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Subject[q] fundamental thing I am still missing about put_user().

I have a question about writing to userspace buffers. Can I do this in
read_kmem() (read method of /dev/kmem):

if (verify_area(VERIFY_WRITE, buf, count))
return -EFAULT;
write to user buf without any worries, even taking spinlocks if needed.

If I can do this then it is very useful because we could then hold a
spinlock in mm/vmalloc.c:vread() which means vmlist can be protected by a
simple spinlock which means vmalloc()/vfree()/ioremap() (i.e. really
vfree() and get_vm_area()) can be made SMP safe, i.e. without forcing
callers to have lock/unlock_kernel().

Thank you for your patient explanation :)
Tigran A. Aivazian |
Escalations Research Group | tel: +44-(0)1923-813796
Santa Cruz Operation Ltd |

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