efi: libstub: Factor out min alignment and preferred kernel load address

Factor out the expressions that describe the preferred placement of the
loaded image as well as the minimum alignment so we can reuse them in
the decompressor.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

1 files changed, 15 insertions, 0 deletions

diff --git a/arch/arm64/include/asm/efi.h b/arch/arm64/include/asm/efi.h
index 8604473a85b8..925364586672 100644
--- a/arch/arm64/include/asm/efi.h
+++ b/arch/arm64/include/asm/efi.h
@@ -84,6 +84,21 @@ static inline unsigned long efi_get_max_initrd_addr(unsigned long image_addr)
 	return (image_addr & ~(SZ_1G - 1UL)) + (1UL << (VA_BITS_MIN - 1));
 }
 
+static inline unsigned long efi_get_kimg_min_align(void)
+{
+	extern bool efi_nokaslr;
+
+	/*
+	 * Although relocatable kernels can fix up the misalignment with
+	 * respect to MIN_KIMG_ALIGN, the resulting virtual text addresses are
+	 * subtly out of sync with those recorded in the vmlinux when kaslr is
+	 * disabled but the image required relocation anyway. Therefore retain
+	 * 2M alignment if KASLR was explicitly disabled, even if it was not
+	 * going to be activated to begin with.
+	 */
+	return efi_nokaslr ? MIN_KIMG_ALIGN : EFI_KIMG_ALIGN;
+}
+
 #define EFI_ALLOC_ALIGN		SZ_64K
 
 /*