[PATCH] kexec: Provide an option to use new kexec system call - kexec - Fedora mailing-lists

3 Sep 2014

Hi,
This is upstream kexec-tools patch which needs to be backported. I built
rpm and it applies without any modifications.
Thanks
Vivek
Hi,
This is v2 of the patch. Since v1, I moved syscall implemented check littler
earlier in the function as per the feedback.
Now a new kexec syscall (kexec_file_load()) has been merged in upstream
kernel. This system call takes file descriptors of kernel and initramfs
as input (as opposed to list of segments to be loaded). This new system
call allows for signature verification of the kernel being loaded.
One use of signature verification of kernel is secureboot systems where
we want to allow kexec into a kernel only if it is validly signed by
a key system trusts.
This patch provides and option --kexec-file-syscall (-s), to force use of
new system call for kexec. Default is to continue to use old syscall.
Currently only bzImage64 on x86_64 can be loaded using this system call.
As kernel adds support for more arches and for more image types, kexec-tools
can be modified accordingly.
Signed-off-by: Vivek Goyal vgoyal@redhat.com
Acked-by: Baoquan He bhe@redhat.com
Signed-off-by: Simon Horman horms@verge.net.au
---
 kexec/arch/x86_64/kexec-bzImage64.c |  86 +++++++++++++++++++++++
 kexec/kexec-syscall.h               |  32 +++++++++
 kexec/kexec.c                       | 132 +++++++++++++++++++++++++++++++++++-
 kexec/kexec.h                       |  11 ++-
 4 files changed, 257 insertions(+), 4 deletions(-)

diff --git a/kexec/arch/x86_64/kexec-bzImage64.c b/kexec/arch/x86_64/kexec-bzImage64.c
index 1983bcf..8edb3e4 100644
--- a/kexec/arch/x86_64/kexec-bzImage64.c
+++ b/kexec/arch/x86_64/kexec-bzImage64.c
@@ -235,6 +235,89 @@ static int do_bzImage64_load(struct kexec_info *info,
    return 0;
 }
+/* This assumes file is being loaded using file based kexec syscall */
+int bzImage64_load_file(int argc, char **argv, struct kexec_info *info)
+{
+	int ret = 0;
+	char *command_line = NULL, *tmp_cmdline = NULL;
+	const char *ramdisk = NULL, *append = NULL;
+	int entry_16bit = 0, entry_32bit = 0;
+	int opt;
+	int command_line_len;
+
+	/* See options.h -- add any more there, too. */
+	static const struct option options[] = {
+		KEXEC_ARCH_OPTIONS
+		{ "command-line",	1, 0, OPT_APPEND },
+		{ "append",		1, 0, OPT_APPEND },
+		{ "reuse-cmdline",	0, 0, OPT_REUSE_CMDLINE },
+		{ "initrd",		1, 0, OPT_RAMDISK },
+		{ "ramdisk",		1, 0, OPT_RAMDISK },
+		{ "real-mode",		0, 0, OPT_REAL_MODE },
+		{ "entry-32bit",	0, 0, OPT_ENTRY_32BIT },
+		{ 0,			0, 0, 0 },
+	};
+	static const char short_options[] = KEXEC_ARCH_OPT_STR "d";
+
+	while ((opt = getopt_long(argc, argv, short_options, options, 0)) != -1) {
+		switch (opt) {
+		default:
+			/* Ignore core options */
+			if (opt < OPT_ARCH_MAX)
+				break;
+		case OPT_APPEND:
+			append = optarg;
+			break;
+		case OPT_REUSE_CMDLINE:
+			tmp_cmdline = get_command_line();
+			break;
+		case OPT_RAMDISK:
+			ramdisk = optarg;
+			break;
+		case OPT_REAL_MODE:
+			entry_16bit = 1;
+			break;
+		case OPT_ENTRY_32BIT:
+			entry_32bit = 1;
+			break;
+		}
+	}
+	command_line = concat_cmdline(tmp_cmdline, append);
+	if (tmp_cmdline)
+		free(tmp_cmdline);
+	command_line_len = 0;
+	if (command_line) {
+		command_line_len = strlen(command_line) + 1;
+	} else {
+		command_line = strdup("\0");
+		command_line_len = 1;
+	}
+
+	if (entry_16bit || entry_32bit) {
+		fprintf(stderr, "Kexec2 syscall does not support 16bit"
+			" or 32bit entry yet\n");
+		ret = -1;
+		goto out;
+	}
+
+	if (ramdisk) {
+		info->initrd_fd = open(ramdisk, O_RDONLY);
+		if (info->initrd_fd == -1) {
+			fprintf(stderr, "Could not open initrd file %s:%s\n",
+					ramdisk, strerror(errno));
+			ret = -1;
+			goto out;
+		}
+	}
+
+	info->command_line = command_line;
+	info->command_line_len = command_line_len;
+	return ret;
+out:
+	free(command_line);
+	return ret;
+}
+
 int bzImage64_load(int argc, char **argv, const char *buf, off_t len,
    struct kexec_info *info)
 {
@@ -247,6 +330,9 @@ int bzImage64_load(int argc, char **argv, const char *buf, off_t len,
    int opt;
    int result;
+	if (info->file_mode)
+		return bzImage64_load_file(argc, argv, info);
+
    /* See options.h -- add any more there, too. */
    static const struct option options[] = {
    	KEXEC_ARCH_OPTIONS
diff --git a/kexec/kexec-syscall.h b/kexec/kexec-syscall.h
index 6238044..ce2e20b 100644
--- a/kexec/kexec-syscall.h
+++ b/kexec/kexec-syscall.h
@@ -53,6 +53,19 @@
 #endif
 #endif /*ifndef __NR_kexec_load*/
+#ifndef __NR_kexec_file_load
+
+#ifdef __x86_64__
+#define __NR_kexec_file_load	320
+#endif
+
+#ifndef __NR_kexec_file_load
+/* system call not available for the arch */
+#define __NR_kexec_file_load	0xffffffff	/* system call not available */
+#endif
+
+#endif /*ifndef __NR_kexec_file_load*/
+
 struct kexec_segment;
static inline long kexec_load(void *entry, unsigned long nr_segments,
@@ -61,10 +74,29 @@ static inline long kexec_load(void *entry, unsigned long nr_segments,
    return (long) syscall(__NR_kexec_load, entry, nr_segments, segments, flags);
 }
+static inline int is_kexec_file_load_implemented(void) {
+	if (__NR_kexec_file_load != 0xffffffff)
+		return 1;
+	return 0;
+}
+
+static inline long kexec_file_load(int kernel_fd, int initrd_fd,
+			unsigned long cmdline_len, const char *cmdline_ptr,
+			unsigned long flags)
+{
+	return (long) syscall(__NR_kexec_file_load, kernel_fd, initrd_fd,
+				cmdline_len, cmdline_ptr, flags);
+}
+
 #define KEXEC_ON_CRASH		0x00000001
 #define KEXEC_PRESERVE_CONTEXT	0x00000002
 #define KEXEC_ARCH_MASK		0xffff0000
+/* Flags for kexec file based system call */
+#define KEXEC_FILE_UNLOAD	0x00000001
+#define KEXEC_FILE_ON_CRASH	0x00000002
+#define KEXEC_FILE_NO_INITRAMFS	0x00000004
+
 /* These values match the ELF architecture values. 
  * Unless there is a good reason that should continue to be the case.
  */
diff --git a/kexec/kexec.c b/kexec/kexec.c
index 133e622..7e7b604 100644
--- a/kexec/kexec.c
+++ b/kexec/kexec.c
@@ -51,6 +51,8 @@
 unsigned long long mem_min = 0;
 unsigned long long mem_max = ULONG_MAX;
 static unsigned long kexec_flags = 0;
+/* Flags for kexec file (fd) based syscall */
+static unsigned long kexec_file_flags = 0;
 int kexec_debug = 0;
void dbgprint_mem_range(const char *prefix, struct memory_range *mr, int nr_mr)
@@ -787,6 +789,19 @@ static int my_load(const char *type, int fileind, int argc, char **argv,
    return result;
 }
+static int kexec_file_unload(unsigned long kexec_file_flags)
+{
+	int ret = 0;
+
+	ret = kexec_file_load(-1, -1, 0, NULL, kexec_file_flags);
+	if (ret != 0) {
+		/* The unload failed, print some debugging information */
+		fprintf(stderr, "kexec_file_load(unload) failed\n: %s\n",
+			strerror(errno));
+	}
+	return ret;
+}
+
 static int k_unload (unsigned long kexec_flags)
 {
    int result;
@@ -925,6 +940,7 @@ void usage(void)
           "                      (0 means it's not jump back or\n"
           "                      preserve context)\n"
           "                      to original kernel.\n"
+	       " -s, --kexec-file-syscall Use file based syscall for kexec operation\n"
           " -d, --debug           Enable debugging to help spot a failure.\n"
           "\n"
           "Supported kernel file types and options: \n");
@@ -1072,6 +1088,82 @@ char *concat_cmdline(const char *base, const char *append)
    return cmdline;
 }
+/* New file based kexec system call related code */
+static int do_kexec_file_load(int fileind, int argc, char **argv,
+			unsigned long flags) {
+
+	char *kernel;
+	int kernel_fd, i;
+	struct kexec_info info;
+	int ret = 0;
+	char *kernel_buf;
+	off_t kernel_size;
+
+	memset(&info, 0, sizeof(info));
+	info.segment = NULL;
+	info.nr_segments = 0;
+	info.entry = NULL;
+	info.backup_start = 0;
+	info.kexec_flags = flags;
+
+	info.file_mode = 1;
+	info.initrd_fd = -1;
+
+	if (!is_kexec_file_load_implemented()) {
+		fprintf(stderr, "syscall kexec_file_load not available.\n");
+		return -1;
+	}
+
+	if (argc - fileind <= 0) {
+		fprintf(stderr, "No kernel specified\n");
+		usage();
+		return -1;
+	}
+
+	kernel = argv[fileind];
+
+	kernel_fd = open(kernel, O_RDONLY);
+	if (kernel_fd == -1) {
+		fprintf(stderr, "Failed to open file %s:%s\n", kernel,
+				strerror(errno));
+		return -1;
+	}
+
+	/* slurp in the input kernel */
+	kernel_buf = slurp_decompress_file(kernel, &kernel_size);
+
+	for (i = 0; i < file_types; i++) {
+		if (file_type[i].probe(kernel_buf, kernel_size) >= 0)
+			break;
+	}
+
+	if (i == file_types) {
+		fprintf(stderr, "Cannot determine the file type " "of %s\n",
+				kernel);
+		return -1;
+	}
+
+	ret = file_type[i].load(argc, argv, kernel_buf, kernel_size, &info);
+	if (ret < 0) {
+		fprintf(stderr, "Cannot load %s\n", kernel);
+		return ret;
+	}
+
+	/*
+	 * If there is no initramfs, set KEXEC_FILE_NO_INITRAMFS flag so that
+	 * kernel does not return error with negative initrd_fd.
+	 */
+	if (info.initrd_fd == -1)
+		info.kexec_flags |= KEXEC_FILE_NO_INITRAMFS;
+
+	ret = kexec_file_load(kernel_fd, info.initrd_fd, info.command_line_len,
+			info.command_line, info.kexec_flags);
+	if (ret != 0)
+		fprintf(stderr, "kexec_file_load failed: %s\n",
+					strerror(errno));
+	return ret;
+}
+
int main(int argc, char *argv[])
 {
@@ -1083,6 +1175,7 @@ int main(int argc, char *argv[])
    int do_ifdown = 0;
    int do_unload = 0;
    int do_reuse_initrd = 0;
+	int do_kexec_file_syscall = 0;
    void *entry = 0;
    char *type = 0;
    char *endptr;
@@ -1095,6 +1188,23 @@ int main(int argc, char *argv[])
    };
    static const char short_options[] = KEXEC_ALL_OPT_STR;
+	/*
+	 * First check if --use-kexec-file-syscall is set. That changes lot of
+	 * things
+	 */
+	while ((opt = getopt_long(argc, argv, short_options,
+				  options, 0)) != -1) {
+		switch(opt) {
+		case OPT_KEXEC_FILE_SYSCALL:
+			do_kexec_file_syscall = 1;
+			break;
+		}
+	}
+
+	/* Reset getopt for the next pass. */
+	opterr = 1;
+	optind = 1;
+
    while ((opt = getopt_long(argc, argv, short_options,
    			  options, 0)) != -1) {
    	switch(opt) {
@@ -1127,6 +1237,8 @@ int main(int argc, char *argv[])
    		do_shutdown = 0;
    		do_sync = 0;
    		do_unload = 1;
+			if (do_kexec_file_syscall)
+				kexec_file_flags |= KEXEC_FILE_UNLOAD;
    		break;
    	case OPT_EXEC:
    		do_load = 0;
@@ -1169,7 +1281,10 @@ int main(int argc, char *argv[])
    		do_exec = 0;
    		do_shutdown = 0;
    		do_sync = 0;
-			kexec_flags = KEXEC_ON_CRASH;
+			if (do_kexec_file_syscall)
+				kexec_file_flags |= KEXEC_FILE_ON_CRASH;
+			else
+				kexec_flags = KEXEC_ON_CRASH;
    		break;
    	case OPT_MEM_MIN:
    		mem_min = strtoul(optarg, &endptr, 0);
@@ -1194,6 +1309,9 @@ int main(int argc, char *argv[])
    	case OPT_REUSE_INITRD:
    		do_reuse_initrd = 1;
    		break;
+		case OPT_KEXEC_FILE_SYSCALL:
+			/* We already parsed it. Nothing to do. */
+			break;
    	default:
    		break;
    	}
@@ -1238,10 +1356,18 @@ int main(int argc, char *argv[])
    }
if (do_unload) {
-		result = k_unload(kexec_flags);
+		if (do_kexec_file_syscall)
+			result = kexec_file_unload(kexec_file_flags);
+		else
+			result = k_unload(kexec_flags);
    }
    if (do_load && (result == 0)) {
-		result = my_load(type, fileind, argc, argv, kexec_flags, entry);
+		if (do_kexec_file_syscall)
+			result = do_kexec_file_load(fileind, argc, argv,
+						 kexec_file_flags);
+		else
+			result = my_load(type, fileind, argc, argv,
+						kexec_flags, entry);
    }
    /* Don't shutdown unless there is something to reboot to! */
    if ((result == 0) && (do_shutdown || do_exec) && !kexec_loaded()) {
diff --git a/kexec/kexec.h b/kexec/kexec.h
index 2fad7dc..4be2b2f 100644
--- a/kexec/kexec.h
+++ b/kexec/kexec.h
@@ -156,6 +156,13 @@ struct kexec_info {
    unsigned long kexec_flags;
    unsigned long backup_src_start;
    unsigned long backup_src_size;
+	/* Set to 1 if we are using kexec file syscall */
+	unsigned long file_mode :1;
+
+	/* Filled by kernel image processing code */
+	int initrd_fd;
+	char *command_line;
+	int command_line_len;
 };
struct arch_map_entry {
@@ -207,6 +214,7 @@ extern int file_types;
 #define OPT_UNLOAD		'u'
 #define OPT_TYPE		't'
 #define OPT_PANIC		'p'
+#define OPT_KEXEC_FILE_SYSCALL	's'
 #define OPT_MEM_MIN             256
 #define OPT_MEM_MAX             257
 #define OPT_REUSE_INITRD	258
@@ -230,9 +238,10 @@ extern int file_types;
    { "mem-min",		1, 0, OPT_MEM_MIN }, \
    { "mem-max",		1, 0, OPT_MEM_MAX }, \
    { "reuseinitrd",	0, 0, OPT_REUSE_INITRD }, \
+	{ "kexec-file-syscall",	0, 0, OPT_KEXEC_FILE_SYSCALL }, \
    { "debug",		0, 0, OPT_DEBUG }, \
-#define KEXEC_OPT_STR "h?vdfxluet:p"
+#define KEXEC_OPT_STR "h?vdfxluet:ps"
extern void dbgprint_mem_range(const char *prefix, struct memory_range *mr, int nr_mr);
 extern void die(const char *fmt, ...)
-- 
1.9.0


    