----- Original Message ----- If it is a kdump, there should be a PAGESIZE vmcoreinfo entry. As far as I can tell, the PAGE_SIZE has always been exported as the second item for all architectures here: static int __init crash_save_vmcoreinfo_init(void) { VMCOREINFO_OSRELEASE(init_uts_ns.name.release); VMCOREINFO_PAGESIZE(PAGE_SIZE); ... What does "help -D" show for the vmcoreinfo data on your dumpfile? I have several old arm64 dumpfiles, with kernel versions 3.19, 4.2, 4.4, 4.5, 4.7, 4.9 and 4.14. However, none of them reach your patch because the code section that you are patching is only used as a third option after: (1) checking the vmcoreinfo data, and (2) checking the kernel image header for the flags field. In Linux 4.4, this patch added the page size to the kernel image header: commit 9d372c9fab34cd8803141871195141995f85c7f7 Author: Ard Biesheuvel <ard.biesheuvel(a)linaro.org&gt; Date: Mon Oct 19 14:19:36 2015 +0100 arm64: Add page size to the kernel image header This patch adds the page size to the arm64 kernel image header so that one can infer the PAGESIZE used by the kernel. This will be helpful to diagnose failures to boot the kernel with page size not supported by the CPU. And later on in Linux 4.6, "_kernel_flags_le" was replaced by "_kernel_flags_le_lo32" and "_kernel_flags_le_hi32": commit 6ad1fe5d9077a1ab40bf74b61994d2e770b00b14 Author: Ard Biesheuvel <ard.biesheuvel(a)linaro.org&gt; Date: Sat Dec 26 13:48:02 2015 +0100 arm64: avoid R_AARCH64_ABS64 relocations for Image header fields Unfortunately, the current way of using the linker to emit build time constants into the Image header will no longer work once we switch to the use of PIE executables. The reason is that such constants are emitted into the binary using R_AARCH64_ABS64 relocations, which are resolved at runtime, not at build time, and the places targeted by those relocations will contain zeroes before that. So refactor the endian swapping linker script constant generation code so that it emits the upper and lower 32-bit words separately. Anyway, given that the page size flags entry was introduced in Linux 4.4, I don't believe your patch checking for LINUX(4,16,0) is correct: + if (THIS_KERNEL_VERSION < LINUX(4,16,0)) { + value = symbol_value("swapper_pg_dir") - + symbol_value("idmap_pg_dir"); + } else { Do you agree? Dave