I'm working on a arm-elf cross compiler for a Brutus board.
My latest problem trying to get a stand-alone system going (yet to happen)
appears to be in a routine to init memory that does the following:
SAir_InitBSSMemory:
STMFD sp!, {v1-v5, lr}
LDR v1, SA_TopOfROM @ Copy predefined variables from here..
LDR v2, SA_StartOfBSS @ ..to here
LDR v3, SA_ZeroBSS @ 'C' BSS starts here
CMP v1, v2 @ Make sure there are some..
BEQ 8f
7:
CMP v2, v3 @ Check if done..
LDRCC v4, [v1], #4 @ if not, get word and store to RAM
STRCC v4, [v2], #4
BCC 7b
I've managed to the get the linker to set these to:
SA_TopOfROM: .word _etext
SA_StartOfBSS: .word .data
SA_ZeroBSS: .word __bss_start__
_etext resulted to the start of .rodata section:
% arm-elf-objdump --header bounce3.elf
bounce3.elf: file format elf32-littlearm
Sections:
Idx Name Size VMA LMA File off Algn
0 .text 000049e8 00008000 00008000 00008000 2**2
CONTENTS, ALLOC, LOAD, READONLY, CODE
1 .rodata 00000100 0000c9e8 0000c9e8 0000c9e8 2**2
CONTENTS, ALLOC, LOAD, READONLY, DATA
2 .data 00000470 0000cbe8 0000cbe8 0000cbe8 2**2
CONTENTS, ALLOC, LOAD, DATA
3 .bss 0013cc0c 00010000 00010000 00010000 2**15
ALLOC
So the above assembler should copy the .rodata section on top
of the .data section until it rearches the .bss section. (Actually
to the end of the .data section, __bss_start__ was assigned 0xd058,
.data + 470)
The .rodata is only 0x100 in size, and the .data
is 0x470, so it not big enough to initialize the whole .data area.
As a result, all the .data section is not inialize correctly.
What happening here?
I've also noticed that some c file that initialize global variables
do not it a .rodata section, while others do.
Mark
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