wrapper/splice.c

   1 /* SPDX-License-Identifier: (GPL-2.0 or LGPL-2.1)
   2  *
   3  * wrapper/splice.c
   4  *
   5  * wrapper around splice_to_pipe. Using KALLSYMS to get its address when
   6  * available, else we need to have a kernel that exports this function to GPL
   7  * modules. The export was introduced in kernel 4.2.
   8  *
   9  * Copyright (C) 2011-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  10  */
  11
  12 #include <lttng-kernel-version.h>
  13
  14 #if (defined(CONFIG_KALLSYMS) \
  15         && (LINUX_VERSION_CODE < KERNEL_VERSION(4,2,0)))
  16
  17 #include <linux/kallsyms.h>
  18 #include <linux/fs.h>
  19 #include <linux/splice.h>
  20 #include <wrapper/kallsyms.h>
  21
  22 static
  23 ssize_t (*splice_to_pipe_sym)(struct pipe_inode_info *pipe,
  24                               struct splice_pipe_desc *spd);
  25
  26 ssize_t wrapper_splice_to_pipe(struct pipe_inode_info *pipe,
  27                                struct splice_pipe_desc *spd)
  28 {
  29         if (!splice_to_pipe_sym)
  30                 splice_to_pipe_sym = (void *) kallsyms_lookup_funcptr("splice_to_pipe");
  31         if (splice_to_pipe_sym) {
  32                 return splice_to_pipe_sym(pipe, spd);
  33         } else {
  34                 printk_once(KERN_WARNING "LTTng: splice_to_pipe symbol lookup failed.\n");
  35                 return -ENOSYS;
  36         }
  37 }
  38
  39 /*
  40  * Canary function to check for 'splice_to_pipe()' at compile time.
  41  *
  42  * From 'include/linux/splice.h':
  43  *
  44  *   extern ssize_t splice_to_pipe(struct pipe_inode_info *,
  45  *                                 struct splice_pipe_desc *spd);
  46  */
  47 __attribute__((unused)) static
  48 ssize_t __canary__splice_to_pipe(struct pipe_inode_info *pipe,
  49                                 struct splice_pipe_desc *spd)
  50 {
  51         return splice_to_pipe(pipe, spd);
  52 }
  53
  54 #else
  55
  56 #include <linux/fs.h>
  57 #include <linux/splice.h>
  58
  59 ssize_t wrapper_splice_to_pipe(struct pipe_inode_info *pipe,
  60                                struct splice_pipe_desc *spd)
  61 {
  62         return splice_to_pipe(pipe, spd);
  63 }
  64
  65 #endif