src/wrapper/splice.c

   1 /* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
   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 #ifdef CONFIG_KALLSYMS
  15
  16 #include <linux/kallsyms.h>
  17 #include <linux/fs.h>
  18 #include <linux/splice.h>
  19 #include <wrapper/kallsyms.h>
  20
  21 static
  22 ssize_t (*splice_to_pipe_sym)(struct pipe_inode_info *pipe,
  23                               struct splice_pipe_desc *spd);
  24
  25 ssize_t wrapper_splice_to_pipe(struct pipe_inode_info *pipe,
  26                                struct splice_pipe_desc *spd)
  27 {
  28         if (!splice_to_pipe_sym)
  29                 splice_to_pipe_sym = (void *) kallsyms_lookup_funcptr("splice_to_pipe");
  30         if (splice_to_pipe_sym) {
  31                 return splice_to_pipe_sym(pipe, spd);
  32         } else {
  33                 printk_once(KERN_WARNING "LTTng: splice_to_pipe symbol lookup failed.\n");
  34                 return -ENOSYS;
  35         }
  36 }
  37
  38 /*
  39  * Canary function to check for 'splice_to_pipe()' at compile time.
  40  *
  41  * From 'include/linux/splice.h':
  42  *
  43  *   extern ssize_t splice_to_pipe(struct pipe_inode_info *,
  44  *                                 struct splice_pipe_desc *spd);
  45  */
  46 __attribute__((unused)) static
  47 ssize_t __canary__splice_to_pipe(struct pipe_inode_info *pipe,
  48                                 struct splice_pipe_desc *spd)
  49 {
  50         return splice_to_pipe(pipe, spd);
  51 }
  52
  53 #else
  54
  55 #include <linux/fs.h>
  56 #include <linux/splice.h>
  57
  58 ssize_t wrapper_splice_to_pipe(struct pipe_inode_info *pipe,
  59                                struct splice_pipe_desc *spd)
  60 {
  61         return splice_to_pipe(pipe, spd);
  62 }
  63
  64 #endif