kexec: Introduce --load-live-update for xen

Support loading a live update image for xen from kexec userspace.
For a multiboot2 Elf on a xen setup, this will:
- load the Elf into KEXEC_RANGE_MA_XEN
- load purgatory and modules into KEXEC_RANGE_MA_LIVEUPDATE
- append the Elf cmdline with " liveupdate=<size>@<addr>

v2: define xen related symbols outside of HAVE_LIBXENCTRL

Signed-off-by: Varad Gautam <vrd@amazon.de>
Signed-off-by: Simon Horman <horms@verge.net.au>

5 files changed, 125 insertions, 10 deletions

diff --git a/kexec/arch/i386/kexec-mb2-x86.c b/kexec/arch/i386/kexec-mb2-x86.c
index b839d594..1ad8aeda 100644
--- a/kexec/arch/i386/kexec-mb2-x86.c
+++ b/kexec/arch/i386/kexec-mb2-x86.c
@@ -42,6 +42,8 @@
 #include "../../kexec.h"
 #include "../../kexec-elf.h"
 #include "kexec-x86.h"
+#include "../../kexec-syscall.h"
+#include "../../kexec-xen.h"
 #include <arch/options.h>
 
 /* From GNU GRUB */
@@ -388,6 +390,15 @@ static uint64_t multiboot2_mbi_end(void *mbi_buf, uint64_t mbi_ptr)
 	return mbi_ptr;
 }
 
+static inline int multiboot2_rel_valid(struct multiboot_header_tag_relocatable *rel_tag,
+					uint64_t rel_start, uint64_t rel_end)
+{
+	if (rel_start >= rel_tag->min_addr && rel_end <= rel_tag->max_addr)
+		return 1;
+
+	return 0;
+}
+
 int multiboot2_x86_load(int argc, char **argv, const char *buf, off_t len,
 			struct kexec_info *info)
 {
@@ -413,6 +424,7 @@ int multiboot2_x86_load(int argc, char **argv, const char *buf, off_t len,
 		{ 0, 				0, 0, 0 },
 	};
 	static const char short_options[] = KEXEC_ARCH_OPT_STR "";
+	uint64_t rel_min, rel_max;
 
 	/* Probe for the MB header if it's not already found */
 	if (mbh == NULL && multiboot_x86_probe(buf, len) != 1)
@@ -459,19 +471,59 @@ int multiboot2_x86_load(int argc, char **argv, const char *buf, off_t len,
 	if (tmp_cmdline) {
 		free(tmp_cmdline);
 	}
+
+	if (xen_present() && info->kexec_flags & KEXEC_LIVE_UPDATE ) {
+		if (!mhi.rel_tag) {
+			fprintf(stderr, "Multiboot2 image must be relocatable"
+				"for KEXEC_LIVE_UPDATE.\n");
+			return -1;
+		}
+		cmdline_add_liveupdate(&command_line);
+	}
+
 	command_line_len = strlen(command_line) + 1;
 
 	/* Load the ELF executable */
-	if (mhi.rel_tag)
+	if (mhi.rel_tag) {
+		rel_min = mhi.rel_tag->min_addr;
+		rel_max = mhi.rel_tag->max_addr;
+
+		if (info->kexec_flags & KEXEC_LIVE_UPDATE && xen_present()) {
+			/* TODO also check if elf is xen */
+			/* On a live update, load target xen over the current xen image. */
+			uint64_t xen_start, xen_end;
+
+			xen_get_kexec_range(KEXEC_RANGE_MA_XEN, &xen_start, &xen_end);
+			if (multiboot2_rel_valid(mhi.rel_tag, xen_start, xen_end)) {
+				rel_min = xen_start;
+			} else {
+				fprintf(stderr, "Cannot place Elf into "
+				"KEXEC_RANGE_MA_XEN for KEXEC_LIVE_UPDATE.\n");
+				return -1;
+			}
+		}
+
 		elf_exec_build_load_relocatable(info, &ehdr, buf, len, 0,
-						mhi.rel_tag->min_addr, mhi.rel_tag->max_addr,
-						mhi.rel_tag->align);
-	else
+						rel_min, rel_max, mhi.rel_tag->align);
+	} else
 		elf_exec_build_load(info, &ehdr, buf, len, 0);
 
+	if (info->kexec_flags & KEXEC_LIVE_UPDATE && xen_present()) {
+		uint64_t lu_start, lu_end;
+
+		xen_get_kexec_range(7 /* KEXEC_RANGE_MA_LIVEUPDATE */, &lu_start, &lu_end);
+		/* Fit everything else into lu_start-lu_end. First page after lu_start is
+		 * reserved for LU breadcrumb. */
+		rel_min = lu_start + 4096;
+		rel_max = lu_end;
+	} else {
+		rel_min = 0;
+		rel_max = ULONG_MAX;
+	}
+
 	/* Load the setup code */
 	elf_rel_build_load(info, &info->rhdr, purgatory, purgatory_size,
-			   0, ULONG_MAX, 1, 0);
+			   rel_min, rel_max, 1, 0);
 
 	/* Construct information tags. */
 	mbi_bytes = multiboot2_get_mbi_size(info->memory_ranges, command_line_len, modules, mod_command_line_space);
@@ -480,6 +532,18 @@ int multiboot2_x86_load(int argc, char **argv, const char *buf, off_t len,
 	mbi_ptr = multiboot2_make_mbi(info, command_line, command_line_len, info->rhdr.rel_addr, mbi_buf, mbi_bytes);
 	free(command_line);
 
+	if (info->kexec_flags & KEXEC_LIVE_UPDATE && xen_present()) {
+		if (multiboot2_rel_valid(mhi.rel_tag, rel_min, rel_max)) {
+			/* Shrink the reloc range to fit into LU region for xen. */
+			mhi.rel_tag->min_addr = rel_min;
+			mhi.rel_tag->max_addr = rel_max;
+		} else {
+			fprintf(stderr, "Multiboot2 image cannot be relocated into "
+				"KEXEC_RANGE_MA_LIVEUPDATE for KEXEC_LIVE_UPDATE.\n");
+			return -1;
+		}
+	}
+
 	/* Load modules */
 	if (modules) {
 		char *mod_filename, *mod_command_line, *mod_clp, *buf;
diff --git a/kexec/kexec-xen.c b/kexec/kexec-xen.c
index afcfc5b8..83629baf 100644
--- a/kexec/kexec-xen.c
+++ b/kexec/kexec-xen.c
@@ -177,8 +177,12 @@ int xen_kexec_load(struct kexec_info *info)
 		seg++;
 	}
 
-	type = (info->kexec_flags & KEXEC_ON_CRASH) ? KEXEC_TYPE_CRASH
-		: KEXEC_TYPE_DEFAULT;
+	if (info->kexec_flags & KEXEC_ON_CRASH)
+		type = KEXEC_TYPE_CRASH;
+	else if (info->kexec_flags & KEXEC_LIVE_UPDATE )
+		type = KEXEC_TYPE_LIVE_UPDATE;
+	else
+		type = KEXEC_TYPE_DEFAULT;
 
 	arch = (info->kexec_flags & KEXEC_ARCH_MASK) >> 16;
 #if defined(__i386__) || defined(__x86_64__)
diff --git a/kexec/kexec-xen.h b/kexec/kexec-xen.h
index 94d22cda..70fb576e 100644
--- a/kexec/kexec-xen.h
+++ b/kexec/kexec-xen.h
@@ -64,9 +64,24 @@ extern int __xc_interface_close(xc_interface *xch);
 
 #endif /* CONFIG_LIBXENCTRL_DL */
 
-
 #endif /* HAVE_LIBXENCTRL */
 
+#ifndef KEXEC_RANGE_MA_XEN
+#define KEXEC_RANGE_MA_XEN 1
+#endif
+
+#ifndef KEXEC_RANGE_MA_LIVEUPDATE
+#define KEXEC_RANGE_MA_LIVEUPDATE 7
+#endif
+
+#ifndef KEXEC_TYPE_LIVE_UPDATE
+#define KEXEC_TYPE_LIVE_UPDATE 2
+#endif
+
+#ifndef KEXEC_LIVE_UPDATE
+#define KEXEC_LIVE_UPDATE 0x00000004
+#endif
+
 int xen_get_kexec_range(int range, uint64_t *start, uint64_t *end);
 
 #endif /* KEXEC_XEN_H */
diff --git a/kexec/kexec.c b/kexec/kexec.c
index 6601f1f6..da61d6dd 100644
--- a/kexec/kexec.c
+++ b/kexec/kexec.c
@@ -47,6 +47,7 @@
 #include "kexec.h"
 #include "kexec-syscall.h"
 #include "kexec-elf.h"
+#include "kexec-xen.h"
 #include "kexec-sha256.h"
 #include "kexec-zlib.h"
 #include "kexec-lzma.h"
@@ -1022,6 +1023,8 @@ void usage(void)
 	       "                      context of current kernel during kexec.\n"
 	       "     --load-jump-back-helper Load a helper image to jump back\n"
 	       "                      to original kernel.\n"
+	       "     --load-live-update Load the new kernel to overwrite the\n"
+	       "                      running kernel.\n"
 	       "     --entry=<addr>   Specify jump back address.\n"
 	       "                      (0 means it's not jump back or\n"
 	       "                      preserve context)\n"
@@ -1171,6 +1174,25 @@ char *concat_cmdline(const char *base, const char *append)
 	return cmdline;
 }
 
+void cmdline_add_liveupdate(char **base)
+{
+	uint64_t lu_start, lu_end, lu_sizeM;
+	char *str;
+	char buf[64];
+	size_t len;
+
+	if ( !xen_present() )
+		return;
+
+	xen_get_kexec_range(KEXEC_RANGE_MA_LIVEUPDATE, &lu_start, &lu_end);
+	lu_sizeM = (lu_end - lu_start) / (1024 * 1024) + 1;
+	sprintf(buf, " liveupdate=%luM@0x%lx", lu_sizeM, lu_start);
+	len = strlen(*base) + strlen(buf) + 1;
+	str = xmalloc(len);
+	sprintf(str, "%s%s", *base, buf);
+	*base = str;
+}
+
 /* New file based kexec system call related code */
 static int do_kexec_file_load(int fileind, int argc, char **argv,
 			unsigned long flags) {
@@ -1402,11 +1424,13 @@ int main(int argc, char *argv[])
 			}
 			break;
 		case OPT_LOAD_PRESERVE_CONTEXT:
+		case OPT_LOAD_LIVE_UPDATE:
 			do_load = 1;
 			do_exec = 0;
 			do_shutdown = 0;
 			do_sync = 1;
-			kexec_flags = KEXEC_PRESERVE_CONTEXT;
+			kexec_flags = (opt == OPT_LOAD_PRESERVE_CONTEXT) ?
+				       KEXEC_PRESERVE_CONTEXT : KEXEC_LIVE_UPDATE;
 			break;
 		case OPT_TYPE:
 			type = optarg;
@@ -1504,6 +1528,11 @@ int main(int argc, char *argv[])
 		    "\"--mem-max\" parameter\n");
 	}
 
+	if (do_load && (kexec_flags & KEXEC_LIVE_UPDATE) &&
+	    !xen_present()) {
+		die("--load-live-update can only be used with xen\n");
+	}
+
 	fileind = optind;
 	/* Reset getopt for the next pass; called in other source modules */
 	opterr = 1;
diff --git a/kexec/kexec.h b/kexec/kexec.h
index 28fd1290..8021f39d 100644
--- a/kexec/kexec.h
+++ b/kexec/kexec.h
@@ -233,7 +233,8 @@ extern int file_types;
 #define OPT_LOAD_JUMP_BACK_HELPER 260
 #define OPT_ENTRY		261
 #define OPT_PRINT_CKR_SIZE	262
-#define OPT_MAX			263
+#define OPT_LOAD_LIVE_UPDATE	263
+#define OPT_MAX			264
 #define KEXEC_OPTIONS \
 	{ "help",		0, 0, OPT_HELP }, \
 	{ "version",		0, 0, OPT_VERSION }, \
@@ -246,6 +247,7 @@ extern int file_types;
 	{ "exec",		0, 0, OPT_EXEC }, \
 	{ "load-preserve-context", 0, 0, OPT_LOAD_PRESERVE_CONTEXT}, \
 	{ "load-jump-back-helper", 0, 0, OPT_LOAD_JUMP_BACK_HELPER }, \
+	{ "load-live-update", 0, 0, OPT_LOAD_LIVE_UPDATE }, \
 	{ "entry",		1, 0, OPT_ENTRY }, \
 	{ "type",		1, 0, OPT_TYPE }, \
 	{ "load-panic",         0, 0, OPT_PANIC }, \
@@ -319,6 +321,7 @@ const char * proc_iomem(void);
 #define MAX_LINE	160
 
 char *concat_cmdline(const char *base, const char *append);
+void cmdline_add_liveupdate(char **base);
 
 int xen_present(void);
 int xen_kexec_load(struct kexec_info *info);