> Date: Wed, 31 Oct 2018 22:01:14 +0530 > From: Siddharth Muralee <siddharth.mura...@gmail.com> > > Hello All, > I have recently been working on porting the kcov(4) feature to NetBSD. > The feature comes as a /dev module. I have been stuck for a while with the > mmap() function of the device. I have been trying to populate a buffer from > the module and then pass it to the userspace program. > > The mmap function of the device is here > <https://github.com/R3x/src/blob/32806c3abfcfb5e82d1a0c69e00749ef97fdaf21/sys/dev/kcov.c#L205> > and the function populating the buffer is here > <https://github.com/R3x/src/blob/32806c3abfcfb5e82d1a0c69e00749ef97fdaf21/sys/dev/kcov.c#L86>
There is no MI API for turning a paddr or kva into a pmap mmap cookie, which is what the struct cdev::d_mmap routine is supposed to return. For bus space, there's bus_space_mmap; for bus DMA buffers, there's bus_dmamem_mmap; but nothing that takes an arbitrary paddr or kva. The pmap_phys_address and pmap_mmap_flags functions _take_ a pmap mmap cookie and turn them into a physical address and a set of flags, but that's the reverse. For the moment, as a provisional workaround to make progress, you can probably get by with `pa << PGSHIFT', where pa is the physical (byte) address of the page you want -- but make sure to add a big scary XXX comment saying that this is not right and needs to be fixed. Beware that you'll also have to pmap_page_protect(PROT_NONE) all physical addresses in the uvm_km buffer before you can uvm_km_free, too. Not sure offhand whether this might have a bad interaction with uvm_km_free(UVM_KMF_WIRED), so be careful!
