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
>
--
- Daniel
