On Wed, 2 Feb 2011, Russell King - ARM Linux wrote: > On Wed, Feb 02, 2011 at 03:43:29PM +0100, Per Fransson wrote: > > When restarting using the kernel kexec functionality the MMU > > needs to be turned off. Any code which does this needs to use > > identity mapped addresses to get reliable results. In the ARM > > kexec case this identity mapping is done: > > > > - using the page table of the current task > > > > - for all addresses normally used by user space, > > i.e. 0x00000000-PAGE_OFFSET > > > > If kexec is used at a kernel crash to collect a core dump this > > means that we lose important information. > > > > This is what this patches does: > > > > * Actually turns off the MMU, which has been omitted by mistake > > > > * Sets up a more selective identity mapping > > > > * Restores the old mapping once the MMU is off > > > > Signed-off-by: Per Fransson <per.xx.fransson at stericsson.com> > > --- > > v2 changes: > > > > * now uses (modified versions of) the identity mapping functions in idmap.c > > as they look in 2.6.38-rc1. Some pud-level code has been added there in > > linux-next. > > Thanks. As this been tested with ARMv4/v5 CPUs as well? I have doubts about the effectiveness of setup_mm_for_reboot() on any machine where physical RAM starts at 0xc0000000 or above, such as on SA1100. Nicolas
