mm: handle mmap() for device files

src/memory/mmap.c

@@ -9,10 +9,12 @@
 #include <stdlib.h>
 #include <string.h>
 #include <sys/types.h>
+#include <kernel/logger.h>
 #include <kernel/memory.h>
 #include <kernel/file.h>
 #include <kernel/sched.h>
 #include <kernel/servers.h>
+#include <platform/platform.h>
 
 /* mmap(): creates a memory mapping for a file descriptor
  * params: t - calling thread
@@ -60,4 +62,52 @@ void *mmap(Thread *t, uint64_t id, void *addr, size_t len, int prot, int flags,
     int status = requestServer(t, command);
     free(command);
     return (void *) (intptr_t) status;
+}
+
+/* mmapHandle(): handler for mmap() response message from a driver
+ * params: msg - response message
+ * params: req - relevant system call request
+ * returns: nothing
+ */
+
+void mmapHandle(MmapCommand *msg, SyscallRequest *req) {
+    struct MmapSyscallParams *p = (struct MmapSyscallParams *) req->params[0];
+
+    if(msg->responseType) {
+        /* memory-mapped device file */
+        size_t pageCount = (msg->len+PAGE_SIZE-1) / PAGE_SIZE;
+        int pageFlags = PLATFORM_PAGE_PRESENT | PLATFORM_PAGE_USER;
+        if(msg->prot & PROT_WRITE) pageFlags |= PLATFORM_PAGE_WRITE;
+        if(msg->prot & PROT_EXEC) pageFlags |= PLATFORM_PAGE_EXEC;
+
+        // allocate one extra page for the mmap() header so we can unmap later
+        // the difference between this and malloc() is that this must always be
+        // page-aligned to comply with POSIX
+        uintptr_t base = vmmAllocate(USER_MMIO_BASE, USER_LIMIT_ADDRESS, pageCount+1, VMM_USER | VMM_WRITE);
+        if(!base) {
+            req->ret = -ENOMEM;
+            return;
+        }
+
+        MmapHeader *header = (MmapHeader *) base;
+        header->device = true;
+        header->fd = p->fd;
+        header->flags = p->flags;
+        header->length = msg->len;
+        header->offset = msg->off;
+        header->prot = msg->prot;
+        header->pid = req->thread->pid;
+        header->tid = req->thread->tid;
+
+        base += PAGE_SIZE;      // skip over to the next page
+
+        for(size_t i = 0; i < pageCount; i++)
+            platformMapPage(base + (i*PAGE_SIZE), msg->mmio + (i*PAGE_SIZE), pageFlags);
+
+        req->ret = base;
+    } else {
+        /* memory-mapped regular file */
+        KWARN("TODO: implement memory-mapped regular files\n");
+        req->ret = -ENOSYS;
+    }
 }