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s390/sclp: make early sclp irq handler more robust 

Make the early sclp interrupt handler more robust:

- disable all interrupt sub classes except for the service signal subclass
- extend ctlreg0 union so it is easily possible to set the service signal
  subclass mask bit without using a magic number
- disable lowcore protection before writing to it
- make sure that all write accesses are done before the original content
  of control register 0 is restored, which could enable lowcore protection

Reviewed-by: Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Heiko Carstens 2017-01-11 09:14:45 +01:00 committed by Martin Schwidefsky
parent 68cc795d19
commit 742dc5773c
2 changed files with 13 additions and 6 deletions
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4
arch/s390/include/asm/ctl_reg.h
View File

@ -62,7 +62,9 @@ union ctlreg0 {
unsigned long : 4;
unsigned long afp : 1; /* AFP-register control */
unsigned long vx : 1; /* Vector enablement control */
unsigned long : 17;
unsigned long : 7;
unsigned long sssm : 1; /* Service signal subclass mask */
unsigned long : 9;
};
};

15
arch/s390/kernel/sclp.c
View File

@ -18,12 +18,16 @@ static bool have_linemode __section(data);
static void _sclp_wait_int(void)
{
unsigned long cr0, cr0_new, psw_mask, addr;
unsigned long psw_mask, addr, flags;
psw_t psw_ext_save, psw_wait;
union ctlreg0 cr0, cr0_new;
__ctl_store(cr0, 0, 0);
cr0_new = cr0 | 0x200;
__ctl_load(cr0_new, 0, 0);
raw_local_irq_save(flags);
__ctl_store(cr0.val, 0, 0);
cr0_new.val = cr0.val & ~CR0_IRQ_SUBCLASS_MASK;
cr0_new.lap = 0;
cr0_new.sssm = 1;
__ctl_load(cr0_new.val, 0, 0);
psw_ext_save = S390_lowcore.external_new_psw;
psw_mask = __extract_psw();
@ -45,8 +49,9 @@ static void _sclp_wait_int(void)
: "cc", "memory");
} while (S390_lowcore.ext_int_code != EXT_IRQ_SERVICE_SIG);
__ctl_load(cr0, 0, 0);
S390_lowcore.external_new_psw = psw_ext_save;
__ctl_load(cr0.val, 0, 0);
raw_local_irq_restore(flags);
}
static int _sclp_servc(unsigned int cmd, char *sccb)