On 10/14/2015 04:48 PM, Lucas Stach wrote:
> Install a non-faulting handler just before unmasking imprecise aborts
> and switch back to the regular one after unmasking is done.
>
> This catches any pending imprecise abort that the firmware/bootloader
> may have left behind that would normally crash the kernel at that point.
> As there are apparently a lot of bootlaoders out there that do such a
> thing it makes sense to handle it in the common startup code.
>
> Signed-off-by: Lucas Stach <l.stach@xxxxxxxxxxxxxx>
> ---
> arch/arm/mm/fault.c | 15 +++++++++++++++
> arch/arm/mm/fault.h | 2 ++
> arch/arm/mm/mmu.c | 19 ++++++++++++++++++-
> 3 files changed, 35 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
> index 0d629b8f973f..519f694ec9db 100644
> --- a/arch/arm/mm/fault.c
> +++ b/arch/arm/mm/fault.c
> @@ -538,6 +538,21 @@ hook_fault_code(int nr, int (*fn)(unsigned long, unsigned int, struct pt_regs *)
> fsr_info[nr].name = name;
> }
>
> +void * __init
> +swap_fault_function(int nr,
> + int (*fn)(unsigned long, unsigned int, struct pt_regs *))
> +{
> + void *old_fn;
> +
> + if (nr < 0 || nr >= ARRAY_SIZE(fsr_info))
> + BUG();
> +
> + old_fn = fsr_info[nr].fn;
> + fsr_info[nr].fn = fn;
> +
> + return old_fn;
> +}
> +
> /*
> * Dispatch a data abort to the relevant handler.
> */
> diff --git a/arch/arm/mm/fault.h b/arch/arm/mm/fault.h
> index cf08bdfbe0d6..2deb7494d84f 100644
> --- a/arch/arm/mm/fault.h
> +++ b/arch/arm/mm/fault.h
> @@ -24,5 +24,7 @@ static inline int fsr_fs(unsigned int fsr)
>
> void do_bad_area(unsigned long addr, unsigned int fsr, struct pt_regs *regs);
> unsigned long search_exception_table(unsigned long addr);
> +void *swap_fault_function(int nr,
> + int (*fn)(unsigned long, unsigned int, struct pt_regs *));
>
> #endif /* __ARCH_ARM_FAULT_H */
> diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
> index f65a6f344b6d..78c420776f4c 100644
> --- a/arch/arm/mm/mmu.c
> +++ b/arch/arm/mm/mmu.c
> @@ -38,6 +38,7 @@
> #include <asm/mach/pci.h>
> #include <asm/fixmap.h>
>
> +#include "fault.h"
> #include "mm.h"
> #include "tcm.h"
>
> @@ -1259,6 +1260,20 @@ void __init arm_mm_memblock_reserve(void)
> }
>
> /*
> + * Abort handler to be used only during unmasking of imprecise aborts. This
> + * makes sure that the machine will not die if the firmware/bootloader left an
> + * imprecise abort pending for us to trip over.
> + */
> +static int __init early_abort_handler(unsigned long addr, unsigned int fsr,
> + struct pt_regs *regs)
> +{
> + pr_warn("Hit pending imprecise external abort during first unmask, "
> + "this is most likely caused by a firmware/bootloader bug.\n");
Why don't you add the fsr value into the print, so it is easier to debug.
Otherwise:
Acked-by: Hauke Mehrtens <hauke@xxxxxxxxxx>
> +
> + return 0;
> +}
> +
> +/*
> * Set up the device mappings. Since we clear out the page tables for all
> * mappings above VMALLOC_START, except early fixmap, we might remove debug
> * device mappings. This means earlycon can be used to debug this function
> @@ -1269,7 +1284,7 @@ static void __init devicemaps_init(const struct machine_desc *mdesc)
> {
> struct map_desc map;
> unsigned long addr;
> - void *vectors;
> + void *vectors, *saved_fault_fn;
>
> /*
> * Allocate the vector page early.
> @@ -1365,7 +1380,9 @@ static void __init devicemaps_init(const struct machine_desc *mdesc)
> flush_cache_all();
>
> /* Enable asynchronous aborts */
> + saved_fault_fn = swap_fault_function(22, early_abort_handler);
> local_abt_enable();
> + swap_fault_function(22, saved_fault_fn);
> }
>
> static void __init kmap_init(void)
>
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