linux-kernel - [PATCH v5 0/3] Handle memmap and mem kernel options in boot stage kaslr

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Date:   Sat, 13 May 2017 13:46:27 +0800
From:   Baoquan He <bhe@...hat.com>
To:     tglx@...utronix.de, keescook@...omium.org, mingo@...nel.org,
        m.mizuma@...fujitsu.com
Cc:     linux-kernel@...r.kernel.org, dyoung@...hat.com,
        douly.fnst@...fujitsu.com, dan.j.williams@...el.com, hpa@...or.com,
        x86@...nel.org, Baoquan He <bhe@...hat.com>
Subject: [PATCH v5 0/3] Handle memmap and mem kernel options in boot stage kaslr

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, and it sits on top of
tip:x86/boot branch.

Changelog
v4->v5:
  1. Change patch log according to Thomas's comment.

  2. Put "Fall through" to the right place in parse_memmap() according
  to Kees's suggestion.

v3->v4:
  1. Code improved patch 1/3 according to Kees's suggestion.

  2. Add 'Fall through' in switch case of parse_memmap() which
  is suggestd by Kees.

v2->v3:
  No functionality change in this round.
  1. Use local static variable insted of global variable
  mem_avoid_memmap_index in patch 1/3.

  2. Fix a typo in patch 3/3.

v1->v2:
  1. The original patch 1/4 has been put in tip:x86/boot and no update,
  so it's not included in this post.

  2. Use patch log Ingo reorganized.

  3. lib/ctype.c and lib/cmdline.c are needed for kaslr.c, while those
  EXPORT_SYMBOL(x) contained caused failure of 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
  ......
  Disabling the symbol exporting removes the build failure.

  4. Use dynamic allocation to allocate memory to contain copied kernel cmdline
  buffer, it's implemented in include/linux/decompress/mm.h.

Baoquan He (3):
  KASLR: Parse all memmap entries in command line
  KASLR: Handle memory limit specified by memmap and mem option
  Documentation/kernel-parameters.txt: Update 'memmap=' option
    description

 Documentation/admin-guide/kernel-parameters.txt |   9 ++
 arch/x86/boot/compressed/cmdline.c              |   2 +-
 arch/x86/boot/compressed/kaslr.c                | 190 ++++++++++++++++--------
 arch/x86/boot/string.c                          |   8 +
 4 files changed, 143 insertions(+), 66 deletions(-)

-- 
2.5.5