Messages in this thread | | | Subject | Re: [PATCH 1/3] MIPS: kernel: Support extracting off-line stack traces from user-space with perf | From | Tiezhu Yang <> | Date | Fri, 29 Jan 2021 10:48:52 +0800 |
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On 01/28/2021 05:15 AM, Thomas Bogendoerfer wrote: > On Tue, Jan 05, 2021 at 11:18:06AM +0100, Peter Zijlstra wrote: >> On Tue, Jan 05, 2021 at 11:45:37AM +0800, Jiaxun Yang wrote: >>> 在 2021/1/4 下午6:59, Peter Zijlstra 写道: >>>> On Tue, Dec 29, 2020 at 08:55:59PM +0800, Tiezhu Yang wrote: >>>>> +u64 perf_reg_abi(struct task_struct *tsk) >>>>> +{ >>>>> + if (test_tsk_thread_flag(tsk, TIF_32BIT_REGS)) >>>>> + return PERF_SAMPLE_REGS_ABI_32; >>>>> + else >>>>> + return PERF_SAMPLE_REGS_ABI_64; >>>>> +} >>>> So we recently changed this on x86 to not rely on TIF flags. IIRC the >>>> problem is that on x86 you can change the mode of a task without the >>>> kernel being aware of it. Is something like that possible on MIPS as >>>> well? >>> Hi all, >>> >>> In MIPS world it's impossible to raise a thread to 64bit without kernel >>> aware. >>> Without STATUS.UX set it will trigger reserved instruction exception when >>> trying >>> to run 64bit instructions. >> The other way around is the case on x86, a 64bit program can create and >> execute 32bit code sections without the kernel being aware. But if >> clearing STATUS.UX has the same issue as setting it, that should not be >> a problem for you. >> >>> However it may be possible to run with 32bit ABI without >>> TIF_32BIT_REGS if user program didn't get ELF ABI right. I think >>> that's out of our current consideration. >> Fair enough. >> >>>> The thing x86 does today is look at it's pt_regs state to determine the >>>> actual state. >>> It is possible to look at pt_regs Status.UX bit on MIPS. But it seems >>> unnecessary >>> as user can't change it. >> Ok, good. Then no objection, proceed! :-) > this patch aims more to mips-next, while patch 2 and 3 are targeting > tools/perf. Should I take them into mips-next, too ?
If it is possible, I prefer to merge this three patches together through mips-next tree.
Thanks, Tiezhu
> > Thomas. >
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