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zipl: fix stfle zero padding

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The stfle inline assembly returns the number of double words written
(condition code 0) or the double words it would have written
(condition code 3), if the memory array it got as parameter would have
been large enough.

The current stfle implementation assumes that the array is always
large enough and clears those parts of the array that have not been
written to with a subsequent memset call.

If however the array is not large enough memset will get a negative
length parameter, which means that memset clears memory until it gets
an exception and the system crashes.

To fix this simply limit the maximum length. Move also the inline
assembly to an extra function to avoid clobbering of register 0, which
might happen because of the added MIN invocation together with code
instrumentation.

Reviewed-by: Stefan Haberland <sth@linux.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>
This commit is contained in:
Heiko Carstens
2019-06-17 14:42:14 +02:00
committed by Jan Höppner
parent 87f47f60e4
commit 1b318fe114
1 changed files with 14 additions and 7 deletions
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21
zipl/boot/s390.h
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@@ -452,6 +452,18 @@ static inline int test_facility(unsigned long nr)
return __test_facility(nr, &S390_lowcore.stfle_fac_list);
}
static unsigned long __stfle_asm(u64 *stfle_fac_list, int size)
{
register unsigned long reg0 asm("0") = size - 1;
asm volatile(
".insn s,0xb2b00000,0(%1)" /* stfle */
: "+d" (reg0)
: "a" (stfle_fac_list)
: "memory", "cc");
return reg0;
}
/**
* stfle - Store facility list extended
* @stfle_fac_list: array where facility list can be stored
@@ -470,13 +482,8 @@ static inline void stfle(u64 *stfle_fac_list, int size)
memcpy(stfle_fac_list, &S390_lowcore.stfl_fac_list, 4);
if (S390_lowcore.stfl_fac_list & 0x01000000) {
/* More facility bits available with stfle */
register unsigned long reg0 asm("0") = size - 1;
asm volatile(".insn s,0xb2b00000,0(%1)" /* stfle */
: "+d" (reg0)
: "a" (stfle_fac_list)
: "memory", "cc");
nr = (reg0 + 1) * 8; /* # bytes stored by stfle */
nr = __stfle_asm(stfle_fac_list, size);
nr = MIN((nr + 1) * 8, size * 8UL);
}
memset((char *) stfle_fac_list + nr, 0, size * 8 - nr);
}