Weinan Liu <wnliu@xxxxxxxxxx> writes: > This patchset implements a generic kernel sframe-based [1] unwinder. > The main goal is to support reliable stacktraces on arm64. > > On x86 orc unwinder provides reliable stacktraces. But arm64 misses the > required support from objtool: it cannot generate orc unwind tables for > arm64. > > Currently, there's already a sframe unwinder proposed for userspace: [2]. > Since the sframe unwind table algorithm is similar, these two proposal > could integrate common functionality in the future. > > There are some incomplete features or challenges: > - The unwinder doesn't yet work with kernel modules. The `start_addr` of > FRE from kernel modules doesn't appear correct, preventing us from > unwinding functions from kernel modules. > - Currently, only GCC supports sframe. > > Ref: > [1]: https://sourceware.org/binutils/docs/sframe-spec.html > [2]: https://lore.kernel.org/lkml/cover.1730150953.git.jpoimboe@xxxxxxxxxx/ > Hi Weinan, Thanks for working on this. I tested this set on my setup and faced some issues, here are the details: Here is my setup [on AWS c6gd.16xlarge instance]: ------------------------------------------------- [root@ip-172-31-32-86 linux-upstream]# uname -a Linux ip-172-31-32-86.ec2.internal 6.14.0-rc1+ #1 SMP Tue Feb 4 14:15:55 UTC 2025 aarch64 aarch64 aarch64 GNU/Linux [root@ip-172-31-32-86 linux-upstream]# git log --oneline e9a702365 (HEAD -> master) arm64: Enable livepatch for ARM64 5dedc956e arm64: Define TIF_PATCH_PENDING for livepatch ba563b31a unwind: arm64: add reliable stacktrace support for arm64 d807d392d unwind: arm64: Add sframe unwinder on arm64 7872f050b unwind: Implement generic sframe unwinder library 03d2ad003 unwind: add sframe v2 header 5e95cc051 arm64: entry: add unwind info for various kernel entries faff6cbc3 unwind: build kernel with sframe info 0de63bb7d (origin/master, origin/HEAD) Merge tag 'pull-fix' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 902e09c8a fix braino in "9p: fix ->rename_sem exclusion" f286757b6 Merge tag 'timers-urgent-2025-02-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip a360f3ffd (grafted) Merge tag 'irq-urgent-2025-02-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip bb2784d9a (grafted) jiffies: Cast to unsigned long in secs_to_jiffies() conversion 30d61efe1 (grafted) 9p: fix ->rename_sem exclusion [root@ip-172-31-32-86 linux-upstream]# grep SFRAME .config CONFIG_AS_HAS_SFRAME_SUPPORT=y CONFIG_SFRAME_UNWIND_TABLE=y CONFIG_SFRAME_UNWINDER=y [root@ip-172-31-32-86 linux-upstream]# grep LIVEPATCH .config CONFIG_HAVE_LIVEPATCH=y CONFIG_LIVEPATCH=y CONFIG_SAMPLE_LIVEPATCH=m [root@ip-172-31-32-86 linux-upstream]# as --version GNU assembler version 2.41-50.al2023.0.2 Copyright (C) 2023 Free Software Foundation, Inc. This program is free software; you may redistribute it under the terms of the GNU General Public License version 3 or later. This program has absolutely no warranty. This assembler was configured for a target of `aarch64-amazon-linux'. [root@ip-172-31-32-86 linux-upstream]# gcc --version gcc (GCC) 11.4.1 20230605 (Red Hat 11.4.1-2) Copyright (C) 2021 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. Loading the livepatch-sameple module: ------------------------------------- [root@ip-172-31-32-86 linux-upstream]# kpatch load /lib/modules/6.14.0-rc1+/kernel/samples/livepatch/livepatch-sample.ko loading patch module: /lib/modules/6.14.0-rc1+/kernel/samples/livepatch/livepatch-sample.ko waiting (up to 15 seconds) for patch transition to complete... patch transition has stalled! <4>kpatch: Livepatch process signaling is performed automatically on your system. <4>kpatch: Skipping manual process signaling. waiting (up to 60 seconds) for patch transition to complete... Stalled processes: 340 kdevtmpfs stack: [<0>] devtmpfs_work_loop+0x2cc/0x2d8 [<0>] devtmpfsd+0x4c/0x58 [<0>] kthread+0xf0/0x100 [<0>] ret_from_fork+0x10/0x20 module livepatch_sample did not complete its transition, unloading... disabling patch module: livepatch_sample waiting (up to 15 seconds) for patch transition to complete... transition complete (3 seconds) unloading patch module: livepatch_sample <4>kpatch: error: failed to load module livepatch_sample (transition stalled) Useful messages from kernel log [pr_debug enabled]: --------------------------------------------------- livepatch: enabling patch 'livepatch_sample' livepatch: 'livepatch_sample': initializing patching transition livepatch: 'livepatch_sample': starting patching transition livepatch: klp_try_switch_task: kdevtmpfs:340 has an unreliable stack livepatch: klp_try_switch_task: insmod:9226 has an unreliable stack livepatch: klp_try_switch_task: swapper/63:0 is running [......SNIP.......] livepatch: klp_try_switch_task: kdevtmpfs:340 has an unreliable stack [......SNIP.......] livepatch: signaling remaining tasks livepatch: klp_try_switch_task: kdevtmpfs:340 has an unreliable stack livepatch: 'livepatch_sample': reversing transition from patching to unpatching livepatch: 'livepatch_sample': starting unpatching transition livepatch: klp_try_switch_task: swapper/45:0 is running livepatch: 'livepatch_sample': completing unpatching transition livepatch: 'livepatch_sample': unpatching complete Please let me know if you are aware of this already or if this is expected behaviour with this version. I will try to debug this from my side as well. Also let me know if you need more details for debugging this. P.S. - I also saw multiple build warning like: ld: warning: orphan section `.eh_frame' from `arch/arm64/kernel/entry.o' being placed in section `.eh_frame' ld: warning: orphan section `.init.sframe' from `arch/arm64/kernel/pi/lib-fdt.pi.o' being placed in section `.init.sframe' Thanks, Puranjay
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