Questions about the LMA and VMA in a linker script

[Yubin Ruan]

On 2016年07月16日 02:42, Dave Hylands wrote:
>
> On Thu, Jul 14, 2016 at 1:45 AM, Yubin Ruan <ablacktshirt at gmail.com
> <mailto:ablacktshirt at gmail.com>> wrote:
>
>         On Wed, Jul 13, 2016 at 7:33 PM, Yubin Ruan
>         <ablacktshirt at gmail.com <mailto:ablacktshirt at gmail.com>
>         <mailto:ablacktshirt at gmail.com <mailto:ablacktshirt at 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.