add kexecboot

This allows booting a new image from a running OS, creating a phram mtd for the root squashfs * enable CONFIG_KEXEC * add modules/kexecboot * patch kexec-tools to add --map-file option for the squashfs * patch kernel kexec code to call new kernel with DTB
2023-03-19 09:49:32 +00:00 · 2023-03-19 09:49:32 +00:00 · 4b19568f1b
commit 4b19568f1b
parent 429ffa8e7d
6 changed files with 243 additions and 0 deletions
--- a/modules/base.nix
+++ b/modules/base.nix
@ -74,6 +74,7 @@ in {
        IKCONFIG_PROC = "y";
        PROC_FS = "y";

+        KEXEC = "y";
        MODULES = "y";
        MODULE_SIG = "y";
        DEBUG_FS = "y";
--- a/modules/kexecboot.nix
+++ b/modules/kexecboot.nix
@ -0,0 +1,50 @@
+{
+  config
+, pkgs
+, lib
+, ...
+}:
+let
+  inherit (lib) mkOption mkForce types concatStringsSep;
+in {
+  imports = [ ./ramdisk.nix ];
+  config = {
+    boot.ramdisk.enable = true;
+
+    kernel.config.MIPS_CMDLINE_FROM_DTB = "y";
+    kernel.config.MIPS_CMDLINE_FROM_BOOTLOADER = mkForce "n";
+
+    outputs.kexecboot =
+      let o = config.outputs; in
+      pkgs.runCommand "kexecboot" {} ''
+        mkdir $out
+        cd $out
+        ln -s ${o.squashfs} squashfs
+        ln -s ${o.kernel} kernel
+        ln -s ${o.manifest} manifest
+        ln -s ${o.boot-sh} boot.sh
+        ln -s ${pkgs.kexec-tools}/bin/kexec ./kexec
+        ln -s ${o.dtb} dtb
+     '';
+
+    outputs.boot-sh =
+      let
+        inherit (pkgs) kexec-tools;
+        inherit (pkgs.lib.trivial) toHexString;
+        inherit (config.outputs) squashfs kernel;
+        cmdline = concatStringsSep " " config.boot.commandLine;
+      in
+        pkgs.buildPackages.runCommand "boot.sh.sh" {
+        } ''
+          squashfsStart=${toString (100 * 1024 * 1024)}
+          squashfsBytes=$(stat -L -c %s ${squashfs})
+          append_cmd="mtdparts=phram0:''${squashfsBytes}(rootfs) phram.phram=phram0,''${squashfsStart},''${squashfsBytes} memmap=''${squashfsBytes}\$''${squashfsStart}";
+          cat > $out <<EOF
+          #!/bin/sh
+          test -d \$1
+          cd \$1
+          ./kexec -f -d --map-file squashfs@$squashfsStart --dtb dtb --command-line '${cmdline} $append_cmd' kernel
+          EOF
+        '';
+  };
+}
--- a/overlay.nix
+++ b/overlay.nix
@ -6,6 +6,17 @@ in
 extraPkgs // {
  strace = prev.strace.override { libunwind = null; };

+  kexec-tools = prev.kexec-tools.overrideAttrs(o: {
+    patches = o.patches ++ [
+      (fetchpatch {
+        # merge user command line options into DTB chosen
+        url = "https://patch-diff.githubusercontent.com/raw/horms/kexec-tools/pull/3.patch";
+        hash = "sha256-MvlJhuex9dlawwNZJ1sJ33YPWn1/q4uKotqkC/4d2tk=";
+      })
+      pkgs/kexec-map-file.patch
+    ];
+  });
+
  s6 = prev.s6.overrideAttrs(o:
    let patch = fetchpatch {
          # add "p" directive in s6-log
--- a/pkgs/kernel/default.nix
+++ b/pkgs/kernel/default.nix
@ -61,6 +61,11 @@ stdenv.mkDerivation rec {
  '';

  patchScripts = ''
+    # Make kexec pass dtb in register when invoking new kernel. The
+    # code to do this is already present, but bracketed by UHI_BOOT
+    # which we can't enable.
+    sed -i arch/mips/kernel/machine_kexec.c -e 's/CONFIG_UHI_BOOT/CONFIG_MIPS/g'
+
    patchShebangs scripts/
  '';

--- a/pkgs/kexec-map-file.patch
+++ b/pkgs/kexec-map-file.patch
@ -0,0 +1,172 @@
+From 35b8bad0343a4afd9ad914e377e64bd02667c563 Mon Sep 17 00:00:00 2001
+From: Daniel Barlow <dan@telent.net>
+Date: Sun, 19 Mar 2023 17:30:30 +0000
+Subject: [PATCH] add --map-file option to map arbitrary files into physmem
+
+This is useful e.g. in conjunction with the MTD PHRAM device on
+embedded devices: a kernel can be booted with kexec and a root
+filesystem entirely in RAM to see if it works before writing it
+to flash.
+---
+ kexec/kexec.8 | 14 ++++++++++++-
+ kexec/kexec.c | 57 +++++++++++++++++++++++++++++++++++++++++++++++++++
+ kexec/kexec.h |  4 +++-
+ 3 files changed, 73 insertions(+), 2 deletions(-)
+
+diff --git a/kexec/kexec.8 b/kexec/kexec.8
+index 3a344c5..3140ccb 100644
+--- a/kexec/kexec.8
+++ b/kexec/kexec.8
+@@ -143,10 +143,17 @@ into the current kernel.
+ .B \-p\ (\-\-load\-panic)
+ Load the new kernel for use on panic.
+ .TP
+-.BI \-t\ (\-\-type= type )
+.BI \-m\ (\-\-type= type )
+ Specify that the new kernel is of this
+ .I type.
+ .TP
+.BI \-t\ (\-\-map-file= filename@addr )
+Read
+.I filename
+and arrange for it to be mapped into physical memory at the address
+.I addr.
+This option may be repeated if there are multiple files to map.
+.TP
+ .BI \-s\ (\-\-kexec-file-syscall)
+ Specify that the new KEXEC_FILE_LOAD syscall should be used exclusively.
+ .TP
+@@ -206,6 +213,11 @@ Reuse initrd from first boot.
+ .BI \-\-print-ckr-size
+ Print crash kernel region size, if available.
+ 
+.PP
+Options taking an
+.I addr
+parameter will accept a memory address written in hexadecimal (with leading
+0x), or octal (leading 0), or decimal (no leading sigil).
+ 
+ .SH SUPPORTED KERNEL FILE TYPES AND OPTIONS
+ .B Beoboot-x86
+diff --git a/kexec/kexec.c b/kexec/kexec.c
+index 36bb2ad..c3b40a4 100644
+--- a/kexec/kexec.c
+++ b/kexec/kexec.c
+@@ -63,6 +63,13 @@ static unsigned long kexec_flags = 0;
+ static unsigned long kexec_file_flags = 0;
+ int kexec_debug = 0;
+ 
+#define MAPPED_FILES_MAX 10 	/* arbitrary number */
+struct mapped_file {
+	const char *filename;
+	unsigned long long phys_address;
+} mapped_files[MAPPED_FILES_MAX] = { { .filename = NULL } };
+
+
+ void dbgprint_mem_range(const char *prefix, struct memory_range *mr, int nr_mr)
+ {
+ 	int i;
+@@ -771,6 +778,19 @@ static int my_load(const char *type, int fileind, int argc, char **argv,
+ 	}
+ 	info.kexec_flags |= native_arch;
+ 
+	for(struct mapped_file *m = mapped_files; m->filename; m++) {
+		off_t file_size = 0;
+		char *buf = slurp_file(m->filename, &file_size);
+		add_buffer(&info,
+			   buf, file_size, file_size, sizeof (void *),
+			   m->phys_address,
+			   mem_max, 1);
+		free(m->filename);
+		/* do we free() memory returned by slurp_file()?
+		 * we don't know if it was mmaped, so maybe not
+		 */
+	};
+
+ 	result = file_type[i].load(argc, argv, kernel_buf, kernel_size, &info);
+ 	if (result < 0) {
+ 		switch (result) {
+@@ -1035,6 +1055,8 @@ void usage(void)
+ 	       "                      load code into.\n"
+ 	       "     --mem-max=<addr> Specify the highest memory address to\n"
+ 	       "                      load code into.\n"
+	       "     --map-file=<filename@addr> Map a file into memory for the\n"
+	       "                      new kernel before kexec.\n"
+ 	       "     --reuseinitrd    Reuse initrd from first boot.\n"
+ 	       "     --print-ckr-size Print crash kernel region size.\n"
+ 	       "     --load-preserve-context Load the new kernel and preserve\n"
+@@ -1396,6 +1418,33 @@ static void print_crashkernel_region_size(void)
+ 	printf("%" PRIu64 "\n", (start != end) ? (end - start + 1) : 0UL);
+ }
+ 
+static int add_mapped_file(char * optarg)
+{
+	char *at = strchr(optarg, '@');
+	if(!at)
+		return 1;
+
+	struct mapped_file *m = mapped_files;
+	struct mapped_file *m_end = mapped_files +
+	    ((sizeof mapped_files) / (sizeof mapped_files[0]));
+
+	while(m->filename && m < m_end)
+		m++;
+
+	if(m >= m_end)
+		return 1;
+
+	m->phys_address = strtoull(at + 1, NULL, 0);
+	if(m->phys_address == 0)
+		return 1;
+
+	m->filename = strndup(optarg, at - optarg);
+
+	(m+1)->filename = NULL;
+	return 0;
+}
+
+
+ int main(int argc, char *argv[])
+ {
+ 	int has_opt_load = 0;
+@@ -1521,6 +1570,14 @@ int main(int argc, char *argv[])
+ 			kexec_file_flags |= KEXEC_FILE_ON_CRASH;
+ 			kexec_flags = KEXEC_ON_CRASH;
+ 			break;
+		case OPT_MAP_FILE:
+			if(add_mapped_file(optarg)) {
+				fprintf(stderr,
+					"Bad option value or too many mapped files in --mapped-file=%s\n",
+					optarg);
+				return 1;
+			}
+			break;
+ 		case OPT_MEM_MIN:
+ 			mem_min = strtoul(optarg, &endptr, 0);
+ 			if (*endptr) {
+diff --git a/kexec/kexec.h b/kexec/kexec.h
+index 0d820ad..78022b6 100644
+--- a/kexec/kexec.h
+++ b/kexec/kexec.h
+@@ -224,6 +224,7 @@ extern int file_types;
+ #define OPT_STATUS		'S'
+ #define OPT_MEM_MIN             256
+ #define OPT_MEM_MAX             257
+#define OPT_MAP_FILE		'm'
+ #define OPT_REUSE_INITRD	258
+ #define OPT_LOAD_PRESERVE_CONTEXT 259
+ #define OPT_LOAD_JUMP_BACK_HELPER 260
+@@ -258,8 +259,9 @@ extern int file_types;
+ 	{ "debug",		0, 0, OPT_DEBUG }, \
+ 	{ "status",		0, 0, OPT_STATUS }, \
+ 	{ "print-ckr-size",     0, 0, OPT_PRINT_CKR_SIZE }, \
+	{ "map-file",		1, 0, OPT_MAP_FILE }, \
+ 
+-#define KEXEC_OPT_STR "h?vdfixyluet:pscaS"
+#define KEXEC_OPT_STR "h?vdfixyluet:pscaSm"
+ 
+ extern void dbgprint_mem_range(const char *prefix, struct memory_range *mr, int nr_mr);
+ extern void die(const char *fmt, ...)
+-- 
+2.38.1
+
--- a/pkgs/openwrt/default.nix
+++ b/pkgs/openwrt/default.nix
@ -20,6 +20,10 @@ let
    }
    patches ${src}/target/linux/generic/backport-5.15/*.patch
    patches ${src}/target/linux/generic/pending-5.15/*.patch
+    # This patch breaks passing the DTB to kexeced kernel, so let's
+    # get rid of it. It's not needed anyway as we pass the cmdline
+    # in the dtb
+    patch --batch -p1 --reverse <  ${src}/target/linux/generic/pending-5.15/330-MIPS-kexec-Accept-command-line-parameters-from-users.patch
    patches ${src}/target/linux/generic/hack-5.15/*.patch
    patches ${src}/target/linux/${family}/patches-5.15/*.patch
  '';