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supermin/007-Uncompress-kernel-on-RISC-V.patch

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Subject: src: Uncompress kernel on RISC-V
From: Richard W.M. Jones rjones@redhat.com Fri Nov 10 10:20:49 2023 +0000
Date: Fri Nov 10 10:28:21 2023 +0000:
Git: 5230e2c3cd07e82bd6431e871e239f7056bf25ad
diff --git a/src/format_ext2_kernel.ml b/src/format_ext2_kernel.ml
index 36514c6..09a3f21 100644
--- a/src/format_ext2_kernel.ml
+++ b/src/format_ext2_kernel.ml
@@ -25,6 +25,20 @@ open Ext2fs
open Fnmatch
open Glob
+(* Similar but not the same as get_file_type in mode_build. There
+ * is a case for deriving a common base utility. XXX
+ *)
+type compression_type = GZip | Uncompressed
+let get_compression_type file =
+ let chan = open_in file in
+ let buf = Bytes.create 512 in
+ let len = input chan buf 0 (Bytes.length buf) in
+ close_in chan;
+ let buf = Bytes.to_string buf in
+ if len >= 3 && buf.[0] = '\x1f' && buf.[1] = '\x8b' && buf.[2] = '\x08'
+ then GZip
+ else Uncompressed (* or other unknown compression type *)
+
let rec build_kernel debug host_cpu copy_kernel kernel =
(* Locate the kernel.
* SUPERMIN_* environment variables override everything. If those
@@ -54,7 +68,19 @@ let rec build_kernel debug host_cpu copy_kernel kernel =
printf "supermin: kernel: modpath %s\n%!" modpath;
);
- copy_or_symlink_kernel copy_kernel kernel_file kernel;
+ (* RISC-V relies on the bootloader or firmware to uncompress the
+ * kernel and doesn't have a concept of self-extracting kernels.
+ * On Arm which is similar, qemu -kernel will automatically uncompress
+ * the kernel, but qemu-system-riscv won't do that and the code is a
+ * big mess so I don't fancy fixing it. So we have to detect that
+ * case here and uncompress the kernel.
+ *)
+ let kernel_compression_type = get_compression_type kernel_file in
+ if string_prefix "riscv" host_cpu && kernel_compression_type <> Uncompressed
+ then
+ copy_and_uncompress_kernel kernel_compression_type kernel_file kernel
+ else
+ copy_or_symlink_kernel copy_kernel kernel_file kernel;
(kernel_version, modpath)
@@ -308,6 +334,13 @@ and read_string chan offset len =
really_input chan buf 0 len;
Bytes.to_string buf
+and copy_and_uncompress_kernel compression_type src dest =
+ let cmd =
+ match compression_type with
+ | GZip -> sprintf "zcat %s > %s" (quote src) (quote dest)
+ | Uncompressed -> sprintf "cp %s %s" (quote src) (quote dest) in
+ run_command cmd
+
and copy_or_symlink_kernel copy_kernel src dest =
if not copy_kernel then
symlink src dest