[PATCH v5 4/5] kexec: Add option to fall back to KEXEC_LOAD when KEXEC_FILE_LOAD is not supported
Thiago Jung Bauermann
bauerman at linux.vnet.ibm.com
Mon Mar 26 11:52:39 PDT 2018
Michal Suchánek <msuchanek at suse.de> writes:
> On Mon, 26 Mar 2018 17:12:10 +0800
> Dave Young <dyoung at redhat.com> wrote:
>
>> 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 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.
>>
>> 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/
>
> Thanks for catching this. In Linux ENOTSUPP with extra P is different
> from EOPNOTSUPP and ENOTSUP (single P). Since we are talking to the
> kernel and it returns the double P ENOTSUPP we need to define it in
> kexec as well. And we should check ENOTSUP with single P in case
> somebody some day thinks that returning undefined error codes to
> userspace is not nice like in the patch above.
I wasn't aware that ENOTSUPP was an in-kernel only errno. Should I
submit a patch for the kernel so that powerpc returns -EOPNOTSUPP in
case of trying to load kdump kernel with kexec_file_load()?
--
Thiago Jung Bauermann
IBM Linux Technology Center
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