Use the recently introduced EFI_MEMORY_ATTRIBUTES_PROTOCOL in the zboot
implementation to set the right attributes for the code and data
sections of the decompressed image, i.e., EFI_MEMORY_RO for code and
EFI_MEMORY_XP for data.
Cc: Evgeniy Baskov <baskov@xxxxxxxxx>
Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
---
drivers/firmware/efi/libstub/zboot.c | 55 ++++++++++++++++++++
1 file changed, 55 insertions(+)
diff --git a/drivers/firmware/efi/libstub/zboot.c b/drivers/firmware/efi/libstub/zboot.c
index 66be5fdc6b5885b7..89ad9204807b0477 100644
--- a/drivers/firmware/efi/libstub/zboot.c
+++ b/drivers/firmware/efi/libstub/zboot.c
@@ -49,6 +49,59 @@ static unsigned long alloc_preferred_address(unsigned long alloc_size)
return ULONG_MAX;
}
+static void efi_remap_image(unsigned long image_base, unsigned alloc_size,
+ unsigned long code_size)
+{
+ efi_memory_attribute_protocol_t *memattr;
+ efi_status_t status;
+ u64 attr;
+
+ /*
+ * If the firmware implements the EFI_MEMORY_ATTRIBUTE_PROTOCOL, let's
+ * invoke it to remap the text/rodata region of the decompressed image
+ * as read-only and the data/bss region as non-executable.
+ */
+ status = efi_bs_call(locate_protocol, &EFI_MEMORY_ATTRIBUTE_PROTOCOL_GUID,
+ NULL, (void **)&memattr);
+ if (status != EFI_SUCCESS)
+ return;
+
+ // Get the current attributes for the entire region
+ status = memattr->get_memory_attributes(memattr, image_base,
+ alloc_size, &attr);
+ if (status != EFI_SUCCESS) {
+ efi_warn("Failed to retrieve memory attributes for image region: 0x%lx\n",
+ status);
+ return;
+ }
+
+ // Mark the code region as read-only
+ status = memattr->set_memory_attributes(memattr, image_base, code_size,
+ EFI_MEMORY_RO);
+ if (status != EFI_SUCCESS) {
+ efi_warn("Failed to remap code region read-only\n");
+ return;
+ }
+
+ // If the entire region was already mapped as non-exec, clear the
+ // attribute from the code region. Otherwise, set it on the data
+ // region.
+ if (attr & EFI_MEMORY_XP) {
+ status = memattr->clear_memory_attributes(memattr, image_base,
+ code_size,
+ EFI_MEMORY_XP);
+ if (status != EFI_SUCCESS)
+ efi_warn("Failed to remap code region executable\n");
+ } else {
+ status = memattr->set_memory_attributes(memattr,
+ image_base + code_size,
+ alloc_size - code_size,
+ EFI_MEMORY_XP);
+ if (status != EFI_SUCCESS)
+ efi_warn("Failed to remap data region non-executable\n");
+ }
+}
+
void __weak efi_cache_sync_image(unsigned long image_base,
unsigned long alloc_size,
unsigned long code_size)
@@ -137,6 +190,8 @@ efi_zboot_entry(efi_handle_t handle, efi_system_table_t *systab)
efi_cache_sync_image(image_base, alloc_size, code_size);
+ efi_remap_image(image_base, alloc_size, code_size);
+
status = efi_stub_common(handle, image, image_base, cmdline_ptr);
free_image:
--
2.39.0
