Messages in this thread | | | Date | Tue, 18 Apr 2017 19:38:10 +0800 | From | Baoquan He <> | Subject | Re: [PATCH 0/4] Handle memmap and mem kernel options in boot stage kaslr |
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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.
> > Please also pick up the fixed/rewritten changelogs from the git log below for the > next version.
Will do, thanks a lot!
> > Thanks, > > Ingo > > ====================> > > Documentation/kernel-parameters.txt: Update 'memmap=' option description > > In commit: > > 9710f581bb4c ("x86, mm: Let "memmap=" take more entries one time") > > ... 'memmap=' was changed to adopt multiple, comma delimited values in a > single entry, so update the related description. > > In the special case of only specifying size value without an offset, > like memmap=nn[KMG], memmap behaves similarly to mem=nn[KMG], so update > it too here. > > Furthermore, for memmap=nn[KMG]$ss[KMG], an escape character needs be added > before '$' for some bootloaders. E.g in grub2, if we specify memmap=100M$5G > as suggested by the documentation, "memmap=100MG" gets passed to the kernel. > > Clarify all this. > > ---- > > KASLR: Handle memory limit specified by memmap and mem option > > Option mem= will limit the max address a system can use and any memory > region above the limit will be removed. > > Furthermore, memmap=nn[KMG] which has no offset specified has the same > behaviour as mem=. > > KASLR needs to consider this when choosing the random position for > decompressing the kernel. > > This patch implements that. > > ---- > > KASLR: Parse all memmap entries in cmdline > > In commit: > > f28442497b5c ("x86/boot: Fix KASLR and memmap= collision") > > ... the memmap= option is parsed so that KASLR can avoid those reserved > regions. It uses cmdline_find_option() to get the value if memmap= > is specified, however the problem is that cmdline_find_option() can only > find the last entry if multiple memmap entries are provided. This > is not correct. > > In this patch, the whole cmdline will be scanned to search each > memmap, all of them will be parsed and handled. > > ---- > > boot/param: Move next_arg() function to lib/cmdline.c for later reuse > > next_arg() will be used to parse boot parameters in the x86/boot/compressed code, > so move it to lib/cmdline.c for better code reuse. > > No change in functionality. >
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