[v2,4/4] tools/nolibc: sys.h: apply __syscall() helper

  Use __syscall() helper to shrink 252 lines of code.

    $ git show HEAD^:tools/include/nolibc/sys.h | wc -l
    1425
    $ git show HEAD:tools/include/nolibc/sys.h | wc -l
    1173
    $ echo "1425-1173" | bc -l
    252

Signed-off-by: Zhangjin Wu <falcon@tinylab.org>
---
 tools/include/nolibc/sys.h | 336 +++++--------------------------------
 1 file changed, 42 insertions(+), 294 deletions(-)
  

Hi Zhangjin,

On 2023-06-06 16:17:38+0800, Zhangjin Wu wrote:
> Use __syscall() helper to shrink 252 lines of code.
> 
>     $ git show HEAD^:tools/include/nolibc/sys.h | wc -l
>     1425
>     $ git show HEAD:tools/include/nolibc/sys.h | wc -l
>     1173
>     $ echo "1425-1173" | bc -l
>     252
> 
> Signed-off-by: Zhangjin Wu <falcon@tinylab.org>
> ---
>  tools/include/nolibc/sys.h | 336 +++++--------------------------------
>  1 file changed, 42 insertions(+), 294 deletions(-)
> 
> diff --git a/tools/include/nolibc/sys.h b/tools/include/nolibc/sys.h
> index f6e3168b3e50..0cfc5157845a 100644
> --- a/tools/include/nolibc/sys.h
> +++ b/tools/include/nolibc/sys.h
> @@ -108,13 +108,7 @@ int sys_chdir(const char *path)
>  static __attribute__((unused))
>  int chdir(const char *path)
>  {
> -	int ret = sys_chdir(path);
> -
> -	if (ret < 0) {
> -		SET_ERRNO(-ret);
> -		ret = -1;
> -	}
> -	return ret;
> +	return __syscall(chdir, path);

To be honest I'm still not a big fan of the __syscall macro.
It's a bit too magic for too little gain.

The commit message argues that the patches make the code shorter.

However doing 

__sysret(sys_chdir(path));

instead of

__syscall(chdir, path);

is only three characters longer and the same amout of lines.

Otherwise we would have syscall() _syscall() and __syscall() each doing
different things.

And __syscall does not behave like a regular function.

The rest of the patchset looks great.

Maybe Willy can break the tie?


Thomas


Note: If we figure out a way to build syscall() without macros I would
like that also :-)
  

> Hi Zhangjin,
> 
> On 2023-06-06 16:17:38+0800, Zhangjin Wu wrote:
> > Use __syscall() helper to shrink 252 lines of code.
> > 
> >     $ git show HEAD^:tools/include/nolibc/sys.h | wc -l
> >     1425
> >     $ git show HEAD:tools/include/nolibc/sys.h | wc -l
> >     1173
> >     $ echo "1425-1173" | bc -l
> >     252
> > 
> > Signed-off-by: Zhangjin Wu <falcon@tinylab.org>
> > ---
> >  tools/include/nolibc/sys.h | 336 +++++--------------------------------
> >  1 file changed, 42 insertions(+), 294 deletions(-)
> > 
> > diff --git a/tools/include/nolibc/sys.h b/tools/include/nolibc/sys.h
> > index f6e3168b3e50..0cfc5157845a 100644
> > --- a/tools/include/nolibc/sys.h
> > +++ b/tools/include/nolibc/sys.h
> > @@ -108,13 +108,7 @@ int sys_chdir(const char *path)
> >  static __attribute__((unused))
> >  int chdir(const char *path)
> >  {
> > -	int ret = sys_chdir(path);
> > -
> > -	if (ret < 0) {
> > -		SET_ERRNO(-ret);
> > -		ret = -1;
> > -	}
> > -	return ret;
> > +	return __syscall(chdir, path);
> 
> To be honest I'm still not a big fan of the __syscall macro.
> It's a bit too magic for too little gain.
> 
> The commit message argues that the patches make the code shorter.
> 
> However doing 
> 
> __sysret(sys_chdir(path));
> 
> instead of
> 
> __syscall(chdir, path);
> 
> is only three characters longer and the same amout of lines.
>

Yeah, I do like your version too, it looks consise too, the only not
comfortable part is there are dual calls in one line.

> Otherwise we would have syscall() _syscall() and __syscall() each doing
> different things.
>

Yes, I'm worried about this too, although the compilers may help a
little, but it is too later.

Just brain storming, What about another non-similar name, for example,
__syswrap() or __sysin() ?

Or even convert __sysret() to __sysout() and __syscall() to __sysin(),
do you like it? or even __sysexit(), __sysentry(), but the __sysexit()
may be misused with sys_exit().

    /* Syscall return helper, set errno as -ret when ret < 0 */
    static __inline__ __attribute__((unused, always_inline))
    long __sysout(long ret)
    {
    	if (ret < 0) {
    		SET_ERRNO(-ret);
    		ret = -1;
    	}
    	return ret;
    }
    
    /* Syscall call helper, use syscall name instead of syscall number */
    #define __sysin(name, ...) __sysout(sys_##name(__VA_ARGS__))

    static __attribute__((unused))
    int brk(void *addr)
    {
    	return __sysout(sys_brk(addr) ? 0 : -ENOMEM);
    }

    static __attribute__((unused))
    int chdir(const char *path)
    {
    	return __sysin(chdir, path);
    }

If we really want something like __syscall()/__sysret(), I do think they
should be a pair ;-)

> And __syscall does not behave like a regular function.
> 
> The rest of the patchset looks great.
>

Thanks for your nice review.

> Maybe Willy can break the tie?
>

If there is no better solution, I think your version is also a first
step to go.

> 
> Thomas
> 
> 
> Note: If we figure out a way to build syscall() without macros I would
> like that also :-)

Yes, but it is not easy to cope with the variable number of arguments
without a macro.

BTW, do you like to convert the my_syscallN() of sys.h to the syscall()
you added? I do worry about it will make the checking of arguments
mismatch, exspecially, the checking of number of them hardly.

Best regards,
Zhangjin
  

Hi,

On Wed, Jun 07, 2023 at 08:34:06AM +0800, Zhangjin Wu wrote:
> > Hi Zhangjin,
> > 
> > On 2023-06-06 16:17:38+0800, Zhangjin Wu wrote:
> > > Use __syscall() helper to shrink 252 lines of code.
> > > 
> > >     $ git show HEAD^:tools/include/nolibc/sys.h | wc -l
> > >     1425
> > >     $ git show HEAD:tools/include/nolibc/sys.h | wc -l
> > >     1173
> > >     $ echo "1425-1173" | bc -l
> > >     252
> > > 
> > > Signed-off-by: Zhangjin Wu <falcon@tinylab.org>
> > > ---
> > >  tools/include/nolibc/sys.h | 336 +++++--------------------------------
> > >  1 file changed, 42 insertions(+), 294 deletions(-)
> > > 
> > > diff --git a/tools/include/nolibc/sys.h b/tools/include/nolibc/sys.h
> > > index f6e3168b3e50..0cfc5157845a 100644
> > > --- a/tools/include/nolibc/sys.h
> > > +++ b/tools/include/nolibc/sys.h
> > > @@ -108,13 +108,7 @@ int sys_chdir(const char *path)
> > >  static __attribute__((unused))
> > >  int chdir(const char *path)
> > >  {
> > > -	int ret = sys_chdir(path);
> > > -
> > > -	if (ret < 0) {
> > > -		SET_ERRNO(-ret);
> > > -		ret = -1;
> > > -	}
> > > -	return ret;
> > > +	return __syscall(chdir, path);
> > 
> > To be honest I'm still not a big fan of the __syscall macro.
> > It's a bit too magic for too little gain.
> > 
> > The commit message argues that the patches make the code shorter.
> > 
> > However doing 
> > 
> > __sysret(sys_chdir(path));
> > 
> > instead of
> > 
> > __syscall(chdir, path);
> > 
> > is only three characters longer and the same amout of lines.
> >
> 
> Yeah, I do like your version too, it looks consise too, the only not
> comfortable part is there are dual calls in one line.

For those who want to debug, having less macros or magic stuff is always
better, and in this essence I too find that Thomas' version is more
expressive about what is being done. Also, if some syscalls require a
specific handling (e.g. mmap() needs to return MAP_FAILED instead), it's
much easier to change only the code dealing with the return value and
errno setting than having to guess how to reimplement what was magically
done in a macro.

> > Otherwise we would have syscall() _syscall() and __syscall() each doing
> > different things.
> >
> 
> Yes, I'm worried about this too, although the compilers may help a
> little, but it is too later.

The issue is for the person who remembers "I need to use 'syscall'" but
never remembering the number of underscores nor the variations.

> Just brain storming, What about another non-similar name, for example,
> __syswrap() or __sysin() ?
> 
> Or even convert __sysret() to __sysout() and __syscall() to __sysin(),
> do you like it? or even __sysexit(), __sysentry(), but the __sysexit()
> may be misused with sys_exit().

I'd rather use "__set_errno()" to explicitly mention that it's only
used to set errno, but sysret would be fine as well IMHO as if we're
purist, it also normalizes the return value.

>     /* Syscall return helper, set errno as -ret when ret < 0 */
>     static __inline__ __attribute__((unused, always_inline))
>     long __sysout(long ret)
>     {
>     	if (ret < 0) {
>     		SET_ERRNO(-ret);
>     		ret = -1;
>     	}
>     	return ret;
>     }
>     
>     /* Syscall call helper, use syscall name instead of syscall number */
>     #define __sysin(name, ...) __sysout(sys_##name(__VA_ARGS__))
> 
>     static __attribute__((unused))
>     int brk(void *addr)
>     {
>     	return __sysout(sys_brk(addr) ? 0 : -ENOMEM);
>     }
> 
>     static __attribute__((unused))
>     int chdir(const char *path)
>     {
>     	return __sysin(chdir, path);
>     }

I still don't find this intuitive at all.

> If we really want something like __syscall()/__sysret(), I do think they
> should be a pair ;-)

Then one being called "call" while the other one being "ret" do form a
pair, no ?

Thanks,
Willy
  

> On Wed, Jun 07, 2023 at 08:34:06AM +0800, Zhangjin Wu wrote:
> > > Hi Zhangjin,
> > > 
> > > On 2023-06-06 16:17:38+0800, Zhangjin Wu wrote:
> > > > Use __syscall() helper to shrink 252 lines of code.
> > > > 
> > > >     $ git show HEAD^:tools/include/nolibc/sys.h | wc -l
> > > >     1425
> > > >     $ git show HEAD:tools/include/nolibc/sys.h | wc -l
> > > >     1173
> > > >     $ echo "1425-1173" | bc -l
> > > >     252
> > > > 
> > > > Signed-off-by: Zhangjin Wu <falcon@tinylab.org>
> > > > ---
> > > >  tools/include/nolibc/sys.h | 336 +++++--------------------------------
> > > >  1 file changed, 42 insertions(+), 294 deletions(-)
> > > > 
> > > > diff --git a/tools/include/nolibc/sys.h b/tools/include/nolibc/sys.h
> > > > index f6e3168b3e50..0cfc5157845a 100644
> > > > --- a/tools/include/nolibc/sys.h
> > > > +++ b/tools/include/nolibc/sys.h
> > > > @@ -108,13 +108,7 @@ int sys_chdir(const char *path)
> > > >  static __attribute__((unused))
> > > >  int chdir(const char *path)
> > > >  {
> > > > -	int ret = sys_chdir(path);
> > > > -
> > > > -	if (ret < 0) {
> > > > -		SET_ERRNO(-ret);
> > > > -		ret = -1;
> > > > -	}
> > > > -	return ret;
> > > > +	return __syscall(chdir, path);
> > > 
> > > To be honest I'm still not a big fan of the __syscall macro.
> > > It's a bit too magic for too little gain.
> > > 
> > > The commit message argues that the patches make the code shorter.
> > > 
> > > However doing 
> > > 
> > > __sysret(sys_chdir(path));
> > > 
> > > instead of
> > > 
> > > __syscall(chdir, path);
> > > 
> > > is only three characters longer and the same amout of lines.
> > >
> > 
> > Yeah, I do like your version too, it looks consise too, the only not
> > comfortable part is there are dual calls in one line.
> 
> For those who want to debug, having less macros or magic stuff is always
> better, and in this essence I too find that Thomas' version is more
> expressive about what is being done. Also, if some syscalls require a
> specific handling (e.g. mmap() needs to return MAP_FAILED instead), it's
> much easier to change only the code dealing with the return value and
> errno setting than having to guess how to reimplement what was magically
> done in a macro.
>

Ok, so, let's go with Thomas' version ;-)

> > > Otherwise we would have syscall() _syscall() and __syscall() each doing
> > > different things.
> > >
> > 
> > Yes, I'm worried about this too, although the compilers may help a
> > little, but it is too later.
> 
> The issue is for the person who remembers "I need to use 'syscall'" but
> never remembering the number of underscores nor the variations.

Yeah, it is hard to remember.

> 
> > Just brain storming, What about another non-similar name, for example,
> > __syswrap() or __sysin() ?
> > 
> > Or even convert __sysret() to __sysout() and __syscall() to __sysin(),
> > do you like it? or even __sysexit(), __sysentry(), but the __sysexit()
> > may be misused with sys_exit().
> 
> I'd rather use "__set_errno()" to explicitly mention that it's only
> used to set errno, but sysret would be fine as well IMHO as if we're
> purist, it also normalizes the return value.
>

Ok, let's take the shorter sysret() seems no similar sys_xxx calls.

> >     /* Syscall return helper, set errno as -ret when ret < 0 */
> >     static __inline__ __attribute__((unused, always_inline))
> >     long __sysout(long ret)
> >     {
> >     	if (ret < 0) {
> >     		SET_ERRNO(-ret);
> >     		ret = -1;
> >     	}
> >     	return ret;
> >     }
> >     
> >     /* Syscall call helper, use syscall name instead of syscall number */
> >     #define __sysin(name, ...) __sysout(sys_##name(__VA_ARGS__))
> > 
> >     static __attribute__((unused))
> >     int brk(void *addr)
> >     {
> >     	return __sysout(sys_brk(addr) ? 0 : -ENOMEM);
> >     }
> > 
> >     static __attribute__((unused))
> >     int chdir(const char *path)
> >     {
> >     	return __sysin(chdir, path);
> >     }
> 
> I still don't find this intuitive at all.
> 
> > If we really want something like __syscall()/__sysret(), I do think they
> > should be a pair ;-)
> 
> Then one being called "call" while the other one being "ret" do form a
> pair, no ?

The 'ret' currently is a part of our old '__syscall', seems not that like a
'pair', it differs from entry/exit ;-)

As a summary, will use 'sysret()' and something like:

   static __attribute__((unused))
   int chdir(const char *path)
   {
   	return sysret(chdir(path));
   }

to renew the syscall helper patchset, Thanks you very much.

Best regards,
Zhangjin

> 
> Thanks,
> Willy
  

Hi Zhangjin,

On 2023-06-07 13:39:20+0800, Zhangjin Wu wrote:
> 
> As a summary, will use 'sysret()' and something like:
> 
>    static __attribute__((unused))
>    int chdir(const char *path)
>    {
>    	return sysret(chdir(path));
>    }
> 
> to renew the syscall helper patchset, Thanks you very much.

But please to use the "__" prefix.
Otherwise it could conflict with user code.

Thomas
  

> Hi Zhangjin,
> 
> On 2023-06-07 13:39:20+0800, Zhangjin Wu wrote:
> > 
> > As a summary, will use 'sysret()' and something like:
> > 
> >    static __attribute__((unused))
> >    int chdir(const char *path)
> >    {
> >    	return sysret(chdir(path));
> >    }
> > 
> > to renew the syscall helper patchset, Thanks you very much.
> 
> But please to use the "__" prefix.
> Otherwise it could conflict with user code.
>

Ok, not yet to modify the code, will reserve the '__sysret()' and convert the
left parts to this style: '__sysret(chdir(path))', a simple sed script may help
to do so.

Thanks a lot.
Zhangjin

> Thomas
  

From: Zhangjin Wu
> Sent: 07 June 2023 06:39
...
> As a summary, will use 'sysret()' and something like:
> 
>    static __attribute__((unused))
>    int chdir(const char *path)
>    {
>    	return sysret(chdir(path));
>    }
> 
> to renew the syscall helper patchset, Thanks you very much.

While I'm all for using 'cpp-magic' to abstract and (hopefully)
simplify things. Token-pasting the sys_ here doesn't seem to gain
anything.
Anyone grepping the code for 'sys_chdir' is also going to
wonder where it is used.

There might be scope for something like:
#define syscall_wrapper(func, type) \
	static __attribute__((unused)) \
	int func(type *arg) \
	{ \
		return sysret(sys_#func(arg)); \
	}
and then:
syscall_wrapper(chdir, const char *)
would expand to the code above.

I think you'd need separate defines for each number of arguments.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
  

From: David Laight
> Sent: 10 June 2023 17:34
> 
> From: Zhangjin Wu
> > Sent: 07 June 2023 06:39
> ...
> > As a summary, will use 'sysret()' and something like:
> >
> >    static __attribute__((unused))
> >    int chdir(const char *path)
> >    {
> >    	return sysret(chdir(path));
> >    }
> >
> > to renew the syscall helper patchset, Thanks you very much.
> 
> While I'm all for using 'cpp-magic' to abstract and (hopefully)
> simplify things. Token-pasting the sys_ here doesn't seem to gain
> anything.
> Anyone grepping the code for 'sys_chdir' is also going to
> wonder where it is used.

I think I've spotted a later version of the patch
that doesn't paste the sys_

> There might be scope for something like:
> #define syscall_wrapper(func, type) \
> 	static __attribute__((unused)) \
> 	int func(type *arg) \
> 	{ \
> 		return sysret(sys_#func(arg)); \
> 	}
> and then:
> syscall_wrapper(chdir, const char *)
> would expand to the code above.
> 
> I think you'd need separate defines for each number of arguments.

It is also worth pointing out that once the 'static unused'
functions have been defined, all the #define 'goop' used to
define them can be summarily #undef'ed.
That (mostly) solves the namespace problem.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)