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jeff | 5 Jun 2007 03:14

AsmIDE update


Announcement:

The DesktopLinuxAsm web site has been updated with the following programs:

program       state   description
-------       ------  ------------------------------------------
AsmMgr        stable  AsmIDE master control module (file manager)
AsmRef        stable  extensive documentation for assembler
AsmBug        alpha   debugger
AsmDis        alpha   disassembler
AsmSrc        alpha   ELF executables to source generator
AsmEdit       stable  editor with assembler development extensions
AsmNano       stable  simple editor
AsmTrace      alpha   program trace with functions and disassembly
AsmLib        beta    terminal and console library
AsmLibx       alpha   x window library
Dos Library   stable  DOS library
AsmFile       stable  file manager
Ainfo         stable  example program and info browser
format_doc    stable  document formatter
file_browse   stable  directory browser
file_info     stable  file status and permission setting
sort          stable  example program and file sort
step test     beta    fitness test and metronome example
walk test     stable  mile walk fitness calculation 
AsmPlan       stable  project planner and todo
AsmPub        stable  crates documentation from source comments
AsmFind       stable  search for files or text in files
AsmView       stable  file viewer with scroll in all directions
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Hendrik Visage | 5 Jun 2007 01:52
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Re: Segment override and lldt instruction

On 5/31/07, Frank Kotler <fbkotler <at> verizon.net> wrote:
> A D wrote:
> > Hi! I have couple of questions regarding gnu assembly. I've heard the word
> > segment override. Where segment register can be manually overriden. so
<snip>
> > But I get segmentation fault error. How can i do it without error?
>
> Use a valid selector. You appear to have "heard about" some 16=bit real
> mode stuff that is not true in protected mode. Take a look here:
>
> http://my.execpc.com/~geezer/johnfine/segments.htm

Nice technical discussions ;)

> In "Linux assembly", there is no reason you'd *want* to use a segment
> override, or alter a segment register.

Not while your program and/or data space  fits in 4GB of memory space ;)

Okay, a "perhaps" easier explanation on the differences between
protected and real mode segment registers (Strange I don't recall this
term in SPARC assembly...)

In Realmode, a segment register basically points to the "bottom"/base
of a 2^16 address space. The actuall address is/was calculated as
Segment register*4+register. This does allow for fancy/interesting
wrap around sitautions at the top of memory.

In Protected mode, the Segment Registers are misnommers to be bland,
they should be called Descriptor Table Indeces... ie. the memory
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makita | 7 Jun 2007 13:52

USB


Hi,
i want to know somthing abou USB device programing. Which book or links
do you advice my?

Thanks
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Saurabh Rawat | 7 Jun 2007 14:35
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Re: USB

> join www.forums.microchip.com
under analog ang PIC interfaces you will find a lot of good links, suggestions
and peoples.
Regards
Saurabh
> Hi,
> i want to know somthing abou USB device programing. Which book or links
> do you advice my?
>
> Thanks
> -
> To unsubscribe from this list: send the line "unsubscribe linux-assembly" in
> the body of a message to majordomo <at> vger.kernel.org
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>

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A D | 11 Jun 2007 02:33
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Re: Segment override and lldt instruction

>>Frank Kotler wrote:
>>In "Linux assembly", there is no reason you'd *want* to use a segment
>>override, or alter a segment register.
>
>Hendrik Visage wrote:
>Not while your program and/or data space  fits in 4GB of memory space ;)

So please correct my understanding if i'm wrong: it is not possible
or necessary to override segment register in protected mode but one can do
the same thing in real mode. right? So if answer is yes, and if more than 
4GB
of memory space is needed for a program how will segmentation register go
beyond 4gig without override?

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Frank Kotler | 11 Jun 2007 03:14
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Re: Segment override and lldt instruction

A D wrote:
>>> Frank Kotler wrote:
>>> In "Linux assembly", there is no reason you'd *want* to use a segment
>>> override, or alter a segment register.
>>
>>
>> Hendrik Visage wrote:
>> Not while your program and/or data space  fits in 4GB of memory space ;)
> 
> 
> So please correct my understanding if i'm wrong: it is not possible
> or necessary to override segment register in protected mode but one can do
> the same thing in real mode. right?

Right. (In Windows, you might want to do [fs:somevalue] - Windows uses 
fs for "thread local storage"(???) - a descriptor that does *not* have a 
base of 0, and limit is... 64k-1(???)... I think)

> So if answer is yes, and if more 
> than 4GB
> of memory space is needed for a program how will segmentation register go
> beyond 4gig without override?

Dunno. I'll leave that one to Hendrik. :)

Best,
Frank

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Brian Raiter | 11 Jun 2007 07:30

Re: Segment override and lldt instruction

> So if answer is yes, and if more than 4GB of memory space is needed
> for a program how will segmentation register go beyond 4gig without
> override?

A single process cannot access more than 4GB in 32-bit Linux. Period.
If you need more than 4GB, then you should be using 64-bit Linux.

b
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A D | 16 Jun 2007 23:20
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ModR/M byte and placement of control register contents

I'm a bit confused about the mov instruction that moves from or to control
register to or from general purpose register. In intel's x86 manual it says:

"At the opcode level, the reg field within the ModR/M byte specifies which 
of the
control registers is loaded or read. The 2 bits in the mod field are always 
11B. The
r/m field specifies the general-purpose register loaded or read."

So you can clearly see that segment register is specified by reg field and 
general
purpose register is specified by r/m field. My question is how processor 
knows looking at the intel instruction that now if i mov the contents of 
control register to general
purpose register(with the mov instruction), the processor now has to read 
contents from
control register(not load to control register) and write to(not read from)
general purpose register? Is there any special bit in the instruction format 
that
speciefies it? Thanks.

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