printk: hash addresses printed with %p

[sfrench/cifs-2.6.git] / Documentation / printk-formats.txt

diff --git a/Documentation/printk-formats.txt b/Documentation/printk-formats.txt
index 71b62db7eca2843c7f4ce1928fbdefef5956c930..b4e668ac4fe33e5b6c05fdfc12266a92baabd327 100644 (file)
--- a/Documentation/printk-formats.txt
+++ b/Documentation/printk-formats.txt
@@ -5,7 +5,6 @@ How to get printk format specifiers right
 :Author: Randy Dunlap <rdunlap@infradead.org>
 :Author: Andrew Murray <amurray@mpc-data.co.uk>
 
-
 Integer types
 =============
 
@@ -45,6 +44,17 @@ return from vsnprintf.
 Raw pointer value SHOULD be printed with %p. The kernel supports
 the following extended format specifiers for pointer types:
 
+Pointer Types
+=============
+
+Pointers printed without a specifier extension (i.e unadorned %p) are
+hashed to give a unique identifier without leaking kernel addresses to user
+space. On 64 bit machines the first 32 bits are zeroed.
+
+::
+
+       %p      abcdef12 or 00000000abcdef12
+
 Symbols/Function Pointers
 =========================