On Thu, Jul 14, 2016 at 1:45 AM, Yubin Ruan <ablacktshirt@xxxxxxxxx> wrote:
On Wed, Jul 13, 2016 at 7:33 PM, Yubin Ruan <ablacktshirt@xxxxxxxxx
<mailto:ablacktshirt@xxxxxxxxx>> 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> 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
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