On Wed, Oct 15 2025, Pasha Tatashin wrote: > On Wed, Oct 15, 2025 at 8:10 AM Pratyush Yadav <[email protected]> wrote: >> >> On Wed, Oct 15 2025, Pasha Tatashin wrote: >> >> > It is invalid for KHO metadata or preserved memory regions to be located >> > within the KHO scratch area, as this area is overwritten when the next >> > kernel is loaded, and used early in boot by the next kernel. This can >> > lead to memory corruption. >> > >> > Adds checks to kho_preserve_* and KHO's internal metadata allocators >> > (xa_load_or_alloc, new_chunk) to verify that the physical address of the >> > memory does not overlap with any defined scratch region. If an overlap >> > is detected, the operation will fail and a WARN_ON is triggered. To >> > avoid performance overhead in production kernels, these checks are >> > enabled only when CONFIG_KEXEC_HANDOVER_DEBUG is selected. >> > >> > Signed-off-by: Pasha Tatashin <[email protected]> >> > --- >> > kernel/liveupdate/Kconfig | 15 ++++++++++ >> > kernel/liveupdate/kexec_handover.c | 32 ++++++++++++++++++--- >> > kernel/liveupdate/kexec_handover_debug.c | 18 ++++++++++++ >> > kernel/liveupdate/kexec_handover_internal.h | 9 ++++++ >> > 4 files changed, 70 insertions(+), 4 deletions(-) >> > >> > diff --git a/kernel/liveupdate/Kconfig b/kernel/liveupdate/Kconfig >> > index 522b9f74d605..d119f4f3f4b1 100644 >> > --- a/kernel/liveupdate/Kconfig >> > +++ b/kernel/liveupdate/Kconfig >> > @@ -27,4 +27,19 @@ config KEXEC_HANDOVER_DEBUGFS >> > Also, enables inspecting the KHO fdt trees with the debugfs binary >> > blobs. >> > >> > +config KEXEC_HANDOVER_DEBUG >> > + bool "Enable Kexec Handover debug checks" >> > + depends on KEXEC_HANDOVER_DEBUGFS >> >> Why the dependency on debugfs? Why can't the debug checks be enabled >> independently? > > Because there is one kexec_handover_debug.c file, that I thought would > make sense to use for both, but now thinking about this, perhaps we > should split the code: KEXEC_HANDOVER_DEBUGFS and > KEXEC_HANDOVER_DEBUG, and add two files: > kexec_handover_debugfs.c and kexec_handover_debug.c, this would avoid > ifdefs in .c.
Sounds good. > >> >> > + help >> > + This option enables extra sanity checks for the Kexec Handover >> > + subsystem. >> > + >> > + These checks verify that neither preserved memory regions nor KHO's >> > + internal metadata are allocated from within a KHO scratch area. >> > + An overlap can lead to memory corruption during a subsequent kexec >> > + operation. >> >> I don't think the checks that are done should be listed here since as >> soon as another check is added this list will become out of date. > > I thought it could be expanded when new features are added, but I can > remove this description. Yes, but it is easy to forget to do so. > >> >> > + >> > + If an overlap is detected, the kernel will print a warning and the >> > + offending operation will fail. This should only be enabled for >> >> This also describes the behaviour of the checks, which might change >> later. Maybe for some checks the operation won't fail? I suppose just >> leave it at "the kernel will print a warning"? > > If it changes, and Kconfig should be updated as well. > >> >> > + debugging purposes due to runtime overhead. >> > endmenu [...] -- Regards, Pratyush Yadav
