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Subject: Re: [PATCH v3 2/2] powerpc/ptrace: Hard wire PT_SOFTE value to 1 in
 gpr_get() too
To:     Oleg Nesterov <oleg@redhat.com>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Madhavan Srinivasan <maddy@linux.vnet.ibm.com>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Paul Mackerras <paulus@samba.org>
Cc:     Al Viro <viro@zeniv.linux.org.uk>,
        "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
        Christophe Leroy <christophe.leroy@c-s.fr>,
        Jan Kratochvil <jan.kratochvil@redhat.com>,
        Nicholas Piggin <npiggin@gmail.com>,
        linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
References: <20201119160154.GA5183@redhat.com>
 <20201119160247.GB5188@redhat.com>
From:   Christophe Leroy <christophe.leroy@csgroup.eu>
Message-ID: <4e132957-c53c-4b06-9546-26d1de0a672f@csgroup.eu>
Date:   Thu, 19 Nov 2020 18:18:23 +0100
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Le 19/11/2020 à 17:02, Oleg Nesterov a écrit :
> The commit a8a4b03ab95f ("powerpc: Hard wire PT_SOFTE value to 1 in
> ptrace & signals") changed ptrace_get_reg(PT_SOFTE) to report 0x1,
> but PTRACE_GETREGS still copies pt_regs->softe as is.
> 
> This is not consistent and this breaks the user-regs-peekpoke test
> from https://sourceware.org/systemtap/wiki/utrace/tests/
> 
> Reported-by: Jan Kratochvil <jan.kratochvil@redhat.com>
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
> ---
>   arch/powerpc/kernel/ptrace/ptrace-tm.c   | 8 +++++++-
>   arch/powerpc/kernel/ptrace/ptrace-view.c | 8 +++++++-
>   2 files changed, 14 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/ptrace/ptrace-tm.c b/arch/powerpc/kernel/ptrace/ptrace-tm.c
> index f8fcbd85d4cb..d0d339f86e61 100644
> --- a/arch/powerpc/kernel/ptrace/ptrace-tm.c
> +++ b/arch/powerpc/kernel/ptrace/ptrace-tm.c
> @@ -87,6 +87,10 @@ int tm_cgpr_get(struct task_struct *target, const struct user_regset *regset,
>   		struct membuf to)
>   {
>   	struct membuf to_msr = membuf_at(&to, offsetof(struct pt_regs, msr));
> +#ifdef CONFIG_PPC64
> +	struct membuf to_softe = membuf_at(&to,
> +					offsetof(struct pt_regs, softe));

Should fit on a single line I think.

> +#endif
>   
>   	if (!cpu_has_feature(CPU_FTR_TM))
>   		return -ENODEV;
> @@ -102,7 +106,9 @@ int tm_cgpr_get(struct task_struct *target, const struct user_regset *regset,
>   				sizeof(struct user_pt_regs));
>   
>   	membuf_store(&to_msr, get_user_ckpt_msr(target));
> -
> +#ifdef CONFIG_PPC64
> +	membuf_store(&to_softe, 0x1ul);
> +#endif
>   	return membuf_zero(&to, ELF_NGREG * sizeof(unsigned long) -
>   				sizeof(struct user_pt_regs));
>   }
> diff --git a/arch/powerpc/kernel/ptrace/ptrace-view.c b/arch/powerpc/kernel/ptrace/ptrace-view.c
> index 39686ede40b3..f554ccfcbfae 100644
> --- a/arch/powerpc/kernel/ptrace/ptrace-view.c
> +++ b/arch/powerpc/kernel/ptrace/ptrace-view.c
> @@ -218,6 +218,10 @@ static int gpr_get(struct task_struct *target, const struct user_regset *regset,
>   		   struct membuf to)
>   {
>   	struct membuf to_msr = membuf_at(&to, offsetof(struct pt_regs, msr));
> +#ifdef CONFIG_PPC64
> +	struct membuf to_softe = membuf_at(&to,
> +					offsetof(struct pt_regs, softe));

Should fit on a single line I think.

> +#endif
>   	int i;
>   
>   	if (target->thread.regs == NULL)
> @@ -233,7 +237,9 @@ static int gpr_get(struct task_struct *target, const struct user_regset *regset,
>   				sizeof(struct user_pt_regs));
>   
>   	membuf_store(&to_msr, get_user_msr(target));
> -
> +#ifdef CONFIG_PPC64
> +	membuf_store(&to_softe, 0x1ul);
> +#endif
>   	return membuf_zero(&to, ELF_NGREG * sizeof(unsigned long) -
>   				sizeof(struct user_pt_regs));
>   }
> 

Christophe