Commit 091cb099 authored by Stephen Boyd's avatar Stephen Boyd Committed by Linus Torvalds
Browse files

lib/hexdump: make print_hex_dump_bytes() a nop on !DEBUG builds 

I'm seeing a bunch of debug prints from a user of print_hex_dump_bytes()
in my kernel logs, but I don't have CONFIG_DYNAMIC_DEBUG enabled nor do I
have DEBUG defined in my build.  The problem is that
print_hex_dump_bytes() calls a wrapper function in lib/hexdump.c that
calls print_hex_dump() with KERN_DEBUG level.  There are three cases to
consider here

  1. CONFIG_DYNAMIC_DEBUG=y  --> call dynamic_hex_dum()
  2. CONFIG_DYNAMIC_DEBUG=n && DEBUG --> call print_hex_dump()
  3. CONFIG_DYNAMIC_DEBUG=n && !DEBUG --> stub it out

Right now, that last case isn't detected and we still call
print_hex_dump() from the stub wrapper.

Let's make print_hex_dump_bytes() only call print_hex_dump_debug() so that
it works properly in all cases.

Case #1, print_hex_dump_debug() calls dynamic_hex_dump() and we get same
behavior.  Case #2, print_hex_dump_debug() calls print_hex_dump() with
KERN_DEBUG and we get the same behavior.  Case #3, print_hex_dump_debug()
is a nop, changing behavior to what we want, i.e.  print nothing.

Link: http://lkml.kernel.org/r/20190816235624.115280-1-swboyd@chromium.org


Signed-off-by: default avatarStephen Boyd <swboyd@chromium.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 8e72a7a4

include/linux/printk.h

+15 −7
Original line number Diff line number Diff line
@@ -488,13 +488,6 @@ extern int hex_dump_to_buffer(const void *buf, size_t len, int rowsize, 
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,
@@ -526,4 +519,19 @@ static inline void print_hex_dump_debug(const char *prefix_str, int prefix_type, 
}

#endif



/**

 * print_hex_dump_bytes - shorthand form of print_hex_dump() with default params

 * @prefix_str: string to prefix each line with;

 *  caller supplies trailing spaces for alignment if desired

 * @prefix_type: controls whether prefix of an offset, address, or none

 *  is printed (%DUMP_PREFIX_OFFSET, %DUMP_PREFIX_ADDRESS, %DUMP_PREFIX_NONE)

 * @buf: data blob to dump

 * @len: number of bytes in the @buf

 *

 * Calls print_hex_dump(), with log level of KERN_DEBUG,

 * rowsize of 16, groupsize of 1, and ASCII output included.

 */

#define print_hex_dump_bytes(prefix_str, prefix_type, buf, len)	\

	print_hex_dump_debug(prefix_str, prefix_type, 16, 1, buf, len, true)



#endif

lib/hexdump.c

+0 −21
Original line number Diff line number Diff line
@@ -270,25 +270,4 @@ void print_hex_dump(const char *level, const char *prefix_str, int prefix_type, 
}

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;

 *  caller supplies trailing spaces for alignment if desired

 * @prefix_type: controls whether prefix of an offset, address, or none

 *  is printed (%DUMP_PREFIX_OFFSET, %DUMP_PREFIX_ADDRESS, %DUMP_PREFIX_NONE)

 * @buf: data blob to dump

 * @len: number of bytes in the @buf

 *

 * Calls print_hex_dump(), with log level of KERN_DEBUG,

 * rowsize of 16, groupsize of 1, and ASCII output included.

 */

void print_hex_dump_bytes(const char *prefix_str, int prefix_type,

			  const void *buf, size_t len)

{

	print_hex_dump(KERN_DEBUG, prefix_str, prefix_type, 16, 1,

		       buf, len, true);

}

EXPORT_SYMBOL(print_hex_dump_bytes);

#endif /* !defined(CONFIG_DYNAMIC_DEBUG) */

#endif /* defined(CONFIG_PRINTK) */

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