linux/arch/s390/include/asm/facility.h
Michael Holzheu 37e37c20ab [S390] Fix stfle() lowcore protection problem
The stfle() function writes into lowcore memory when stfl_fac_list
is initialized with "S390_lowcore.stfl_fac_list = 0". For older
compilers this triggers a lowcore exception. With newer compilers
and "-OXX" compile option the bug does not show up because
the "S390_lowcore.stfl_fac_list" initialization is removed by the
compiler. The reason for thatis the incorrect "=m"
(S390_lowcore.stfl_fac_list) constraint in the stfl inline assembly.

The following shows the disassembly of the stfle() optimized code
that is inlined in the lgr_info_get() function:

000000000011325c <lgr_info_get>:
  11325c:       eb 9f f0 60 00 24       stmg    %r9,%r15,96(%r15)
  113262:       c0 d0 00 29 0e 47       larl    %r13,634ef0 <servi..>
  113268:       a7 f1 3f c0             tml     %r15,16320
  11326c:       b9 04 00 ef             lgr     %r14,%r15
  113270:       a7 84 00 01             je      113272 <lgr_info_g..>
  113274:       a7 fb ff c0             aghi    %r15,-64
  113278:       b9 04 00 c2             lgr     %r12,%r2
  11327c:       a7 29 00 01             lghi    %r2,1
  113280:       e3 e0 f0 98 00 24       stg     %r14,152(%r15)
  113286:       d7 97 c0 00 c0 00       xc      0(152,%r12),0(%r12)
  11328c:       c0 e5 00 28 db 4c       brasl   %r14,62e924 <add_e..>
  113292:       b2 b1 00 00             stfl    0

To fix the problem we now clear the S390_lowcore.stfl_fac_list at
startup in "head.S" for all machine types before lowcore protection
is enabled.

In addition to that the "=m" constraint is replaced by "+m".

Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2012-04-11 14:28:26 +02:00

63 lines
1.6 KiB
C

/*
* Copyright IBM Corp. 1999, 2009
*
* Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
*/
#ifndef __ASM_FACILITY_H
#define __ASM_FACILITY_H
#include <linux/string.h>
#include <linux/preempt.h>
#include <asm/lowcore.h>
#define MAX_FACILITY_BIT (256*8) /* stfle_fac_list has 256 bytes */
/*
* The test_facility function uses the bit odering where the MSB is bit 0.
* That makes it easier to query facility bits with the bit number as
* documented in the Principles of Operation.
*/
static inline int test_facility(unsigned long nr)
{
unsigned char *ptr;
if (nr >= MAX_FACILITY_BIT)
return 0;
ptr = (unsigned char *) &S390_lowcore.stfle_fac_list + (nr >> 3);
return (*ptr & (0x80 >> (nr & 7))) != 0;
}
/**
* stfle - Store facility list extended
* @stfle_fac_list: array where facility list can be stored
* @size: size of passed in array in double words
*/
static inline void stfle(u64 *stfle_fac_list, int size)
{
unsigned long nr;
preempt_disable();
asm volatile(
" .insn s,0xb2b10000,0(0)\n" /* stfl */
"0:\n"
EX_TABLE(0b, 0b)
: "+m" (S390_lowcore.stfl_fac_list));
nr = 4; /* bytes stored by stfl */
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 */
}
memset((char *) stfle_fac_list + nr, 0, size * 8 - nr);
preempt_enable();
}
#endif /* __ASM_FACILITY_H */