Re: Bloated binaries following the use of AT(...) linker script command

[Prasad B <bprasad at cs dot arizona dot edu>]

On Mon, Jun 15, 2009 at 9:01 PM, John Reiser<jreiser@bitwagon.com> wrote:

> Somewhere there is a confusion between physical address and virtual address.
> The bloat amount is about (0xc0000000 - 0x84000000) bytes, which is the
> difference between VirtAddr and PhysAddr.

Hi John,

You are spot on. I built the binary with and without the AT(...)
command and the size difference of the two binaries is exactly the
difference between virtual address (p_vaddr) and load address
(p_paddr).

truncated readelf output:

Start of section headers:      1018763256 (bytes into file) /* with AT(...) */
Start of section headers:          12130296 (bytes into file) /*
without AT(...) */

(gdb) p/x 1018763256 - 12130296 = 0x3c000000
(gdb) p/x 0xc0000000 - 0x84000000 = 0x3c000000

For the case without the AT(...) command:

PHDRS {
/* text PT_LOAD AT(0x84000000) FLAGS(7); */   /* RWX */
text PT_LOAD FLAGS(7);  /* RWX */
    ...
}

Corresponding program headers:

Program Headers:
Type       Offset  VirtAddr   PhysAddr   FileSiz MemSiz  Flg Align
LOAD     0x002000 0xc0000000 0xc0000000 0xb8b8a0 0xbf5f50 RWE 0x2000

thanks,
Prasad.