On Thu, Oct 22, 2015 at 11:17:18AM +0800, Dave Young wrote:
> On 10/21/15 at 04:12pm, Geoff Levand wrote:
> > 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.
>
> I think Vivek was rejecting this --lite since kdump need the purgatory
> integrity checks. Ccing him.
Right. Why are we trying to bypass sha256 hash verification of loaded
segments at run time, that needs to be justified.
Atleast on x86, this integrity verification was fast and we did not
notice any siginificant delays in purgatory. And in that case extra knob
like this is hard to justify.
Thanks
Vivek
>
> >
> > 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.
>
> Pratyush reported the arm64 issue, he sent a patch to fix it with
> enabling cache for purgatory. I think the patch can fix the problem.
> Why not fix it? The fix is simple enough and it does not introduce
> complicate logic.
>
> >
> > -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 */
> > }
> > --
> > 2.5.0
> >
> >
> > _______________________________________________
> > kexec mailing list
> > kexec at lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/kexec
> >
> >
