Re: [RFC PATCH 00/13][V3] kexec: A new system call to allow in kernel loading

[Dave Young]

On 06/03/14 at 09:12am, Vivek Goyal wrote:
> On Tue, Jun 03, 2014 at 09:06:49AM -0400, Vivek Goyal wrote:
> > Hi,
> > 
> > This is V3 of the patchset. Previous versions were posted here.
> > 
> > V1: https://lkml.org/lkml/2013/11/20/540
> > V2: https://lkml.org/lkml/2014/1/27/331
> > 
> > Changes since v2:
> > 
> > - Took care of most of the review comments from V2.
> > - Added support for kexec/kdump on EFI systems.
> > - Dropped support for loading ELF vmlinux.
> > 
> > This patch series is generated on top of 3.15.0-rc8. It also requires a
> > two patch cleanup series which is sitting in -tip tree here.
> 
> I used following kexec-tools patches to test kernel changes.
> 
> Thanks
> Vivek
> 
> 
> kexec-tools: Provide an option to make use of new system call
> 
> This patch provides and option --use-kexec2-syscall, to force use of
> new system call for kexec. Default is to continue to use old syscall.
> 
> Signed-off-by: Vivek Goyal <vgoyal@xxxxxxxxxx>
> ---
>  kexec/arch/x86_64/kexec-bzImage64.c |   86 +++++++++++++++++++++++++
>  kexec/kexec-syscall.h               |   31 +++++++++
>  kexec/kexec.c                       |  123 +++++++++++++++++++++++++++++++++++-
>  kexec/kexec.h                       |    9 ++
>  4 files changed, 246 insertions(+), 3 deletions(-)
> 
> Index: kexec-tools/kexec/kexec.c
> ===================================================================
> --- kexec-tools.orig/kexec/kexec.c	2014-06-02 14:34:16.719774316 -0400
> +++ kexec-tools/kexec/kexec.c	2014-06-02 14:34:42.009036315 -0400
> @@ -51,6 +51,7 @@
>  unsigned long long mem_min = 0;
>  unsigned long long mem_max = ULONG_MAX;
>  static unsigned long kexec_flags = 0;
> +static unsigned long kexec2_flags = 0;
>  int kexec_debug = 0;
>  
>  void dbgprint_mem_range(const char *prefix, struct memory_range *mr, int nr_mr)
> @@ -787,6 +788,19 @@ static int my_load(const char *type, int
>  	return result;
>  }
>  
> +static int kexec2_unload(unsigned long kexec2_flags)
> +{
> +	int ret = 0;
> +
> +	ret = kexec_file_load(-1, -1, NULL, 0, kexec2_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 +939,7 @@ void usage(void)
>  	       "                      (0 means it's not jump back or\n"
>  	       "                      preserve context)\n"
>  	       "                      to original kernel.\n"
> +	       " -s --use-kexec2-syscall Use new 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 +1087,75 @@ char *concat_cmdline(const char *base, c
>  	return cmdline;
>  }
>  
> +/* New file based kexec system call related code */
> +static int kexec2_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 (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 (!is_kexec_file_load_implemented()) {
> +		fprintf(stderr, "syscall kexec_file_load not available.\n");
> +		return -1;
> +	}
> +
> +	ret = kexec_file_load(kernel_fd, info.initrd_fd, info.command_line,
> +			info.command_line_len, info.kexec_flags);

Vivek,

I tried your patch on my uefi test machine, but kexec load fails like below:

[root@localhost ~]# kexec -l /boot/vmlinuz-3.15.0-rc8+ --use-kexec2-syscall
Could not find a free area of memory of 0xa000 bytes ...

Another issue is that the syscall should allow load kernel only without initrd and
cmdline since kernel can mount root and embed cmdline in itself.

AFAIK Slackware installs huge kernels without creating initrd.
> +	if (ret != 0)
> +		fprintf(stderr, "kexec_file_load failed: %s\n",
> +					strerror(errno));
> +	return ret;
> +}
> +
>  
>  int main(int argc, char *argv[])
>  {
> @@ -1083,6 +1167,7 @@ int main(int argc, char *argv[])
>  	int do_ifdown = 0;
>  	int do_unload = 0;
>  	int do_reuse_initrd = 0;
> +	int do_use_kexec2_syscall = 0;
>  	void *entry = 0;
>  	char *type = 0;
>  	char *endptr;
> @@ -1095,6 +1180,23 @@ int main(int argc, char *argv[])
>  	};
>  	static const char short_options[] = KEXEC_ALL_OPT_STR;
>  
> +	/*
> +	 * First check if --use-kexec2-syscall is set. That changes lot of
> +	 * things
> +	 */
> +	while ((opt = getopt_long(argc, argv, short_options,
> +				  options, 0)) != -1) {
> +		switch(opt) {
> +		case OPT_USE_KEXEC2_SYSCALL:
> +			do_use_kexec2_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 +1229,8 @@ int main(int argc, char *argv[])
>  			do_shutdown = 0;
>  			do_sync = 0;
>  			do_unload = 1;
> +			if (do_use_kexec2_syscall)
> +				kexec2_flags |= KEXEC_FILE_UNLOAD;
>  			break;
>  		case OPT_EXEC:
>  			do_load = 0;
> @@ -1169,7 +1273,10 @@ int main(int argc, char *argv[])
>  			do_exec = 0;
>  			do_shutdown = 0;
>  			do_sync = 0;
> -			kexec_flags = KEXEC_ON_CRASH;
> +			if (do_use_kexec2_syscall)
> +				kexec2_flags |= KEXEC_FILE_ON_CRASH;
> +			else
> +				kexec_flags = KEXEC_ON_CRASH;
>  			break;
>  		case OPT_MEM_MIN:
>  			mem_min = strtoul(optarg, &endptr, 0);
> @@ -1194,6 +1301,9 @@ int main(int argc, char *argv[])
>  		case OPT_REUSE_INITRD:
>  			do_reuse_initrd = 1;
>  			break;
> +		case OPT_USE_KEXEC2_SYSCALL:
> +			/* We already parsed it. Nothing to do. */
> +			break;
>  		default:
>  			break;
>  		}
> @@ -1238,10 +1348,17 @@ int main(int argc, char *argv[])
>  	}
>  
>  	if (do_unload) {
> -		result = k_unload(kexec_flags);
> +		if (do_use_kexec2_syscall)
> +			result = kexec2_unload(kexec2_flags);
> +		else
> +			result = k_unload(kexec_flags);
>  	}
>  	if (do_load && (result == 0)) {
> -		result = my_load(type, fileind, argc, argv, kexec_flags, entry);
> +		if (do_use_kexec2_syscall)
> +			result = kexec2_load(fileind, argc, argv, kexec2_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()) {
> Index: kexec-tools/kexec/kexec.h
> ===================================================================
> --- kexec-tools.orig/kexec/kexec.h	2014-06-02 14:34:16.719774316 -0400
> +++ kexec-tools/kexec/kexec.h	2014-06-02 14:34:42.010036325 -0400
> @@ -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 kexec2 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_USE_KEXEC2_SYSCALL	's'
>  #define OPT_MEM_MIN             256
>  #define OPT_MEM_MAX             257
>  #define OPT_REUSE_INITRD	258
> @@ -230,6 +238,7 @@ extern int file_types;
>  	{ "mem-min",		1, 0, OPT_MEM_MIN }, \
>  	{ "mem-max",		1, 0, OPT_MEM_MAX }, \
>  	{ "reuseinitrd",	0, 0, OPT_REUSE_INITRD }, \
> +	{ "use-kexec2-syscall",	0, 0, OPT_USE_KEXEC2_SYSCALL }, \
>  	{ "debug",		0, 0, OPT_DEBUG }, \
>  
>  #define KEXEC_OPT_STR "h?vdfxluet:p"
> Index: kexec-tools/kexec/arch/x86_64/kexec-bzImage64.c
> ===================================================================
> --- kexec-tools.orig/kexec/arch/x86_64/kexec-bzImage64.c	2014-06-02 14:34:16.719774316 -0400
> +++ kexec-tools/kexec/arch/x86_64/kexec-bzImage64.c	2014-06-02 14:34:42.011036336 -0400
> @@ -235,6 +235,89 @@ static int do_bzImage64_load(struct kexe
>  	return 0;
>  }
>  
> +/* This assumes file is being loaded using file based kexec2 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
>  	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
> Index: kexec-tools/kexec/kexec-syscall.h
> ===================================================================
> --- kexec-tools.orig/kexec/kexec-syscall.h	2014-06-02 14:34:16.719774316 -0400
> +++ kexec-tools/kexec/kexec-syscall.h	2014-06-02 14:34:42.011036336 -0400
> @@ -53,6 +53,19 @@
>  #endif
>  #endif /*ifndef __NR_kexec_load*/
>  
> +#ifndef __NR_kexec_file_load
> +
> +#ifdef __x86_64__
> +#define __NR_kexec_file_load	317
> +#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 +74,28 @@ static inline long kexec_load(void *entr
>  	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,
> +			const char *cmdline_ptr, unsigned long cmdline_len,
> +			unsigned long flags)
> +{
> +	return (long) syscall(__NR_kexec_file_load, kernel_fd, initrd_fd,
> +				cmdline_ptr, cmdline_len, 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
> +
>  /* These values match the ELF architecture values. 
>   * Unless there is a good reason that should continue to be the case.
>   */
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