Re: user_to_phys() without mmap?

Ulrich Eckhardt <doomster@xxxxxxxx> writes:
Neil Steiner wrote:

[...]

It appears that anything written into the mmap'ed user memory is in
fact being copied into kernel space.

You mean that every access causes a page fault and the performs the access
from inside the kernel? That would basically mean that the memory-mapping
was incomplete/incorrect. Hard to tell without knowing what is going
on...

Modify the kernel such that it prints the page table flags after setup
and maybe also printks whenever a fault occurs for a particular page
that is part of the area being accessed. Then access it. That should
be fairly noisy, but would easily throw light on this issue.

[...]

Just one thing though: why not use the Linux framebuffer interface?

'The Linux framebuffer interface' is nothing more than a char driver
providing mmap'ed access to some hadrware framebuffer and some
additional ioctl for mode switching.
.

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