linux-kernel - [PATCH 1/5] tools: Add err.h with ERR_PTR PTR

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Date:	Mon,  7 Sep 2015 10:38:03 +0200
From:	Jiri Olsa <jolsa@...nel.org>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	David Ahern <dsahern@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Matt Fleming <matt@...eblueprint.co.uk>,
	Raphaël Beamonte <raphael.beamonte@...il.com>
Subject: [PATCH 1/5] 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.

Link: http://lkml.kernel.org/n/tip-ufgnyf683uab69anmmrabgdf@git.kernel.org
Signed-off-by: Jiri Olsa <jolsa@...nel.org>
---
 tools/include/linux/err.h | 49 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)
 create mode 100644 tools/include/linux/err.h

diff --git a/tools/include/linux/err.h b/tools/include/linux/err.h
new file mode 100644
index 000000000000..c9ada48f5156
--- /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 */
-- 
2.4.3

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