linux-kernel - Re: [PATCH 0/5] Live patching for powerpc

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Message-ID: <20160414164122.7ubcqqm43advdscb@treble>
Date:	Thu, 14 Apr 2016 11:41:22 -0500
From:	Josh Poimboeuf <jpoimboe@...hat.com>
To:	Torsten Duwe <duwe@....de>
Cc:	Michael Ellerman <mpe@...erman.id.au>,
	Jiri Kosina <jikos@...nel.org>,
	Miroslav Benes <mbenes@...e.cz>, linuxppc-dev@...abs.org,
	bsingharora@...il.com, linux-kernel@...r.kernel.org,
	rostedt@...dmis.org, kamalesh@...ux.vnet.ibm.com, pmladek@...e.com,
	jeyu@...hat.com, live-patching@...r.kernel.org
Subject: Re: [PATCH 0/5] Live patching for powerpc

On Thu, Apr 14, 2016 at 05:20:29PM +0200, Torsten Duwe wrote:
> On Thu, Apr 14, 2016 at 11:08:02PM +1000, Michael Ellerman wrote:
> > On Thu, 2016-04-14 at 14:57 +0200, Torsten Duwe wrote:
> > 
> > > FTR: then I still have a few ppc64 hunks floating around to support certain consistency
> > > models...
> > 
> > OK. I'm not quite sure what you mean but post them and we'll see I guess :)
> 
> It's *roughly* the ppc64 equivalent of Josh Poimboeuf's Mar 25
> | [RFC PATCH v1.9 14/14] livepatch: update task universe when exiting kernel
> which only considers x86.
> 
> It's forward ported from an earlier code base; there's some glue missing,
> but here it is, for reference.
> 
> Signed-off-by: Torsten Duwe <duwe@...e.de>

Hi Torsten,

Thanks for sharing.  This is quite fortuitous as Miroslav just today
mentioned to me that we would need something like this.  If you don't
mind, I may pull this patch or some variant of it into v2 of the
consistency model.

> 
> 
> diff --git a/arch/powerpc/include/asm/thread_info.h b/arch/powerpc/include/asm/thread_info.h
> index b034ecd..3e749f4 100644
> --- a/arch/powerpc/include/asm/thread_info.h
> +++ b/arch/powerpc/include/asm/thread_info.h
> @@ -92,6 +92,7 @@ static inline struct thread_info *current_thread_info(void)
>  					   TIF_NEED_RESCHED */
>  #define TIF_32BIT		4	/* 32 bit binary */
>  #define TIF_RESTORE_TM		5	/* need to restore TM FP/VEC/VSX */
> +#define TIF_KLP_NEED_UPDATE	6	/* kGraft patching in progress */
>  #define TIF_SYSCALL_AUDIT	7	/* syscall auditing active */
>  #define TIF_SINGLESTEP		8	/* singlestepping active */
>  #define TIF_NOHZ		9	/* in adaptive nohz mode */
> @@ -115,8 +116,10 @@ static inline struct thread_info *current_thread_info(void)
>  #define _TIF_POLLING_NRFLAG	(1<<TIF_POLLING_NRFLAG)
>  #define _TIF_32BIT		(1<<TIF_32BIT)
>  #define _TIF_RESTORE_TM		(1<<TIF_RESTORE_TM)
> +#define _TIF_KLP_NEED_UPDATE	(1<<TIF_KLP_NEED_UPDATE)
>  #define _TIF_SYSCALL_AUDIT	(1<<TIF_SYSCALL_AUDIT)
>  #define _TIF_SINGLESTEP		(1<<TIF_SINGLESTEP)
> +#define _TIF_NOHZ		(1<<TIF_NOHZ)
>  #define _TIF_SECCOMP		(1<<TIF_SECCOMP)
>  #define _TIF_RESTOREALL		(1<<TIF_RESTOREALL)
>  #define _TIF_NOERROR		(1<<TIF_NOERROR)
> @@ -124,7 +127,7 @@ static inline struct thread_info *current_thread_info(void)
>  #define _TIF_UPROBE		(1<<TIF_UPROBE)
>  #define _TIF_SYSCALL_TRACEPOINT	(1<<TIF_SYSCALL_TRACEPOINT)
>  #define _TIF_EMULATE_STACK_STORE	(1<<TIF_EMULATE_STACK_STORE)
> -#define _TIF_NOHZ		(1<<TIF_NOHZ)
> +
>  #define _TIF_SYSCALL_DOTRACE	(_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
>  				 _TIF_SECCOMP | _TIF_SYSCALL_TRACEPOINT | \
>  				 _TIF_NOHZ)
> @@ -132,7 +135,8 @@ static inline struct thread_info *current_thread_info(void)
>  #define _TIF_USER_WORK_MASK	(_TIF_SIGPENDING | _TIF_NEED_RESCHED | \
>  				 _TIF_NOTIFY_RESUME | _TIF_UPROBE | \
>  				 _TIF_RESTORE_TM)
> -#define _TIF_PERSYSCALL_MASK	(_TIF_RESTOREALL|_TIF_NOERROR)
> +
> +#define _TIF_PERSYSCALL_MASK	(_TIF_RESTOREALL|_TIF_NOERROR|_TIF_KLP_NEED_UPDATE)
>  
>  /* Bits in local_flags */
>  /* Don't move TLF_NAPPING without adjusting the code in entry_32.S */
> diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
> index 5bbd1bc..17f8a18 100644
> --- a/arch/powerpc/kernel/entry_64.S
> +++ b/arch/powerpc/kernel/entry_64.S
> @@ -151,8 +151,8 @@ END_FW_FTR_SECTION_IFSET(FW_FEATURE_SPLPAR)
>  
>  	CURRENT_THREAD_INFO(r11, r1)
>  	ld	r10,TI_FLAGS(r11)
> -	andi.	r11,r10,_TIF_SYSCALL_DOTRACE
> -	bne	syscall_dotrace		/* does not return */
> +	andi.	r10,r10,(_TIF_SYSCALL_DOTRACE|_TIF_KLP_NEED_UPDATE)
> +	bne-	syscall_precall		/* does not return */
>  	cmpldi	0,r0,NR_syscalls
>  	bge-	syscall_enosys
>  
> @@ -245,6 +245,17 @@ syscall_error:
>  	neg	r3,r3
>  	std	r5,_CCR(r1)
>  	b	.Lsyscall_error_cont
> +
> +syscall_precall:
> +	andi.	r10,r10,(_TIF_KLP_NEED_UPDATE)
> +	beq+	syscall_dotrace
> +
> +	addi	r11,r11,TI_FLAGS
> +1:	ldarx	r12,0,r11
> +	andc	r12,r12,r10
> +	stdcx.	r12,0,r11
> +	bne-	1b
> +	subi	r11,r11,TI_FLAGS
>  	
>  /* Traced system call support */
>  syscall_dotrace:

-- 
Josh