RE: [PATCH v2 19/28] arm64/sve: ptrace and ELF coredump support

Hi Dave,

Thank you for your reply.

> Your fix looks correct and seems to work.  For stylistic reasons, I may
> write it like this instead, but the effect should be the same:
> 
> 	header->max_vl = sve_max_vl;
> 	if (WARN_ON(!sve_vl_valid(sve_max_vl))
> 		header->max_vl = header->vl;

It is better than my fix.
Please, apply it at next version.

Best regards,
Takayuki Okamoto

> -----Original Message-----
> From: linux-arm-kernel
> [mailto:[email protected]] On Behalf Of Dave
> Martin
> Sent: Thursday, September 7, 2017 3:17 AM
> To: Okamoto, Takayuki <[email protected]>
> Cc: [email protected]; [email protected]; Ard
> Biesheuvel <[email protected]>; Szabolcs Nagy
> <[email protected]>; [email protected]; Yao Qi <[email protected]>;
> Alan Hayward <[email protected]>; Will Deacon <[email protected]>;
> Oleg Nesterov <[email protected]>; Richard Sandiford
> <[email protected]>; Alexander Viro <[email protected]>;
> Catalin Marinas <[email protected]>; Alex Bennée
> <[email protected]>; [email protected];
> [email protected]
> Subject: Re: [PATCH v2 19/28] arm64/sve: ptrace and ELF coredump support
> 
> On Wed, Sep 06, 2017 at 04:21:50PM +0000, Okamoto, Takayuki wrote:
> > Hi Dave,
> >
> > I am an engineer of the postK computer from Fujitsu.
> >
> > When I tried to read "max_vl" by ptrace with this patch on our local SVE
> > simulator, it was read as zero.
> > I think the cause of this incident is that "max_vl" is set as "header->vl"
> > only on warning case in sve_init_header_from_task().
> > "max_vl" should be set up also on normal case, like the following patch.
> >
> >
> > --- a/arch/arm64/kernel/ptrace.c
> > +++ b/arch/arm64/kernel/ptrace.c
> > @@ -755,6 +755,8 @@ static void sve_init_header_from_task(struct
> user_sve_header *header,
> >
> >         if (WARN_ON(!sve_vl_valid(sve_max_vl)))
> >                 header->max_vl = header->vl;
> > +       else
> > +               header->max_vl = sve_max_vl;
> >
> >         header->size = SVE_PT_SIZE(vq, header->flags);
> >         header->max_size =
> SVE_PT_SIZE(sve_vq_from_vl(header->max_vl),
> 
> Hi, thanks for reporting this.
> 
> It looks like a refactoring mistake I made while removing BUG_ON()s,
> which I missed in my testing.
> 
> Your fix looks correct and seems to work.  For stylistic reasons, I may
> write it like this instead, but the effect should be the same:
> 
> 	header->max_vl = sve_max_vl;
> 	if (WARN_ON(!sve_vl_valid(sve_max_vl))
> 		header->max_vl = header->vl;
> 
> Cheers
> ---Dave
> 
> >
> >
> > Best regards,
> > Takayuki Okamoto
> >
> > -----Original Message-----
> > From: [email protected] [mailto:[email protected]] On
> Behalf Of Dave Martin
> > Sent: Friday, September 1, 2017 2:01 AM
> > To: [email protected]
> > Cc: Catalin Marinas <[email protected]>; Will Deacon
> <[email protected]>; Ard Biesheuvel <[email protected]>; Alex
> Bennée <[email protected]>; Szabolcs Nagy <[email protected]>;
> Richard Sandiford <[email protected]>;
> [email protected]; [email protected];
> [email protected]; [email protected]; Alan Hayward
> <[email protected]>; Yao Qi <[email protected]>; Oleg Nesterov
> <[email protected]>; Alexander Viro <[email protected]>
> > Subject: [PATCH v2 19/28] arm64/sve: ptrace and ELF coredump support
> >
> 
> [...]
> 
> > @@ -702,6 +737,210 @@ static int system_call_set(struct task_struct
> *target,
> >  	return ret;
> >  }
> >
> > +#ifdef CONFIG_ARM64_SVE
> > +
> > +static void sve_init_header_from_task(struct user_sve_header *header,
> > +				      struct task_struct *target)
> > +{
> > +	unsigned int vq;
> > +
> > +	memset(header, 0, sizeof(*header));
> > +
> > +	header->flags = test_tsk_thread_flag(target, TIF_SVE) ?
> > +		SVE_PT_REGS_SVE : SVE_PT_REGS_FPSIMD;
> > +	if (test_tsk_thread_flag(target, TIF_SVE_VL_INHERIT))
> > +		header->flags |= SVE_PT_VL_INHERIT;
> > +
> > +	header->vl = target->thread.sve_vl;
> > +	vq = sve_vq_from_vl(header->vl);
> > +
> > +	if (WARN_ON(!sve_vl_valid(sve_max_vl)))
> > +		header->max_vl = header->vl;
> > +
> > +	header->size = SVE_PT_SIZE(vq, header->flags);
> > +	header->max_size = SVE_PT_SIZE(sve_vq_from_vl(header->max_vl),
> > +				      SVE_PT_REGS_SVE);
> > +}
> 
> [...]
> 
> _______________________________________________
> linux-arm-kernel mailing list
> [email protected]
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

_______________________________________________
kvmarm mailing list
[email protected]
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm