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-rw-r--r--Documentation/printk-formats.txt18
-rw-r--r--lib/vsprintf.c18
-rwxr-xr-xscripts/checkpatch.pl2
3 files changed, 36 insertions, 2 deletions
diff --git a/Documentation/printk-formats.txt b/Documentation/printk-formats.txt
index b4e668ac4fe3..aa0a776c817a 100644
--- a/Documentation/printk-formats.txt
+++ b/Documentation/printk-formats.txt
@@ -49,7 +49,8 @@ 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.
+space. On 64 bit machines the first 32 bits are zeroed. If you _really_
+want the address see %px below.
::
@@ -106,6 +107,21 @@ For printing kernel pointers which should be hidden from unprivileged
users. The behaviour of ``%pK`` depends on the ``kptr_restrict sysctl`` - see
Documentation/sysctl/kernel.txt for more details.
+Unmodified Addresses
+====================
+
+::
+
+ %px 01234567 or 0123456789abcdef
+
+For printing pointers when you _really_ want to print the address. Please
+consider whether or not you are leaking sensitive information about the
+Kernel layout in memory before printing pointers with %px. %px is
+functionally equivalent to %lx. %px is preferred to %lx because it is more
+uniquely grep'able. If, in the future, we need to modify the way the Kernel
+handles printing pointers it will be nice to be able to find the call
+sites.
+
Struct Resources
================
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index d69452a0f2fa..d960aead0336 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -1646,6 +1646,20 @@ char *device_node_string(char *buf, char *end, struct device_node *dn,
return widen_string(buf, buf - buf_start, end, spec);
}
+static noinline_for_stack
+char *pointer_string(char *buf, char *end, const void *ptr,
+ struct printf_spec spec)
+{
+ spec.base = 16;
+ spec.flags |= SMALL;
+ if (spec.field_width == -1) {
+ spec.field_width = 2 * sizeof(ptr);
+ spec.flags |= ZEROPAD;
+ }
+
+ return number(buf, end, (unsigned long int)ptr, spec);
+}
+
static bool have_filled_random_ptr_key __read_mostly;
static siphash_key_t ptr_key __read_mostly;
@@ -1818,6 +1832,8 @@ static char *ptr_to_id(char *buf, char *end, void *ptr, struct printf_spec spec)
* c major compatible string
* C full compatible string
*
+ * - 'x' For printing the address. Equivalent to "%lx".
+ *
* ** Please update also Documentation/printk-formats.txt when making changes **
*
* Note: The difference between 'S' and 'F' is that on ia64 and ppc64
@@ -1940,6 +1956,8 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
case 'F':
return device_node_string(buf, end, ptr, spec, fmt + 1);
}
+ case 'x':
+ return pointer_string(buf, end, ptr, spec);
}
/* default is to _not_ leak addresses, hash before printing */
diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 95cda3ecc66b..040aa79e1d9d 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -5753,7 +5753,7 @@ sub process {
for (my $count = $linenr; $count <= $lc; $count++) {
my $fmt = get_quoted_string($lines[$count - 1], raw_line($count, 0));
$fmt =~ s/%%//g;
- if ($fmt =~ /(\%[\*\d\.]*p(?![\WFfSsBKRraEhMmIiUDdgVCbGNO]).)/) {
+ if ($fmt =~ /(\%[\*\d\.]*p(?![\WFfSsBKRraEhMmIiUDdgVCbGNOx]).)/) {
$bad_extension = $1;
last;
}