BACKPORT: vsprintf: add printk specifier %px
printk specifier %p now hashes all addresses before printing. Sometimes
we need to see the actual unmodified address. This can be achieved using
%lx but then we face the risk that if in future we want to change the
way the Kernel handles printing of pointers we will have to grep through
the already existent 50 000 %lx call sites. Let's add specifier %px as a
clear, opt-in, way to print a pointer and maintain some level of
isolation from all the other hex integer output within the Kernel.
Add printk specifier %px to print the actual unmodified address.
Signed-off-by: Tobin C. Harding <me@tobin.cc>
(cherry picked from commit 7b1924a1d930eb27fc79c4e4e2a6c1c970623e68)
Signed-off-by: Sandeep Patil <sspatil@android.com>
Bug: 78533979
Test: Build and boot cuttlefish
Change-Id: I735db3b72abb318f535d55122f1745d0ead0dbe7
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index ced3289..43f9b90 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -1522,6 +1522,20 @@
return format_flags(buf, end, flags, names);
}
+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;
@@ -1681,6 +1695,8 @@
* g gfp flags (GFP_* and __GFP_*) given as pointer to gfp_t
* v vma flags (VM_*) given as pointer to unsigned long
*
+ * - '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
@@ -1798,6 +1814,8 @@
case 'G':
return flags_string(buf, end, ptr, fmt);
+ case 'x':
+ return pointer_string(buf, end, ptr, spec);
}
/* default is to _not_ leak addresses, hash before printing */