From: Jann Horn <jann@thejh.net>
Date: Sun, 19 May 2013 01:34:31 +0000 (+0200)
Subject: let the kernel module return the symbol name
X-Git-Url: http://git.thejh.net/?p=moctel.git;a=commitdiff_plain;h=d20cca0688694acb09484232ada3aa4d13ac0954

let the kernel module return the symbol name
---

diff --git a/moctel_mod.c b/moctel_mod.c
index 7498584..1273ff3 100644
--- a/moctel_mod.c
+++ b/moctel_mod.c
@@ -15,6 +15,8 @@
 #include <linux/ioctl.h>
 #include <linux/uaccess.h>
 #include <linux/miscdevice.h>
+#include <linux/kallsyms.h>
+#include <linux/blkdev.h>
 
 struct fetch_fops_args {
   int fd;
@@ -27,21 +29,29 @@ static int ioctl_open(struct inode *nodp, struct file *filp) {
   return 0;
 }
 
-static const struct file_operations dummy_fops = {};
-
 static long ioctl_ioctl(struct file *filp_, unsigned int cmd, unsigned long arg) {
   struct fetch_fops_args args;
   struct file *filp;
-  const struct file_operations *fops;
+  void *ioctl_method = NULL;
+  char ioctl_method_name[KSYM_NAME_LEN];
+  int (*lookup_symbol_name_)(unsigned long addr, char *symname);
+
+  lookup_symbol_name_ = (void*)kallsyms_lookup_name("lookup_symbol_name");
 
   if (cmd != MOCTEL_FETCH_FOPS) return -EINVAL;
+  memset(ioctl_method_name, 0, sizeof(ioctl_method_name));
   if (copy_from_user(&args, (struct fetch_fops_args __user *)arg, sizeof(args))) return -EINVAL;
   filp = fget(args.fd);
   if (!filp) return -EBADF;
-  fops = filp->f_op;
-  if (!fops) fops = &dummy_fops;
+  if (filp->f_op) ioctl_method = filp->f_op->unlocked_ioctl;
+  lookup_symbol_name_((unsigned long)ioctl_method, ioctl_method_name);
+  if (strcmp(ioctl_method_name, "block_ioctl") == 0) {
+    struct block_device *bdev = I_BDEV(filp->f_mapping->host);
+    ioctl_method = bdev->bd_disk->fops->ioctl;
+    lookup_symbol_name_((unsigned long)ioctl_method, ioctl_method_name);
+  }
   fput(filp);
-  if (copy_to_user((struct file_operations __user *)args.retp, fops, sizeof(*fops))) return -EINVAL;
+  if (copy_to_user((struct file_operations __user *)args.retp, ioctl_method_name, KSYM_NAME_LEN)) return -EINVAL;
   return 0;
 }
 
@@ -77,3 +87,5 @@ static void __exit cleanup_ioctl(void) {
 
 module_init(init_ioctl);
 module_exit(cleanup_ioctl);
+
+MODULE_LICENSE("GPL v2");
diff --git a/show_ioctl.c b/show_ioctl.c
index d83c860..8e36dbf 100644
--- a/show_ioctl.c
+++ b/show_ioctl.c
@@ -10,6 +10,8 @@
 #include <fcntl.h>
 #include <sys/ioctl.h>
 
+#define KSYM_NAME_LEN 128
+
 struct fetch_fops_args {
   int fd;
   uint64_t retp;
@@ -17,37 +19,6 @@ struct fetch_fops_args {
 
 #define MOCTEL_FETCH_FOPS _IOR('m', 1, struct fetch_fops_args)
 
-struct file_operations {
-        void *owner;
-        void *llseek;
-        void *read;
-        void *write;
-        void *aio_read;
-        void *aio_write;
-        void *readdir;
-        void *poll;
-        void *unlocked_ioctl;
-        void *compat_ioctl;
-        void *mmap;
-        void *open;
-        void *flush;
-        void *release;
-        void *fsync;
-        void *aio_fsync;
-        void *fasync;
-        void *lock;
-        void *sendpage;
-        void *get_unmapped_area;
-        void *check_flags;
-        void *flock;
-        void *splice_write;
-        void *splice_read;
-        void *setlease;
-        void *fallocate;
-};
-
-
-
 int main(int argc, char **argv) {
   if (argc != 2) fputs("Usage: show_ioctl <device>\n", stderr), exit(1);
 
@@ -58,10 +29,10 @@ int main(int argc, char **argv) {
   int ioctlfd = open("/dev/ioctl_info", O_RDONLY);
   if (ioctlfd == -1) fprintf(stderr, "Can't open /dev/ioctl_info: %m\n"), exit(1);
 
-  struct file_operations fops;
+  char resbuf[KSYM_NAME_LEN];
   struct fetch_fops_args ioctl_args = {
     .fd = devfd,
-    .retp = (uint64_t)&fops
+    .retp = (uint64_t)resbuf
   };
   int ret = ioctl(ioctlfd, MOCTEL_FETCH_FOPS, &ioctl_args);
   if (ret) fprintf(stderr, "can't perform MOCTEL_FETCH_FOPS: %m\n"), exit(1);
@@ -69,7 +40,7 @@ int main(int argc, char **argv) {
   close(ioctlfd);
   close(devfd);
 
-  printf("unlocked_ioctl: %llx\n", (unsigned long long)fops.unlocked_ioctl);
+  printf("%s\n", resbuf);
 
   return 0;
 }