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Date: Fri, 25 Jul 2014 11:05:06 -0400
From: Christopher Covington <cov@codeaurora.org>
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Subject: Re: [Qemu-devel] AArch64 ELF File Loading
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To: Peter Maydell <peter.maydell@linaro.org>
Cc: "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>

Hi Peter,

On 07/25/2014 10:41 AM, Peter Maydell wrote:
> On 25 July 2014 15:35, Christopher Covington <cov@codeaurora.org> wrote:
>> qemu-system-aarch64 -nodefaults -nographic -monitor none -M virt \
>>   -cpu cortex-a57 -m 3G -semihosting -kernel hello
>>
>> qemu: fatal: Trying to execute code outside RAM or ROM at 0x0000000000000000
> 
> This means your code took an exception (and there's
> no RAM at the low address where the vector table is
> by default). Try "-d in_asm,exec,int" to get a better idea
> of what's being executed.

qemu-system-aarch64 -nodefaults -nographic -monitor none \
  -M virt -cpu cortex-a57 -m 3G -semihosting -kernel hello \
  -d in_asm,exec,int

qemu: fatal: Trying to execute code outside RAM or ROM at 0x0000000000000000

PC=0000000000000000  SP=0000000000000000
X00=0000000000000000 X01=0000000000000000 X02=0000000000000000 ...

The binary runs fine on at least one other simulator.

> Also, where do you expect the output from that printf
> to be going? Does your gcc/bare metal libc write to
> the UART? How does it know what address the UART is?
> If it's expecting to do semihosting for output, then you're
> running into the fact that we don't implement semihosting
> for AArch64 yet.

I have local patches adding semihosting for AArch64. I hope eventually be able
to share them and other changes, but the approvals will likely take a while
longer. Here is an example that doesn't use semihosting.

wget
http://releases.linaro.org/14.06/components/toolchain/binaries/gcc-linaro-aarch64-none-elf-4.9-2014.06-02_linux.tar.xz
tar xf gcc-linaro-aarch64-none-elf-4.9-2014.06-02_linux.tar.xz
echo '.global _start
_start:
  mrs x0, midr_el1
  b _start' > hello.S
gcc-linaro-aarch64-none-elf-4.9-2014.06-02_linux/bin/aarch64-none-elf-gcc \
  -nostdlib -Ttext=0x40000000 hello.S -o hello
qemu-system-aarch64 -nodefaults -nographic -monitor none -M virt \
  -cpu cortex-a57 -m 3G -semihosting -kernel hello -d in_asm,exec,int

qemu: fatal: Trying to execute code outside RAM or ROM at 0x0000000000000000

Thanks,
Christopher

-- 
Employee of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
hosted by the Linux Foundation.