Re: [PATCH v4 2/3] x86/kexec/64: Error out if try to jump to old 4-level kernel from 5-level kernel
On 05/22/19 at 11:20am, Dave Young wrote:
> How about the userspace kexec-tools? It needs a similar detection, but
> I'm not sure how to detect paging mode, maybe some sysfs entry or
> vmcoreinfo in /proc/vmcore
In usersapce, I plan to parse /proc/kcore to get the starting address
of page_offset or vmalloc. You can see the different level has different
value range.
4-level:
8880 | -119.5 TB | c87f | 64 TB | direct mapping
of all physical memory (page_offset_base)
c880 | -55.5 TB | c8ff | 0.5 TB | ... unused hole
c900 | -55TB | e8ff | 32 TB | vmalloc/ioremap
space (vmalloc_base)
e900 | -23TB | e9ff |1 TB | ... unused hole
ea00 | -22TB | eaff |1 TB | virtual memory
map (vmemmap_base)
5-level:
ff11 | -59.75 PB | ff90 | 32 PB | direct mapping
of all physical memory (page_offset_base)
ff91 | -27.75 PB | ff9f | 3.75 PB | ... unused hole
ffa0 | -24PB | ffd1 | 12.5 PB | vmalloc/ioremap
space (vmalloc_base)
ffd2 | -11.5 PB | ffd3 | 0.5 PB | ... unused hole
ffd4 | -11PB | ffd5 | 0.5 PB | virtual memory
map (vmemmap_base)
>
>
> > 1 file changed, 5 insertions(+)
> >
> > diff --git a/arch/x86/kernel/kexec-bzimage64.c
> > b/arch/x86/kernel/kexec-bzimage64.c
> > index 22f60dd26460..858cc892672f 100644
> > --- a/arch/x86/kernel/kexec-bzimage64.c
> > +++ b/arch/x86/kernel/kexec-bzimage64.c
> > @@ -321,6 +321,11 @@ static int bzImage64_probe(const char *buf, unsigned
> > long len)
> > return ret;
> > }
> >
> > + if (!(header->xloadflags & XLF_5LEVEL) && pgtable_l5_enabled()) {
> > + pr_err("Can not jump to old 4-level kernel from 5-level
> > kernel.\n");
>
> 4-level kernel sounds not very clear, maybe something like below?
>
> "5-level paging enabled, can not kexec into an old kernel without 5-level
> paging facility"?
Oops, tglx commented on this message. He suggested changing it like:
"bzImage cannot handle 5-level paging mode\n"
I forgot updating this part. Any one is fine to me. Will update.
Thanks
Baoquan
Re: [PATCH v4 2/3] x86/kexec/64: Error out if try to jump to old 4-level kernel from 5-level kernel
On 05/22/19 at 11:20am, Dave Young wrote: > On 05/09/19 at 09:36am, Baoquan He wrote: > > If the running kernel has 5-level paging activated, the 5-level paging > > mode is preserved across kexec. If the kexec'ed kernel does not contain > > support for handling active 5-level paging mode in the decompressor, the > > decompressor will crash with #GP. > > > > Prevent this situation at load time. If 5-level paging is active, check the > > xloadflags whether the kexec kernel can handle 5-level paging at least in > > the decompressor. If not, reject the load attempt and print out error > > message. > > > > Signed-off-by: Baoquan He > > Acked-by: Kirill A. Shutemov > > --- > > arch/x86/kernel/kexec-bzimage64.c | 5 + > > How about the userspace kexec-tools? It needs a similar detection, but > I'm not sure how to detect paging mode, maybe some sysfs entry or > vmcoreinfo in /proc/vmcore meant /proc/kcore ... Thanks Dave
Re: [PATCH v4 2/3] x86/kexec/64: Error out if try to jump to old 4-level kernel from 5-level kernel
On 05/09/19 at 09:36am, Baoquan He wrote:
> If the running kernel has 5-level paging activated, the 5-level paging
> mode is preserved across kexec. If the kexec'ed kernel does not contain
> support for handling active 5-level paging mode in the decompressor, the
> decompressor will crash with #GP.
>
> Prevent this situation at load time. If 5-level paging is active, check the
> xloadflags whether the kexec kernel can handle 5-level paging at least in
> the decompressor. If not, reject the load attempt and print out error
> message.
>
> Signed-off-by: Baoquan He
> Acked-by: Kirill A. Shutemov
> ---
> arch/x86/kernel/kexec-bzimage64.c | 5 +
How about the userspace kexec-tools? It needs a similar detection, but
I'm not sure how to detect paging mode, maybe some sysfs entry or
vmcoreinfo in /proc/vmcore
> 1 file changed, 5 insertions(+)
>
> diff --git a/arch/x86/kernel/kexec-bzimage64.c
> b/arch/x86/kernel/kexec-bzimage64.c
> index 22f60dd26460..858cc892672f 100644
> --- a/arch/x86/kernel/kexec-bzimage64.c
> +++ b/arch/x86/kernel/kexec-bzimage64.c
> @@ -321,6 +321,11 @@ static int bzImage64_probe(const char *buf, unsigned
> long len)
> return ret;
> }
>
> + if (!(header->xloadflags & XLF_5LEVEL) && pgtable_l5_enabled()) {
> + pr_err("Can not jump to old 4-level kernel from 5-level
> kernel.\n");
4-level kernel sounds not very clear, maybe something like below?
"5-level paging enabled, can not kexec into an old kernel without 5-level
paging facility"?
> + return ret;
> + }
> +
> /* I've got a bzImage */
> pr_debug("It's a relocatable bzImage64\n");
> ret = 0;
> --
> 2.17.2
>
Thanks
Dave
Re: [PATCH v4 2/3] x86/kexec/64: Error out if try to jump to old 4-level kernel from 5-level kernel
On 05/09/19 at 09:36am, Baoquan He wrote:
> If the running kernel has 5-level paging activated, the 5-level paging
> mode is preserved across kexec. If the kexec'ed kernel does not contain
> support for handling active 5-level paging mode in the decompressor, the
> decompressor will crash with #GP.
>
> Prevent this situation at load time. If 5-level paging is active, check the
> xloadflags whether the kexec kernel can handle 5-level paging at least in
> the decompressor. If not, reject the load attempt and print out error
> message.
>
> Signed-off-by: Baoquan He
> Acked-by: Kirill A. Shutemov
> ---
> arch/x86/kernel/kexec-bzimage64.c | 5 +
> 1 file changed, 5 insertions(+)
>
> diff --git a/arch/x86/kernel/kexec-bzimage64.c
> b/arch/x86/kernel/kexec-bzimage64.c
> index 22f60dd26460..858cc892672f 100644
> --- a/arch/x86/kernel/kexec-bzimage64.c
> +++ b/arch/x86/kernel/kexec-bzimage64.c
> @@ -321,6 +321,11 @@ static int bzImage64_probe(const char *buf, unsigned
> long len)
> return ret;
> }
>
> + if (!(header->xloadflags & XLF_5LEVEL) && pgtable_l5_enabled()) {
> + pr_err("Can not jump to old 4-level kernel from 5-level
> kernel.\n");
Check the old thread again, found Thomas also had comment about this
error message. Just forgot updating it. Will update it with a new one.
> + return ret;
> + }
> +
> /* I've got a bzImage */
> pr_debug("It's a relocatable bzImage64\n");
> ret = 0;
> --
> 2.17.2
>
[PATCH v4 2/3] x86/kexec/64: Error out if try to jump to old 4-level kernel from 5-level kernel
If the running kernel has 5-level paging activated, the 5-level paging
mode is preserved across kexec. If the kexec'ed kernel does not contain
support for handling active 5-level paging mode in the decompressor, the
decompressor will crash with #GP.
Prevent this situation at load time. If 5-level paging is active, check the
xloadflags whether the kexec kernel can handle 5-level paging at least in
the decompressor. If not, reject the load attempt and print out error
message.
Signed-off-by: Baoquan He
Acked-by: Kirill A. Shutemov
---
arch/x86/kernel/kexec-bzimage64.c | 5 +
1 file changed, 5 insertions(+)
diff --git a/arch/x86/kernel/kexec-bzimage64.c
b/arch/x86/kernel/kexec-bzimage64.c
index 22f60dd26460..858cc892672f 100644
--- a/arch/x86/kernel/kexec-bzimage64.c
+++ b/arch/x86/kernel/kexec-bzimage64.c
@@ -321,6 +321,11 @@ static int bzImage64_probe(const char *buf, unsigned long
len)
return ret;
}
+ if (!(header->xloadflags & XLF_5LEVEL) && pgtable_l5_enabled()) {
+ pr_err("Can not jump to old 4-level kernel from 5-level
kernel.\n");
+ return ret;
+ }
+
/* I've got a bzImage */
pr_debug("It's a relocatable bzImage64\n");
ret = 0;
--
2.17.2
