loader.efi: Recognize new memdisk=<url> and memcd=<url> options

Support ipxe downloading of a memory disk (either presented to the OS as
a harddisk or a cd). This requires an ipxe server since it uses the ipxe
download protocol to grab the disk. If there is a disk, we add it to the
environment as a disk, and then the rest of the bootloader just sees it
and boots from it.

I've cribbed code from https://github.com/russor/memdisk_uefi and
adapted it to work in the context of the FreeBSD bootloader.

The ipxe_download.h file was created from the documentation of the
interface.

So a .ipxe file with the line
chain http://10.2.0.1/loader.efi memdisk=${cwduri}FreeBSD-15.1-RELEASE-amd64-bootonly.iso
would use the FreeBSD boot loader to boot the FreeBSD 15.1 release.

md(9) has a bug at the moment that prevents it from probing the
partitions on it.

Also, we'll automatically decompress gzip, bzip2 and zstd files
automatically.

Sponsored by:		Netflix
Differential Revision:	https://reviews.freebsd.org/D57677

1 files changed, 19 insertions, 0 deletions

diff --git a/stand/efi/loader/decompress.h b/stand/efi/loader/decompress.h
new file mode 100644
index 000000000000..43c48078f822
--- /dev/null
+++ b/stand/efi/loader/decompress.h
@@ -0,0 +1,19 @@
+/*
+ * Copyright (c) 2026 Netflix, Inc. Written by Warner Losh
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+enum compression { none, zlib, bzip2, zstd };
+enum step_return { ok, done, err };
+
+typedef struct decomp_state decomp_state;
+
+decomp_state *decomp_init(uint8_t *buf, size_t buflen, size_t size_hint);
+enum step_return decomp_step(decomp_state *dctx, uint8_t *buf, size_t len, size_t offset);
+void decomp_fini(decomp_state *dctx, bool flush);
+EFI_PHYSICAL_ADDRESS decomp_buffer(decomp_state *dctx);
+size_t decomp_buffer_length(decomp_state *dctx);
+