[U-Boot] hashtable lib and escaping

[U-Boot] hashtable lib and escaping

[Mats Kärrman]

Hi,

I used to have a working setup using U-Boot 2009.03 before upgrading to U-Boot 2012.07. The problem I'm facing is related to the escaping policies of lib/hashtable.c.

What I did before was for example having something like this in my default environment:

bootcmd=run first_boot
first_boot=setenv bootcmd my_select\;run ubi_boot;saveenv;boot

The trick accomplished was that the environment was saved after setting the real bootcmd (to "my_select;run ubi_boot") on first boot so that the booted OS could always be relying on a valid environment in one of the flash env partitions.

With the escape parsing of himport_r(), the '\' is simply dropped and it is no longer possible to escape ';' so the "run ubi_boot" is immediately executed and nothing is saved... The function header mentions the possibility for multi-line values but this should not come at the cost of not being able to escape ';'.

I am not sure about what other uses the escape may have or used to have so I have not come up with a patch yet. Does anyone have any feedback/opinions concerning this?

BR // Mats

[U-Boot] hashtable lib and escaping

[Wolfgang Denk]

Dear Mats K?rrman,

In message <ED3E0BCACD909541BA94A34C4A164D4C425CEE7A@post.tritech.se> you wrote:
> 
> I used to have a working setup using U-Boot 2009.03 before upgrading to U-Boot 2012.07. The problem I'm facing is related to the escaping policies of lib/hashtable.c.
> 
> What I did before was for example having something like this in my default environment:
> 
> bootcmd=run first_boot
> first_boot=setenv bootcmd my_select\;run ubi_boot;saveenv;boot

THis syntax has never been correct.  If it ever worked, than only by
chance (read: because of incorrect/imperfect code).

> With the escape parsing of himport_r(), the '\' is simply dropped and it is no longer possible to escape ';' so the "run ubi_boot" is immediately executed and nothing is saved... The function header mentions the possibility for multi-line values but thi
> s should not come at the cost of not being able to escape ';'.

You have to be casreful here and keep in mind that (de-) escaping will
take place in a different places: himport() (resp. setenv()) is only
one part of this story - the other part is when you will actually pass
this string to the command processor (the shell).

See here:

	=> setenv foo 'echo part one\;echo part two' ; print foo ; run foo
	foo=echo part one;echo part two
	part one
	part two
	=> setenv foo 'echo part one\\;echo part two' ; print foo ; run foo
	foo=echo part one\;echo part two
	part one;echo part two
	=> 



Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
"No matter where you go, there you are..."          - Buckaroo Banzai

[U-Boot] hashtable lib and escaping

[Mats Kärrman]

Thanks, but...
If not correct, then what is this supposed to mean (common/main.c :: builtin_run_command()):

		/*
		 * Find separator, or string end
		 * Allow simple escape of ';' by writing "\;"
		 */

This does not indicate "by chance", or was it something else that was not correct?
BR // Mats

> From: Wolfgang Denk [wd at denx.de]
> Sent: Thursday, November 01, 2012 9:00 PM
> To: Mats K?rrman
> Cc: u-boot at lists.denx.de
> Subject: Re: [U-Boot] hashtable lib and escaping
> 
> Dear Mats K?rrman,
> 
> In message <ED3E0BCACD909541BA94A34C4A164D4C425CEE7A@post.tritech.se> you wrote:
> >
> > I used to have a working setup using U-Boot 2009.03 before upgrading to U-Boot 2012.07. The problem I'm facing is related to the escaping policies of lib/hashtable.c.
> >
> > What I did before was for example having something like this in my default environment:
> >
> > bootcmd=run first_boot
> > first_boot=setenv bootcmd my_select\;run ubi_boot;saveenv;boot
> 
> THis syntax has never been correct.  If it ever worked, than only by
> chance (read: because of incorrect/imperfect code).
> 
> > With the escape parsing of himport_r(), the '\' is simply dropped and it is no longer possible to escape ';' so the "run ubi_boot" is immediately executed and nothing is saved... The function header mentions the possibility for multi-line values but thi
> > s should not come at the cost of not being able to escape ';'.
> 
> You have to be casreful here and keep in mind that (de-) escaping will
> take place in a different places: himport() (resp. setenv()) is only
> one part of this story - the other part is when you will actually pass
> this string to the command processor (the shell).
> 
> See here:
> 
>         => setenv foo 'echo part one\;echo part two' ; print foo ; run foo
>         foo=echo part one;echo part two
>         part one
>         part two
>         => setenv foo 'echo part one\\;echo part two' ; print foo ; run foo
>         foo=echo part one\;echo part two
>         part one;echo part two
>         =>
> 
> 
> 
> Best regards,
> 
> Wolfgang Denk
> 
> --
> DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
> HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
> Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
> "No matter where you go, there you are..."          - Buckaroo Banzai
> 

[U-Boot] hashtable lib and escaping

[Wolfgang Denk]

Dear Mats K?rrman,

please don't top post/full quote.  If needed, please read
http://www.netmeister.org/news/learn2quote.html

In message <ED3E0BCACD909541BA94A34C4A164D4C425D0244@post.tritech.se> you wrote:
>
> If not correct, then what is this supposed to mean (common/main.c :: builtin_run_command()):
> 
> 		/*
> 		 * Find separator, or string end
> 		 * Allow simple escape of ';' by writing "\;"
> 		 */

As I metioned, this is the _second_ part of escaping, that which
happens when processing the commands.  The first part happens when
reading the environment.

The examples I gave should show pretty well how it works:

> > See here:
> > 
> >         => setenv foo 'echo part one\;echo part two' ; print foo ; run > foo
> >         foo=echo part one;echo part two
> >         part one
> >         part two
> >         => setenv foo 'echo part one\\;echo part two' ; print foo ; run>  foo
> >         foo=echo part one\;echo part two
> >         part one;echo part two
> >         =>

Here is one more:

	=> setenv foo echo part one\\\;echo part two ; print foo ; run foo 
	foo=echo part one\;echo part two
	part one;echo part two
	=>

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
Prediction is very difficult, especially of the future.  - Niels Bohr

[U-Boot] hashtable lib and escaping

[Mats Kärrman]

Thanks for your advice.
I did not say so, but I'm primarily relying on the default environment and not so much the command line. I see now how to make this work by providing the necessary amount of backslash'es. Maybe it was your statement:

> THis syntax has never been correct.  If it ever worked, than only by
> chance (read: because of incorrect/imperfect code).

that set me off wrong, because in 2009.03 (before the introduction of hashtable) it did work and there were no confusing parsing of escapes.
Still the parsing I see now is not exactly user friendly, example (U-Boot 2012.07):

    => setenv foo echo part one\\\;echo part two
    => print foo
    foo=echo part one\\;echo part two
    => run foo
    part one\;echo part two
    => printenv foo
    foo=echo part one\\;echo part two
    => printenv
    <snip>
    foo=echo part one\\\\;echo part two
    <snip>

here the run and print commands yields the expected result based on the setenv but not "printenv" alone, and my results does not match your example which were

>        => setenv foo echo part one\\\;echo part two ; print foo ; run foo
>        foo=echo part one\;echo part two
>        part one;echo part two

Best Regards,
Mats

[U-Boot] hashtable lib and escaping

[Wolfgang Denk]

Dear Mats K?rrman,

In message <ED3E0BCACD909541BA94A34C4A164D4C425D1384@post.tritech.se> you wrote:
>
> that set me off wrong, because in 2009.03 (before the introduction of hasht
> able) it did work and there were no confusing parsing of escapes.

That's not true.  AFAICT, quoting resp. escape rules haven't changed
at all, with a single exception: the old code did not support
multi-line variables, i. e. variables containing newline characters.

> Still the parsing I see now is not exactly user friendly, example (U-Boot 2
> 012.07):
> 
>     => setenv foo echo part one\\\;echo part two
>     => print foo
>     foo=echo part one\\;echo part two

This is not what I'm seeing.

> here the run and print commands yields the expected result based on the set
> env but not "printenv" alone, and my results does not match your example which were
> 
> >        => setenv foo echo part one\\\;echo part two ; print foo ; run foo
> >        foo=echo part one\;echo part two
> >        part one;echo part two

Any chance that you are not using the hush shell, but the old, simple
command interpreter?

I don't think this has seen much (if any) testing lately, so it is well
possible that there are bugs there...

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
Computers are not intelligent. They only think they are.

[U-Boot] hashtable lib and escaping

[Mats Kärrman]

Hi,

> Any chance that you are not using the hush shell, but the old, simple
> command interpreter?

Yup, a 100% chance. As I wrote before I rely only on the default environment, apart from development work, so I removed everything I don't need, hush included.
With some luck I will have time to look more at this later on.

Best regards,
Mats