On 13/04/12 12:05, Richard Earnshaw wrote:
> On 13/04/12 11:58, Mans Rullgard wrote:
>> On 13 April 2012 11:47, Richard Earnshaw <richard.earns...@arm.com> wrote:
>>> On 12/04/12 20:10, Allen Martin wrote:
>>>> I have a cross toolchain I configured with "--with-arch=armv7-a
>>>> --with-cpu=cortex-a9 --with-tune=cortex-a9" and I want the linker to emit
>>>> armv4t compatible thumb interworking, but I can't seem to get it to.
>>>>
>>>> I noticed that if I create a armv4t toolchain with "--with-arch=armv4t
>>>> --with-cpu=arm7tdmi --with-tune=arm7tdmi" and then I pass "--use-blx" to
>>>> the linker it will emit armv7 thumb interworking. There doesn't seem to
>>>> be any inverse "--no-use-blx" type switch though. Is this a
>>>> bug/limitation of the linker or am I misunderstanding something?
>>>>
>>>
>>> it's all in the friendly manual :-)
>>>
>>> The option you need is --fix-v4bx.
>>
>> That option is for supporting pre-thumb cores, which is not necessary
>> here.
>
> Oops, misread the question. Sorry.
>
> To get v4t style interworking you need to ensure all your objects are
> built for v4t. The use of blx should only occur if the linker detects
> an object file in the input list that already contains support for blx
> (for example, because it was compiled with v5 or later).
>
> R.
>
>
I've just built an assembler/linker with the options you mention.
Compiling the following testcase:
.text
.arm
.cpu arm7tdmi
.global _start
.type _start, %function
_start:
bl bar
bx lr
.thumb
.global bar
.type bar, %function
bar:
bx lr
Results in:
.../as /tmp/asm.s -o /tmp/asm.o
.../ld -o /tmp/asm /tmp/asm.o
.../objdump -d /tmp/asm
/tmp/asm: file format elf32-littlearm
Disassembly of section .text:
00008000 <_start>:
8000: eb000002 bl 8010 <__bar_from_arm>
8004: e12fff1e bx lr
00008008 <bar>:
8008: 4770 bx lr
800a: 46c0 nop ; (mov r8, r8)
800c: 0000 movs r0, r0
...
00008010 <__bar_from_arm>:
8010: e59fc000 ldr ip, [pc] ; 8018
<__bar_from_arm+0x8>
8014: e12fff1c bx ip
8018: 00008009 .word 0x00008009
801c: 00000000 .word 0x00000000
Change the .cpu directive to
.cpu cortex-a9
and you get
objdump -d /tmp/asm
/tmp/asm: file format elf32-littlearm
Disassembly of section .text:
00008000 <_start>:
8000: fa000000 blx 8008 <bar>
8004: e12fff1e bx lr
00008008 <bar>:
8008: 4770 bx lr
800a: bf00 nop
So exactly how are you calling the linker?
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