Re: [PATCH v3 1/2] x86_64,signal: Fix SS handling for signals delivered to 64-bit programs

Cyrill Gorcunov
2015-03-18T18:14:19Z

On Wed, Mar 18, 2015 at 06:48:43PM +0100, Oleg Nesterov wrote:
> On 03/18, Andrey Wagin wrote:
> >
> > This commit breaks CRIU. I don't have any details yet. I'm going to
> > investigate this issue and provide more details tomorrow.
> >
> > [root@avagin-fc19-cr criu]# setsid sleep 1000 &
> > [1] 1225
> > [root@avagin-fc19-cr criu]# ps -C sleep
> > PID TTY TIME CMD
> > 1226 ? 00:00:00 sleep
> > [root@avagin-fc19-cr criu]# ./criu dump -t 1226 -D dump --shell-job
> > [root@avagin-fc19-cr criu]# ./criu restore -D dump --shell-job
> > Error (parasite-syscall.c:923): Task is in unexpected state: b7f (SIGSEGV)
>
> This is funny. Because currenty I am looking into criu sources for quite
> different reason (and I HATE this reason ;)
>
> Shot in a dark afer a quick grep: restore_gpregs() should initialize ->ss?

It hasn't been needed earlier, if this would help it means abi is broken, no? :)
Otherwise I don't understand what's happening.

> perhaps something like below... obviously uncompiled/untested.
>
> And my grep can't find the definition of UserX86RegsEntry in crtools...
> Perhaps the change below needs CPREG1(ss, anothername).
>
> Seriously, where is UserX86RegsEntry?

It's in protobif/core-x86.proto, welcome to protobuf hell.

>
> Oleg.
>
>
> --- a/arch/x86/crtools.c
> +++ b/arch/x86/crtools.c
> @@ -475,6 +475,7 @@ int restore_gpregs(struct rt_sigframe *f, UserX86RegsEntry *r)
> CPREG2(rip, ip);
> CPREG2(eflags, flags);
> CPREG1(cs);
> + CPREG1(ss);
> CPREG1(gs);
> CPREG1(fs);
>
> diff --git a/arch/x86/include/asm/restorer.h b/arch/x86/include/asm/restorer.h
> index 70199fb..c04fb94 100644
> --- a/arch/x86/include/asm/restorer.h
> +++ b/arch/x86/include/asm/restorer.h
> @@ -53,7 +53,7 @@ struct rt_sigcontext {
> unsigned short cs;
> unsigned short gs;
> unsigned short fs;
> - unsigned short __pad0;
> + unsigned short ss;
> unsigned long err;
> unsigned long trapno;
> unsigned long oldmask;
>

Cyrill