linux-kernel - Re: [PATCH v4 0/6] implement KASLR for powerpc/fsl

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Date:   Fri, 20 Mar 2020 14:19:57 +1100
From:   Daniel Axtens <dja@...ens.net>
To:     Jason Yan <yanaijie@...wei.com>, mpe@...erman.id.au,
        linuxppc-dev@...ts.ozlabs.org, diana.craciun@....com,
        christophe.leroy@....fr, benh@...nel.crashing.org,
        paulus@...ba.org, npiggin@...il.com, keescook@...omium.org,
        kernel-hardening@...ts.openwall.com, oss@...error.net
Cc:     linux-kernel@...r.kernel.org, zhaohongjiang@...wei.com,
        Jason Yan <yanaijie@...wei.com>
Subject: Re: [PATCH v4 0/6] implement KASLR for powerpc/fsl_booke/64

Hi Jason,

I tried to compile this series and got the following error:

/home/dja/dev/linux/linux/arch/powerpc/mm/nohash/kaslr_booke.c: In function ‘kaslr_early_init’:
/home/dja/dev/linux/linux/arch/powerpc/mm/nohash/kaslr_booke.c:357:33: error: ‘linear_sz’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
  357 |  regions.pa_end = memstart_addr + linear_sz;
      |                   ~~~~~~~~~~~~~~^~~~~~~~~~~
/home/dja/dev/linux/linux/arch/powerpc/mm/nohash/kaslr_booke.c:317:21: note: ‘linear_sz’ was declared here
  317 |  unsigned long ram, linear_sz;
      |                     ^~~~~~~~~
/home/dja/dev/linux/linux/arch/powerpc/mm/nohash/kaslr_booke.c:187:8: error: ‘ram’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
  187 |  ret = parse_crashkernel(boot_command_line, size, &crash_size,
      |        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  188 |     &crash_base);
      |     ~~~~~~~~~~~~
/home/dja/dev/linux/linux/arch/powerpc/mm/nohash/kaslr_booke.c:317:16: note: ‘ram’ was declared here
  317 |  unsigned long ram, linear_sz;
      |                ^~~
cc1: all warnings being treated as errors
make[4]: *** [/home/dja/dev/linux/linux/scripts/Makefile.build:268: arch/powerpc/mm/nohash/kaslr_booke.o] Error 1
make[3]: *** [/home/dja/dev/linux/linux/scripts/Makefile.build:505: arch/powerpc/mm/nohash] Error 2
make[2]: *** [/home/dja/dev/linux/linux/scripts/Makefile.build:505: arch/powerpc/mm] Error 2
make[2]: *** Waiting for unfinished jobs....

I have attached my .config file.

I'm using
powerpc64-linux-gnu-gcc (Ubuntu 9.2.1-9ubuntu1) 9.2.1 20191008

Regards,
Daniel


Download attachment ".config" of type "application/octet-stream" (93922 bytes)



> This is a try to implement KASLR for Freescale BookE64 which is based on
> my earlier implementation for Freescale BookE32:
> https://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=131718&state=*
>
> The implementation for Freescale BookE64 is similar as BookE32. One
> difference is that Freescale BookE64 set up a TLB mapping of 1G during
> booting. Another difference is that ppc64 needs the kernel to be
> 64K-aligned. So we can randomize the kernel in this 1G mapping and make
> it 64K-aligned. This can save some code to creat another TLB map at
> early boot. The disadvantage is that we only have about 1G/64K = 16384
> slots to put the kernel in.
>
>     KERNELBASE
>
>           64K                     |--> kernel <--|
>            |                      |              |
>         +--+--+--+    +--+--+--+--+--+--+--+--+--+    +--+--+
>         |  |  |  |....|  |  |  |  |  |  |  |  |  |....|  |  |
>         +--+--+--+    +--+--+--+--+--+--+--+--+--+    +--+--+
>         |                         |                        1G
>         |----->   offset    <-----|
>
>                               kernstart_virt_addr
>
> I'm not sure if the slot numbers is enough or the design has any
> defects. If you have some better ideas, I would be happy to hear that.
>
> Thank you all.
>
> v3->v4:
>   Do not define __kaslr_offset as a fixed symbol. Reference __run_at_load and
>     __kaslr_offset by symbol instead of magic offsets.
>   Use IS_ENABLED(CONFIG_PPC32) instead of #ifdef CONFIG_PPC32.
>   Change kaslr-booke32 to kaslr-booke in index.rst
>   Switch some instructions to 64-bit.
> v2->v3:
>   Fix build error when KASLR is disabled.
> v1->v2:
>   Add __kaslr_offset for the secondary cpu boot up.
>
> Jason Yan (6):
>   powerpc/fsl_booke/kaslr: refactor kaslr_legal_offset() and
>     kaslr_early_init()
>   powerpc/fsl_booke/64: introduce reloc_kernel_entry() helper
>   powerpc/fsl_booke/64: implement KASLR for fsl_booke64
>   powerpc/fsl_booke/64: do not clear the BSS for the second pass
>   powerpc/fsl_booke/64: clear the original kernel if randomized
>   powerpc/fsl_booke/kaslr: rename kaslr-booke32.rst to kaslr-booke.rst
>     and add 64bit part
>
>  Documentation/powerpc/index.rst               |  2 +-
>  .../{kaslr-booke32.rst => kaslr-booke.rst}    | 35 +++++++-
>  arch/powerpc/Kconfig                          |  2 +-
>  arch/powerpc/kernel/exceptions-64e.S          | 23 +++++
>  arch/powerpc/kernel/head_64.S                 | 13 +++
>  arch/powerpc/kernel/setup_64.c                |  3 +
>  arch/powerpc/mm/mmu_decl.h                    | 23 ++---
>  arch/powerpc/mm/nohash/kaslr_booke.c          | 88 +++++++++++++------
>  8 files changed, 144 insertions(+), 45 deletions(-)
>  rename Documentation/powerpc/{kaslr-booke32.rst => kaslr-booke.rst} (59%)
>
> -- 
> 2.17.2