Re: [PATCH v13 3/3] mm, powerpc, x86: introduce an additional vma bit for powerpc pkey
From: Dave Hansen
Date: Fri May 04 2018 - 18:57:40 EST
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index 0c9e392..3ddddc7 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -679,6 +679,7 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)
> [ilog2(VM_PKEY_BIT1)] = "",
> [ilog2(VM_PKEY_BIT2)] = "",
> [ilog2(VM_PKEY_BIT3)] = "",
> + [ilog2(VM_PKEY_BIT4)] = "",
> #endif /* CONFIG_ARCH_HAS_PKEYS */
...
> +#if defined(CONFIG_PPC)
> +# define VM_PKEY_BIT4 VM_HIGH_ARCH_4
> +#else
> +# define VM_PKEY_BIT4 0
> +#endif
> #endif /* CONFIG_ARCH_HAS_PKEYS */
That new line boils down to:
[ilog2(0)] = "",
on x86. It wasn't *obvious* to me that it is OK to do that. The other
possibly undefined bits (VM_SOFTDIRTY for instance) #ifdef themselves
out of this array.
I would just be a wee bit worried that this would overwrite the 0 entry
("??") with "".