dynamic_debug: dynamic hex dump

Introduce print_hex_dump_debug() that can be dynamically controlled, similar to
pr_debug.

Also, make print_hex_dump_bytes() dynamically controlled

Implement only 'p' flag (_DPRINTK_FLAGS_PRINT) to keep it simple since hex dump prints
multiple lines and long prefix would impact readability.
To provide line/file etc. information, use pr_debug or similar
before/after print_hex_dump_debug()

Signed-off-by: Vladimir Kondratiev <[e-mail]>
Signed-off-by: Jason Baron <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

Documentation/dynamic-debug-howto.txt

···
 
 Dynamic debug is designed to allow you to dynamically enable/disable
 kernel code to obtain additional kernel information.  Currently, if
-CONFIG_DYNAMIC_DEBUG is set, then all pr_debug()/dev_dbg() calls can
-be dynamically enabled per-callsite.
+CONFIG_DYNAMIC_DEBUG is set, then all pr_debug()/dev_dbg() and
+print_hex_dump_debug()/print_hex_dump_bytes() calls can be dynamically
+enabled per-callsite.
+
+If CONFIG_DYNAMIC_DEBUG is not set, print_hex_dump_debug() is just
+shortcut for print_hex_dump(KERN_DEBUG).
+
+For print_hex_dump_debug()/print_hex_dump_bytes(), format string is
+its 'prefix_str' argument, if it is constant string; or "hexdump"
+in case 'prefix_str' is build dynamically.
 
 Dynamic debug has even more useful features:
 
···
   m    Include module name in the printed message
   t    Include thread ID in messages not generated from interrupt context
   _    No flags are set. (Or'd with others on input)
+
+For print_hex_dump_debug() and print_hex_dump_bytes(), only 'p' flag
+have meaning, other flags ignored.
 
 For display, the flags are preceded by '='
 (mnemonic: what the flags are currently equal to).

include/linux/dynamic_debug.h

···
 				     ##__VA_ARGS__);		\
 } while (0)
 
+#define dynamic_hex_dump(prefix_str, prefix_type, rowsize,	\
+			 groupsize, buf, len, ascii)		\
+do {								\
+	DEFINE_DYNAMIC_DEBUG_METADATA(descriptor,		\
+		__builtin_constant_p(prefix_str) ? prefix_str : "hexdump");\
+	if (unlikely(descriptor.flags & _DPRINTK_FLAGS_PRINT))	\
+		print_hex_dump(KERN_DEBUG, prefix_str,		\
+			       prefix_type, rowsize, groupsize,	\
+			       buf, len, ascii);		\
+} while (0)
+
 #else
 
 #include <linux/string.h>

include/linux/printk.h

···
 extern void print_hex_dump(const char *level, const char *prefix_str,
 			   int prefix_type, int rowsize, int groupsize,
 			   const void *buf, size_t len, bool ascii);
+#if defined(CONFIG_DYNAMIC_DEBUG)
+#define print_hex_dump_bytes(prefix_str, prefix_type, buf, len)	\
+	dynamic_hex_dump(prefix_str, prefix_type, 16, 1, buf, len, true)
+#else
 extern void print_hex_dump_bytes(const char *prefix_str, int prefix_type,
 				 const void *buf, size_t len);
+#endif /* defined(CONFIG_DYNAMIC_DEBUG) */
 #else
 static inline void print_hex_dump(const char *level, const char *prefix_str,
 				  int prefix_type, int rowsize, int groupsize,
···
 }
 
 #endif
+
+#if defined(CONFIG_DYNAMIC_DEBUG)
+#define print_hex_dump_debug(prefix_str, prefix_type, rowsize,	\
+			     groupsize, buf, len, ascii)	\
+	dynamic_hex_dump(prefix_str, prefix_type, rowsize,	\
+			 groupsize, buf, len, ascii)
+#else
+#define print_hex_dump_debug(prefix_str, prefix_type, rowsize,		\
+			     groupsize, buf, len, ascii)		\
+	print_hex_dump(KERN_DEBUG, prefix_str, prefix_type, rowsize,	\
+		       groupsize, buf, len, ascii)
+#endif /* defined(CONFIG_DYNAMIC_DEBUG) */
 
 #endif

lib/hexdump.c

···
 }
 EXPORT_SYMBOL(print_hex_dump);
 
+#if !defined(CONFIG_DYNAMIC_DEBUG)
 /**
  * print_hex_dump_bytes - shorthand form of print_hex_dump() with default params
  * @prefix_str: string to prefix each line with;
···
 		       buf, len, true);
 }
 EXPORT_SYMBOL(print_hex_dump_bytes);
-#endif
+#endif /* !defined(CONFIG_DYNAMIC_DEBUG) */
+#endif /* defined(CONFIG_PRINTK) */