Hello, I hope somebody could check this case. It’s easily reproducible for anybody working with qemu and arm64 linux. I returned to this problem and made another observation.(showing the back-trace is really broken). In another incident of breakpoint at function __driver_attach, (right after it stopped at the function) (gdb) bt #0 __driver_attach (dev=dev@entry=0xffff0000401d1810, data="" <mxc_gpio_driver+40>) at drivers/base/dd.c:1046 #1 0xffff8000107684f8 in bus_for_each_dev (bus=0xffff800011cba910 <platform_bus_type>, start=0x0, data="" <mxc_gpio_driver+40>, fn=0xffff80001076b860 <__driver_attach>) at drivers/base/bus.c:307 #2 0xb8cd80001076a594 in ?? () Backtrace stopped: previous frame identical to this frame (corrupt stack?) (gdb) x/5g $sp 0xffff800011dcbcc0: 0xffff800011dcbd20 0xb8cd80001076a594 0xffff800011dcbcd0: 0xffff80001076b860 0xffff800011bbbbb8 0xffff800011dcbce0: 0x0000000000000000 Because it's right after the pc reached the function __driver_attach, the sp is still not updated from previous function (bus_for_each_dev). And the first two values at the $sp are supposed to be the fp and lr of the previous function (see https://stackoverflow.com/questions/66098678/understanding-aarch64-assembly-function-call-how-is-stack-operated arm64 stores previous function's fp and lr at the bottom of new stack frame as it enters a function). The lr (link register, the address to return after this bus_for_each_dev function) is really 0xb8cd80001076a594 which is weird (not a kernel address). The following 3 values are function arguments for bus_for_each_dev and they look correct. From: Chan Kim <ckim@xxxxxxxxxx>
Sent: Saturday, April 23, 2022 8:37 AM
To: 'Mulyadi Santosa' <mulyadi.santosa@xxxxxxxxx>
Cc: 'qemu-devel' <qemu-devel@xxxxxxxxxx>; 'kernelnewbies' <kernelnewbies@xxxxxxxxxxxxxxxxx>
Subject: RE: Backtrace stopped: previous frame identical to this frame (corrupt stack?) , even with fresh qemu and linux build Hi, Mulyadi Thank you for replying. I found CONFIG_DEBUG_FRAME_POINTER, CONFIG_DEBUG_INFO are already set by default. And I tried adding CONFIG_DEBUG_KERNEL, CONFIG_KGDB, CONFIG_GDB_SCRIPTS, CONFIG_STACKTRACE all to no avail. Regards, Chan Hello all,
Really strange thing happening here.. I can't see the full stack trace with
'bt' command in gdb.
So I tried with fresh linux-5.10.122 source and qemu-6.2.0 source and it's
happening too!
(it's happening when I do combinations with linux 5.10.0 and qemu-5.1.0. But
it's not happening with linux-5.4.21)
I would be grateful if somebody could check if this happens to other people
or just me.
1. download linux-5.1.122 tarball from https://www.kernel.org/
2. uncompress it and set env variable ARCH=arm64,
CROSS_COMPILE=aarch64-none-elf- , do "make defconfig" and "make -j`nproc`
Image"
3. download qemu-6.2.0 from https://www.qemu.org/
4. uncompress it and do "mkdir build" "cd build" "../configure
--target-list=aarch64-softmmu --enable-debug"
5. run qemu and wait for debugger to attach.
qemu-6.2.0/build/aarch64-softmmu/qemu-system-aarch64 -machine
virt,gic-version=max,secure=off,virtualization=true -cpu max -kernel
linux-5.10.112/arch/arm64/boot/Image -m 2G -nographic -netdev
user,id=vnet,hostfwd=:127.0.0.1:0-:22,tftp=/srv/tftp -device
virtio-net-pci,netdev=vnet -machine iommu=smmuv3 --append "root=/dev/ram
init=/init nokaslr earlycon ip=dhcp hugepages=16" -s -S
6. run debugger, do "aarch64-none-elf-gdb linux-6.10.112/vmlinux -x\
It has been long time since I compiled linux kernel but I guess, either you need to compile kernel with enabled frame pointer, and/or you need to enable debug symbol embedded into final kernel image. cmiiw gdb_script"
(gdb_script content :
target remote :1234
layout src
b start_kernel
b __driver_attach
)
Now, in gdb, when you press 'c' twice, it'll stop at the first
__driver_attach. (first one stops at start_kernel).
When you are at __attach_driver, type 'bt'. See if you see the full function
stack trace.
This is what I see.
(gdb) bt
#0 __driver_attach (dev=0xffff000002582810, data=""><dummy_regulator_driver+40>)
at drivers/base/dd.c:1060
#1 0xffff8000107a3ed0 in bus_for_each_dev (bus=<optimized out>,
start=<optimized out>,
data="" <dummy_regulator_driver+40>,
fn=0xffff8000107a6f60 <__driver_attach>)
at drivers/base/bus.c:305
#2 0xd6d78000107a5c58 in ?? ()
Backtrace stopped: previous frame identical to this frame (corrupt stack?)
I used to see more thatn 20 stacks trace but strangely I see only two.
I can still see many stacks for linux-5.4.21 that I was working with in the
past.
Could anyone check if this happens to anyone?
I think if I add BLK_DEV_RAM and set initramfs.cpio.gz in the linux build,
the kernel will boot ok to the shell prompt.
Only the gdb can't show the stack levels.
My OS : ubuntu-20.04 5.13.0-35-generic
$ aarch64-none-elf-gdb --version
GNU gdb (GNU Toolchain for the A-profile Architecture 10.2-2020.11
(arm-10.16)) 10.1.90.20201028-git
Copyright (C) 2020 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later
<http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Thank you.
Chan Kim
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