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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: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Stephen Boyd 2019-09-25 16:46:29 -07:00 committed by Linus Torvalds
parent 8e72a7a44d
commit 091cb0994e
2 changed files with 15 additions and 28 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
include/linux/printk.h
View File

@ -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

21
lib/hexdump.c
View File

@ -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) */