kernel.git/arch/s390/kernel/entry.S, branch linux-4.11.y

s390/kvm: do not rely on the ILC on kvm host protection fauls

2017-06-17T04:44:18Z

commit c0e7bb38c07cbd8269549ee0a0566021a3c729de upstream. For most cases a protection exception in the host (e.g. copy on write or dirty tracking) on the sie instruction will indicate an instruction length of 4. Turns out that there are some corner cases (e.g. runtime instrumentation) where this is not necessarily true and the ILC is unpredictable. Let's replace our 4 byte rewind_pad with 3 byte nops to prepare for all possible ILCs. Signed-off-by: Christian Borntraeger Signed-off-by: Martin Schwidefsky Signed-off-by: Greg Kroah-Hartman

s390/cputime: fix incorrect system time

2017-05-25T13:46:14Z

commit 07a63cbe8bcb6ba72fb989dcab1ec55ec6c36c7e upstream. git commit c5328901aa1db134 "[S390] entry[64].S improvements" removed the update of the exit_timer lowcore field from the critical section cleanup of the .Lsysc_restore/.Lsysc_done and .Lio_restore/.Lio_done blocks. If the PSW is updated by the critical section cleanup to point to user space again, the interrupt entry code will do a vtime calculation after the cleanup completed with an exit_timer value which has *not* been updated. Due to this incorrect system time deltas are calculated. If an interrupt occured with an old PSW between .Lsysc_restore/.Lsysc_done or .Lio_restore/.Lio_done update __LC_EXIT_TIMER with the system entry time of the interrupt. Tested-by: Christian Borntraeger Signed-off-by: Martin Schwidefsky Signed-off-by: Greg Kroah-Hartman

s390: fix in-kernel program checks

2017-03-01T08:59:27Z

A program check inside the kernel takes a slightly different path in entry.S compare to a normal user fault. A recent change moved the store of the breaking event address into the path taken for in-kernel program checks as well, but %r14 has not been setup to point to the correct location. A wild store is the consequence. Move the store of the breaking event address to the code path for user space faults. Fixes: 34525e1f7e8d ("s390: store breaking event address only for program checks") Reported-by: Michael Holzheu Signed-off-by: Martin Schwidefsky

s390: restore address space when returning to user space

2017-02-23T09:06:38Z

Unbalanced set_fs usages (e.g. early exit from a function and a forgotten set_fs(USER_DS) call) may lead to a situation where the secondary asce is the kernel space asce when returning to user space. This would allow user space to modify kernel space at will. This would only be possible with the above mentioned kernel bug, however we can detect this and fix the secondary asce before returning to user space. Therefore a new TIF_ASCE_SECONDARY which is used within set_fs. When returning to user space check if TIF_ASCE_SECONDARY is set, which would indicate a bug. If it is set print a message to the console, fixup the secondary asce, and then return to user space. This is similar to what is being discussed for x86 and arm: "[RFC] syscalls: Restore address limit after a syscall". Reviewed-by: Christian Borntraeger Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

s390: rename CIF_ASCE to CIF_ASCE_PRIMARY

2017-02-23T09:06:38Z

This is just a preparation patch in order to keep the "restore address space after syscall" patch small. Rename CIF_ASCE to CIF_ASCE_PRIMARY to be unique and specific when introducing a second CIF_ASCE_SECONDARY CIF flag. Suggested-by: Martin Schwidefsky Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

s390/syscall: fix single stepped system calls

2017-02-20T11:38:01Z

Fix PER tracing of system calls after git commit 34525e1f7e8dc478 "s390: store breaking event address only for program checks" broke it. Signed-off-by: Martin Schwidefsky

s390: add no-execute support

2017-02-08T13:13:25Z

Bit 0x100 of a page table, segment table of region table entry can be used to disallow code execution for the virtual addresses associated with the entry. There is one tricky bit, the system call to return from a signal is part of the signal frame written to the user stack. With a non-executable stack this would stop working. To avoid breaking things the protection fault handler checks the opcode that caused the fault for 0x0a77 (sys_sigreturn) and 0x0aad (sys_rt_sigreturn) and injects a system call. This is preferable to the alternative solution with a stub function in the vdso because it works for vdso=off and statically linked binaries as well. Signed-off-by: Martin Schwidefsky

s390: store breaking event address only for program checks

2017-01-31T09:46:53Z

The principles of operations specifies that the breaking event address is stored to the address 0x110 in the prefix page only for program checks. The last branch in user space is lost as soon as a branch in kernel space is executed after e.g. an svc. This makes it impossible to accurately maintain the breaking event address for a user space process. Simplify the code, just copy the current breaking event address from 0x110 to the task structure for program checks from user space. Signed-off-by: Martin Schwidefsky

s390: remove unused labels from entry.S

2016-12-12T11:04:26Z

Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

s390: fix machine check panic stack switch

2016-12-07T06:22:13Z

For system damage machine checks or machine checks due to invalid PSW fields the system will be stopped. In order to get an oops message out before killing the system the machine check handler branches to .Lmcck_panic, switches to the panic stack and then does the usual machine check handling. The switch to the panic stack is incomplete, the stack pointer in %r15 is replaced, but the pt_regs pointer in %r11 is not. The result is a program check which will kill the system in a slightly different way. Signed-off-by: Martin Schwidefsky