[IA64] Do not assume output registers be reservered.

We found an issue in pal.S.

According to the software runtime SPEC,
The caller's output registers do not need to be preserved for
caller. The callee may reuse input registers for any other
purpose within the procedure.

in ia64_pal_call_phys_stacked,

input registers are copied to output registers before call
into ia64_switch_mode_phys, then used to call into PAL. This
assumes output registers are preserved in ia64_switch_mode_phys,
which may not be true.

In this particular case, ia64_switch_mode_phys alloc a null frame
, and mask off psr.i.
If an interrupt comes at this small window,
or an MCA comes inside the procedure, output registers
maybe changed,
then the pal call may got some staled input registers.

This patch moves the copies from input to output
after ia64_switch_mode_phys to follow the software
runtime convention.

It  also removed some unused labels in
ia64_pal_call_phys_stacked.

Signed-off-by: Zou Nan hai <nanhai.zou@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

diff --git a/arch/ia64/kernel/pal.S b/arch/ia64/kernel/pal.S
index 5018c7f2e7a898b01f4e6213e7681de11f9ff67a..ebaf1e685f5e350312bf72f3efbcb47288f58f1e 100644 (file)
--- a/arch/ia64/kernel/pal.S
+++ b/arch/ia64/kernel/pal.S
@@ -217,12 +217,7 @@ GLOBAL_ENTRY(ia64_pal_call_phys_stacked)
        .body
        ;;
        ld8 loc2 = [loc2]               // loc2 <- entry point
-       mov out0 = in0          // first argument
-       mov out1 = in1          // copy arg2
-       mov out2 = in2          // copy arg3
-       mov out3 = in3          // copy arg3
-       ;;
-       mov loc3 = psr          // save psr
+       mov loc3 = psr                  // save psr
        ;;
        mov loc4=ar.rsc                 // save RSE configuration
        dep.z loc2=loc2,0,61            // convert pal entry point to physical
@@ -236,18 +231,23 @@ GLOBAL_ENTRY(ia64_pal_call_phys_stacked)
        ;;
        andcm r16=loc3,r16              // removes bits to clear from psr
        br.call.sptk.many rp=ia64_switch_mode_phys
-.ret6:
+
+       mov out0 = in0                  // first argument
+       mov out1 = in1                  // copy arg2
+       mov out2 = in2                  // copy arg3
+       mov out3 = in3                  // copy arg3
        mov loc5 = r19
        mov loc6 = r20
+
        br.call.sptk.many rp=b7         // now make the call
-.ret7:
+
        mov ar.rsc=0                    // put RSE in enforced lazy, LE mode
        mov r16=loc3                    // r16= original psr
        mov r19=loc5
        mov r20=loc6
        br.call.sptk.many rp=ia64_switch_mode_virt      // return to virtual mode
 
-.ret8: mov psr.l  = loc3               // restore init PSR
+       mov psr.l  = loc3               // restore init PSR
        mov ar.pfs = loc1
        mov rp = loc0
        ;;