Re: [PATCH 6/6] s390: scrub registers on kernel entry and KVM exit

QingFeng Hao
2018-01-19T06:29:20Z

在 2018/1/17 17:48, Martin Schwidefsky 写道:
> Clear all user space registers on entry to the kernel and all KVM guest
> registers on KVM guest exit if the register does not contain either a
> parameter or a result value.
I am not sure if I understand this but it will be safer?
And can we abstract the operations to be a macro like CLEAR_REG_7?
Thanks
>
> Suggested-by: Christian Borntraeger <borntraeger@de.ibm.com>
> Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
> ---
> arch/s390/kernel/entry.S | 41 +++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 41 insertions(+)
>
> diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
> index 2a22c03..47227d3 100644
> --- a/arch/s390/kernel/entry.S
> +++ b/arch/s390/kernel/entry.S
> @@ -322,6 +322,12 @@ ENTRY(sie64a)
> sie_exit:
> lg %r14,__SF_EMPTY+8(%r15) # load guest register save area
> stmg %r0,%r13,0(%r14) # save guest gprs 0-13
> + xgr %r0,%r0 # clear guest registers
> + xgr %r1,%r1
> + xgr %r2,%r2
> + xgr %r3,%r3
> + xgr %r4,%r4
> + xgr %r5,%r5
> lmg %r6,%r14,__SF_GPRS(%r15) # restore kernel registers
> lg %r2,__SF_EMPTY+16(%r15) # return exit reason code
> br %r14
> @@ -358,6 +364,7 @@ ENTRY(system_call)
> UPDATE_VTIME %r8,%r9,__LC_SYNC_ENTER_TIMER
> BPENTER __TI_flags(%r12),_TIF_NOBP
> stmg %r0,%r7,__PT_R0(%r11)
> + xgr %r0,%r0
> mvc __PT_R8(64,%r11),__LC_SAVE_AREA_SYNC
> mvc __PT_PSW(16,%r11),__LC_SVC_OLD_PSW
> mvc __PT_INT_CODE(4,%r11),__LC_SVC_ILC
> @@ -640,6 +647,14 @@ ENTRY(pgm_check_handler)
> 4: lgr %r13,%r11
> la %r11,STACK_FRAME_OVERHEAD(%r15)
> stmg %r0,%r7,__PT_R0(%r11)
> + xgr %r0,%r0 # clear user space registers
> + xgr %r1,%r1
> + xgr %r2,%r2
> + xgr %r3,%r3
> + xgr %r4,%r4
> + xgr %r5,%r5
> + xgr %r6,%r6
> + xgr %r7,%r7
> mvc __PT_R8(64,%r11),__LC_SAVE_AREA_SYNC
> stmg %r8,%r9,__PT_PSW(%r11)
> mvc __PT_INT_CODE(4,%r11),__LC_PGM_ILC
> @@ -706,6 +721,15 @@ ENTRY(io_int_handler)
> lmg %r8,%r9,__LC_IO_OLD_PSW
> SWITCH_ASYNC __LC_SAVE_AREA_ASYNC,__LC_ASYNC_ENTER_TIMER
> stmg %r0,%r7,__PT_R0(%r11)
> + xgr %r0,%r0 # clear user space registers
> + xgr %r1,%r1
> + xgr %r2,%r2
> + xgr %r3,%r3
> + xgr %r4,%r4
> + xgr %r5,%r5
> + xgr %r6,%r6
> + xgr %r7,%r7
> + xgr %r10,%r10
> mvc __PT_R8(64,%r11),__LC_SAVE_AREA_ASYNC
> stmg %r8,%r9,__PT_PSW(%r11)
> mvc __PT_INT_CODE(12,%r11),__LC_SUBCHANNEL_ID
> @@ -924,6 +948,15 @@ ENTRY(ext_int_handler)
> lmg %r8,%r9,__LC_EXT_OLD_PSW
> SWITCH_ASYNC __LC_SAVE_AREA_ASYNC,__LC_ASYNC_ENTER_TIMER
> stmg %r0,%r7,__PT_R0(%r11)
> + xgr %r0,%r0 # clear user space registers
> + xgr %r1,%r1
> + xgr %r2,%r2
> + xgr %r3,%r3
> + xgr %r4,%r4
> + xgr %r5,%r5
> + xgr %r6,%r6
> + xgr %r7,%r7
> + xgr %r10,%r10
> mvc __PT_R8(64,%r11),__LC_SAVE_AREA_ASYNC
> stmg %r8,%r9,__PT_PSW(%r11)
> lghi %r1,__LC_EXT_PARAMS2
> @@ -1133,6 +1166,14 @@ ENTRY(mcck_int_handler)
> .Lmcck_skip:
> lghi %r14,__LC_GPREGS_SAVE_AREA+64
> stmg %r0,%r7,__PT_R0(%r11)
> + xgr %r0,%r0 # clear user space registers
> + xgr %r2,%r2
> + xgr %r3,%r3
> + xgr %r4,%r4
> + xgr %r5,%r5
> + xgr %r6,%r6
> + xgr %r7,%r7
> + xgr %r10,%r10
> mvc __PT_R8(64,%r11),0(%r14)
> stmg %r8,%r9,__PT_PSW(%r11)
> xc __PT_FLAGS(8,%r11),__PT_FLAGS(%r11)

--
Regards
QingFeng Hao