nasm-devel

[Nasm-devel] Override extern with global for header files

[Lars M. <lar...@te...>]

Hello at all,
I'm working a lot with nasm and after a while I created a little library
I use in all nasm-Projects. Therefor some header files are very useful
(e.g. defining constants and externs).
I don't want to mess around with some macros for simple imports. I
thought of a c-prototype-like symbol definition for externs. What if a
defined extern could be redefined as global.

I had a look at the source code and found two possible solutions:

1.) see http://repo.or.cz/w/nasm.git/blob/HEAD:/labels.c#l278
one could allow in line 294, that externs could be redefined as global.
By a quick look, I think, that this wouldn't be a problem for the
labelmanager. find_lable simply returns the label and define_lable would
refill it with the global singal data. The bigger problem is the ofmt,
because the ofmt->symdef is explicitly called _once_ for each symbol.
Looking at, for example, the objobj.c you can see, that symbols are
stored in linked lists and there is no check for double names or
something like that. -> Bad solution (update all objformats, looping
through list for each symbol)

2.) if somehow possible, and symbols do not need to passed to the ofmt
directly after they were found (somehow context dependend), then you
could buffer the extern symbols until the whole analysis is ready. every
extern symbol that was not replaced by a global would then be passed the
the ofmt. exclude extern symbols at
http://repo.or.cz/w/nasm.git/blob/HEAD:/labels.c#l327 and introduce a
new function, that loops through all symbols and passes the missing
externs to the ofmt. call the function in the main function at the right
place (maybe here: http://repo.or.cz/w/nasm.git/blob/HEAD:/nasm.c#l466).

I would love to from you!
Lars

Re: [Nasm-devel] Override extern with global for header files

[suresh b. <k_s...@ya...>]

Hi Lars,

If an extern is used in any program, it mean that the defined variable / label / name is globally defined.  Then why again making it a gloabl?

You said in your old mails that you are making a single library for all exe formats.  Can you give your objective of modifying the nasm and its purpose before we understand the code you are referring here.

DEVELOPING AN OPTIONs WINDOW FOR NASM
=======================================


I am interested to develop a simple window with options set through a menu to run nasm.  In the command line we give options but instead we can give them through a menu and save the options file similar to a project file in build systems.

Looking for suggestions and comments for my initiative.



regards,
sureshbk.



On Monday, September 29, 2014 5:25 AM, Lars Maier <lar...@te...> wrote:
 


Hello at all,
I'm working a lot with nasm and after a while I created a little library
I use in all nasm-Projects. Therefor some header files are very useful
(e.g. defining constants and externs).
I don't want to mess around with some macros for simple imports. I
thought of a c-prototype-like symbol definition for externs. What if a
defined extern could be redefined as global.

I had a look at the source code and found two possible solutions:

1.) see http://repo.or.cz/w/nasm.git/blob/HEAD:/labels.c#l278
one could allow in line 294, that externs could be redefined as global.
By a quick look, I think, that this wouldn't be a problem for the
labelmanager. find_lable simply returns the label and define_lable would
refill it with the global singal data. The bigger problem is the ofmt,
because the ofmt->symdef is explicitly called _once_ for each symbol.
Looking at, for example, the objobj.c you can see, that symbols are
stored in linked lists and there is no check for double names or
something like that. -> Bad solution (update all objformats, looping
through list for each symbol)

2.) if somehow possible, and symbols do not need to passed to the ofmt
directly after they were found (somehow context dependend), then you
could buffer the extern symbols until the whole analysis is ready. every
extern symbol that was not replaced by a global would then be passed the
the ofmt. exclude extern symbols at
http://repo.or.cz/w/nasm.git/blob/HEAD:/labels.c#l327 and introduce a
new function, that loops through all symbols and passes the missing
externs to the ofmt. call the function in the main function at the right
place (maybe here: http://repo.or.cz/w/nasm.git/blob/HEAD:/nasm.c#l466).

I would love to from you!
Lars




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Re: [Nasm-devel] Override extern with global for header files

[H. P. A. <hp...@zy...>]

On 09/28/2014 04:39 PM, Lars Maier wrote:
> Hello at all,
> I'm working a lot with nasm and after a while I created a little library
> I use in all nasm-Projects. Therefor some header files are very useful
> (e.g. defining constants and externs).
> I don't want to mess around with some macros for simple imports. I
> thought of a c-prototype-like symbol definition for externs. What if a
> defined extern could be redefined as global.
> 
> I had a look at the source code and found two possible solutions:
> 
> 1.) see http://repo.or.cz/w/nasm.git/blob/HEAD:/labels.c#l278
> one could allow in line 294, that externs could be redefined as global.
> By a quick look, I think, that this wouldn't be a problem for the
> labelmanager. find_lable simply returns the label and define_lable would
> refill it with the global singal data. The bigger problem is the ofmt,
> because the ofmt->symdef is explicitly called _once_ for each symbol.
> Looking at, for example, the objobj.c you can see, that symbols are
> stored in linked lists and there is no check for double names or
> something like that. -> Bad solution (update all objformats, looping
> through list for each symbol)
> 
> 2.) if somehow possible, and symbols do not need to passed to the ofmt
> directly after they were found (somehow context dependend), then you
> could buffer the extern symbols until the whole analysis is ready. every
> extern symbol that was not replaced by a global would then be passed the
> the ofmt. exclude extern symbols at
> http://repo.or.cz/w/nasm.git/blob/HEAD:/labels.c#l327 and introduce a
> new function, that loops through all symbols and passes the missing
> externs to the ofmt. call the function in the main function at the right
> place (maybe here: http://repo.or.cz/w/nasm.git/blob/HEAD:/nasm.c#l466).
> 
> I would love to from you!
> Lars
> 

It would seem like a reasonable thing to do, and is obviously use in C
to good effect.  I agree that option 2 would by far be preferable, and
it looks like you have thought of this a lot.  Would you be willing to
write up a patch?

	-hpa

Re: [Nasm-devel] Override extern with global for header files

[Lars M. <lar...@te...>]

Hi,

Am 02.10.2014 um 22:02 schrieb Cyrill Gorcunov:
> Hi Lars, sorry for delays! I'll reply hopefully on weekend once
> I get more free time. That said the email is seen and not lost.
I didn't expect any answer since I saw the date of the last activity. :D

Am 02.10.2014 um 06:54 schrieb suresh babu:
> If an extern is used in any program, it mean that the defined variable 
> / label / name is globally defined. Then why again making it a gloabl?

> You mean like MASM's EXTERNDEF?
>
> http://msdn.microsoft.com/en-us/library/91sxd44w.aspx

To make it clear, here is an example:

myfunc.inc:

%define MY_FUNC_FLAG_A     0x0001
%define MY_FUNC_FLAG_B     0x0002
[...]

; myfunc(param1, param2) : result
; this function does something and returns a value of it
[extern myfunc]


myfunc.asm:
%include 'include/myfunc.inc'
[global myfunc]

section .code

myfunc:
     push ebp
     mov ebp, esp
     mov eax, [ebp+0x08]
     test eax, MY_FUNC_FLAG_A
     jnz .flagA
[...]


otherfile.asm
%include 'include/myfunc.inc'

section .code

   push 0
   push MY_FUNC_FLAG_A
   call myfunc



Am 02.10.2014 um 17:31 schrieb H. Peter Anvin:
> Would you be willing to
> write up a patch?
I dont have much time in the next few weeks because university starts 
again,
but I'll do my best to find time and implement this feature, if wanted.
It would be great if you could support me if there are any questions.

Re: [Nasm-devel] Override extern with global for header files

[Lars M. <lar...@te...>]

Hi,
today and yesterday I worked a bit at the feature we previously talked 
about.
This is not as easy as it might seems to be.

It took very long for me to understand the programm mechanics. Now I'm 
at the following point:
I can record extern definitions and prevent nasm from passing them to 
the ofmt. Although a redefinition as global is possible and they were 
treated as "unseen" labels. So the old function of a global label still 
works. There is just one problem: when passing the recorded extern 
labels, exept those wich are globals now, after the assembling is done, 
then the reloc adresses are broken in the output file. I guess this is 
because while assembling nasm is unable to resolve the label references. 
I would fix this, but I have no idea where and when this resolving takes 
places?


Just to make the problem clearer:

nasm -f elf test\externdef.asm

[extern externFunc]
[extern externFunc2]
[extern myFunc]

[global myFunc]

[section .text use32 class=code]

   ; just some senseless code to create references and relocs
   myFunc:
     push ebp
     mov ebp, esp
   .local:
     mov eax, 0x01
     jmp .local
     leave
     ret 4
   abc:
     call [externFunc]
     call [externFunc2]
     call [myFunc]
     ret 4




objdump -x test\externdef.o
nasm-2.11.05\test\externdef.o:     file format elf32-i386
nasm-2.11.05\test\externdef.o
architecture: i386, flags 0x00000011:
HAS_RELOC, HAS_SYMS
start address 0x00000000

Sections:
Idx Name          Size      VMA       LMA       File off  Algn
   0 .text         00000023  00000000  00000000  00000130  2**4
                   CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE
SYMBOL TABLE:
00000000 l    df *ABS*  00000000 test\externdef.asm
00000000 l    d  .text  00000000 .text
00000003 l       .text  00000000 myFunc.local
0000000e l       .text  00000000 abc
00000000         *UND*  00000000 externFunc
00000000         *UND*  00000000 externFunc2
00000000 g       .text  00000000 myFunc


RELOCATION RECORDS FOR [.text]:
OFFSET   TYPE              VALUE
00000010 R_386_32          myFunc
00000016 R_386_32          myFunc
0000001c R_386_32          myFunc

Re: [Nasm-devel] Override extern with global for header files

[anonymous c. <nas...@us...>]

>> You mean like MASM's EXTERNDEF?
>>
>> http://msdn.microsoft.com/en-us/library/91sxd44w.aspx
>
> To make it clear, here is an example:
>
> myfunc.inc:
>
> %define MY_FUNC_FLAG_A     0x0001
> %define MY_FUNC_FLAG_B     0x0002
> [...]
>
> ; myfunc(param1, param2) : result
> ; this function does something and returns a value of it
> [extern myfunc]
>
>
> myfunc.asm:
> %include 'include/myfunc.inc'
> [global myfunc]
>
> section .code
>
> myfunc:
>      push ebp
>      mov ebp, esp
>      mov eax, [ebp+0x08]
>      test eax, MY_FUNC_FLAG_A
>      jnz .flagA
> [...]
>
>
> otherfile.asm
> %include 'include/myfunc.inc'
>
> section .code
>
>    push 0
>    push MY_FUNC_FLAG_A
>    call myfunc

Yup, that's the EXTERNDEF behavior.

You should called it that.

Re: [Nasm-devel] Override extern with global for header files

[suresh b. <k_s...@ya...>]

Yes right exactly and thanks for more clear clarification.



On Sunday, October 12, 2014 8:17 AM, anonymous coward <nas...@us...> wrote:
 


>> You mean like MASM's EXTERNDEF?
>>
>> http://msdn.microsoft.com/en-us/library/91sxd44w.aspx
>
> To make it clear, here is an example:
>
> myfunc.inc:
>
> %define MY_FUNC_FLAG_A     0x0001
> %define MY_FUNC_FLAG_B     0x0002
> [...]
>
> ; myfunc(param1, param2) : result
> ; this function does something and returns a value of it
> [extern myfunc]
>
>
> myfunc.asm:
> %include 'include/myfunc.inc'
> [global myfunc]
>
> section .code
>
> myfunc:
>      push ebp
>      mov ebp, esp
>      mov eax, [ebp+0x08]
>      test eax, MY_FUNC_FLAG_A
>      jnz .flagA
> [...]
>
>
> otherfile.asm
> %include 'include/myfunc.inc'
>
> section .code
>
>    push 0
>    push MY_FUNC_FLAG_A
>    call myfunc

Yup, that's the EXTERNDEF behavior.

You should called it that.

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Re: [Nasm-devel] Override extern with global for header files

[Lars M. <lar...@te...>]

Okay. So why we don't just introduce externdef as keyword?

This would be less work, than caching the extern definitions and wait 
for their redefinition.


Am 13.10.2014 um 02:03 schrieb suresh babu:
> Yes right exactly and thanks for more clear clarification.
>
>
> On Sunday, October 12, 2014 8:17 AM, anonymous coward 
> <nas...@us...> wrote:
>
>
> >> You mean like MASM's EXTERNDEF?
> >>
> >> http://msdn.microsoft.com/en-us/library/91sxd44w.aspx
> >
> > To make it clear, here is an example:
> >
> > myfunc.inc:
> >
> > %define MY_FUNC_FLAG_A    0x0001
> > %define MY_FUNC_FLAG_B    0x0002
> > [...]
> >
> > ; myfunc(param1, param2) : result
> > ; this function does something and returns a value of it
> > [extern myfunc]
> >
> >
> > myfunc.asm:
> > %include 'include/myfunc.inc'
> > [global myfunc]
> >
> > section .code
> >
> > myfunc:
> >      push ebp
> >      mov ebp, esp
> >      mov eax, [ebp+0x08]
> >      test eax, MY_FUNC_FLAG_A
> >      jnz .flagA
> > [...]
> >
> >
> > otherfile.asm
> > %include 'include/myfunc.inc'
> >
> > section .code
> >
> >    push 0
> >    push MY_FUNC_FLAG_A
> >    call myfunc
>
> Yup, that's the EXTERNDEF behavior.
>
> You should called it that.
>
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>
>
>
>
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>
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Re: [Nasm-devel] Override extern with global for header files

[suresh b. <k_s...@ya...>]

Hi Lars,

We can do it.  externdef as  a user-level directive for the extern primitive directive.

regards,
sureshbk.



On Saturday, October 18, 2014 4:46 PM, Lars Maier <lar...@te...> wrote:
 


Okay. So why we don't just introduce externdef as keyword?

This would be less work, than caching the extern definitions and
      wait for their redefinition.


Am 13.10.2014 um 02:03 schrieb suresh babu:

Yes right exactly and thanks for more clear clarification.
>
>
>
>
>On Sunday, October 12, 2014 8:17 AM, anonymous coward <nas...@us...> wrote:
> 
>
>
>>> You mean like MASM's EXTERNDEF?
>>>
>>> http://msdn.microsoft.com/en-us/library/91sxd44w.aspx
>>
>> To make it clear, here is an example:
>>
>> myfunc.inc:
>>
>> %define MY_FUNC_FLAG_A    0x0001
>> %define MY_FUNC_FLAG_B    0x0002
>> [...]
>>
>> ; myfunc(param1, param2) : result
>> ; this function does something and returns a value
                of it
>> [extern myfunc]
>>
>>
>> myfunc.asm:
>> %include 'include/myfunc.inc'
>> [global myfunc]
>>
>> section .code
>>
>> myfunc:
>>      push ebp
>>      mov ebp, esp
>>      mov eax, [ebp+0x08]
>>      test eax, MY_FUNC_FLAG_A
>>      jnz .flagA
>> [...]
>>
>>
>> otherfile.asm
>> %include 'include/myfunc.inc'
>>
>> section .code
>>
>>    push 0
>>    push MY_FUNC_FLAG_A
>>    call myfunc
>
>Yup, that's the EXTERNDEF behavior.
>
>You should called it that.
>
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>
>
>
>
>
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Re: [Nasm-devel] Override extern with global for header files

[Cyrill G. <gor...@gm...>]

On Mon, Sep 29, 2014 at 01:39:51AM +0200, Lars Maier wrote:
...
> 
> I would love to from you!

Hi Lars, sorry for delays! I'll reply hopefully on weekend once
I get more free time. That said the email is seen and not lost.

Re: [Nasm-devel] Override extern with global for header files

[anonymous c. <nas...@us...>]

> What if a defined extern could be redefined as global.

You mean like MASM's EXTERNDEF?

http://msdn.microsoft.com/en-us/library/91sxd44w.aspx