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

[Dave Young <dyoung@redhat.com>]

On 03/26/18 at 05:08pm, Dave Young wrote:
> 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@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.

Oops for the hurry reply,  I means -ENOTSUPP might be able to replaced
with -EOPNOTSUPP, a similar change like this:
https://patchwork.kernel.org/patch/8490791/

> 
> > +					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
> > 
> > 
> > _______________________________________________
> > kexec mailing list
> > kexec@lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/kexec
> 
> Thanks
> Dave

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