On 2016?07?16? 02:42, Dave Hylands wrote:

On Thu, Jul 14, 2016 at 1:45 AM, Yubin Ruan <ablacktshirt@gmail.com
<mailto:ablacktshirt@gmail.com>> wrote:

        On Wed, Jul 13, 2016 at 7:33 PM, Yubin Ruan
        <ablacktshirt at gmail.com <mailto:ablacktshirt@gmail.com>
        <mailto:ablacktshirt at gmail.com <mailto:ablacktshirt@gmail.com>>>
        wrote:

             Hi,
             I got some question about the AT directive in linker
        script. I have
             post this question to binutils{at}sourceware.org
        <http://sourceware.org>
             <http://sourceware.org> with no reply.

             Hopefully someone can help me out.

             After some searching and asking, I finally know that the AT
        directive
             tell the linker about LMA of  a section.

             For example there is some linker script like this:

                  SECTIONS
                  {
                      . = 0X80100000;
                      .text : AT(0x100000) {
                          *(.text .stub .text.* .gnu.linkonce.t.*)
                      }

                    ... blah blah ...
                  }

             Now 0x8010000 is a VMA, and 0x100000 is a LMA.

             My question is, is LMA the same as the physical address in
        a ELF
             program header ? A typical ELF declaration would be
        something like
             this:

             typedef struct
             {
                Elf32_Word    p_type;                 /* Segment type */
                Elf32_Off     p_offset;               /* Segment file
        offset */
                Elf32_Addr    p_vaddr;                /* Segment virtual
        address */
                Elf32_Addr    p_paddr;                /* Segment
        physical address */
                Elf32_Word    p_filesz;               /* Segment size in
        file */
                Elf32_Word    p_memsz;                /* Segment size in
        memory */
                Elf32_Word    p_flags;                /* Segment flags */
                Elf32_Word    p_align;                /* Segment
        alignment */
             } Elf32_Phdr;

             Is LMA just **p_paddr** in the program header?

...snip...

    Thank you for replying. I think I understand what you mean.
    But I still want the answer to my question, that is, is LMA just
    **p_paddr** in the program header?


I'm pretty sure that's the case. There are actually 2 sets of headers.
You can use:

objdump -p foo.elf

to view the "private" headers which shows you the p_vaddr and p_paddr
fields.

And you can use

objdump -h foo.elf

to view the section headers.

Here's some example output for a typical embedded program:

2216 >objdump -p firmware.elf

firmware.elf:     file format elf32-little

Program Header:
     LOAD off    0x00008000 vaddr 0x08000000 paddr 0x08000000 align 2**15
          filesz 0x0000288c memsz 0x0000288c flags r-x
     LOAD off    0x00010000 vaddr 0x08020000 paddr 0x08020000 align 2**15
          filesz 0x00040470 memsz 0x00040470 flags r-x
     LOAD off    0x00058000 vaddr 0x20000000 paddr 0x08060470 align 2**15
          filesz 0x00000108 memsz 0x000064f0 flags rw-
     LOAD off    0x0005e4f0 vaddr 0x200064f0 paddr 0x08060578 align 2**15
          filesz 0x00000000 memsz 0x00004000 flags rw-
     LOAD off    0x0005a4f0 vaddr 0x2000a4f0 paddr 0x08060578 align 2**15
          filesz 0x00000000 memsz 0x00000800 flags rw-

2217 >objdump -h firmware.elf

firmware.elf:     file format elf32-little

Sections:
Idx Name          Size      VMA       LMA       File off  Algn
   0 .isr_vector   0000288c  08000000  08000000  00008000  2**2
                   CONTENTS, ALLOC, LOAD, READONLY, CODE
   1 .text         00040470  08020000  08020000  00010000  2**2
                   CONTENTS, ALLOC, LOAD, READONLY, CODE
   2 .data         00000108  20000000  08060470  00058000  2**2
                   CONTENTS, ALLOC, LOAD, DATA
   3 .bss          000063e8  20000108  08060578  00058108  2**2
                   ALLOC
   4 .heap         00004000  200064f0  08060578  0005e4f0  2**0
                   ALLOC
   5 .stack        00000800  2000a4f0  08060578  0005a4f0  2**0
                   ALLOC
   6 .ARM.attributes 00000037  00000000  00000000  00058108  2**0
                   CONTENTS, READONLY
   7 .comment      000000e0  00000000  00000000  0005813f  2**0
                   CONTENTS, READONLY

--
Dave Hylands
Shuswap, BC, Canada
http://www.davehylands.com

Thanks :-)
Your reply really eliminate my doubts.

Regards,
Ruan.