[tip:perf/core] tools: Add err.h with ERR_PTR PTR_ERR interface

[tip-bot for Jiri Olsa]

Commit-ID:  01ca9fd41d6f2ad796a6b109b5253e06b6ae6dc7
Gitweb:     http://git.kernel.org/tip/01ca9fd41d6f2ad796a6b109b5253e06b6ae6dc7
Author:     Jiri Olsa <jolsa@xxxxxxxxxx>
AuthorDate: Mon, 7 Sep 2015 10:38:03 +0200
Committer:  Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitDate: Tue, 15 Sep 2015 09:48:32 -0300

tools: Add err.h with ERR_PTR PTR_ERR interface

Adding part of the kernel's <linux/err.h> interface:

  inline void * __must_check ERR_PTR(long error);
  inline long   __must_check PTR_ERR(__force const void *ptr);
  inline bool   __must_check IS_ERR(__force const void *ptr);

It will be used to propagate error through pointers in following
patches.

Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Reviewed-by: Raphael Beamonte <raphael.beamonte@xxxxxxxxx>
Cc: David Ahern <dsahern@xxxxxxxxx>
Cc: Matt Fleming <matt@xxxxxxxxxxxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Link: http://lkml.kernel.org/r/1441615087-13886-2-git-send-email-jolsa@xxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
 tools/include/linux/err.h | 49 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)

diff --git a/tools/include/linux/err.h b/tools/include/linux/err.h
new file mode 100644
index 0000000..c9ada48
--- /dev/null
+++ b/tools/include/linux/err.h
@@ -0,0 +1,49 @@
+#ifndef __TOOLS_LINUX_ERR_H
+#define __TOOLS_LINUX_ERR_H
+
+#include <linux/compiler.h>
+#include <linux/types.h>
+
+#include <asm/errno.h>
+
+/*
+ * Original kernel header comment:
+ *
+ * Kernel pointers have redundant information, so we can use a
+ * scheme where we can return either an error code or a normal
+ * pointer with the same return value.
+ *
+ * This should be a per-architecture thing, to allow different
+ * error and pointer decisions.
+ *
+ * Userspace note:
+ * The same principle works for userspace, because 'error' pointers
+ * fall down to the unused hole far from user space, as described
+ * in Documentation/x86/x86_64/mm.txt for x86_64 arch:
+ *
+ * 0000000000000000 - 00007fffffffffff (=47 bits) user space, different per mm hole caused by [48:63] sign extension
+ * ffffffffffe00000 - ffffffffffffffff (=2 MB) unused hole
+ *
+ * It should be the same case for other architectures, because
+ * this code is used in generic kernel code.
+ */
+#define MAX_ERRNO	4095
+
+#define IS_ERR_VALUE(x) unlikely((x) >= (unsigned long)-MAX_ERRNO)
+
+static inline void * __must_check ERR_PTR(long error)
+{
+	return (void *) error;
+}
+
+static inline long __must_check PTR_ERR(__force const void *ptr)
+{
+	return (long) ptr;
+}
+
+static inline bool __must_check IS_ERR(__force const void *ptr)
+{
+	return IS_ERR_VALUE((unsigned long)ptr);
+}
+
+#endif /* _LINUX_ERR_H */
--
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