On Sat, Dec 13, 2003 at 05:41:16PM -0800, Linus Torvalds wrote: > > On Sat, 13 Dec 2003, Jamie Lokier wrote: > > > > Peter Horton wrote: > > > A quick look at sparc and sparc64 seem to show the same problem. > > > > D-cache incoherence with unsuitably aligned multiple MAP_FIXED > > mappings is also observed on SH4, SH5, PA-RISC 1.1d. The kernel may > > have the same behaviour on those platforms: allowing a mapping that > > should not be allowed. > > Why? > > If the user asks for it, it's the users own damn fault. Nobody guarantees > cache coherency to users who require fixed addresses. > > Just document it as a bug in the user program if this causes problems. > Don't blame the kernel - the kernel is only doing what the user asked it > to do. > I've seen code written for X86 use MAP_FIXED to create self wrapping ring buffers. Surely it's better to fail the mmap() on other archs rather than for the code to fail in unexpected ways? It's a bug either way ... either the test should be fixed up or it should be removed from arch_get_unmapped_area() to save confusion. P.
