linux.git/arch/s390/kernel/dumpstack.c, branch v5.5

s390/unwind: add stack pointer alignment sanity checks

2019-11-30T09:52:48+00:00

ABI requires SP to be aligned 8 bytes, report unwinding error otherwise.

Link: https://lkml.kernel.org/r/20191106095601.29986-5-mbenes@suse.cz
Reviewed-by: Heiko Carstens 
Tested-by: Miroslav Benes 
Signed-off-by: Miroslav Benes 
Signed-off-by: Vasily Gorbik

s390/test_unwind: print verbose unwinding results

2019-11-30T09:52:48+00:00

Add stack name, sp and reliable information into test unwinding
results. Also consider ip outside of kernel text as failure if the
state is reported reliable.

Acked-by: Heiko Carstens 
Signed-off-by: Vasily Gorbik

s390/unwind: unify task is current checks

2019-11-30T09:52:45+00:00

Avoid mixture of task == NULL and task == current meaning the same
thing and simply always initialize task with current in unwind_start.

Reviewed-by: Heiko Carstens 
Signed-off-by: Vasily Gorbik

s390/unwind: remove stack recursion warning

2019-08-06T11:58:35+00:00

Remove pointless stack recursion on stack type ... warning, which
only confuses people. There is no way to make backchain unwinder 100%
reliable. When a task is interrupted in-between stack frame allocation
and backchain write instructions new stack frame backchain pointer is
left uninitialized (there are also sometimes additional instruction
in-between stack frame allocation and backchain write instructions due
to gcc shrink-wrapping). In attempt to unwind such stack the unwinder
would still try to use that invalid backchain value and perform all kind
of sanity checks on it to make sure we are not pointed out of stack. In
some cases that invalid backchain value would be 0 and we would falsely
treat next stackframe as pt_regs and again gprs[15] in those pt_regs
might happen to point at some address within the task's stack.

Acked-by: Heiko Carstens 
Signed-off-by: Vasily Gorbik

s390: enforce CONFIG_SMP

2019-06-07T08:09:37+00:00

There never have been distributions that shiped with CONFIG_SMP=n for
s390. In addition the kernel currently doesn't even compile with
CONFIG_SMP=n for s390. Most likely it wouldn't even work, even if we
fix the compile error, since nobody tests it, since there is no use
case that I can think of.
Therefore simply enforce CONFIG_SMP and get rid of some more or
less unused code.

Reviewed-by: Christian Borntraeger 
Signed-off-by: Heiko Carstens

s390/unwind: introduce stack unwind API

2019-05-02T11:54:11+00:00

Rework the dump_trace() stack unwinder interface to support different
unwinding algorithms. The new interface looks like this:

	struct unwind_state state;
	unwind_for_each_frame(&state, task, regs, start_stack)
		do_something(state.sp, state.ip, state.reliable);

The unwind_bc.c file contains the implementation for the classic
back-chain unwinder.

One positive side effect of the new code is it now handles ftraced
functions gracefully. It prints the real name of the return function
instead of 'return_to_handler'.

Signed-off-by: Martin Schwidefsky

s390/dumpstack: print psw mask and address again

2018-10-10T05:37:20+00:00

With pointer obfuscation the output of show_registers() became quite useless:

Krnl PSW : (____ptrval____) (____ptrval____) (__list_add_valid+0x98/0xa8)

In order to print the psw mask and address use %px instead of %p.
And the output looks again like this:

Krnl PSW : 0404d00180000000 00000000007c0dd0 (__list_add_valid+0x98/0xa8)

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

s390/dumpstack: disable __dump_trace kasan instrumentation

2018-10-09T09:21:27+00:00

Walking async_stack produces false positives. Disable __dump_trace
function instrumentation for now.

Signed-off-by: Vasily Gorbik 
Signed-off-by: Martin Schwidefsky

s390: unify stack size definitions

2018-10-09T09:20:58+00:00

Remove STACK_ORDER and STACK_SIZE in favour of identical THREAD_SIZE_ORDER
and THREAD_SIZE definitions. THREAD_SIZE and THREAD_SIZE_ORDER naming is
misleading since it is used as general kernel stack size information. But
both those definitions are used in the common code and throughout
architectures specific code, so changing the naming is problematic.

Reviewed-by: Martin Schwidefsky 
Signed-off-by: Vasily Gorbik 
Signed-off-by: Martin Schwidefsky

s390: add support for virtually mapped kernel stacks

2018-10-09T09:20:57+00:00

With virtually mapped kernel stacks the kernel stack overflow detection
is now fault based, every stack has a guard page in the vmalloc space.
The panic_stack is renamed to nodat_stack and is used for all function
that need to run without DAT, e.g. memcpy_real or do_start_kdump.

The main effect is a reduction in the kernel image size as with vmap
stacks the old style overflow checking that adds two instructions per
function is not needed anymore. Result from bloat-o-meter:

add/remove: 20/1 grow/shrink: 13/26854 up/down: 2198/-216240 (-214042)

In regard to performance the micro-benchmark for fork has a hit of a
few microseconds, allocating 4 pages in vmalloc space is more expensive
compare to an order-2 page allocation. But with real workload I could
not find a noticeable difference.

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