On Fri, Jul 10, 2020 at 03:57:05PM +0200, Christoph Hellwig wrote:
> Add helpers to wraper the get_fs/set_fs magic for undoing any damange
> done by set_fs(KERNEL_DS). There is no real functional benefit, but this
> documents the intent of these calls better, and will allow stubbing the
> functions out easily for kernels builds that do not allow address space
> overrides in the future.
> diff --git a/arch/m68k/include/asm/tlbflush.h b/arch/m68k/include/asm/tlbflush.h
> index 191e75a6bb249e..30471549e1e224 100644
> --- a/arch/m68k/include/asm/tlbflush.h
> +++ b/arch/m68k/include/asm/tlbflush.h
> @@ -13,13 +13,13 @@ static inline void flush_tlb_kernel_page(void *addr)
> if (CPU_IS_COLDFIRE) {
> mmu_write(MMUOR, MMUOR_CNL);
> } else if (CPU_IS_040_OR_060) {
> - mm_segment_t old_fs = get_fs();
> - set_fs(KERNEL_DS);
> + mm_segment_t old_fs = force_uaccess_begin();
> +
This used to set KERNEL_DS, and now it sets USER_DS, which looks wrong
superficially.
If the new behaviour is fine it suggests that the old behaviour was
wrong, or that this is superfluous and could go entirely.
Geert?
Mark.
> __asm__ __volatile__(".chip 68040\n\t"
> "pflush (%0)\n\t"
> ".chip 68k"
> : : "a" (addr));
> - set_fs(old_fs);
> + force_uaccess_end(old_fs);
> } else if (CPU_IS_020_OR_030)
> __asm__ __volatile__("pflush #4,#4,(%0)" : : "a" (addr));
> +/*
> + * Force the uaccess routines to be wired up for actual userspace access,
> + * overriding any possible set_fs(KERNEL_DS) still lingering around. Undone
> + * using force_uaccess_end below.
> + */
> +static inline mm_segment_t force_uaccess_begin(void)
> +{
> + mm_segment_t fs = get_fs();
> +
> + set_fs(USER_DS);
> + return fs;
> +}
> +
> +static inline void force_uaccess_end(mm_segment_t oldfs)
> +{
> + set_fs(oldfs);
> +}
