[9fans] executable memory map

[9fans] executable memory map

[Steve Simon]

Just to check I understand 386 executables on plan9.

.text is linked to the address 4096 + size of the a.out header (32 bytes) => 4096 + 32.
.data starts at the begining of the next 4096byte page after the .text.
.bss follows the data with no gap.

On exec the a.out file is read in its entirity to virtual address
4096 and the remainder of the file falls into place.

The parts I am unsure of are:

	1/ Is there any padding (to a 32 bit boundry or more) between .data and .bss?

	2/ Does the a.out file contain padding to ensure .data starts on a 4k boundry
	or does the kernel's loader move .data (using memcpy() or MMU mapping)?

Thanks.

-Steve

Re: [9fans] executable memory map

[ron minnich]

On 7/2/07, Steve Simon <steve@quintile.net> wrote:

>         2/ Does the a.out file contain padding to ensure .data starts on a 4k boundry
>         or does the kernel's loader move .data (using memcpy() or MMU mapping)?

loader for a.out has to align the .data segment via move -- it is not
aligned in the file.

ron

Re: [9fans] executable memory map

[Russ Cox]

>         1/ Is there any padding (to a 32 bit boundry or more) between .data and .bss?

no.