Date:	Sat,  5 Mar 2016 00:24:58 +0800
From:	Baoquan He <bhe@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	yinghai@...nel.org, keescook@...omium.org, hpa@...or.com,
	vgoyal@...hat.com, mingo@...hat.com, bp@...en8.de, luto@...nel.org,
	lasse.collin@...aani.org, akpm@...ux-foundation.org,
	dyoung@...hat.com, Baoquan He <bhe@...hat.com>
Subject: [PATCH v3 00/19] x86, boot: kaslr cleanup and 64bit kaslr support

***Background:
Previously a bug is reported that kdump didn't work when kaslr is enabled. During
discussing that bug fix, we found current kaslr has a limilation that it can
only randomize in 1GB region.

This is because in curent kaslr implementaion only physical address of kernel
loading is randomized. Then calculate the delta of physical address where
vmlinux was linked to load and where it is finally loaded. If delta is not
equal to 0, namely there's a new physical address where kernel is actually
decompressed, relocation handling need be done. Then delta is added to offset
of kernel symbol relocation, this makes the address of kernel text mapping move
delta long. Though in principle kernel can be randomized to any physical address,
kernel text mapping address space is limited and only 1G, namely as follows on
x86_64:
	[0xffffffff80000000, 0xffffffffc0000000)

In one word, kernel text physical address and virtual address randomization is
coupled. This causes the limitation.

Then hpa and Vivek suggested we should change this. To decouple the physical
address and virtual address randomization of kernel text and let them work
separately. Then kernel text physical address can be randomized in region
[16M, 64T), and kernel text virtual address can be randomized in region
[0xffffffff80000000, 0xffffffffc0000000).

***Problems we need solved:
  - For kernel boot from startup_32 case, only 0~4G identity mapping is built.
    If kernel will be randomly put anywhere from 16M to 64T at most, the price
    to build all region of identity mapping is too high. We need build the
    identity mapping on demand, not covering all physical address space.

  - Decouple the physical address and virtual address randomization of kernel
    text and let them work separately.

***Parts:
   - The 1st part is Yinghai's identity mapping building on demand patches.
     This is used to solve the first problem mentioned above.
     (Patch 09-10/19)
   - The 2nd part is decoupling the physical address and virtual address
     randomization of kernel text and letting them work separately patches
     based on Yinghai's ident mapping patches.
     (Patch 12-19/19)
   - The 3rd part is some clean up patches which Yinghai found when he reviewed
     my patches and the related code around.
     (Patch 01-08/19)

***Patch status:
This patchset went through several rounds of review.

   - The first round can be found here:
	https://lwn.net/Articles/637115/

   - In 2nd round Yinghai made a big patchset including this kaslr fix and another
     setup_data related fix. The link is here:
      http://lists-archives.com/linux-kernel/28346903-x86-updated-patches-for-kaslr-and-setup_data-etc-for-v4-3.html
     You can get the code from Yinghai's git branch:
     git://git.kernel.org/pub/scm/linux/kernel/git/yinghai/linux-yinghai.git for-x86-v4.3-next

   - This post is the 3rd round. It only takes care of the kaslr related patches.
     For reviewers it's better to discuss only one issue in one thread.
       * I take off one patch as follows from Yinghai's because I think it's unnecessay. 
          - Patch 05/19 x86, kaslr: rename output_size to output_run_size
         output_size is enough to represen the value:
		output_len > run_size ? output_len : run_size
      
       * I add Patch 04/19, it's a comment update patch. For other patches, I just
         adjust patch log and do several places of change comparing with 2nd round.
         Please check the change log under patch log of each patch for details.

       * I adjust sequence of several patches to make review easier. It doesn't
         affect codes.

   - You can also get this patchset from my github:
     https://github.com/baoquan-he/linux.git kaslr-above-4G

Any comments and suggestions are welcome. Code changes, code comments, patch logs,
anything you think it's unclear, please add your comment.

Baoquan He (8):
  x86, kaskr: Update the description for decompressor worst case
  x86, kaslr: Fix a bug that relocation can not be handled when kernel
    is loaded above 2G
  x86, kaslr: Introduce struct slot_area to manage randomization slot
    info
  x86, kaslr: Add two functions which will be used later
  x86, kaslr: Introduce fetch_random_virt_offset to randomize the kernel
    text mapping address
  x86, kaslr: Randomize physical and virtual address of kernel
    separately
  x86, kaslr: Add support of kernel physical address randomization above
    4G
  x86, kaslr: Remove useless codes

Yinghai Lu (11):
  x86, kaslr: Remove not needed parameter for choose_kernel_location
  x86, boot: Move compressed kernel to end of buffer before
    decompressing
  x86, boot: Move z_extract_offset calculation to header.S
  x86, boot: Fix run_size calculation
  x86, kaslr: Clean up useless code related to run_size.
  x86, kaslr: Get correct max_addr for relocs pointer
  x86, kaslr: Consolidate mem_avoid array filling
  x86, boot: Split kernel_ident_mapping_init to another file
  x86, 64bit: Set ident_mapping for kaslr
  x86, boot: Add checking for memcpy
  x86, kaslr: Allow random address to be below loaded address

 arch/x86/boot/Makefile                 |  13 +-
 arch/x86/boot/compressed/Makefile      |  19 ++-
 arch/x86/boot/compressed/aslr.c        | 258 +++++++++++++++++++++++----------
 arch/x86/boot/compressed/head_32.S     |  14 +-
 arch/x86/boot/compressed/head_64.S     |  15 +-
 arch/x86/boot/compressed/misc.c        |  94 +++++++-----
 arch/x86/boot/compressed/misc.h        |  34 +++--
 arch/x86/boot/compressed/misc_pgt.c    |  91 ++++++++++++
 arch/x86/boot/compressed/mkpiggy.c     |  28 +---
 arch/x86/boot/compressed/string.c      |  29 +++-
 arch/x86/boot/compressed/vmlinux.lds.S |   1 +
 arch/x86/boot/header.S                 |  22 ++-
 arch/x86/include/asm/boot.h            |  19 +++
 arch/x86/include/asm/page.h            |   5 +
 arch/x86/kernel/asm-offsets.c          |   1 +
 arch/x86/kernel/vmlinux.lds.S          |   1 +
 arch/x86/mm/ident_map.c                |  74 ++++++++++
 arch/x86/mm/init_64.c                  |  74 +---------
 arch/x86/tools/calc_run_size.sh        |  42 ------
 19 files changed, 543 insertions(+), 291 deletions(-)
 create mode 100644 arch/x86/boot/compressed/misc_pgt.c
 create mode 100644 arch/x86/mm/ident_map.c
 delete mode 100644 arch/x86/tools/calc_run_size.sh

-- 
2.5.0

Powered by blists - more mailing lists