diff options
| author | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2012-11-21 16:36:27 +0100 |
|---|---|---|
| committer | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2012-11-23 11:14:33 +0100 |
| commit | 39efd4ec9a2967e9720be7b66d9a4b31a58dbf61 (patch) | |
| tree | 084c2ba72e4ffaf2dcc3d3c89f7ce32ab93d9827 /arch/s390/kernel/entry64.S | |
| parent | c68dba202f54a4c9c68a8bb83d426bf8a00c99f8 (diff) | |
| download | linux-39efd4ec9a2967e9720be7b66d9a4b31a58dbf61.tar.bz2 | |
s390/ptrace: race of single stepping vs signal delivery
The current single step code is racy in regard to concurrent delivery
of signals. If a signal is delivered after a PER program check occurred
but before the TIF_PER_TRAP bit has been checked in entry[64].S the code
clears TIF_PER_TRAP and then calls do_signal. This is wrong, if the
instruction completed (or has been suppressed) a SIGTRAP should be
delivered to the debugger in any case. Only if the instruction has been
nullified the SIGTRAP may not be send.
The new logic always sets TIF_PER_TRAP if the program check indicates PER
tracing but removes it again for all program checks that are nullifying.
The effect is that for each change in the PSW address we now get a
single SIGTRAP.
Reported-by: Andreas Arnez <arnez@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390/kernel/entry64.S')
| -rw-r--r-- | arch/s390/kernel/entry64.S | 7 |
1 files changed, 3 insertions, 4 deletions
diff --git a/arch/s390/kernel/entry64.S b/arch/s390/kernel/entry64.S index e42842a3072b..7a2d22dda9ef 100644 --- a/arch/s390/kernel/entry64.S +++ b/arch/s390/kernel/entry64.S @@ -262,12 +262,12 @@ sysc_work: jo sysc_mcck_pending tm __TI_flags+7(%r12),_TIF_NEED_RESCHED jo sysc_reschedule + tm __TI_flags+7(%r12),_TIF_PER_TRAP + jo sysc_singlestep tm __TI_flags+7(%r12),_TIF_SIGPENDING jo sysc_sigpending tm __TI_flags+7(%r12),_TIF_NOTIFY_RESUME jo sysc_notify_resume - tm __TI_flags+7(%r12),_TIF_PER_TRAP - jo sysc_singlestep j sysc_return # beware of critical section cleanup # @@ -288,7 +288,6 @@ sysc_mcck_pending: # _TIF_SIGPENDING is set, call do_signal # sysc_sigpending: - ni __TI_flags+7(%r12),255-_TIF_PER_TRAP # clear TIF_PER_TRAP lgr %r2,%r11 # pass pointer to pt_regs brasl %r14,do_signal tm __TI_flags+7(%r12),_TIF_SYSCALL @@ -313,7 +312,7 @@ sysc_notify_resume: # _TIF_PER_TRAP is set, call do_per_trap # sysc_singlestep: - ni __TI_flags+7(%r12),255-(_TIF_SYSCALL | _TIF_PER_TRAP) + ni __TI_flags+7(%r12),255-_TIF_PER_TRAP lgr %r2,%r11 # pass pointer to pt_regs larl %r14,sysc_return jg do_per_trap |