nopage is obsolete in vm_operations_struct, saving

.gitignore

@@ -27,3 +27,6 @@
 *.i*86
 *.x86_64
 *.hex
+
+# editor
+*.swp

205.fault/Makefile

@@ -0,0 +1,14 @@
+# invoke as 
+#
+# make -C /path/to/kernel/source SUBDIRS=$PWD modules
+#
+# e.g.,
+# make -C /lib/modules/3.13.0-24-generic/build/ SUBDIRS=$PWD  modules
+#
+
+obj-m := kex.o
+
+rig: rig.c
+
+clean:
+	rm -f rig

205.fault/README.md

@@ -0,0 +1,47 @@
+Pagefault
+vma ops
+
+This kex module implements mmap and includes a test rig to exercise it.
+When the test rig invokes mmap on the device, kex uses alloc_page 
+to get as many pages as the rig requested. It uses vm_insert_page on
+each page to map it into rig's address space. These pages, while 
+physically disjoint, appear as a single contiguous virtual memory area
+(VMA) inside the rig address space. The VMA is visible using pmap:
+
+```
+    % ./build.sh
+    % sudo insmod kex.ko 
+    % cat /proc/devices | grep kex
+250 kex
+    % sudo mknod dev c 250 0
+    % sudo chmod a+rw dev
+    % ./rig dev 1
+pid: 10195
+press a key to exercise memory write
+```
+
+Leave the rig waiting. In another terminal run pmap. See the dev VMA:
+
+```
+    %  pmap -x 10195
+Address           Kbytes     RSS   Dirty Mode  Mapping
+00007fd0125b6000       4       4       0 rw-s- dev
+```
+
+It's 4kb because rig asked for one page (the final argument), which is 4kb.
+Now we can ask rig to write to this memory. In the original terminal, press
+enter.  Then re-run pmap in the second terminal:
+
+```
+Address           Kbytes     RSS   Dirty Mode  Mapping
+00007fd0125b6000       4       4       4 rw-s- dev
+```
+
+Notice that the Dirty column now shows the mapped page is Dirty.  (TODO: is
+this an MMU flag set on write to the page?). Press enter to terminate rig.
+
+Clean up:
+
+    % rm dev
+    % sudo rmmod kex
+    % ./build.sh clean

205.fault/build.sh

@@ -0,0 +1,10 @@
+#!/bin/bash
+KERNELHEADERS=/lib/modules/$(uname -r)/build/
+make -C ${KERNELHEADERS} SUBDIRS=$PWD $1
+
+if [ "$1" == "clean" ]
+then 
+  make clean
+else
+  make rig
+fi

205.fault/kex.c

@@ -0,0 +1,93 @@
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <asm/uaccess.h>
+#include <linux/cdev.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/fs.h>
+#include <linux/mm.h>
+
+/* module information */
+MODULE_AUTHOR("Troy D. Hanson");
+MODULE_DESCRIPTION("Example of character device");
+MODULE_LICENSE("Dual BSD/GPL");
+
+#define NUM_MINORS 1
+
+DEFINE_MUTEX(mutex);
+
+struct chardev_t {
+  dev_t dev;        /* has major and minor bits */
+  struct cdev cdev; /* has our ops, owner, etc */
+} c;
+
+static 
+struct page *fault(struct vm_area_struct *vma, unsigned long addr, int *type) {
+  struct page *page=NULL;
+  //get_page();
+  if (type) *type=VM_FAULT_MINOR;
+  return page;
+}
+
+/* ops for VMA open, close and fault. See Linux Device Drivers, 3rd ed, p427. */
+static struct vm_operations_struct vm_ops = {
+  .nopage = fault, /* page fault handler */
+};
+
+int _mmap(struct file *f, struct vm_area_struct *vma) {
+  unsigned long pages = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
+  int rc=-ENODEV;
+  printk(KERN_DEBUG "vma->vm_end %lu vm_start %lu len %lu pages %lu vm_pgoff %lu\n",
+    vma->vm_end, vma->vm_start, vma->vm_end - vma->vm_start, pages, vma->vm_pgoff);
+
+  if (0) goto done;
+  vma->vm_ops = &vm_ops;
+  vma->vm_private_data = (void*)0xa1fa1fa; /* could store private data here */
+
+  rc = 0;
+
+ done:
+  return rc;
+}
+
+struct file_operations ops = {
+  .mmap = _mmap
+};
+
+int __init chardev_init(void) {
+  int rc;
+
+  /* ask for a dynamic major */
+  rc = alloc_chrdev_region(&c.dev, 0, NUM_MINORS, "kex");
+  if (rc) { 
+    rc = -ENODEV;
+    goto done; 
+  }
+
+  /* init the struct cdev */
+  cdev_init(&c.cdev, &ops);
+  c.cdev.owner = THIS_MODULE;
+
+  /* make device live */
+  rc = cdev_add(&c.cdev, c.dev, NUM_MINORS);
+  if (rc) {
+    rc = -ENODEV;
+    printk(KERN_WARNING "cdev_add: can't add device\n");
+    unregister_chrdev_region(c.dev, NUM_MINORS);
+    cdev_del(&c.cdev);
+    goto done;
+  }
+
+  rc = 0;
+
+ done:
+  return rc;
+}
+
+void __exit chardev_cleanup(void) {
+  cdev_del(&c.cdev);
+  unregister_chrdev_region(c.dev, NUM_MINORS);
+}
+
+module_init(chardev_init);
+module_exit(chardev_cleanup);

205.fault/rig.c

@@ -0,0 +1,48 @@
+#include <stdio.h>
+#include <errno.h>
+#include <string.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+#include <sys/types.h>
+#include <sys/fcntl.h>
+
+
+int main(int argc, char * argv[]) {
+  char *file = (argc > 1) ? argv[1] : "dev";
+  int npages = (argc > 2) ? atoi(argv[2]) : 1;
+  int fd,rc=-1;
+  char *buf, *b, unused;
+  size_t len = 4096 * npages; // FIXME getpagesz
+
+  fprintf(stderr,"pid: %u\n", (int)getpid());
+
+  if ( (fd = open(file, O_RDWR)) == -1) {
+      fprintf(stderr,"can't open %s: %s\n", file, strerror(errno));
+      goto done;
+  }
+
+  buf = mmap(0, len, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
+  if (buf == MAP_FAILED) {
+    fprintf(stderr, "failed to mmap %s: %s\n", file, strerror(errno));
+    goto done;
+  }
+
+  rc = 0;
+
+  /* make the program block so we can examine it */
+
+  fprintf(stderr,"press a key to exercise memory write\n");
+  read(STDIN_FILENO,&unused,sizeof(unused));
+  for(b=buf; b < buf+len; b++) *b=1;
+
+  fprintf(stderr,"press a key to terminate\n");
+  read(STDIN_FILENO,&unused,sizeof(unused));
+
+
+ done:
+  munmap(buf, len);
+  close(fd);
+  return rc;
+}

README.md

@@ -14,4 +14,8 @@ TODO
 * ops: poll, mmap
 * kernel linked list, kfifo
 * pci, usb
-
+* kgdb
+* initramfs
+* kvm
+* net nic
+* waitqueues