Objdump output

[Ian Lance Taylor]

andy@softbookpress.com writes:

> I have a couple of questions about objdump -output
> 1.
> "
> Program Header:
>     LOAD off    0x00008000 vaddr 0xc0038000 paddr 0xc0038000 align 2**15
>          filesz 0x000aa234 memsz 0x000c4270 flags rwx
> "
> What is LOAD off ?

``LOAD'' is the type of the segment (PT_LOAD).  off is short for
``offset;'' the number is the p_offset field of the segment--which is
to say, the offset of the segment data within the executable file.

> 2.
> "
> Sections:
> Idx Name          Size      VMA       LMA       File off  Algn
>   0 .text.init    0000054c  c0038000  c0038000  00008000  2**5
>                   CONTENTS, ALLOC, LOAD, READONLY, CODE
>   1 .data.init    00000328  c003854c  c003854c  0000854c  2**2
>                   CONTENTS, ALLOC, LOAD, DATA
>   2 .text.real    00090190  c0039000  c0039000  00009000  2**5
>                   CONTENTS, ALLOC, LOAD, READONLY, CODE
>   3 .rodata       000098e4  c00c9190  c00c9190  00099190  2**2
>                   CONTENTS, ALLOC, LOAD, READONLY, DATA
>   4 __ex_table    00000ce0  c00d2a80  c00d2a80  000a2a80  2**3
>                   CONTENTS, ALLOC, LOAD, READONLY, DATA
>   5 .data         0000e234  c00d4000  c00d4000  000a4000  2**5
>                   CONTENTS, ALLOC, LOAD, DATA
>   6 .bss          0001a030  c00e2240  c00e2240  000b2240  2**4
>                   ALLOC
>   7 .stab         001ef57c  00000000  00000000  000b2240  2**2
>                   CONTENTS, READONLY, DEBUGGING
>   8 .stabstr      000a62e2  00000000  00000000  002a17bc  2**0
>                   CONTENTS, READONLY, DEBUGGING
>   9 .comment      00001cc0  00000000  00000000  00347a9e  2**0
>                   CONTENTS, READONLY
>  10 .text         00000000  c0038000  c0038000  0034975e  2**0
>                   CONTENTS, READONLY"
> 
> What are "CONTENTS, ALLOC, LOAD, READONLY, CODE" ,etc ? Are they runtime
> directives ?

They are flags set on the section.  I don't know what you mean by
runtime directives.  These flags tell programs how the sections should
be interpreted.

> Where can I find the description of how they are interpreted ?

I don't know.  I thought they were documented somewhere, but I'm not
sure that they really are.

Briefly, CONTENTS means that the section has contents, ALLOC means
that the section should be allocated in memory space when the program
is executed, LOAD means that the contents of the section should be
loaded into memory, READONLY means that the allocated memory should be
marked as read only when the program is run, CODE means that the
section contains code, DATA means that the section contains data
(i.e., not code), DEBUGGING means that the section contains debugging
information.

Ian