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

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Date:	Wed, 18 Mar 2015 18:48:43 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Andrey Wagin <avagin@...il.com>
Cc:	Andy Lutomirski <luto@...nel.org>, Ingo Molnar <mingo@...nel.org>,
	Andi Kleen <andi@...stfloor.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Al Viro <viro@...iv.linux.org.uk>, X86 ML <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Borislav Petkov <bp@...en8.de>,
	Andy Lutomirski <luto@...capital.net>,
	Cyrill Gorcunov <gorcunov@...nvz.org>,
	Pavel Emelyanov <xemul@...nvz.org>
Subject: Re: [PATCH v3 1/2] x86_64,signal: Fix SS handling for signals
	delivered to 64-bit programs

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@...gin-fc19-cr criu]# setsid sleep 1000 &
> [1] 1225
> [root@...gin-fc19-cr criu]# ps -C sleep
>   PID TTY          TIME CMD
>  1226 ?        00:00:00 sleep
> [root@...gin-fc19-cr criu]# ./criu dump -t 1226 -D dump --shell-job
> [root@...gin-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?

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?

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;

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