Messages in this thread | | | Subject | Re: [PATCH] ARM: Remove the special printing format of pc and lr in __show_regs() | From | "Leizhen (ThunderTown)" <> | Date | Tue, 9 Aug 2022 10:09:17 +0800 |
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On 2022/8/8 17:41, Russell King (Oracle) wrote: > On Mon, Aug 01, 2022 at 11:20:16AM +0800, Zhen Lei wrote: >> Currently, instruction pointers are printed in [<%08lx>] format to make >> them more visible. However, it is not necessary in __show_regs() because >> they have the prefix 'pc :' or 'lr :', and it is also inconsistent with >> that of other registers, which causes misalignment. > > The formatting is not "to make them more visible" - it was to mark the > addresses that we wanted the ksymoops utility to translate to kernel > symbols before we had kallsyms in the kernel. If one disables kallsyms, > then we still need a way to translate kernel addresses to symbols.
I searched the git log and found that the ksymoops utility is discarded.
See: 073a9ecb3a73401662430bb955aedeac1de643d1 However, a commit in the pre-git era [1] had added the statement, "ksymoops is useless on 2.6. Please use the Oops in its original format".
That statement existed until commit 4eb9241127a0 ("Documentation: admin-guide: update bug-hunting.rst") finally removed the stale ksymoops information.
4eb9241127a0b5ac3aaaf1b246728009527ebc86 - delete all references to ksymoops since it is no longer applicable;
> > I notice there is a script which helps with this that is part of the > kernel source - scripts/decode_stacktrace.sh. I haven't tried this on > arm32 since I always use kallsyms - and I suspect that is rather > universally true as it avoids needing System.map files etc to decode > the oops. That said, if you're building a kernel for small systems, > you probably don't want the overhead of kallsyms.
Yes, I read scripts/decode_stacktrace.sh, it requires the format "[<...>]". But if that's the only concern, maybe we can do the conversion from "pc: addr" and "lr: addr" to "[<addr>]" first in scripts/decode_stacktrace.sh
I'm usually "objdump -d vmlinux > asm_file", then search "addr:" in asm_file.
Honestly, I think format "[<...>]" is dump_backtrace()'s requirement, not __show_regs()'s.
> > So, there's an argument for keeping it - it's an API in that it > provides hints to scripting to identify which values need to be > converted to symbols. There's also the argument for getting rid of it, > which is that hardly anyone does that anymore. > > The question is, which is the more important argument, and I don't > think there's a definite answer. So I'm inclined to leave this > as-is.
OK
>
-- Regards, Zhen Lei
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