I was wondering if there is a way to exit from qemu from within the guest system in the aarch64 version. For instance the x86 has the isa-debug-exit device which is used for this purpose.
Any ideas?
Cheers
The general answer to this question is "do whatever you would do on the real hardware to cause a power-off". The details of this depend on which machine QEMU is emulating. For the aarch64 "virt" board, you can use the emulated PSCI firmware interface to request a powerdown using the SYSTEM_OFF function.
The PSCI API documentation is here: http://infocenter.arm.com/help/topic/com.arm.doc.den0022d/Power_State_Coordination_Interface_PDD_v1_1_DEN0022D.pdf
For debug/test purposes you might also be interested in the semihosting API (https://developer.arm.com/docs/dui0003/b) which has a SYS_EXIT function, but some caveats: for QEMU you can only use semihosting if you enable it via the -semihosting commandline argument, and only from kernel mode in the guest, and you must only use it if you absolutely trust the guest code, because it provides access to functions that allow the guest to read and write any host file. But for explicitly trusted small test programs it can be a nice way to do easy debug printing and exit with a given exit status.
Related
I have been developing the OS for a prototype device using hardware. Unfortunately, it's a very manual and buggy process to flash the OS each time and then debug the issues.
I'd like to switch to developing the OS in QEMU, so that I can be sure that the OS is loading correctly before going through the faff of programming the device for real. This will come in handy later for Continuous Integration work.
I have a full copy of the NVM device that is generated from my build process. This is a known working image I'd like to run in QEMU as a start point. This is ready to then be JTAG'd onto the device. The partition layout is:
P0 - loader - Flash of IDBLoader from rockchip loader binaries
P1 - Uboot - Flash of Uboot
P2 - trust - Flash of Trust image for rockchip specific loader
P3 - / - Root partition with Debian based image and packages required for application
P4 - data partition - Application Data
I have not changed anything with the Rockchip partitions (P0 - P2) apart from the serial console settings. When trying to boot the image though, nothing happens. There is no output at all, but the VM shows as still running. I use the following command to run it:
qemu-system-aarch64 -machine virt -cpu cortex-a53 \
-kernel u-boot-nodtb.bin \
-drive format=raw,file=image.img \
-boot c -serial stdio
I have no error information to go on to understand what is going on with it, where can I get more information or debug?
QEMU cannot not emulate arbitrary hardware. You will have to compile U-Boot to match the hardware that QEMU emulates, e.g. using make qemu_arm64_defconfig. The OS must also provide drivers for QEMU's emulated hardware.
If you want to emulate the complete hardware to debug drivers, Renode (https://renode.io/) is a good choice.
For anyone else trying to figure this out, I found good resources here:
https://translatedcode.wordpress.com/2017/07/24/installing-debian-on-qemus-64-bit-arm-virt-board/
and
https://azeria-labs.com/emulate-raspberry-pi-with-qemu/
Looking at the information though, you need to extract the kernel from your image and provide that to the qemu command line as an argument. You'll also need to append an argument telling the system which partition to use as a root drive.
My final command line for starting the machine looks like this:
qemu-system-aarch64 -machine virt -cpu cortex-a53 \
-drive format=raw,file=image.img,id=hd \
-boot c -serial stdio
-kernel <kernelextracted> -append "root=fe04"
Different Arm boards can be significantly different from one another in where they put their hardware, including where they put basic hardware required for bootup (UART, RAM, interrupt controller, etc). It is therefore pretty much expected that if you take a piece of low-level software like u-boot or a Linux kernel that was compiled to run on one board and try to run it on a different one that it will fail to boot. Generally it won't be able to output anything because it won't even have been able to find the UART. (Linux kernels can be compiled to be generic and include drivers for a wider variety of hardware, so if you have that sort of kernel it can be booted on a different board type: it will use a device tree blob, provided either by you or autogenerated by QEMU for the 'virt' board, to figure out what hardware it's running on and adapt to it. But kernels compiled for a specific embedded target are often built with only the device drivers they need, and that kind of kernel can't boot on a different system.)
There are broadly speaking two paths you can take:
(1) build the guest for the board you're emulating (here the 'virt' one). u-boot and Linux both have support for QEMU's 'virt' board. This may or may not be useful for what you're trying to do -- you would be able to test any userspace level code that doesn't care what hardware it runs on, but obviously not anything that's specific to the real hardware you're targeting.
(2) In theory you could add emulation support to QEMU for the hardware you're trying to run on. However this is generally a fair amount of work and isn't trivial if you're not already familiar with QEMU internals. I usually ballpark estimate it as "about as much work as it would take to port the kernel to the hardware"; though it depends a bit on how much functionality you/your guest need to have working, and whether QEMU already has a model of the SoC your hardware is using.
To answer the general "what's the best way to debug a guest image that doesn't boot", the best thing is usually to connect an arm-aware gdb to QEMU's gdbstub. This gives you debug access broadly similar to a JTAG debug connection to real hardware and is probably sufficient to let you find out where the guest is crashing. QEMU also has some debug logging options under the '-d' option, although the logging is partially intended to assist in debugging problems within QEMU itself and can be a bit tricky to interpret.
I found in QEMU NIOS IP https://wiki.qemu.org/Documentation/Platforms/Nios2
I have downloaded intel tool chain from their website : https://www.intel.com/content/www/us/en/programmable/products/boards_and_kits/dev-kits/altera/kit-niosii-2s60.html
I have few questions:
Is the NIOS2 in QEMU IP matching intel’s NIOS IP ?
What is the toolchain you use to compile and run it in QEMU ? Is it same tool-chain as provided by intel’s website ?
How to general Firmware code and run it on NIOS over QEMU. In the Wiki it says:
qemu-system-nios2 -M 10m50-ghrd -kernel -dtb -nographic
How to generate dtb file for it?
Do we need to take products created by the quartos/EDS for the running of the QEMU, other from the compiled binary? (DTB - board specification?)
Do we need to run it with specific QEMU parameters/arguments ?
Do you have code examples for NIOS using its peripherals?
Basically, I didn’t find any documentations/examples about how to use the NIOS2 in QEMU. Can you help with some additional info ?
Even some basic “hello would” (compile and run in QEMU) would be great…
UPDATE: the most up-to-date answer to this question may be to analyse the linux console nios test at https://gitlab.com/qemu-project/qemu/-/blob/master/tests/acceptance/boot_linux_console.py#L1029 (or of course contact a maintainer). The kernel image from advent calendar 2018 day 14 runs great. It looks like it can all be done with buildroot.
My comments started bearing fruit, so I'll try to put a partial answer together. I haven't gotten this to work yet, but maybe this can be helpful to others who might work farther.
NOTE: If you just want to run a single nios2 binary, you can pass it straight to qemu-nios2. qemu-system-nios2 is for running linux.
I believe the qemu behavior is functionality rather than intellectual property. It would be a bug if it mismatched. I do not know whether it does. Mentioning IP here, please remember that open source projects are generally run by a handful of vulnerable caring devs who usually have no legal team if ownership of intellectual property is challenged. If there's an issue, it would be polite to refer the concerning party to https://eff.org/ who often legally represents such things.
I expect that any nios2 toolchain works. Here's a toolchain from a quick internet search that led me to bootlin.com. Appears to include instructions on how to duplicate it from source.
See 4
Here is what I have so far for firmware generation:
# set up a toolchain (note: this old step is redundant with buildroot, lower down, which also installs a toolchain and even builds a kernel if asked)
wget https://toolchains.bootlin.com/downloads/releases/toolchains/nios2/tarballs/nios2--glibc--stable-2020.08-1.tar.bz2
tar -jxvf nios2--glibc--stable-2020.08-1.tar.bz2
# get kernel sources (pass --depth 1 to speed up)
git clone https://github.com/altera-opensource/linux-socfpga.git
# build kernel and device tree
cd linux-socfpga
make ARCH=nios2 CROSS_COMPILE=$(pwd)/../nios2--glibc--stable-2020.08-1/bin/nios2-linux- 10m50_defconfig 10m50_devboard.dtb vmlinux -j5
cd ..
# kernel is now at linux-socfpga/vmlinux
# device tree is now at linux-socfpga/arch/nios2/boot/dts/10m50_devboard.dtb
# set up buildroot to build a root image
git clone https://github.com/buildroot/buildroot.git
cd buildroot
# configure for qemu nios2
make qemu_nios2_10m50_defconfig
# build root image
PERL_MM_OPT= LDFLAGS= CPPFLAGS= LD_LIBRARY_PATH= make
cd ..
# rootfs images are now in buildroot/output/images/
I'm afraid I'm just a visitor and I don't know who quartos/eds are or what compiled binary you are referring to.
The qemu command line appears to be qemu-system-nios2 -M <machine> -kernel <kernel file> -dtb <dtb file> <rootfs image file>. The example machine is 10m50-ghrd which we built the kernel for above, and this may be the only one.
not yet! i'll try to update this answer if i get farther. feel free to edit it if you get farther.
What should be the best approach to run a C code in Qemu riscv and observe the output? I installed Qemu riscv following this link.What should I do now?
https://risc-v-getting-started-guide.readthedocs.io/en/latest/linux-qemu.html
You probably want to use the static user mode version of Qemu for most applications.
Then make sure to compile for RISC-V with the -static flag, and call qemu-riscv64-static [executable].
I highly recommend this, the system mode is a massive pain to handle if you don't need it
(have fun debugging the UART).
You can use libriscv to run RISC-V programs: https://github.com/fwsGonzo/libriscv
Inside the emulator folder there are 2 ways to build the emulator. build.sh produces emulators that run programs with no instruction listing. debug.sh produces debugging variant that shows the state of registers and instructions all the way through the program.
Building Qemu from sources is complete overkill.
My laptop support hardware virtualization & enabled in bios & i am trying to compile qemu from source. So Is it possible to compile qemu in a way that i do not enter "-enable-kvm" flage from command line every time?
You could try passing configure --disable-tcg, which will disable the CPU emulation entirely (this only works for some target architectures like x86 at the moment). Then I think QEMU will default to KVM as the only available accelerator.
Alternatively if you rename your executable to something whose name ends with "kvm" then QEMU will default to the KVM accelerator rather than TCG. (I think a hardlink or maybe even a symlink to the binary will also work as well as simply renaming it, but haven't tested this.)
When compile QEMU from source code, I find in file configure, option --target-list supports arm-linux-user and **armeb-linux-user". I know xx-linux-user is for User Emulation. What is the difference between "arm-linux-user" and "armeb-linux-user"?
armeb-linux-user is for big-endian Linux ARM binaries, and arm-linux-user is for little-endian ARM binaries. If you don't know you want big-endian then you don't want it. (The usual setup for user-mode QEMU uses the host-kernel's binfmt-misc support so it can automatically pick the right -linux-user QEMU binary to run for the guest executable anyway.)