Re: [PATCH 0/4] Handle memmap and mem kernel options in boot stage kaslr

Ingo Molnar
2017-04-18T12:52:03Z

* Baoquan He <bhe@redhat.com> wrote:

> On 04/18/17 at 11:47am, Ingo Molnar wrote:
> >
> > * Baoquan He <bhe@redhat.com> wrote:
> >
> > > People reported kernel panic occurs during system boots up with mem boot option.
> > > After checking code, several problems are found about memmap= and mem= in boot stage
> > > kaslr.
> > >
> > > *) In commit f28442497b5c ("x86/boot: Fix KASLR and memmap= collision"), only one memmap
> > > entry is considered and only the last one if multiple memmap entries are specified.
> > >
> > > *) mem= and memmap=nn[KMG] are not considered yet. They are used to limit max address
> > > of system. Kernel can't be randomized to be above the limit.
> > >
> > > *) kernel-parameters.txt doesn't tell the updated behaviour of memmap=.
> > >
> > > This patchset tries to solve above issues.
> > >
> > > Baoquan He (4):
> > > param: Move function next_arg to lib/cmdline.c for later reuse
> > > KASLR: Parse all memmap entries in cmdline
> > > KASLR: Handle memory limit specified by memmap and mem option
> > > doc: Update description about memmap option in kernel-parameter.txt
> > >
> > > Documentation/admin-guide/kernel-parameters.txt | 9 ++
> > > arch/x86/boot/compressed/cmdline.c | 2 +-
> > > arch/x86/boot/compressed/kaslr.c | 161 ++++++++++++++----------
> > > arch/x86/boot/string.c | 8 ++
> > > include/linux/kernel.h | 1 +
> > > kernel/params.c | 52 --------
> > > lib/cmdline.c | 57 +++++++++
> > > 7 files changed, 172 insertions(+), 118 deletions(-)
> >
> > I ported this series to tip:x86/boot (please post future versions against that),
> > and beyond a trivial conflict with e820entry => e820_entry, it fails to build on
> > 32-bit allmodconfig:
> >
> > ld: -r and -shared may not be used together
> > scripts/Makefile.build:294: recipe for target 'arch/x86/boot/compressed/kaslr.o' failed
> >
> > ... which could be due to bad relocations, but I've not dug any further.
>
> Thanks, Ingo!
>
> I will find a x86_32 system to try allmodconfig.

No need, on a 64-bit system just do:

make ARCH=i386 allmodconfig

and build the kernel the regular way.

Thanks,

Ingo