[PATCH] kexec: Add --lite option

[Jeremy Kerr]

Hi Geoff,

> Add a new option --lite to kexec that allows for a fast reboot
> by avoiding the purgatory integrity checks.  This option is
> intended for use by kexec based bootloaders that load a new
> image and then immediately transfer control to it.

Can we call this something other than 'lite'? I'd want to prevent any
confusion when referring to 'kexec-lite', which is a separate project.

Cheers,


Jeremy

> 
> Signed-off-by: Geoff Levand <geoff at infradead.org>
> ---
> Hi Simon,
> 
> It was reported that on some systems where purgatory is running
> without caches enabled the sha256 calculations would take several
> minutes.  For bootloaders that just load a new image and
> immediately jump into it the loss of the integrity check is worth
> the increase in boot speed.  Please consider.  
> 
> -Geoff
> 
>  kexec/kexec.8         |  3 +++
>  kexec/kexec.c         | 19 +++++++++++++++++--
>  kexec/kexec.h         |  4 ++++
>  purgatory/purgatory.c |  3 ++-
>  4 files changed, 26 insertions(+), 3 deletions(-)
> 
> diff --git a/kexec/kexec.8 b/kexec/kexec.8
> index 4d0c1d1..93ed588 100644
> --- a/kexec/kexec.8
> +++ b/kexec/kexec.8
> @@ -126,6 +126,9 @@ in one call.
>  Open a help file for
>  .BR kexec .
>  .TP
> +.B \-i\ (\-\-lite)
> +Fast reboot, no memory integrity checks.
> +.TP
>  .BI \-l\ (\-\-load) \ kernel
>  Load the specified
>  .I kernel
> diff --git a/kexec/kexec.c b/kexec/kexec.c
> index ff024f3..ebb1310 100644
> --- a/kexec/kexec.c
> +++ b/kexec/kexec.c
> @@ -613,6 +613,15 @@ static void update_purgatory(struct kexec_info *info)
>  		return;
>  	}
>  	arch_update_purgatory(info);
> +
> +	if (info->kexec_lite) {
> +		unsigned int tmp = 1;
> +
> +		elf_rel_set_symbol(&info->rhdr, "kexec_lite", &tmp,
> +			sizeof(tmp));
> +		return;
> +	}
> +
>  	memset(region, 0, sizeof(region));
>  	sha256_starts(&ctx);
>  	/* Compute a hash of the loaded kernel */
> @@ -652,7 +661,7 @@ static void update_purgatory(struct kexec_info *info)
>   *	Load the new kernel
>   */
>  static int my_load(const char *type, int fileind, int argc, char **argv,
> -		   unsigned long kexec_flags, void *entry)
> +		   unsigned long kexec_flags, int kexec_lite, void *entry)
>  {
>  	char *kernel;
>  	char *kernel_buf;
> @@ -665,6 +674,7 @@ static int my_load(const char *type, int fileind, int argc, char **argv,
>  
>  	memset(&info, 0, sizeof(info));
>  	info.kexec_flags = kexec_flags;
> +	info.kexec_lite = kexec_lite;
>  
>  	result = 0;
>  	if (argc - fileind <= 0) {
> @@ -914,6 +924,7 @@ void usage(void)
>  	       " -v, --version        Print the version of kexec.\n"
>  	       " -f, --force          Force an immediate kexec,\n"
>  	       "                      don't call shutdown.\n"
> +	       " -i, --lite           Fast reboot, no memory integrity checks.\n"
>  	       " -x, --no-ifdown      Don't bring down network interfaces.\n"
>  	       " -y, --no-sync        Don't sync filesystems before kexec.\n"
>  	       " -l, --load           Load the new kernel into the\n"
> @@ -1173,6 +1184,7 @@ int main(int argc, char *argv[])
>  	int do_unload = 0;
>  	int do_reuse_initrd = 0;
>  	int do_kexec_file_syscall = 0;
> +	int do_lite = 0;
>  	void *entry = 0;
>  	char *type = 0;
>  	char *endptr;
> @@ -1314,6 +1326,9 @@ int main(int argc, char *argv[])
>  		case OPT_KEXEC_FILE_SYSCALL:
>  			/* We already parsed it. Nothing to do. */
>  			break;
> +		case OPT_LITE:
> +			do_lite = 1;
> +			break;
>  		default:
>  			break;
>  		}
> @@ -1374,7 +1389,7 @@ int main(int argc, char *argv[])
>  						 kexec_file_flags);
>  		else
>  			result = my_load(type, fileind, argc, argv,
> -						kexec_flags, entry);
> +						kexec_flags, do_lite, 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 7c97b25..06e08f4 100644
> --- a/kexec/kexec.h
> +++ b/kexec/kexec.h
> @@ -165,6 +165,8 @@ struct kexec_info {
>  	int initrd_fd;
>  	char *command_line;
>  	int command_line_len;
> +
> +	int kexec_lite;
>  };
>  
>  struct arch_map_entry {
> @@ -218,6 +220,7 @@ extern int file_types;
>  #define OPT_TYPE		't'
>  #define OPT_PANIC		'p'
>  #define OPT_KEXEC_FILE_SYSCALL	's'
> +#define OPT_LITE		'i'
>  #define OPT_MEM_MIN             256
>  #define OPT_MEM_MAX             257
>  #define OPT_REUSE_INITRD	258
> @@ -243,6 +246,7 @@ extern int file_types;
>  	{ "mem-max",		1, 0, OPT_MEM_MAX }, \
>  	{ "reuseinitrd",	0, 0, OPT_REUSE_INITRD }, \
>  	{ "kexec-file-syscall",	0, 0, OPT_KEXEC_FILE_SYSCALL }, \
> +	{ "lite",		0, 0, OPT_LITE }, \
>  	{ "debug",		0, 0, OPT_DEBUG }, \
>  
>  #define KEXEC_OPT_STR "h?vdfxyluet:ps"
> diff --git a/purgatory/purgatory.c b/purgatory/purgatory.c
> index 3bbcc09..7e99b92 100644
> --- a/purgatory/purgatory.c
> +++ b/purgatory/purgatory.c
> @@ -8,6 +8,7 @@
>  
>  struct sha256_region sha256_regions[SHA256_REGIONS] = {};
>  sha256_digest_t sha256_digest = { };
> +int kexec_lite = 0;
>  
>  int verify_sha256_digest(void)
>  {
> @@ -43,7 +44,7 @@ void purgatory(void)
>  {
>  	printf("I'm in purgatory\n");
>  	setup_arch();
> -	if (verify_sha256_digest()) {
> +	if (!kexec_lite && verify_sha256_digest()) {
>  		for(;;) {
>  			/* loop forever */
>  		}
>