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Commit 0fe1ef24 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

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: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 4d8a743c

lib/vsprintf.c

+40 −1
Original line number Original line Diff line number Diff line
@@ -22,6 +22,8 @@ 
#include <linux/string.h>

#include <linux/string.h>

#include <linux/ctype.h>

#include <linux/ctype.h>

#include <linux/kernel.h>

#include <linux/kernel.h>

#include <linux/kallsyms.h>

#include <linux/uaccess.h>





#include <asm/page.h>		/* for PAGE_SIZE */

#include <asm/page.h>		/* for PAGE_SIZE */

#include <asm/div64.h>

#include <asm/div64.h>
@@ -511,15 +513,52 @@ static char *string(char *buf, char *end, char *s, int field_width, int precisio 
	return buf;

	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

 * Show a '%p' thing.  A kernel extension is that the '%p' is followed

 * by an extra set of alphanumeric characters that are extended format

 * by an extra set of alphanumeric characters that are extended format

 * specifiers.

 * 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)

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;

	flags |= SMALL;

	if (field_width == -1) {

	if (field_width == -1) {

		field_width = 2*sizeof(void *);

		field_width = 2*sizeof(void *);