sparc64: rtrap must set PSTATE.mcde before handling outstanding user work

The kernel must execute with PSTATE.mcde=1 for ADI version checking to
be enabled when the kernel reads or writes user memory mapped with ADI
enabled using versioned addresses.  If PSTATE.mcde=0 then the MMU
interprets version bits in an address as address bits, and an access
attempt results in a data access exception.  Until now setting
PSTATE.mcde=1 in the kernel has been handled only by patching etrap to
ensure that is set on entry into the kernel.  However, there are code
paths in rtrap that overwrite PSTATE and inadvertently clear PSTATE.mcde
before additional execution happens in the kernel.

rtrap is executed to exit the kernel and return to user mode execution.
Before restoring registers and returning to user mode, rtrap checks for
work to do.  The check is done with interrupts disabled, and if there is
work to do, then interrupts are enabled before calling a function to
complete the work after which interrupts are disabled again and the
check is repeated.  Interrupts are disabled and enabled by overwriting
PSTATE.  Possible work includes (but is not limited to) preemption,
signal delivery, and  writing out buffered user register windows to the
stack.  All of these may lead to accessing user addresses.  In the case
of preemption, a resumed thread will run with PSTATE.mcde=0 until it
completes a return to user mode or is rescheduled on a CPU where
PSTATE.mcde is set.  If the thread accesses ADI-enabled user memory with
a versioned address (e.g. to complete some I/O) in that timeframe then
the access will fail.  To fix the problem, patch rtrap to set
PSTATE.mcde when interrupts are enabled before handling the work.

Orabug: 25853545
Signed-off-by: Anthony Yznaga <anthony.yznaga@oracle.com>
Reviewed-by: Khalid Aziz <khalid.aziz@oracle.com>
Reviewed-by: Steve Sistare <steven.sistare@oracle.com>
Signed-off-by: Allen Pais <allen.pais@oracle.com>

diff --git a/arch/sparc/kernel/rtrap_64.S b/arch/sparc/kernel/rtrap_64.S
index 709a82ebd294c07bd4b87698c695325e5093a7e4..173af08ae46eeb6d4b1348de0102ca5f2c8c11d0 100644 (file)
--- a/arch/sparc/kernel/rtrap_64.S
+++ b/arch/sparc/kernel/rtrap_64.S
@@ -24,13 +24,21 @@
                .align                  32
 __handle_preemption:
                call                    SCHEDULE_USER
-                wrpr                   %g0, RTRAP_PSTATE, %pstate
+661:            wrpr                   %g0, RTRAP_PSTATE, %pstate
+               .section                .sun4v_adi_1insn_patch, "ax"
+               .word                   661b
+                wrpr                   %g0, RTRAP_PSTATE | PSTATE_MCDE, %pstate
+               .previous
                ba,pt                   %xcc, __handle_preemption_continue
                 wrpr                   %g0, RTRAP_PSTATE_IRQOFF, %pstate
 
 __handle_user_windows:
                call                    fault_in_user_windows
-                wrpr                   %g0, RTRAP_PSTATE, %pstate
+661:            wrpr                   %g0, RTRAP_PSTATE, %pstate
+               .section                .sun4v_adi_1insn_patch, "ax"
+               .word                   661b
+                wrpr                   %g0, RTRAP_PSTATE | PSTATE_MCDE, %pstate
+               .previous
                ba,pt                   %xcc, __handle_preemption_continue
                 wrpr                   %g0, RTRAP_PSTATE_IRQOFF, %pstate
 
@@ -47,7 +55,11 @@ __handle_signal:
                add                     %sp, PTREGS_OFF, %o0
                mov                     %l0, %o2
                call                    do_notify_resume
-                wrpr                   %g0, RTRAP_PSTATE, %pstate
+661:            wrpr                   %g0, RTRAP_PSTATE, %pstate
+               .section                .sun4v_adi_1insn_patch, "ax"
+               .word                   661b
+                wrpr                   %g0, RTRAP_PSTATE | PSTATE_MCDE, %pstate
+               .previous
                wrpr                    %g0, RTRAP_PSTATE_IRQOFF, %pstate
 
                /* Signal delivery can modify pt_regs tstate, so we must

diff --git a/arch/sparc/kernel/urtt_fill.S b/arch/sparc/kernel/urtt_fill.S
index ca1a0c1b9d76f811ae180a014dfb52d10f2447c8..e1b9a99180bdb885429d771282fff802d3561733 100644 (file)
--- a/arch/sparc/kernel/urtt_fill.S
+++ b/arch/sparc/kernel/urtt_fill.S
@@ -49,7 +49,11 @@ user_rtt_fill_fixup_common:
                SET_GL(0)
                .previous
 
-               wrpr    %g0, RTRAP_PSTATE, %pstate
+661:           wrpr    %g0, RTRAP_PSTATE, %pstate
+               .section                .sun4v_adi_1insn_patch, "ax"
+               .word                   661b
+               wrpr    %g0, RTRAP_PSTATE | PSTATE_MCDE, %pstate
+               .previous
 
                mov     %l1, %g6
                ldx     [%g6 + TI_TASK], %g4