Hi! > > [projected buffers]
On Sat, 27 Aug 2011 19:14:06 +0200, Samuel Thibault <samuel.thiba...@gnu.org>
wrote:
> Ah, right (hard to answer sanely while following the GHM). Well, anyway,
> grepping through the whole hurd+gnumach+glibc code didn't show any use
> of this.
In fact, this projected buffer interface is not even exported from GNU
Mach. I quickly created an (untested) patch to completely remove the
code.
But: perhaps this functionality can be userful for user-space device
drivers? For DMA, for example?
vm/vm_kern.c:
/*
* projected_buffer_allocate
*
* Allocate a wired-down buffer shared between kernel and user task.
* Fresh, zero-filled memory is allocated.
* If persistence is false, this buffer can only be deallocated from
* user task using projected_buffer_deallocate, and deallocation
* from user task also deallocates the buffer from the kernel map.
* projected_buffer_collect is called from vm_map_deallocate to
* automatically deallocate projected buffers on task_deallocate.
* Sharing with more than one user task is achieved by using
* projected_buffer_map for the second and subsequent tasks.
* The user is precluded from manipulating the VM entry of this buffer
* (i.e. changing protection, inheritance or machine attributes).
*/
kern_return_t
projected_buffer_allocate(map, size, persistence, kernel_p,
user_p, protection, inheritance)
vm_map_t map;
vm_size_t size;
int persistence;
vm_offset_t *kernel_p;
vm_offset_t *user_p;
vm_prot_t protection;
vm_inherit_t inheritance; /*Currently only VM_INHERIT_NONE
supported*/
[...]
/*
* projected_buffer_map
*
* Map an area of kernel memory onto a task's address space.
* No new memory is allocated; the area must previously exist in the
* kernel memory map.
*/
kern_return_t
projected_buffer_map(map, kernel_addr, size, user_p, protection,
inheritance)
vm_map_t map;
vm_offset_t kernel_addr;
vm_size_t size;
vm_offset_t *user_p;
vm_prot_t protection;
vm_inherit_t inheritance; /*Currently only VM_INHERIT_NONE
supported*/
[...]
/*
* projected_buffer_deallocate
*
* Unmap projected buffer from task's address space.
* May also unmap buffer from kernel map, if buffer is not
* persistent and only the kernel reference remains.
*/
kern_return_t
projected_buffer_deallocate(map, start, end)
vm_map_t map;
vm_offset_t start, end;
Grüße,
Thomas
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