arm64/efi: move SetVirtualAddressMap() to UEFI stub

In order to support kexec, the kernel needs to be able to deal with the
state of the UEFI firmware after SetVirtualAddressMap() has been called.
To avoid having separate code paths for non-kexec and kexec, let's move
the call to SetVirtualAddressMap() to the stub: this will guarantee us
that it will only be called once (since the stub is not executed during
kexec), and ensures that the UEFI state is identical between kexec and
normal boot.

This implies that the layout of the virtual mapping needs to be created
by the stub as well. All regions are rounded up to a naturally aligned
multiple of 64 KB (for compatibility with 64k pages kernels) and recorded
in the UEFI memory map. The kernel proper reads those values and installs
the mappings in a dedicated set of page tables that are swapped in during
UEFI Runtime Services calls.

Acked-by: Leif Lindholm <leif.lindholm@linaro.org>
Acked-by: Matt Fleming <matt.fleming@intel.com>
Tested-by: Leif Lindholm <leif.lindholm@linaro.org>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

1 files changed, 59 insertions, 3 deletions

diff --git a/drivers/firmware/efi/libstub/fdt.c b/drivers/firmware/efi/libstub/fdt.c
index c846a9608cbd..91da56c4fd54 100644
--- a/drivers/firmware/efi/libstub/fdt.c
+++ b/drivers/firmware/efi/libstub/fdt.c
@@ -14,6 +14,8 @@
 #include <linux/libfdt.h>
 #include <asm/efi.h>
 
+#include "efistub.h"
+
 efi_status_t update_fdt(efi_system_table_t *sys_table, void *orig_fdt,
                         unsigned long orig_fdt_size,
                         void *fdt, int new_fdt_size, char *cmdline_ptr,
@@ -193,9 +195,26 @@ efi_status_t allocate_new_fdt_and_exit_boot(efi_system_table_t *sys_table,
         unsigned long map_size, desc_size;
         u32 desc_ver;
         unsigned long mmap_key;
-        efi_memory_desc_t *memory_map;
+        efi_memory_desc_t *memory_map, *runtime_map;
         unsigned long new_fdt_size;
         efi_status_t status;
+        int runtime_entry_count = 0;
+
+        /*
+         * Get a copy of the current memory map that we will use to prepare
+         * the input for SetVirtualAddressMap(). We don't have to worry about
+         * subsequent allocations adding entries, since they could not affect
+         * the number of EFI_MEMORY_RUNTIME regions.
+         */
+        status = efi_get_memory_map(sys_table, &runtime_map, &map_size,
+                                    &desc_size, &desc_ver, &mmap_key);
+        if (status != EFI_SUCCESS) {
+                pr_efi_err(sys_table, "Unable to retrieve UEFI memory map.\n");
+                return status;
+        }
+
+        pr_efi(sys_table,
+               "Exiting boot services and installing virtual address map...\n");
 
         /*
          * Estimate size of new FDT, and allocate memory for it. We
@@ -248,12 +267,48 @@ efi_status_t allocate_new_fdt_and_exit_boot(efi_system_table_t *sys_table,
                 }
         }
 
+        /*
+         * Update the memory map with virtual addresses. The function will also
+         * populate @runtime_map with copies of just the EFI_MEMORY_RUNTIME
+         * entries so that we can pass it straight into SetVirtualAddressMap()
+         */
+        efi_get_virtmap(memory_map, map_size, desc_size, runtime_map,
+                        &runtime_entry_count);
+
         /* Now we are ready to exit_boot_services.*/
         status = sys_table->boottime->exit_boot_services(handle, mmap_key);
 
+        if (status == EFI_SUCCESS) {
+                efi_set_virtual_address_map_t *svam;
 
-        if (status == EFI_SUCCESS)
-                return status;
+                /* Install the new virtual address map */
+                svam = sys_table->runtime->set_virtual_address_map;
+                status = svam(runtime_entry_count * desc_size, desc_size,
+                              desc_ver, runtime_map);
+
+                /*
+                 * We are beyond the point of no return here, so if the call to
+                 * SetVirtualAddressMap() failed, we need to signal that to the
+                 * incoming kernel but proceed normally otherwise.
+                 */
+                if (status != EFI_SUCCESS) {
+                        int l;
+
+                        /*
+                         * Set the virtual address field of all
+                         * EFI_MEMORY_RUNTIME entries to 0. This will signal
+                         * the incoming kernel that no virtual translation has
+                         * been installed.
+                         */
+                        for (l = 0; l < map_size; l += desc_size) {
+                                efi_memory_desc_t *p = (void *)memory_map + l;
+
+                                if (p->attribute & EFI_MEMORY_RUNTIME)
+                                        p->virt_addr = 0;
+                        }
+                }
+                return EFI_SUCCESS;
+        }
 
         pr_efi_err(sys_table, "Exit boot services failed.\n");
 
@@ -264,6 +319,7 @@ fail_free_new_fdt:
         efi_free(sys_table, new_fdt_size, *new_fdt_addr);
 
 fail:
+        sys_table->boottime->free_pool(runtime_map);
         return EFI_LOAD_ERROR;
 }