lkml.org 
[lkml]   [2017]   [Mar]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v6 4/4] sparc64: Add support for ADI (Application Data Integrity)
From
Date

> On Feb 28, 2017, at 10:35 AM, Khalid Aziz <khalid.aziz@oracle.com> wrote:
>
> diff --git a/arch/sparc/kernel/etrap_64.S b/arch/sparc/kernel/etrap_64.S
> index 1276ca2..7be33bf 100644
> --- a/arch/sparc/kernel/etrap_64.S
> +++ b/arch/sparc/kernel/etrap_64.S
> @@ -132,7 +132,33 @@ etrap_save: save %g2, -STACK_BIAS, %sp
> stx %g6, [%sp + PTREGS_OFF + PT_V9_G6]
> stx %g7, [%sp + PTREGS_OFF + PT_V9_G7]
> or %l7, %l0, %l7
> - sethi %hi(TSTATE_TSO | TSTATE_PEF), %l0
> +661: sethi %hi(TSTATE_TSO | TSTATE_PEF), %l0
> + /*
> + * If userspace is using ADI, it could potentially pass
> + * a pointer with version tag embedded in it. To maintain
> + * the ADI security, we must enable PSTATE.mcde. Userspace
> + * would have already set TTE.mcd in an earlier call to
> + * kernel and set the version tag for the address being
> + * dereferenced. Setting PSTATE.mcde would ensure any
> + * access to userspace data through a system call honors
> + * ADI and does not allow a rogue app to bypass ADI by
> + * using system calls. Setting PSTATE.mcde only affects
> + * accesses to virtual addresses that have TTE.mcd set.
> + * Set PMCDPER to ensure any exceptions caused by ADI
> + * version tag mismatch are exposed before system call
> + * returns to userspace. Setting PMCDPER affects only
> + * writes to virtual addresses that have TTE.mcd set and
> + * have a version tag set as well.
> + */
> + .section .sun_m7_1insn_patch, "ax"
> + .word 661b
> + sethi %hi(TSTATE_TSO | TSTATE_PEF | TSTATE_MCDE), %l0
> + .previous
> +661: nop
> + .section .sun_m7_1insn_patch, "ax"
> + .word 661b
> + .word 0xaf902001 /* wrpr %g0, 1, %pmcdper */

Since PMCDPER is never cleared, setting it here is quickly going to set it on all CPUs and then become an expensive "nop" that burns ~50 cycles each time through etrap. Consider setting it at boot time and when a CPU is DR'd into the system.

Anthony

\
 
 \ /
  Last update: 2017-03-07 01:21    [W:1.228 / U:0.080 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site