[PATCH v4 0/3] Handle memmap and mem kernel options in boot stage kaslr

[Baoquan He]

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

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

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

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

 *Fix a typo in patch 3/3.

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

 *Use patch log Ingo reorganized.

 *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.

 *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 cmdline
  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                | 191 ++++++++++++++++--------
 arch/x86/boot/string.c                          |   8 +
 4 files changed, 144 insertions(+), 66 deletions(-)

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2.5.5