Messages in this thread | | | Date | Tue, 9 Mar 2021 11:40:15 +0100 | From | Thomas Bogendoerfer <> | Subject | Re: [PATCH v3] MIPS: kernel: Reserve exception base early to prevent corruption |
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On Mon, Mar 08, 2021 at 10:24:47AM +0100, Thomas Bogendoerfer wrote: > BMIPS is one of the few platforms that do change the exception base. > After commit 2dcb39645441 ("memblock: do not start bottom-up allocations > with kernel_end") we started seeing BMIPS boards fail to boot with the > built-in FDT being corrupted. > > Before the cited commit, early allocations would be in the [kernel_end, > RAM_END] range, but after commit they would be within [RAM_START + > PAGE_SIZE, RAM_END]. > > The custom exception base handler that is installed by > bmips_ebase_setup() done for BMIPS5000 CPUs ends-up trampling on the > memory region allocated by unflatten_and_copy_device_tree() thus > corrupting the FDT used by the kernel. > > To fix this, we need to perform an early reservation of the custom > exception space. Additional we reserve the first 4k (1k for R3k) for > either normal exception vector space (legacy CPUs) or special vectors > like cache exceptions. > > Huge thanks to Serge for analysing and proposing a solution to this > issue. > > Fixes: 2dcb39645441 ("memblock: do not start bottom-up allocations with kernel_end") > Reported-by: Kamal Dasu <kdasu.kdev@gmail.com> > Debugged-by: Serge Semin <Sergey.Semin@baikalelectronics.ru> > Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de> > --- > Changes in v3: > - always reserve the first 4k for all CPUs (1k for R3k) > > Changes in v2: > - do only memblock reservation in reserve_exception_space() > - reserve 0..0x400 for all CPUs without ebase register and > to addtional reserve_exception_space for BMIPS CPUs > > arch/mips/include/asm/traps.h | 3 +++ > arch/mips/kernel/cpu-probe.c | 6 ++++++ > arch/mips/kernel/cpu-r3k-probe.c | 3 +++ > arch/mips/kernel/traps.c | 10 +++++----- > 4 files changed, 17 insertions(+), 5 deletions(-)
applied to mips-fixes.
Thomas.
-- Crap can work. Given enough thrust pigs will fly, but it's not necessarily a good idea. [ RFC1925, 2.3 ]
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