lkml.org 
[lkml]   [2019]   [May]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [PATCH 4/9] ARC: mm: do_page_fault refactor #3: tidyup vma access permission code
Date
On Tue, 2019-05-14 at 17:29 -0700, Vineet Gupta wrote:
> The coding pattern to NOT intialize variables at declaration time but
> rather near code which makes us eof them makes it much easier to grok
> the overall logic, specially when the init is not simply 0 or 1
>
> Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
> ---
> arch/arc/mm/fault.c | 39 +++++++++++++++++++++------------------
> 1 file changed, 21 insertions(+), 18 deletions(-)
>
> diff --git a/arch/arc/mm/fault.c b/arch/arc/mm/fault.c
> index f1175685d914..ae890a8d5ebf 100644
> --- a/arch/arc/mm/fault.c
> +++ b/arch/arc/mm/fault.c
> @@ -67,9 +67,9 @@ void do_page_fault(unsigned long address, struct pt_regs *regs)
> struct task_struct *tsk = current;
> struct mm_struct *mm = tsk->mm;
> int si_code = SEGV_MAPERR;
> + unsigned int write = 0, exec = 0, mask;

Probably it's better to use 'bool' type for 'write' and 'exec' as we really use them as a boolean variables.


> vm_fault_t fault;
> - int write = regs->ecr_cause & ECR_C_PROTV_STORE; /* ST/EX */
> - unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
> + unsigned int flags;
>
> /*
> * NOTE! We MUST NOT take any locks for this case. We may
> @@ -91,8 +91,18 @@ void do_page_fault(unsigned long address, struct pt_regs *regs)
> if (faulthandler_disabled() || !mm)
> goto no_context;
>
> + if (regs->ecr_cause & ECR_C_PROTV_STORE) /* ST/EX */
> + write = 1;
> + else if ((regs->ecr_vec == ECR_V_PROTV) &&
> + (regs->ecr_cause == ECR_C_PROTV_INST_FETCH))
> + exec = 1;
> +
> + flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
> if (user_mode(regs))
> flags |= FAULT_FLAG_USER;
> + if (write)
> + flags |= FAULT_FLAG_WRITE;
> +
> retry:
> down_read(&mm->mmap_sem);
>
> @@ -105,24 +115,17 @@ void do_page_fault(unsigned long address, struct pt_regs *regs)
> }
>
> /*
> - * Ok, we have a good vm_area for this memory access, so
> - * we can handle it..
> + * vm_area is good, now check permissions for this memory access
> */
> - si_code = SEGV_ACCERR;
> -
> - /* Handle protection violation, execute on heap or stack */
> -
> - if ((regs->ecr_vec == ECR_V_PROTV) &&
> - (regs->ecr_cause == ECR_C_PROTV_INST_FETCH))
> + mask = VM_READ;
> + if (write)
> + mask = VM_WRITE;
> + if (exec)
> + mask = VM_EXEC;
> +
> + if (!(vma->vm_flags & mask)) {
> + si_code = SEGV_ACCERR;
> goto bad_area;
> -
> - if (write) {
> - if (!(vma->vm_flags & VM_WRITE))
> - goto bad_area;
> - flags |= FAULT_FLAG_WRITE;
> - } else {
> - if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
> - goto bad_area;
> }
>
> /*
--
Eugeniy Paltsev
\
 
 \ /
  Last update: 2019-05-16 19:24    [W:0.107 / U:0.888 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site