CODEWITHSUNDEEP
clinuxmemory-managementlinux-kernelkernel
ddmanlin
ddmanlin

Reputation: 41

Use do_mmap() in Linux device driver

The device we work at now need to have a user space virtual memory address, we try to use do_mmap() as below:

*uvaddr = (void *)do_mmap(0, 0, size, PROT_READ|PROT_WRITE, MAP_ANONYMOUS, 0);

But we got following error

Unable to handle kernel paging request for data at ad8

Is it okay to use "do_mmap()" in a device driver? If not, any correct way to do it?

Upvotes: 4

Views: 2324

Answers (1)

Adrian Cox
Adrian Cox

Reputation: 6334

It's possible that do_mmap is succeeding, but uvaddr does not point to a valid location to store the result. To check this for sure, do something like:

void *mmap_result;
printk(KERN_DEBUG "uvaddr = %p", uvaddr);
mmap_result = (void *)do_mmap(0, 0, size, PROT_READ|PROT_WRITE, MAP_ANONYMOUS, 0);
printk(KERN_DEBUG "mmap_result = %p", mmap_result);
*uvaddr = mmap_result;

This should tell you for certain which is failing: the call to do_mmap or the assignment to *uvaddr.

Upvotes: 1

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