Regarding virtual to physical memory mapping..

Regarding virtual to physical memory mapping..

[kiran pawar]

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Hi all,
    I am working on grub-1.97.1. I wanted to know if there is any mechanism
in grub2 that maps virtual addresses to physical addresses below 1 MB?
    When I checked the code for grub-0.97, I found that there are function
as below
           #define  phys_to_virt(x) (x)
           #define  virt_to_phys(x) (x)

Are there any similar functions in grub-1.97.1?

Also, when I allocated memory using grub_malloc() and printed the address
returned from the function it was (0x7da6d810). This seems to be a 32-bit
address. I wanted to know whether I can allocate some memory in the region
below 1MB?

Regards,
Kiran Pawar.

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Re: Regarding virtual to physical memory mapping..

[Vladimir 'φ-coder/phcoder' Serbinenko]

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kiran pawar wrote:
> Hi all,
>     I am working on grub-1.97.1. I wanted to know if there is any
> mechanism in grub2 that maps virtual addresses to physical addresses
> below 1 MB?
>     When I checked the code for grub-0.97, I found that there are
> function as below
>            #define  phys_to_virt(x) (x)
>            #define  virt_to_phys(x) (x)
>  
grub runs without paging enabled. So such function is identity on x86.
> Are there any similar functions in grub-1.97.1? 
>
> Also, when I allocated memory using grub_malloc() and printed the
> address returned from the function it was (0x7da6d810). This seems to
> be a 32-bit address. I wanted to know whether I can allocate some
> memory in the region below 1MB?
Only in experimental branch. But we're not currently sure if we will use
this. If you want to make a BIOS call then use memory at
GRUB_SCRATCH_ADDR. If you do something else please explain
>
> Regards,
> Kiran Pawar.
> ------------------------------------------------------------------------
>
> _______________________________________________
> Grub-devel mailing list
> Grub-devel@gnu.org
> http://lists.gnu.org/mailman/listinfo/grub-devel
>   


-- 
Regards
Vladimir 'φ-coder/phcoder' Serbinenko



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Re: Regarding virtual to physical memory mapping..

[Javier Martín]

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El jue, 31-12-2009 a las 13:31 +0100, Vladimir 'φ-coder/phcoder'
Serbinenko escribió:
> kiran pawar wrote:
> > Also, when I allocated memory using grub_malloc() and printed the
> > address returned from the function it was (0x7da6d810). This seems to
> > be a 32-bit address. I wanted to know whether I can allocate some
> > memory in the region below 1MB?
> Only in experimental branch. But we're not currently sure if we will use
> this. If you want to make a BIOS call then use memory at
> GRUB_SCRATCH_ADDR. If you do something else please explain
How come not? Here's how it's done in drivemap, for example
    handler_base = grub_mmap_malign_and_register (16, total_size,
                       &drivemap_mmap, GRUB_MACHINE_MEMORY_RESERVED,
                       GRUB_MMAP_MALLOC_LOW);

-- 
-- Lazy, Oblivious, Recurrent Disaster -- Habbit

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Re: Regarding virtual to physical memory mapping..

[Robert Millan]

On Thu, Dec 31, 2009 at 01:31:05PM +0100, Vladimir 'φ-coder/phcoder' Serbinenko wrote:
> > I wanted to know whether I can allocate some
> > memory in the region below 1MB?
> Only in experimental branch. But we're not currently sure if we will use
> this.

We can use this.  My concerns are with making intrusive changes in the
standard heap.  I think it's important that kern/mm.c is small and simple,
but this doesn't preclude doing more fancy stuff in non-core areas.

Sorry if I was unclear about it.

-- 
Robert Millan

  "Be the change you want to see in the world" -- Gandhi

Re: Regarding virtual to physical memory mapping..

[kiran pawar]

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Hi all,
  Sorry for replying late.. and thanks everyone for replying. i am not clear
with answers that are given to the question .
  I have written a function in assembly that i have called form C code and
done the linking correctly. But i want
  this code should run in real mode. The address that i am getting for the
function is 0x5e45c000 which is a virtual address
  so i need to get its actual physical address to execute it in real mode
(which should be less than 1 MB).
 So i wanted to ask is there any way to do mapping from virtual to physical
in grub?
 Also is there any way by which i can have that assembly function placed
below 1 MB ?


Best regards,
Kiran Pawar.

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