kernel/linux.git/arch/s390/include/asm/stacktrace.h, branch v6.6.132

s390/kdump: remove nodat stack restriction for calling nodat functions

2023-04-19T15:24:16+00:00

To allow calling of DAT-off code from kernel the stack needs to be switched to nodat_stack (or other stack mapped as 1:1). Before call_nodat() macro was introduced that was necessary to provide the very same memory address for STNSM and STOSM instructions. If the kernel would stay on a random stack (e.g. a virtually mapped one) then a virtual address provided for STNSM instruction could differ from the physical address needed for the corresponding STOSM instruction. After call_nodat() macro is introduced the kernel stack does not need to be mapped 1:1 anymore, since the macro stores the physical memory address of return PSW in a register before entering DAT-off mode. This way the return LPSWE instruction is able to pick the correct memory location and restore the DAT-on mode. That however might fail in case the 16-byte return PSW happened to cross page boundary: PSW mask and PSW address could end up in two separate non-contiguous physical pages. Align the return PSW on 16-byte boundary so it always fits into a single physical page. As result any stack (including the virtually mapped one) could be used for calling DAT-off code and prior switching to nodat_stack becomes unnecessary. Signed-off-by: Alexander Gordeev Reviewed-by: Heiko Carstens Signed-off-by: Heiko Carstens Signed-off-by: Vasily Gorbik

s390/kdump: rework invocation of DAT-off code

2023-04-19T15:24:16+00:00

Calling kdump kernel is a two-step process that involves invocation of the purgatory code: first time - to verify the new kernel checksum and second time - to call the new kernel itself. The purgatory code operates on real addresses and does not expect any memory protection. Therefore, before the purgatory code is entered the DAT mode is always turned off. However, it is only restored upon return from the new kernel checksum verification. In case the purgatory was called to start the new kernel and failed the control is returned to the old kernel, but the DAT mode continues staying off. The new kernel start failure is unlikely and leads to the disabled wait state anyway. Still that poses a risk, since the kernel code in general is not DAT-off safe and even calling the disabled_wait() function might crash. Introduce call_nodat() macro that allows entering DAT-off mode, calling an arbitrary function and restoring DAT mode back on. Switch all invocations of DAT-off code to that macro and avoid the above described scenario altogether. Name the call_nodat() macro in small letters after the already existing call_on_stack() and put it to the same header file. Signed-off-by: Alexander Gordeev Reviewed-by: Heiko Carstens [hca@linux.ibm.com: some small modifications to call_nodat() macro] Signed-off-by: Heiko Carstens Signed-off-by: Vasily Gorbik

s390/stacktrace: remove call_on_stack_noreturn()

2023-04-04T16:34:56+00:00

There is no user left of call_on_stack_noreturn() - remove it. Reviewed-by: Vasily Gorbik Signed-off-by: Heiko Carstens Signed-off-by: Vasily Gorbik

s390/entry: sort out physical vs virtual pointers usage in sie64a

2022-10-26T12:27:41+00:00

Fix virtual vs physical address confusion (which currently are the same). sie_block is accessed in entry.S and passed it to hardware, which is why both its physical and virtual address are needed. To avoid every caller having to do the virtual-physical conversion, add a new function sie64a() which converts the virtual address to physical. Signed-off-by: Nico Boehr Reviewed-by: Alexander Gordeev Reviewed-by: Claudio Imbrenda Link: https://lore.kernel.org/r/20221020143159.294605-3-nrb@linux.ibm.com Message-Id: <20221020143159.294605-3-nrb@linux.ibm.com> Signed-off-by: Janosch Frank

s390/stack: add union to reflect kvm stack slot usages

2022-06-01T10:03:17+00:00

Add a union which describes how the empty stack slots are being used by kvm and perf. This should help to avoid another bug like the one which was fixed with commit c9bfb460c3e4 ("s390/perf: obtain sie_block from the right address"). Reviewed-by: Nico Boehr Tested-by: Nico Boehr Signed-off-by: Heiko Carstens

s390/stack: merge empty stack frame slots

2022-06-01T10:03:17+00:00

Merge empty1 and empty2 arrays within the stack frame to one single array. This is possible since with commit 42b01a553a56 ("s390: always use the packed stack layout") the alternative stack frame layout is gone. Reviewed-by: Nico Boehr Reviewed-by: Alexander Gordeev Signed-off-by: Heiko Carstens

s390: current_stack_pointer shouldn't be a function

2022-04-12T09:56:08+00:00

s390 defines current_stack_pointer as function while all other architectures use 'register unsigned long asm(""). This make codes like the following from check_stack_object() fail: if (IS_ENABLED(CONFIG_STACK_GROWSUP)) { if ((void *)current_stack_pointer < obj + len) return BAD_STACK; } else { if (obj < (void *)current_stack_pointer) return BAD_STACK; } because this would compare the address of current_stack_pointer() and not the stackpointer value. Reported-by: Karsten Graul Fixes: 2792d84e6da5 ("usercopy: Check valid lifetime via stack depth") Cc: Kees Cook Cc: Vasily Gorbik Cc: Alexander Gordeev Signed-off-by: Sven Schnelle Reviewed-by: Heiko Carstens Signed-off-by: Heiko Carstens

s390: always use the packed stack layout

2022-03-01T20:05:09+00:00

-mpacked-stack option has been supported by both minimum gcc and clang versions for a while. With commit e2bc3e91d91e ("scripts/min-tool-version.sh: Raise minimum clang version to 13.0.0 for s390") minimum clang version now also supports a combination of flags -mpacked-stack -mbackchain -pg -mfentry and fulfills all requirements to always enable the packed stack layout. Reviewed-by: Heiko Carstens Signed-off-by: Vasily Gorbik

s390/unwind: use current_frame_address() to unwind current task

2021-09-07T11:38:27+00:00

current_stack_pointer() simply returns current value of %r15. If current_stack_pointer() caller allocates stack (which is the case in unwind code) %r15 points to a stack frame allocated for callees, meaning current_stack_pointer() caller (e.g. stack_trace_save) will end up in the stacktrace. This is not expected by stack_trace_save*() callers and causes problems. current_frame_address() on the other hand returns function stack frame address, which matches %r15 upon function invocation. Using it in get_stack_pointer() makes it more aligned with x86 implementation (according to BACKTRACE_SELF_TEST output) and meets stack_trace_save*() caller's expectations, notably KCSAN. Also make sure unwind_start is always inlined. Reported-by: Nathan Chancellor Suggested-by: Marco Elver Signed-off-by: Vasily Gorbik Tested-by: Marco Elver Tested-by: Nathan Chancellor Link: https://lore.kernel.org/r/patch.git-04dd26be3043.your-ad-here.call-01630504868-ext-6188@work.hours Signed-off-by: Heiko Carstens

s390: rename CALL_ON_STACK_NORETURN() to call_on_stack_noreturn()

2021-07-08T20:12:18+00:00

Lower case matches the call_on_stack() macro and is easier to read. Reviewed-by: Sven Schnelle Signed-off-by: Heiko Carstens Signed-off-by: Vasily Gorbik