• Huang Ying's avatar
    kexec jump · 3ab83521
    Huang Ying authored
    This patch provides an enhancement to kexec/kdump.  It implements the
    following features:
    - Backup/restore memory used by the original kernel before/after
    - Save/restore CPU state before/after kexec.
    The features of this patch can be used as a general method to call program in
    physical mode (paging turning off).  This can be used to call BIOS code under
    kexec-tools needs to be patched to support kexec jump. The patches and
    the precompiled kexec can be download from the following URL:
           source: http://khibernation.sourceforge.net/download/release_v10/kexec-tools/kexec-tools-src_git_kh10.tar.bz2
           patches: http://khibernation.sourceforge.net/download/release_v10/kexec-tools/kexec-tools-patches_git_kh10.tar.bz2
           binary: http://khibernation.sourceforge.net/download/release_v10/kexec-tools/kexec_git_kh10
    Usage example of calling some physical mode code and return:
    1. Compile and install patched kernel with following options selected:
    2. Build patched kexec-tool or download the pre-built one.
    3. Build some physical mode executable named such as "phy_mode"
    4. Boot kernel compiled in step 1.
    5. Load physical mode executable with /sbin/kexec. The shell command
       line can be as follow:
       /sbin/kexec --load-preserve-context --args-none phy_mode
    6. Call physical mode executable with following shell command line:
       /sbin/kexec -e
    Implementation point:
    To support jumping without reserving memory.  One shadow backup page (source
    page) is allocated for each page used by kexeced code image (destination
    page).  When do kexec_load, the image of kexeced code is loaded into source
    pages, and before executing, the destination pages and the source pages are
    swapped, so the contents of destination pages are backupped.  Before jumping
    to the kexeced code image and after jumping back to the original kernel, the
    destination pages and the source pages are swapped too.
    C ABI (calling convention) is used as communication protocol between
    kernel and called code.
    A flag named KEXEC_PRESERVE_CONTEXT for sys_kexec_load is added to
    indicate that the loaded kernel image is used for jumping back.
    Now, only the i386 architecture is supported.
    Signed-off-by: default avatarHuang Ying <ying.huang@intel.com>
    Acked-by: default avatarVivek Goyal <vgoyal@redhat.com>
    Cc: "Eric W. Biederman" <ebiederm@xmission.com>
    Cc: Pavel Machek <pavel@ucw.cz>
    Cc: Nigel Cunningham <nigel@nigel.suspend2.net>
    Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
    Cc: Ingo Molnar <mingo@elte.hu>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
machine_kexec_64.c 6.05 KB