Hi Erik,
> >2)Can a process have two different pages (in linear address space)
> >that are allocated same frame.
>I think I don't understand your question. A process can have a single
>physical page mapped at two different virtual locations in its address
>space. Mapping a single virtual page to two different physical pages is
>inpossible.
Your first guess is right. My question is whether same physical page is mapped to two diffrent virtual address of a process. You said it is possble.
Can you give an example?? In which occasions it will happen??
KR
different virtual address
Erik Mouw <J.A.K.Mouw@its.tudelft.nl> wrote:
On Wed, Feb 05, 2003 at 06:10:22PM -0800, kernel rakshakudu wrote:
> I have following questions regrading linux process memory management.
>
> 1) Can a process modify its own text region(code).
No, cause it is mapped read-only.
> 2)Can a process have two different pages (in linear address space)
> that are allocated same frame.
I think I don't understand your question. A process can have a single
physical page mapped at two different virtual locations in its address
space. Mapping a single virtual page to two different physical pages is
inpossible.
> 3) Process reads its text region for intructions to execute. But Is
> there an occasion when a process reads data from its text region ??
Sure:
int foo(int bar)
{
return bar+1;
}
int main(void)
{
unsigned int *gnu = (unsigned int *)foo;
printf("foo() is at 0x%08x and has value 0x%08x\n",
(unsigned int)gnu, *gnu);
return 0;
}
Which on my system prints:
foo() is at 0x080483f0 and has value 0x8be58955
Put *gnu = 0 in it, and the program will die because of a segfault: you
can't write the text section.
Erik
--
J.A.K. (Erik) Mouw
Email: J.A.K.Mouw@its.tudelft.nl mouw@nl.linux.org
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