syscall: add Mmap tests

syscall: add Mmap tests Update issue 4929 A followup CL will add syscall constants and enable this test for for the remaining UNIX platforms.

[cookieo9, 2013-03-01 02:13:19]

https://codereview.appspot.com/7432046/diff/5001/src/pkg/syscall/mmap_test.go File src/pkg/syscall/mmap_test.go (right): https://codereview.appspot.com/7432046/diff/5001/src/pkg/syscall/mmap_test.go... src/pkg/syscall/mmap_test.go:23: _ = syscall.MAP_ANONYMOUS darwin doesn't have MAP_ANONYMOUS; it does have MAP_ANON which serves a similar purpose (allocate memory). These tests fail to compile as a result. http://developer.apple.com/library/mac/#documentation/Darwin/Reference/ManPag... bsds work the same way: http://www.unix.com/man-page/FreeBSD/2/mmap/ However, at least my version of FreeBSD (9.1) defines MAP_ANONYMOUS as identical to MAP_ANON. I'm not sure of the others.

[minux1, 2013-03-02 19:10:09]

https://codereview.appspot.com/7432046/diff/5001/src/pkg/syscall/mmap_test.go File src/pkg/syscall/mmap_test.go (right): https://codereview.appspot.com/7432046/diff/5001/src/pkg/syscall/mmap_test.go... src/pkg/syscall/mmap_test.go:54: n, err := f.Write(make([]byte, 8192)) // larger than a page use syscall.Getpagesize()? https://codereview.appspot.com/7432046/diff/5001/src/pkg/syscall/mmap_test.go... src/pkg/syscall/mmap_test.go:63: b, err := syscall.Mmap(fd, 0, n, tt.prot, tt.flag) perhaps we could verify &b[0] is a valid address (and aligned to page size)?