liminix/pkgs/kexec-map-file.patch

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