arm64/efi: do not assume DRAM base is aligned to 2 MB

The current arm64 Image relocation code in the UEFI stub assumes that
the dram_base argument it receives is always a multiple of 2 MB. In
reality, it is simply the lowest start address of all RAM entries in
the UEFI memory map, which means it could be any multiple of 4 KB.

Since the arm64 kernel Image needs to reside TEXT_OFFSET bytes beyond
a 2 MB aligned base, or it will fail to boot, make sure we round dram_base
to 2 MB before using it to calculate the relocation address.

Fixes: e38457c361b30c5a ("arm64: efi: prefer AllocatePages() over efi_low_alloc() for vmlinux")
Reported-by: Timur Tabi <timur@codeaurora.org>
Tested-by: Timur Tabi <timur@codeaurora.org>
Acked-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 816120ece6bcecfbcbc1c25be51324c5197b65cd..78dfbd34b6bffd2fa36312da89dc6ca43f036c3c 100644 (file)
--- a/arch/arm64/kernel/efi-stub.c
+++ b/arch/arm64/kernel/efi-stub.c
@@ -25,10 +25,20 @@ efi_status_t __init handle_kernel_image(efi_system_table_t *sys_table_arg,
        unsigned long kernel_size, kernel_memsize = 0;
        unsigned long nr_pages;
        void *old_image_addr = (void *)*image_addr;
+       unsigned long preferred_offset;
+
+       /*
+        * The preferred offset of the kernel Image is TEXT_OFFSET bytes beyond
+        * a 2 MB aligned base, which itself may be lower than dram_base, as
+        * long as the resulting offset equals or exceeds it.
+        */
+       preferred_offset = round_down(dram_base, SZ_2M) + TEXT_OFFSET;
+       if (preferred_offset < dram_base)
+               preferred_offset += SZ_2M;
 
        /* Relocate the image, if required. */
        kernel_size = _edata - _text;
-       if (*image_addr != (dram_base + TEXT_OFFSET)) {
+       if (*image_addr != preferred_offset) {
                kernel_memsize = kernel_size + (_end - _edata);
 
                /*
@@ -42,7 +52,7 @@ efi_status_t __init handle_kernel_image(efi_system_table_t *sys_table_arg,
                 * Mustang), we can still place the kernel at the address
                 * 'dram_base + TEXT_OFFSET'.
                 */
-               *image_addr = *reserve_addr = dram_base + TEXT_OFFSET;
+               *image_addr = *reserve_addr = preferred_offset;
                nr_pages = round_up(kernel_memsize, EFI_ALLOC_ALIGN) /
                           EFI_PAGE_SIZE;
                status = efi_call_early(allocate_pages, EFI_ALLOCATE_ADDRESS,