Hi all,
I am fairly new to openbsd so if this is something obvious that I missed
please be understanding.
I am adding a syscall to openbsd 6.8. I am working on a raspberry pi.
During the syscall I allocate some memory that I want to share between the
kernel
and the calling process.
When it's time to wrap up and unmap the memory, I unmap it both from the
kernel
map and from the process map.
The unmapping from the process map goes fine, the unmapping from the kernel
map
fails by saying that the virtual address in kernel map is not aligned to
the page size
( it's actually 4 bytes off ).
What have I missed? I assumed that umm_map would return a page aligned
virtual
address for the kernel mapping as well.
Here is my code for creating the shared memory chunk:
--------------------------------------------------------------------------------
// memory_size is a multiple of page size
uvm_object = uao_create(memory_size, 0);
if(!uvm_object) return;
// TODO(ale): make sure that this memory cannot be swapped out
uao_reference(uvm_object)
if(uvm_map(kernel_map, (vaddr_t *)&memory, round_page(memory_size),
uvm_object,
0, 0, UVM_MAPFLAG(PROT_READ | PROT_WRITE, PROT_READ | PROT_WRITE,
MAP_INHERIT_SHARED, MADV_NORMAL, 0))) {
uao_detach(uvm_object);
uvm_object = 0;
return;
}
uao_reference(uvm_object);
if(uvm_map(&p->p_vmspace->vm_map, &memory_in_proc_space,
round_page(memory_size), uvm_object,
0, 0, UVM_MAPFLAG(PROT_READ | PROT_WRITE, PROT_READ | PROT_WRITE,
MAP_INHERIT_NONE, MADV_NORMAL, 0))) {
memory = 0;
uao_detach(uvm_object);
uao_detach(uvm_object);
uvm_object = 0;
return;
}
--------------------------------------------------------------------------------
Thanks,
A
