[PATCH v5 4/5] kexec: Add option to fall back to KEXEC_LOAD when KEXEC_FILE_LOAD is not supported

[Dave Young]

On 03/20/18 at 04:56pm, Michal Suchanek wrote:
> Not all architectures implement KEXEC_FILE_LOAD. However, on some
> archiectures KEXEC_FILE_LOAD is required when secure boot is enabled in
> locked-down mode. Previously users had to select the KEXEC_FILE_LOAD
> syscall with undocumented -s option. However, if they did pass the
> option kexec would fail on architectures that do not support it.
> 
> So add an -a option that tries KEXEC_FILE_LOAD and when it is not
> supported tries KEXEC_LOAD.
> 
> Signed-off-by: Michal Suchanek <msuchanek at suse.de>
> ---
> v3: instead of changing the deafult add extra option
> v4: actually check -ENOSYS as well
> v5: add missing break
> ---
>  kexec/kexec.c | 58 +++++++++++++++++++++++++++++++++++++++++++++++++++++-----
>  kexec/kexec.h |  6 +++++-
>  2 files changed, 58 insertions(+), 6 deletions(-)
> 
> diff --git a/kexec/kexec.c b/kexec/kexec.c
> index 68ae0594d4a7..44042345a16e 100644
> --- a/kexec/kexec.c
> +++ b/kexec/kexec.c
> @@ -1243,6 +1243,7 @@ int main(int argc, char *argv[])
>  	int do_unload = 0;
>  	int do_reuse_initrd = 0;
>  	int do_kexec_file_syscall = 0;
> +	int do_kexec_fallback = 0;
>  	int do_status = 0;
>  	void *entry = 0;
>  	char *type = 0;
> @@ -1367,6 +1368,15 @@ int main(int argc, char *argv[])
>  			break;
>  		case OPT_KEXEC_FILE_SYSCALL:
>  			do_kexec_file_syscall = 1;
> +			do_kexec_fallback = 0;
> +			break;
> +		case OPT_KEXEC_SYSCALL:
> +			do_kexec_file_syscall = 0;
> +			do_kexec_fallback = 0;
> +			break;
> +		case OPT_KEXEC_SYSCALL_AUTO:
> +			do_kexec_file_syscall = 1;
> +			do_kexec_fallback = 1;
>  			break;
>  		case OPT_STATUS:
>  			do_status = 1;
> @@ -1433,7 +1443,7 @@ int main(int argc, char *argv[])
>  		}
>  	}
>  	if (do_kexec_file_syscall) {
> -		if (do_load_jump_back_helper)
> +		if (do_load_jump_back_helper && !do_kexec_fallback)
>  			die("--load-jump-back-helper not supported with kexec_file_load\n");
>  		if (kexec_flags & KEXEC_PRESERVE_CONTEXT)
>  			die("--load-preserve-context not supported with kexec_file_load\n");
> @@ -1447,16 +1457,54 @@ int main(int argc, char *argv[])
>  		result = k_status(kexec_flags);
>  	}
>  	if (do_unload) {
> -		if (do_kexec_file_syscall)
> +		if (do_kexec_file_syscall) {
>  			result = kexec_file_unload(kexec_file_flags);
> -		else
> +			if ((result == -ENOSYS) && do_kexec_fallback)
> +				do_kexec_file_syscall = 0;
> +		}
> +		if (!do_kexec_file_syscall)
>  			result = k_unload(kexec_flags);
>  	}
>  	if (do_load && (result == 0)) {
> -		if (do_kexec_file_syscall)
> +		if (do_kexec_file_syscall) {
>  			result = do_kexec_file_load(fileind, argc, argv,
>  						 kexec_file_flags);
> -		else
> +			if (do_kexec_fallback) switch (result) {
> +				/*
> +				 * Something failed with signature verification.
> +				 * Reject the image.
> +				 */
> +				case -ELIBBAD:
> +				case -EKEYREJECTED:
> +				case -ENOPKG:
> +				case -ENOKEY:
> +				case -EBADMSG:
> +				case -EMSGSIZE:
> +					/*
> +					 * By default reject or do nothing if
> +					 * succeded
> +					 */
> +				default: break;
> +				case -ENOSYS: /* not implemented */
> +					/*
> +					 * Parsing image or other options failed
> +					 * The image may be invalid or image
> +					 * type may not supported by kernel so
> +					 * retry parsing in kexec-tools.
> +					 */
> +				case -EINVAL:
> +				case -ENOEXEC:
> +					 /*
> +					  * ENOTSUPP can be unsupported image
> +					  * type or unsupported PE signature
> +					  * wrapper type, duh
> +					  */
> +				case -ENOTSUP:

Hmm, this is still used in latest version.  kernel does not return such
error number,  I might not say clearly previously.  Please check the
kernel code, the only one place I know is because no kdump support in
power kexec_file:
arch/powerpc/kernel/machine_kexec_file_64.c

        /* We don't support crash kernels yet. */
        if (image->type == KEXEC_TYPE_CRASH)
                return -ENOTSUPP;

So I suggest not checking this as well since -ENOTSUPP is not populated
in userspace headers, and -ENOTSUP is not used at all.

Also as I mentioned in another reply -EINVAL and -ENOEXEC is also not
ncessary.

For -ENOTSUP, maybe someone can submit a patch to switch to -ENOTSUPP
so that userspace can check it.
Ccing Thiago and Hari for the -ENOTSUPP errno issue.

> +					do_kexec_file_syscall = 0;
> +					break;
> +			}
> +		}
> +		if (!do_kexec_file_syscall)
>  			result = my_load(type, fileind, argc, argv,
>  						kexec_flags, entry);
>  	}
> diff --git a/kexec/kexec.h b/kexec/kexec.h
> index 26225d2c002a..d445fbe3e486 100644
> --- a/kexec/kexec.h
> +++ b/kexec/kexec.h
> @@ -219,6 +219,8 @@ extern int file_types;
>  #define OPT_TYPE		't'
>  #define OPT_PANIC		'p'
>  #define OPT_KEXEC_FILE_SYSCALL	's'
> +#define OPT_KEXEC_SYSCALL	'c'
> +#define OPT_KEXEC_SYSCALL_AUTO	'a'
>  #define OPT_STATUS		'S'
>  #define OPT_MEM_MIN             256
>  #define OPT_MEM_MAX             257
> @@ -246,11 +248,13 @@ 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 }, \
> +	{ "kexec-syscall",	0, 0, OPT_KEXEC_SYSCALL }, \
> +	{ "kexec-syscall-auto",	0, 0, OPT_KEXEC_SYSCALL_AUTO }, \
>  	{ "debug",		0, 0, OPT_DEBUG }, \
>  	{ "status",		0, 0, OPT_STATUS }, \
>  	{ "print-ckr-size",     0, 0, OPT_PRINT_CKR_SIZE }, \
>  
> -#define KEXEC_OPT_STR "h?vdfxyluet:psS"
> +#define KEXEC_OPT_STR "h?vdfxyluet:pscaS"
>  
>  extern void dbgprint_mem_range(const char *prefix, struct memory_range *mr, int nr_mr);
>  extern void die(const char *fmt, ...)
> -- 
> 2.13.6
> 
> 
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Thanks
Dave