On Wed, 2020-01-08 at 15:29 +0100, Daniel Schwierzeck wrote: > > Am 08.01.20 um 04:00 schrieb Weijie Gao: > > In U-Boot the exception vector base will be moved to top of memory, to be > > used to display register dump when exception occurs. > > > > But some old linux kernel does not honor the base set in CP0_EBASE. A > > modified exception vector base will cause kernel crash. > > > > This patch adds an option to enable reset exception vector base to > > 0x80000000 before booting linux kernel. > > > > Signed-off-by: Weijie Gao <[email protected]> > > --- > > arch/mips/Kconfig | 13 +++++++++++++ > > arch/mips/lib/bootm.c | 9 +++++++++ > > 2 files changed, 22 insertions(+) > > > > diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig > > index a3ae603044..4688717593 100644 > > --- a/arch/mips/Kconfig > > +++ b/arch/mips/Kconfig > > @@ -287,6 +287,19 @@ config MIPS_RELOCATION_TABLE_SIZE > > > > If unsure, leave at the default value. > > > > +config RESTORE_EXCEPTION_VECTOR_BASE > > + bool "Restore exception vector base before booting linux kernel" > > + default n > > + help > > + In U-Boot the exception vector base will be moved to top of memory, > > + to be used to display register dump when exception occurs. > > + But some old linux kernel does not honor the base set in CP0_EBASE. > > + A modified exception vector base will cause kernel crash. > > + > > + This option will set exception vector base to 0x80000000. > > Does it make sense to make the base address configurable and let it > default to 0x80000000? > > > + > > + If unsure, say N. > > + > > endmenu > > > > menu "OS boot interface" > > diff --git a/arch/mips/lib/bootm.c b/arch/mips/lib/bootm.c > > index 8c0d7672f2..86ea082fd0 100644 > > --- a/arch/mips/lib/bootm.c > > +++ b/arch/mips/lib/bootm.c > > @@ -294,6 +294,15 @@ static void boot_jump_linux(bootm_headers_t *images) > > bootstage_report(); > > #endif > > > > +#ifdef CONFIG_RESTORE_EXCEPTION_VECTOR_BASE > > + /* Restore EBASE for compatibility */ > > + set_c0_status(ST0_BEV); > > + execution_hazard_barrier(); > > + write_c0_ebase(KSEG0); > > + clear_c0_status(ST0_BEV); > > + execution_hazard_barrier(); > > +#endif > > + > > could you move this to a function trap_restore() in arch/mips/lib/traps.c? > > Also prefer the following over #ifdef: > > if (CONFIG_IS_ENABLED(RESTORE_EXCEPTION_VECTOR_BASE)) > trap_restore(); > > Alternatively you could simply define trap_restore() as empty static > inline function if RESTORE_EXCEPTION_VECTOR_BASE is disabled. > > > if (images->ft_len) > > kernel(-2, (ulong)images->ft_addr, 0, 0); > > else > > >
Hi Daniel, 0x80000000 is the power-on value of EBASE. I think there is no need to change it to a different value. For the rest parts, I'll take your advice. Best Regards, Weijie
