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

Baoquan He
2017-04-20T14:00:00Z

On 04/18/17 at 02:51pm, Ingo Molnar wrote:
>
> * 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.

Sorry for late update. I tried on a x86 64 system with "make ARCH=i386
allmodconfig", and saw the ld warning. I added a '-r' after -pie, the
building passed. Seems including lib/ctype.c or lib/cmdline.c caused
this. Will dig further to see what's going on.

ifeq ($(CONFIG_X86_32),y)
LDFLAGS += $(call ld-option, -pie -r) $(call ld-option, --no-dynamic-linker)
else

Thanks
Baoquan