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List:       busybox
Subject:    Re: dc's stack breaks when doing modulo-0
From:       Denys Vlasenko <vda.linux () googlemail ! com>
Date:       2019-05-16 7:41:20
Message-ID: CAK1hOcNvdyPSBkRykAeQ9OEF7nF63i4OE9=h=nVrZky55XD54w () mail ! gmail ! com
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ok

On Sat, May 11, 2019 at 2:47 AM Markus Gothe <nietzsche@lysator.liu.se> wrote:
> 
> You're right; I did dig into this and it seems to be a (MIPS-)kernel issue indeed.
> 
> However I think it would be nice to fix this in busybox as well as we cannot know \
> if there is a buggy kernel or not because different architectures handles the \
> exception in different ways; if it would have been fixed on latest kernel named X \
> for architecture Y there is no warranties about kernel X+N for architecture Z. 
> See my point of handling it in user-space as well?
> 
> //M
> 
> Sent from my BlackBerry — the most secure mobile device
> 
> 
> Original Message
> 
> 
> 
> From: vda.linux@googlemail.com
> Sent: 9 May 2019 15:50
> To: nietzsche@lysator.liu.se
> Cc: busybox@busybox.net
> Subject: Re: dc's stack breaks when doing modulo-0
> 
> 
> On Wed, May 8, 2019 at 7:31 PM Markus Gothe <nietzsche@lysator.liu.se> wrote:
> > dc -e '4 0 % p' mess up the stack so bad that my MIPS kernel traps it and \
> > reboots.
> 
> $ strace ./busybox dc -e '4 0 % p'
> execve("./busybox", ["./busybox", "dc", "-e", "4 0 % p"],
> 0x7ffd62d779e8 /* 53 vars */) = 0
> strace: [ Process PID=28924 runs in 32 bit mode. ]
> ioctl(0, TCGETS, {B38400 opost isig icanon echo ...}) = 0
> ioctl(1, TCGETS, {B38400 opost isig icanon echo ...}) = 0
> prctl(PR_SET_NAME, "busybox")           = 0
> getuid32()                              = 0
> --- SIGFPE {si_signo=SIGFPE, si_code=FPE_INTDIV, si_addr=0x8048600} ---
> +++ killed by SIGFPE (core dumped) +++
> 
> Please report to your kernel's MIPS people that their signal handling is broken.
> I would imagine they definitely do not want that to persist.
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