[PATCH 1/2] [v2] lib/hexdump: introduce DUMP_PREFIX_UNHASHED for unhashed addresses

[PATCH 1/2] [v2] lib/hexdump: introduce DUMP_PREFIX_UNHASHED for unhashed addresses

[Timur Tabi]

Hashed addresses are useless in hexdumps unless you're comparing
with other hashed addresses, which is unlikely.  However, there's
no need to break existing code, so introduce a new prefix type
that prints unhashed addresses.

Signed-off-by: Timur Tabi <timur@kernel.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Roman Fietze <roman.fietze@magna.com>
---
 fs/seq_file.c          | 3 +++
 include/linux/printk.h | 8 +++++---
 lib/hexdump.c          | 9 +++++++--
 lib/seq_buf.c          | 9 +++++++--
 4 files changed, 22 insertions(+), 7 deletions(-)

diff --git a/fs/seq_file.c b/fs/seq_file.c
index 03a369ccd28c..b5b49a855894 100644
--- a/fs/seq_file.c
+++ b/fs/seq_file.c
@@ -864,6 +864,9 @@ void seq_hex_dump(struct seq_file *m, const char *prefix_str, int prefix_type,
 		remaining -= rowsize;
 
 		switch (prefix_type) {
+		case DUMP_PREFIX_UNHASHED:
+			seq_printf(m, "%s%px: ", prefix_str, ptr + i);
+			break;
 		case DUMP_PREFIX_ADDRESS:
 			seq_printf(m, "%s%p: ", prefix_str, ptr + i);
 			break;
diff --git a/include/linux/printk.h b/include/linux/printk.h
index fe7eb2351610..d3c08095a9a3 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -567,7 +567,8 @@ extern const struct file_operations kmsg_fops;
 enum {
 	DUMP_PREFIX_NONE,
 	DUMP_PREFIX_ADDRESS,
-	DUMP_PREFIX_OFFSET
+	DUMP_PREFIX_OFFSET,
+	DUMP_PREFIX_UNHASHED,
 };
 extern int hex_dump_to_buffer(const void *buf, size_t len, int rowsize,
 			      int groupsize, char *linebuf, size_t linebuflen,
@@ -612,8 +613,9 @@ static inline void print_hex_dump_debug(const char *prefix_str, int prefix_type,
  * 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)
+ * @prefix_type: controls whether prefix of an offset, hashed address,
+ *  unhashed address, or none is printed (%DUMP_PREFIX_OFFSET,
+ *  %DUMP_PREFIX_ADDRESS, %DUMP_PREFIX_UNHASHED, %DUMP_PREFIX_NONE)
  * @buf: data blob to dump
  * @len: number of bytes in the @buf
  *
diff --git a/lib/hexdump.c b/lib/hexdump.c
index 9301578f98e8..b5acfc4168a8 100644
--- a/lib/hexdump.c
+++ b/lib/hexdump.c
@@ -211,8 +211,9 @@ EXPORT_SYMBOL(hex_dump_to_buffer);
  * @level: kernel log level (e.g. KERN_DEBUG)
  * @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)
+ * @prefix_type: controls whether prefix of an offset, hashed address,
+ *  unhashed address, or none is printed (%DUMP_PREFIX_OFFSET,
+ *  %DUMP_PREFIX_ADDRESS, %DUMP_PREFIX_UNHASHED, %DUMP_PREFIX_NONE)
  * @rowsize: number of bytes to print per line; must be 16 or 32
  * @groupsize: number of bytes to print at a time (1, 2, 4, 8; default = 1)
  * @buf: data blob to dump
@@ -256,6 +257,10 @@ void print_hex_dump(const char *level, const char *prefix_str, int prefix_type,
 				   linebuf, sizeof(linebuf), ascii);
 
 		switch (prefix_type) {
+		case DUMP_PREFIX_UNHASHED:
+			printk("%s%s%px: %s\n",
+			       level, prefix_str, ptr + i, linebuf);
+			break;
 		case DUMP_PREFIX_ADDRESS:
 			printk("%s%s%p: %s\n",
 			       level, prefix_str, ptr + i, linebuf);
diff --git a/lib/seq_buf.c b/lib/seq_buf.c
index 707453f5d58e..017c4d7e93f1 100644
--- a/lib/seq_buf.c
+++ b/lib/seq_buf.c
@@ -335,8 +335,9 @@ int seq_buf_to_user(struct seq_buf *s, char __user *ubuf, int cnt)
  * @s: seq_buf descriptor
  * @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)
+ * @prefix_type: controls whether prefix of an offset, hashed address,
+ *  unhashed address, or none is printed (%DUMP_PREFIX_OFFSET,
+ *  %DUMP_PREFIX_ADDRESS, %DUMP_PREFIX_UNHASHED, %DUMP_PREFIX_NONE)
  * @rowsize: number of bytes to print per line; must be 16 or 32
  * @groupsize: number of bytes to print at a time (1, 2, 4, 8; default = 1)
  * @buf: data blob to dump
@@ -374,6 +375,10 @@ int seq_buf_hex_dump(struct seq_buf *s, const char *prefix_str, int prefix_type,
 				   linebuf, sizeof(linebuf), ascii);
 
 		switch (prefix_type) {
+		case DUMP_PREFIX_UNHASHED:
+			ret = seq_buf_printf(s, "%s%px: %s\n",
+			       prefix_str, ptr + i, linebuf);
+			break;
 		case DUMP_PREFIX_ADDRESS:
 			ret = seq_buf_printf(s, "%s%p: %s\n",
 			       prefix_str, ptr + i, linebuf);
-- 
2.25.1

Re: [PATCH 1/2] [v2] lib/hexdump: introduce DUMP_PREFIX_UNHASHED for unhashed addresses

[Andy Shevchenko]

On Sun, Jan 17, 2021 at 12:12 AM Timur Tabi <timur@kernel.org> wrote:

(Hint: -v<n> to the git format-patch will create a versioned subject
prefix for you automatically)

> Hashed addresses are useless in hexdumps unless you're comparing
> with other hashed addresses, which is unlikely.  However, there's
> no need to break existing code, so introduce a new prefix type
> that prints unhashed addresses.

Any user of this? (For the record, I don't see any other mail except this one)

...

>  enum {
>         DUMP_PREFIX_NONE,
>         DUMP_PREFIX_ADDRESS,
> -       DUMP_PREFIX_OFFSET
> +       DUMP_PREFIX_OFFSET,
> +       DUMP_PREFIX_UNHASHED,

Since it's an address, I would like to group them together, i.e. put
after DUMP_PREFIX_ADDRESS.
Perhaps even add _ADDRESS to DUMP_PREFIX_UNHASHED, but this maybe too long.

>  };

...

> + * @prefix_type: controls whether prefix of an offset, hashed address,
> + *  unhashed address, or none is printed (%DUMP_PREFIX_OFFSET,
> + *  %DUMP_PREFIX_ADDRESS, %DUMP_PREFIX_UNHASHED, %DUMP_PREFIX_NONE)

Yeah, exactly, here you use different ordering.

...

> + * @prefix_type: controls whether prefix of an offset, hashed address,
> + *  unhashed address, or none is printed (%DUMP_PREFIX_OFFSET,
> + *  %DUMP_PREFIX_ADDRESS, %DUMP_PREFIX_UNHASHED, %DUMP_PREFIX_NONE)

In both cases I would rather use colon and list one per line. What do you think?

...

> +               case DUMP_PREFIX_UNHASHED:

Here is a third type of ordering, can you please be consistent?

>                 case DUMP_PREFIX_ADDRESS:

...

> + * @prefix_type: controls whether prefix of an offset, hashed address,
> + *  unhashed address, or none is printed (%DUMP_PREFIX_OFFSET,
> + *  %DUMP_PREFIX_ADDRESS, %DUMP_PREFIX_UNHASHED, %DUMP_PREFIX_NONE)

As above.

...

> +               case DUMP_PREFIX_UNHASHED:

As above.

>                 case DUMP_PREFIX_ADDRESS:


-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH 1/2] [v2] lib/hexdump: introduce DUMP_PREFIX_UNHASHED for unhashed addresses

[Timur Tabi]

On 1/18/21 4:03 AM, Andy Shevchenko wrote:
> On Sun, Jan 17, 2021 at 12:12 AM Timur Tabi <timur@kernel.org> wrote:
> 
> (Hint: -v<n> to the git format-patch will create a versioned subject
> prefix for you automatically)

I like to keep the version in the git repo  itself so that I don't need 
to keep track of it separately, but thanks for the hint.  I might use it 
somewhere else.

>> Hashed addresses are useless in hexdumps unless you're comparing
>> with other hashed addresses, which is unlikely.  However, there's
>> no need to break existing code, so introduce a new prefix type
>> that prints unhashed addresses.
> 
> Any user of this? (For the record, I don't see any other mail except this one)

It's patch #2 of this set.  They were all sent together.

http://lkml.iu.edu/hypermail/linux/kernel/2101.2/00245.html

Let me know what you think.

>>          DUMP_PREFIX_NONE,
>>          DUMP_PREFIX_ADDRESS,
>> -       DUMP_PREFIX_OFFSET
>> +       DUMP_PREFIX_OFFSET,
>> +       DUMP_PREFIX_UNHASHED,
> 
> Since it's an address, I would like to group them together, i.e. put
> after DUMP_PREFIX_ADDRESS.

I didn't want to change the numbering of any existing enums, just in 
case there are users that accidentally hard-code the values.  I'm trying 
to make this patch as unobtrusive as possible.

 > Perhaps even add _ADDRESS to DUMP_PREFIX_UNHASHED, but this maybe too 
long.

I think DUMP_PREFIX_ADDRESS_UNHASHED is too long.

>> + * @prefix_type: controls whether prefix of an offset, hashed address,
>> + *  unhashed address, or none is printed (%DUMP_PREFIX_OFFSET,
>> + *  %DUMP_PREFIX_ADDRESS, %DUMP_PREFIX_UNHASHED, %DUMP_PREFIX_NONE)
> 
> Yeah, exactly, here you use different ordering.

That's because it's a comment.

>> + * @prefix_type: controls whether prefix of an offset, hashed address,
>> + *  unhashed address, or none is printed (%DUMP_PREFIX_OFFSET,
>> + *  %DUMP_PREFIX_ADDRESS, %DUMP_PREFIX_UNHASHED, %DUMP_PREFIX_NONE)
> 
> In both cases I would rather use colon and list one per line. What do you think?

Hmmmm.... if I'm going to change the patch anyway, sure.

>> +               case DUMP_PREFIX_UNHASHED:
> 
> Here is a third type of ordering, can you please be consistent?
> 
>>                  case DUMP_PREFIX_ADDRESS:

Fair enough.

Re: [PATCH 1/2] [v2] lib/hexdump: introduce DUMP_PREFIX_UNHASHED for unhashed addresses

[Andy Shevchenko]

On Mon, Jan 18, 2021 at 09:57:55AM -0600, Timur Tabi wrote:
> On 1/18/21 4:03 AM, Andy Shevchenko wrote:
> > On Sun, Jan 17, 2021 at 12:12 AM Timur Tabi <timur@kernel.org> wrote:

...

> > Any user of this? (For the record, I don't see any other mail except this one)

> It's patch #2 of this set.

I haven't got that one.

> They were all sent together.

Apparently not to me.

> http://lkml.iu.edu/hypermail/linux/kernel/2101.2/00245.html
> 
> Let me know what you think.

Makes sense. Hint: use lore.kernel.org references as they are much better in
terms of provided features and patch representation.

...

> > >          DUMP_PREFIX_NONE,
> > >          DUMP_PREFIX_ADDRESS,
> > > -       DUMP_PREFIX_OFFSET
> > > +       DUMP_PREFIX_OFFSET,
> > > +       DUMP_PREFIX_UNHASHED,
> > 
> > Since it's an address, I would like to group them together, i.e. put
> > after DUMP_PREFIX_ADDRESS.
> 
> I didn't want to change the numbering of any existing enums, just in case
> there are users that accidentally hard-code the values.  I'm trying to make
> this patch as unobtrusive as possible.

But isn't it good to expose those issues (and fix them)?

...

> > Perhaps even add _ADDRESS to DUMP_PREFIX_UNHASHED, but this maybe too
> long.
> 
> I think DUMP_PREFIX_ADDRESS_UNHASHED is too long.

What about introducing new two like these:

	DUMP_PREFIX_OFFSET,
	DUMP_PREFIX_ADDRESS,
	DUMP_PREFIX_ADDR_UNHASHED,
	DUMP_PREFIX_ADDR_HASHED,

and allow people step-by-step move to them?

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH 1/2] [v2] lib/hexdump: introduce DUMP_PREFIX_UNHASHED for unhashed addresses

[Timur Tabi]

On 1/18/21 11:14 AM, Andy Shevchenko wrote:
> But isn't it good to expose those issues (and fix them)?

I suppose.

>>> Perhaps even add _ADDRESS to DUMP_PREFIX_UNHASHED, but this maybe too
>> long.
>>
>> I think DUMP_PREFIX_ADDRESS_UNHASHED is too long.
> What about introducing new two like these:
> 
> 	DUMP_PREFIX_OFFSET,
> 	DUMP_PREFIX_ADDRESS,
> 	DUMP_PREFIX_ADDR_UNHASHED,
> 	DUMP_PREFIX_ADDR_HASHED,

I think we're approaching bike-shedding.  DUMP_PREFIX_ADDR_HASHED and 
DUMP_PREFIX_ADDRESS are the same thing.

I don't want people to have to move from DUMP_PREFIX_ADDRESS to some 
other enum for no change in functionality.  I'm willing to rearrange the 
code so that it's enumerated more consistently, but I don't think 
there's anything wrong with DUMP_PREFIX_UNHASHED.  It's succinct and clear.