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4f18d869ff
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 kernel 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_t invocation together with code instrumentation. The bug was introduced with commit14375bc4eb("[S390] cleanup facility list handling") but was rather harmless, since it would only write to a rather large array. It became a potential problem with commit3ab121ab18("[S390] kernel: Add z/VM LGR detection"). Since then it writes to an array with only four double words, while some machines already deliver three double words. As soon as machines have a facility bit within the fifth double a crash on IPL would happen. Fixes:14375bc4eb("[S390] cleanup facility list handling") Cc: <stable@vger.kernel.org> # v2.6.37+ Reviewed-by: Vasily Gorbik <gor@linux.ibm.com> Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
104 lines
2.5 KiB
C
104 lines
2.5 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Copyright IBM Corp. 1999, 2009
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*
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* Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
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*/
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#ifndef __ASM_FACILITY_H
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#define __ASM_FACILITY_H
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#include <asm/facility-defs.h>
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#include <linux/string.h>
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#include <linux/preempt.h>
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#include <asm/lowcore.h>
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#define MAX_FACILITY_BIT (sizeof(((struct lowcore *)0)->stfle_fac_list) * 8)
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static inline void __set_facility(unsigned long nr, void *facilities)
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{
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unsigned char *ptr = (unsigned char *) facilities;
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if (nr >= MAX_FACILITY_BIT)
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return;
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ptr[nr >> 3] |= 0x80 >> (nr & 7);
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}
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static inline void __clear_facility(unsigned long nr, void *facilities)
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{
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unsigned char *ptr = (unsigned char *) facilities;
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if (nr >= MAX_FACILITY_BIT)
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return;
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ptr[nr >> 3] &= ~(0x80 >> (nr & 7));
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}
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static inline int __test_facility(unsigned long nr, void *facilities)
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{
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unsigned char *ptr;
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if (nr >= MAX_FACILITY_BIT)
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return 0;
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ptr = (unsigned char *) facilities + (nr >> 3);
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return (*ptr & (0x80 >> (nr & 7))) != 0;
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}
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/*
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* The test_facility function uses the bit odering where the MSB is bit 0.
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* That makes it easier to query facility bits with the bit number as
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* documented in the Principles of Operation.
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*/
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static inline int test_facility(unsigned long nr)
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{
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unsigned long facilities_als[] = { FACILITIES_ALS };
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if (__builtin_constant_p(nr) && nr < sizeof(facilities_als) * 8) {
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if (__test_facility(nr, &facilities_als))
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return 1;
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}
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return __test_facility(nr, &S390_lowcore.stfle_fac_list);
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}
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static inline unsigned long __stfle_asm(u64 *stfle_fac_list, int size)
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{
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register unsigned long reg0 asm("0") = size - 1;
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asm volatile(
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".insn s,0xb2b00000,0(%1)" /* stfle */
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: "+d" (reg0)
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: "a" (stfle_fac_list)
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: "memory", "cc");
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return reg0;
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}
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/**
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* stfle - Store facility list extended
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* @stfle_fac_list: array where facility list can be stored
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* @size: size of passed in array in double words
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*/
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static inline void __stfle(u64 *stfle_fac_list, int size)
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{
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unsigned long nr;
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asm volatile(
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" stfl 0(0)\n"
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: "=m" (S390_lowcore.stfl_fac_list));
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nr = 4; /* bytes stored by stfl */
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memcpy(stfle_fac_list, &S390_lowcore.stfl_fac_list, 4);
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if (S390_lowcore.stfl_fac_list & 0x01000000) {
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/* More facility bits available with stfle */
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nr = __stfle_asm(stfle_fac_list, size);
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nr = min_t(unsigned long, (nr + 1) * 8, size * 8);
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}
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memset((char *) stfle_fac_list + nr, 0, size * 8 - nr);
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}
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static inline void stfle(u64 *stfle_fac_list, int size)
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{
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preempt_disable();
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__stfle(stfle_fac_list, size);
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preempt_enable();
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}
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#endif /* __ASM_FACILITY_H */
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