Re: [patch 072/198] x86_64: Use a VMA for the 32bit vsyscall

[Muli Ben-Yehuda <mulix@mulix.org>]

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On Tue, Apr 12, 2005 at 03:31:43AM -0700, akpm@osdl.org wrote:

> From: Andi Kleen <ak@muc.de>
> 
> Use a real VMA to map the 32bit vsyscall page

[...]

> +/* Setup a VMA at program startup for the vsyscall page */
> +int syscall32_setup_pages(struct linux_binprm *bprm, int exstack)
> +{
> +	int npages = (VSYSCALL32_END - VSYSCALL32_BASE) >> PAGE_SHIFT;
> +	struct vm_area_struct *vma;
> +	struct mm_struct *mm = current->mm;
> +
> +	vma = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
> +	if (!vma)
> +		return -ENOMEM;
> +	if (security_vm_enough_memory(npages)) {
> +		kmem_cache_free(vm_area_cachep, vma);
> +		return -ENOMEM;
> +	}
> +
> +	memset(vma, 0, sizeof(struct vm_area_struct));
> +	/* Could randomize here */
> +	vma->vm_start = VSYSCALL32_BASE;
> +	vma->vm_end = VSYSCALL32_END;
> +	/* MAYWRITE to allow gdb to COW and set breakpoints */
> +	vma->vm_flags = VM_READ|VM_EXEC|VM_MAYREAD|VM_MAYEXEC|VM_MAYEXEC|VM_MAYWRITE;

Any reason for VM_MAYEXEC to be specified twice? did you mean something else?

Cheers,
Muli
-- 
Muli Ben-Yehuda
http://www.mulix.org | http://mulix.livejournal.com/


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