From: Ram Pai <linuxram@us.ibm.com>
To: mpe@ellerman.id.au
Cc: linuxppc-dev@lists.ozlabs.org, hbabu@us.ibm.com,
mhocko@kernel.org, bauerman@linux.vnet.ibm.com,
Ulrich.Weigand@de.ibm.com, fweimer@redhat.com, msuchanek@suse.de
Subject: Re: [PATCH] powerpc/pkeys: preallocate execute_only key only if the key is available.
Date: Wed, 20 Jun 2018 18:14:14 -0700 [thread overview]
Message-ID: <20180621011414.GI5294@ram.oc3035372033.ibm.com> (raw)
In-Reply-To: <1529472862-26506-1-git-send-email-linuxram@us.ibm.com>
On Tue, Jun 19, 2018 at 10:34:22PM -0700, Ram Pai wrote:
> Key 2 is preallocated and reserved for execute-only key. In rare
> cases if key-2 is unavailable, mprotect(PROT_EXEC) will behave
> incorrectly. NOTE: mprotect(PROT_EXEC) uses execute-only key.
>
> Ensure key 2 is available for preallocation before reserving it for
> execute_only purpose.
>
> CC: Michael Ellerman <mpe@ellerman.id.au>
> CC: Thiago Jung Bauermann <bauerman@linux.ibm.com>
> Signed-off-by: Ram Pai <linuxram@us.ibm.com>
> ---
> arch/powerpc/mm/pkeys.c | 14 +++++++++-----
> 1 files changed, 9 insertions(+), 5 deletions(-)
>
> diff --git a/arch/powerpc/mm/pkeys.c b/arch/powerpc/mm/pkeys.c
> index cec990c..2013ef0 100644
> --- a/arch/powerpc/mm/pkeys.c
> +++ b/arch/powerpc/mm/pkeys.c
> @@ -19,6 +19,7 @@
> u64 pkey_amr_mask; /* Bits in AMR not to be touched */
> u64 pkey_iamr_mask; /* Bits in AMR not to be touched */
> u64 pkey_uamor_mask; /* Bits in UMOR not to be touched */
> +u32 execute_only_key = 2;
this cannot be unsigned, since it can get set to -1 if key 2 is not available. :(
Please ignore this patch. Will resend a fixed version.
>
> #define AMR_BITS_PER_PKEY 2
> #define AMR_RD_BIT 0x1UL
> @@ -26,7 +27,6 @@
> #define IAMR_EX_BIT 0x1UL
> #define PKEY_REG_BITS (sizeof(u64)*8)
> #define pkeyshift(pkey) (PKEY_REG_BITS - ((pkey+1) * AMR_BITS_PER_PKEY))
> -#define EXECUTE_ONLY_KEY 2
>
> static void scan_pkey_feature(void)
> {
> @@ -122,8 +122,12 @@ int pkey_initialize(void)
> #else
> os_reserved = 0;
> #endif
> +
> + if ((pkeys_total - os_reserved) <= execute_only_key)
> + execute_only_key = -1;
> +
.snip..
RP
prev parent reply other threads:[~2018-06-21 1:14 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-20 5:34 [PATCH] powerpc/pkeys: preallocate execute_only key only if the key is available Ram Pai
2018-06-21 1:14 ` Ram Pai [this message]
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