linux-kernel - Re: [RFC v6 35/62] powerpc: Deliver SEGV signal on pkey violation

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Date:   Sat, 19 Aug 2017 14:09:58 -0500
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     Ram Pai <linuxram@...ibm.com>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-mm@...ck.org, x86@...nel.org,
        linux-doc@...r.kernel.org, linux-kselftest@...r.kernel.org,
        benh@...nel.crashing.org, paulus@...ba.org, mpe@...erman.id.au,
        khandual@...ux.vnet.ibm.com, aneesh.kumar@...ux.vnet.ibm.com,
        bsingharora@...il.com, dave.hansen@...el.com, hbabu@...ibm.com,
        arnd@...db.de, akpm@...ux-foundation.org, corbet@....net,
        mingo@...hat.com, mhocko@...nel.org
Subject: Re: [RFC v6 35/62] powerpc: Deliver SEGV signal on pkey violation

Ram Pai <linuxram@...ibm.com> writes:

> diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
> index d4e545d..fe1e7c7 100644
> --- a/arch/powerpc/kernel/traps.c
> +++ b/arch/powerpc/kernel/traps.c
> @@ -20,6 +20,7 @@
>  #include <linux/sched/debug.h>
>  #include <linux/kernel.h>
>  #include <linux/mm.h>
> +#include <linux/pkeys.h>
>  #include <linux/stddef.h>
>  #include <linux/unistd.h>
>  #include <linux/ptrace.h>
> @@ -247,6 +248,15 @@ void user_single_step_siginfo(struct task_struct *tsk,
>  	info->si_addr = (void __user *)regs->nip;
>  }
>  
> +#ifdef CONFIG_PPC64_MEMORY_PROTECTION_KEYS
> +static void fill_sig_info_pkey(int si_code, siginfo_t *info, unsigned long addr)
> +{
> +	if (si_code != SEGV_PKUERR)
> +		return;

Given that SEGV_PKUERR is a signal specific si_code this test is
insufficient to detect an pkey error.  You also need to check
that signr == SIGSEGV

> +	info->si_pkey = get_paca()->paca_pkey;
> +}
> +#endif /* CONFIG_PPC64_MEMORY_PROTECTION_KEYS */
> +
>  void _exception(int signr, struct pt_regs *regs, int code, unsigned long addr)
>  {
>  	siginfo_t info;
> @@ -274,6 +284,11 @@ void _exception(int signr, struct pt_regs *regs, int code, unsigned long addr)
>  	info.si_signo = signr;
>  	info.si_code = code;
>  	info.si_addr = (void __user *) addr;
> +
> +#ifdef CONFIG_PPC64_MEMORY_PROTECTION_KEYS
> +	fill_sig_info_pkey(code, &info, addr);
> +#endif /* CONFIG_PPC64_MEMORY_PROTECTION_KEYS */
> +
>  	force_sig_info(signr, &info, current);
>  }

Eric