ *
+ * @fdt: Pointer to device tree
+ */
+void efi_purge_kaslr_seed(void *fdt)
+{
+	int nodeoff = fdt_path_offset(fdt, "/chosen");
+	int err = 0;
+
+	if (nodeoff < 0)
+		return;
+
+	err = fdt_delprop(fdt, nodeoff, "kaslr-seed");
+	if (err < 0)
+		log_err("Error deleting kaslr-seed\n");
+}
+
 /**
  * efi_carve_out_dt_rsv() - Carve out DT reserved memory ranges
  *
-- 
2.30.2