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@xxxxxxxxx> --- linux-2.6.18-rc2/arch/ia64/kernel/pal.S 2006-07-26 11:59:06.000000000 +0800 +++ linux-2.6.18-rc2-fix/arch/ia64/kernel/pal.S 2006-07-26 12:04:18.000000000 +0800 @@ -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 ;; - : send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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