vsprintf: add support for '%pS' and '%pF' pointer formats
They print out a pointer in symbolic format, if possible (ie using
symbolic KALLSYMS information). The '%pS' format is for regular direct
pointers (which can point to data or code and that you find on the stack
during backtraces etc), while '%pF' is for C function pointer types.
On most architectures, the two mean exactly the same thing, but some
architectures use an indirect pointer for C function pointers, where the
function pointer points to a function descriptor (which in turn contains
the actual pointer to the code). The '%pF' code automatically does the
appropriate function descriptor dereference on such architectures.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 5d6f071..1dc2d1d 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -22,6 +22,8 @@
#include <linux/string.h>
#include <linux/ctype.h>
#include <linux/kernel.h>
+#include <linux/kallsyms.h>
+#include <linux/uaccess.h>
#include <asm/page.h> /* for PAGE_SIZE */
#include <asm/div64.h>
@@ -511,15 +513,52 @@
return buf;
}
+static inline void *dereference_function_descriptor(void *ptr)
+{
+#if defined(CONFIG_IA64) || defined(CONFIG_PPC64)
+ void *p;
+ if (!probe_kernel_address(ptr, p))
+ ptr = p;
+#endif
+ return ptr;
+}
+
+static char *symbol_string(char *buf, char *end, void *ptr, int field_width, int precision, int flags)
+{
+ unsigned long value = (unsigned long) ptr;
+#ifdef CONFIG_KALLSYMS
+ char sym[KSYM_SYMBOL_LEN];
+ sprint_symbol(sym, value);
+ return string(buf, end, sym, field_width, precision, flags);
+#else
+ field_width = 2*sizeof(void *);
+ flags |= SPECIAL | SMALL | ZEROPAD;
+ return number(buf, end, value, 16, field_width, precision, flags);
+#endif
+}
+
/*
* Show a '%p' thing. A kernel extension is that the '%p' is followed
* by an extra set of alphanumeric characters that are extended format
* specifiers.
*
- * Right now don't actually handle any such, but we will..
+ * Right now we just handle 'F' (for symbolic Function descriptor pointers)
+ * and 'S' (for Symbolic direct pointers), but this can easily be
+ * extended in the future (network address types etc).
+ *
+ * The difference between 'S' and 'F' is that on ia64 and ppc64 function
+ * pointers are really function descriptors, which contain a pointer the
+ * real address.
*/
static char *pointer(const char *fmt, char *buf, char *end, void *ptr, int field_width, int precision, int flags)
{
+ switch (*fmt) {
+ case 'F':
+ ptr = dereference_function_descriptor(ptr);
+ /* Fallthrough */
+ case 'S':
+ return symbol_string(buf, end, ptr, field_width, precision, flags);
+ }
flags |= SMALL;
if (field_width == -1) {
field_width = 2*sizeof(void *);