arm64: efi: prefer AllocatePages() over efi_low_alloc() for vmlinux

When allocating memory for the kernel image, try the AllocatePages()
boot service to obtain memory at the preferred offset of
'dram_base + TEXT_OFFSET', and only revert to efi_low_alloc() if that
fails. This is the only way to allocate at the base of DRAM if DRAM
starts at 0x0, since efi_low_alloc() refuses to allocate at 0x0.

Tested-by: Haojian Zhuang <haojian.zhuang@linaro.org>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>

diff --git a/arch/arm64/kernel/efi-stub.c b/arch/arm64/kernel/efi-stub.c
index f537406..816120e 100644 (file)
--- a/arch/arm64/kernel/efi-stub.c
+++ b/arch/arm64/kernel/efi-stub.c
@@ -13,7 +13,7 @@
 #include <asm/efi.h>
 #include <asm/sections.h>
 
-efi_status_t __init handle_kernel_image(efi_system_table_t *sys_table,
+efi_status_t __init handle_kernel_image(efi_system_table_t *sys_table_arg,
                                        unsigned long *image_addr,
                                        unsigned long *image_size,
                                        unsigned long *reserve_addr,
@@ -23,21 +23,44 @@ efi_status_t __init handle_kernel_image(efi_system_table_t *sys_table,
 {
        efi_status_t status;
        unsigned long kernel_size, kernel_memsize = 0;
+       unsigned long nr_pages;
+       void *old_image_addr = (void *)*image_addr;
 
        /* Relocate the image, if required. */
        kernel_size = _edata - _text;
        if (*image_addr != (dram_base + TEXT_OFFSET)) {
                kernel_memsize = kernel_size + (_end - _edata);
-               status = efi_low_alloc(sys_table, kernel_memsize + TEXT_OFFSET,
-                                      SZ_2M, reserve_addr);
+
+               /*
+                * First, try a straight allocation at the preferred offset.
+                * This will work around the issue where, if dram_base == 0x0,
+                * efi_low_alloc() refuses to allocate at 0x0 (to prevent the
+                * address of the allocation to be mistaken for a FAIL return
+                * value or a NULL pointer). It will also ensure that, on
+                * platforms where the [dram_base, dram_base + TEXT_OFFSET)
+                * interval is partially occupied by the firmware (like on APM
+                * Mustang), we can still place the kernel at the address
+                * 'dram_base + TEXT_OFFSET'.
+                */
+               *image_addr = *reserve_addr = dram_base + TEXT_OFFSET;
+               nr_pages = round_up(kernel_memsize, EFI_ALLOC_ALIGN) /
+                          EFI_PAGE_SIZE;
+               status = efi_call_early(allocate_pages, EFI_ALLOCATE_ADDRESS,
+                                       EFI_LOADER_DATA, nr_pages,
+                                       (efi_physical_addr_t *)reserve_addr);
                if (status != EFI_SUCCESS) {
-                       pr_efi_err(sys_table, "Failed to relocate kernel\n");
-                       return status;
+                       kernel_memsize += TEXT_OFFSET;
+                       status = efi_low_alloc(sys_table_arg, kernel_memsize,
+                                              SZ_2M, reserve_addr);
+
+                       if (status != EFI_SUCCESS) {
+                               pr_efi_err(sys_table_arg, "Failed to relocate kernel\n");
+                               return status;
+                       }
+                       *image_addr = *reserve_addr + TEXT_OFFSET;
                }
-               memcpy((void *)*reserve_addr + TEXT_OFFSET, (void *)*image_addr,
-                      kernel_size);
-               *image_addr = *reserve_addr + TEXT_OFFSET;
-               *reserve_size = kernel_memsize + TEXT_OFFSET;
+               memcpy((void *)*image_addr, old_image_addr, kernel_size);
+               *reserve_size = kernel_memsize;
        }