s390/asm-offsets: Remove ASM_OFFSETS_C

Remove ASM_OFFSETS_C which is used as guard in thread_info.h to decide if
asm-offsets can be included or not.

There is no reason to include asm-offsets.h in t

s390/asm-offsets: Remove ASM_OFFSETS_C

Remove ASM_OFFSETS_C which is used as guard in thread_info.h to decide if
asm-offsets can be included or not.

There is no reason to include asm-offsets.h in thread_info.h anymore.
Remove the define and the not needed include. Explicitly include
asm-offsets.h in all header files which require it, and where it used
to be included implicitly via thread_info.h.

This reduces header dependencies.

Acked-by: Vasily Gorbik <[email protected]>
Signed-off-by: Heiko Carstens <[email protected]>
Signed-off-by: Vasily Gorbik <[email protected]>

show more ...

s390/stacktrace: Use break instead of return statement

arch_stack_walk_user_common() contains a return statement instead of a
break statement in case store_ip() fails while trying to store a callcha

s390/stacktrace: Use break instead of return statement

arch_stack_walk_user_common() contains a return statement instead of a
break statement in case store_ip() fails while trying to store a callchain
entry of a user space process.
This may lead to a missing pagefault_enable() call.

If this happens any subsequent page fault of the process won't be resolved
by the page fault handler and this in turn will lead to the process being
killed.

Use a break instead of a return statement to fix this.

Fixes: ebd912ff9919 ("s390/stacktrace: Merge perf_callchain_user() and arch_stack_walk_user()")
Cc: [email protected]
Reviewed-by: Jens Remus <[email protected]>
Signed-off-by: Heiko Carstens <[email protected]>

show more ...

s390/ftrace: Avoid calling unwinder in ftrace_return_address()

ftrace_return_address() is called extremely often from
performance-critical code paths when debugging features like
CONFIG_TRACE_IRQFLA

s390/ftrace: Avoid calling unwinder in ftrace_return_address()

ftrace_return_address() is called extremely often from
performance-critical code paths when debugging features like
CONFIG_TRACE_IRQFLAGS are enabled. For example, with debug_defconfig,
ftrace selftests on my LPAR currently execute ftrace_return_address()
as follows:

ftrace_return_address(0) - 0 times (common code uses __builtin_return_address(0) instead)
ftrace_return_address(1) - 2,986,805,401 times (with this patch applied)
ftrace_return_address(2) - 140 times
ftrace_return_address(>2) - 0 times

The use of __builtin_return_address(n) was replaced by return_address()
with an unwinder call by commit cae74ba8c295 ("s390/ftrace:
Use unwinder instead of __builtin_return_address()") because
__builtin_return_address(n) simply walks the stack backchain and doesn't
check for reaching the stack top. For shallow stacks with fewer than
"n" frames, this results in reads at low addresses and random
memory accesses.

While calling the fully functional unwinder "works", it is very slow
for this purpose. Moreover, potentially following stack switches and
walking past IRQ context is simply wrong thing to do for
ftrace_return_address().

Reimplement return_address() to essentially be __builtin_return_address(n)
with checks for reaching the stack top. Since the ftrace_return_address(n)
argument is always a constant, keep the implementation in the header,
allowing both GCC and Clang to unroll the loop and optimize it to the
bare minimum.

Fixes: cae74ba8c295 ("s390/ftrace: Use unwinder instead of __builtin_return_address()")
Cc: [email protected]
Reported-by: Sumanth Korikkar <[email protected]>
Reviewed-by: Heiko Carstens <[email protected]>
Acked-by: Sumanth Korikkar <[email protected]>
Signed-off-by: Vasily Gorbik <[email protected]>

show more ...

s390/stackstrace: Detect vdso stack frames

Clear the backchain of the extra stack frame added by the vdso user wrapper
code. This allows the user stack walker to detect and skip the non-standard
sta

s390/stackstrace: Detect vdso stack frames

Clear the backchain of the extra stack frame added by the vdso user wrapper
code. This allows the user stack walker to detect and skip the non-standard
stack frame. Without this an incorrect instruction pointer would be added
to stack traces, and stack frame walking would be continued with a more or
less random back chain.

Fixes: aa44433ac4ee ("s390: add USER_STACKTRACE support")
Reviewed-by: Jens Remus <[email protected]>
Signed-off-by: Heiko Carstens <[email protected]>
Signed-off-by: Alexander Gordeev <[email protected]>

show more ...

s390/stacktrace: Improve detection of invalid instruction pointers

Add basic checks to identify invalid instruction pointers when walking
stack frames:

Instruction pointers must

- have even addres

s390/stacktrace: Improve detection of invalid instruction pointers

Add basic checks to identify invalid instruction pointers when walking
stack frames:

Instruction pointers must

- have even addresses
- be larger than mmap_min_addr
- lower than the asce_limit of the process

Alternatively it would also be possible to walk page tables similar to fast
GUP and verify that the mapping of the corresponding page is executable,
however that seems to be overkill.

Fixes: aa44433ac4ee ("s390: add USER_STACKTRACE support")
Reviewed-by: Jens Remus <[email protected]>
Signed-off-by: Heiko Carstens <[email protected]>
Signed-off-by: Alexander Gordeev <[email protected]>

show more ...

s390/stacktrace: Skip first user stack frame

When walking user stack frames the first stack frame (where the stack
pointer points to) should be skipped: the return address of the current
function is

s390/stacktrace: Skip first user stack frame

When walking user stack frames the first stack frame (where the stack
pointer points to) should be skipped: the return address of the current
function is saved in the previous stack frame, not the current stack frame,
which is allocated for to be called functions.

Fixes: aa44433ac4ee ("s390: add USER_STACKTRACE support")
Reviewed-by: Jens Remus <[email protected]>
Signed-off-by: Heiko Carstens <[email protected]>
Signed-off-by: Alexander Gordeev <[email protected]>

show more ...

s390/stacktrace: Merge perf_callchain_user() and arch_stack_walk_user()

The two functions perf_callchain_user() and arch_stack_walk_user() are
nearly identical. Reduce code duplication and add a com

s390/stacktrace: Merge perf_callchain_user() and arch_stack_walk_user()

The two functions perf_callchain_user() and arch_stack_walk_user() are
nearly identical. Reduce code duplication and add a common helper which can
be called by both functions.

Fixes: aa44433ac4ee ("s390: add USER_STACKTRACE support")
Reviewed-by: Jens Remus <[email protected]>
Signed-off-by: Heiko Carstens <[email protected]>
Signed-off-by: Alexander Gordeev <[email protected]>

show more ...

s390/ftrace: Use unwinder instead of __builtin_return_address()

Using __builtin_return_address(n) might return undefined values
when used with values of n outside of the stack. This was noticed
when

s390/ftrace: Use unwinder instead of __builtin_return_address()

Using __builtin_return_address(n) might return undefined values
when used with values of n outside of the stack. This was noticed
when __builtin_return_address() was called in ftrace on top level
functions like the interrupt handlers.

As this behaviour cannot be fixed, use the s390 stack unwinder and
remove the ftrace compilation flags for unwind_bc.c and stacktrace.c
to prevent the unwinding function polluting function traces.

Another advantage is that this also works with clang.

Reviewed-by: Heiko Carstens <[email protected]>
Signed-off-by: Sven Schnelle <[email protected]>
Signed-off-by: Alexander Gordeev <[email protected]>

show more ...

s390: add USER_STACKTRACE support

Use the perf_callchain_user() code as blueprint to also add support for
USER_STACKTRACE. To describe how to use this cite the commit message of the
LoongArch implem

s390: add USER_STACKTRACE support

Use the perf_callchain_user() code as blueprint to also add support for
USER_STACKTRACE. To describe how to use this cite the commit message of the
LoongArch implementation which came with commit 4d7bf939df08 ("LoongArch:
Add USER_STACKTRACE support"), but replace -fno-omit-frame-pointer option
with the s390 specific -mbackchain option:
====================================================================== To
get the best stacktrace output, you can compile your userspace programs
with frame pointers (at least glibc + the app you are tracing).

1, export "CC = gcc -mbackchain";
2, compile your programs with "CC";
3, use uprobe to get stacktrace output.

...
echo 'p:malloc /usr/lib64/libc.so.6:0x0a4704 size=%r2:u64' > uprobe_events
echo 'p:free /usr/lib64/libc.so.6:0x0a4d50 ptr=%r2:u64' >> uprobe_events
echo 'comm == "demo"' > ./events/uprobes/malloc/filter
echo 'comm == "demo"' > ./events/uprobes/free/filter
echo 1 > ./options/userstacktrace
echo 1 > ./options/sym-userobj
...
======================================================================

Signed-off-by: Heiko Carstens <[email protected]>
Signed-off-by: Vasily Gorbik <[email protected]>

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s390/kprobes: replace kretprobe with rethook

That's an adaptation of commit f3a112c0c40d ("x86,rethook,kprobes:
Replace kretprobe with rethook on x86") to s390.

Replaces the kretprobe code with ret

s390/kprobes: replace kretprobe with rethook

That's an adaptation of commit f3a112c0c40d ("x86,rethook,kprobes:
Replace kretprobe with rethook on x86") to s390.

Replaces the kretprobe code with rethook on s390. With this patch,
kretprobe on s390 uses the rethook instead of kretprobe specific
trampoline code.

Tested-by: Ilya Leoshkevich <[email protected]>
Signed-off-by: Vasily Gorbik <[email protected]>
Signed-off-by: Heiko Carstens <[email protected]>

show more ...

s390: remove invalid email address of Heiko Carstens

Remove my old invalid email address which can be found in a couple of
files. Instead of updating it, just remove my contact data completely
from

s390: remove invalid email address of Heiko Carstens

Remove my old invalid email address which can be found in a couple of
files. Instead of updating it, just remove my contact data completely
from source files.
We have git and other tools which allow to figure out who is responsible
for what with recent contact data.

Signed-off-by: Heiko Carstens <[email protected]>
Signed-off-by: Vasily Gorbik <[email protected]>

show more ...

kprobes: treewide: Make it harder to refer kretprobe_trampoline directly

Since now there is kretprobe_trampoline_addr() for referring the
address of kretprobe trampoline code, we don't need to acces

kprobes: treewide: Make it harder to refer kretprobe_trampoline directly

Since now there is kretprobe_trampoline_addr() for referring the
address of kretprobe trampoline code, we don't need to access
kretprobe_trampoline directly.

Make it harder to refer by renaming it to __kretprobe_trampoline().

Link: https://lkml.kernel.org/r/163163045446.489837.14510577516938803097.stgit@devnote2

Suggested-by: Ingo Molnar <[email protected]>
Signed-off-by: Masami Hiramatsu <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>

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stacktrace: Move documentation for arch_stack_walk_reliable() to header

Currently arch_stack_walk_reliable() is documented with an identical
comment in both x86 and S/390 implementations which is a

stacktrace: Move documentation for arch_stack_walk_reliable() to header

Currently arch_stack_walk_reliable() is documented with an identical
comment in both x86 and S/390 implementations which is a bit redundant.
Move this to the header and convert to kerneldoc while we're at it.

Signed-off-by: Mark Brown <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Reviewed-by: Miroslav Benes <[email protected]>
Acked-by: Vasily Gorbik <[email protected]>
Acked-by: Randy Dunlap <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]

show more ...

stacktrace: Remove reliable argument from arch_stack_walk() callback

Currently the callback passed to arch_stack_walk() has an argument called
reliable passed to it to indicate if the stack entry is

stacktrace: Remove reliable argument from arch_stack_walk() callback

Currently the callback passed to arch_stack_walk() has an argument called
reliable passed to it to indicate if the stack entry is reliable, a comment
says that this is used by some printk() consumers. However in the current
kernel none of the arch_stack_walk() implementations ever set this flag to
true and the only callback implementation we have is in the generic
stacktrace code which ignores the flag. It therefore appears that this
flag is redundant so we can simplify and clarify things by removing it.

Signed-off-by: Mark Brown <[email protected]>
Reviewed-by: Miroslav Benes <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Will Deacon <[email protected]>

show more ...

s390/livepatch: Implement reliable stack tracing for the consistency model

The livepatch consistency model requires reliable stack tracing
architecture support in order to work properly. In order to

s390/livepatch: Implement reliable stack tracing for the consistency model

The livepatch consistency model requires reliable stack tracing
architecture support in order to work properly. In order to achieve
this, two main issues have to be solved. First, reliable and consistent
call chain backtracing has to be ensured. Second, the unwinder needs to
be able to detect stack corruptions and return errors.

The "zSeries ELF Application Binary Interface Supplement" says:

"The stack pointer points to the first word of the lowest allocated
stack frame. If the "back chain" is implemented this word will point to
the previously allocated stack frame (towards higher addresses), except
for the first stack frame, which shall have a back chain of zero (NULL).
The stack shall grow downwards, in other words towards lower addresses."

"back chain" is optional. GCC option -mbackchain enables it. Quoting
Martin Schwidefsky [1]:

"The compiler is called with the -mbackchain option, all normal C
function will store the backchain in the function prologue. All
functions written in assembler code should do the same, if you find one
that does not we should fix that. The end result is that a task that
*voluntarily* called schedule() should have a proper backchain at all
times.

Dependent on the use case this may or may not be enough. Asynchronous
interrupts may stop the CPU at the beginning of a function, if kernel
preemption is enabled we can end up with a broken backchain. The
production kernels for IBM Z are all compiled *without* kernel
preemption. So yes, we might get away without the objtool support.

On a side-note, we do have a line item to implement the ORC unwinder for
the kernel, that includes the objtool support. Once we have that we can
drop the -mbackchain option for the kernel build. That gives us a nice
little performance benefit. I hope that the change from backchain to the
ORC unwinder will not be too hard to implement in the livepatch tools."

Since -mbackchain is enabled by default when the kernel is compiled, the
call chain backtracing should be currently ensured and objtool should
not be necessary for livepatch purposes.

Regarding the second issue, stack corruptions and non-reliable states
have to be recognized by the unwinder. Mainly it means to detect
preemption or page faults, the end of the task stack must be reached,
return addresses must be valid text addresses and hacks like function
graph tracing and kretprobes must be properly detected.

Unwinding a running task's stack is not a problem, because there is a
livepatch requirement that every checked task is blocked, except for the
current task. Due to that, the implementation can be much simpler
compared to the existing non-reliable infrastructure. We can consider a
task's kernel/thread stack only and skip the other stacks.

[1] 20180912121106.31ffa97c@mschwideX1 [not archived on lore.kernel.org]

Link: https://lkml.kernel.org/r/[email protected]
Reviewed-by: Heiko Carstens <[email protected]>
Tested-by: Miroslav Benes <[email protected]>
Signed-off-by: Miroslav Benes <[email protected]>
Signed-off-by: Vasily Gorbik <[email protected]>

show more ...

s390/stacktrace: use common arch_stack_walk infrastructure

Use common arch_stack_walk infrastructure to avoid duplicated code and
avoid taking care of the stack storage and filtering.

Common code a

s390/stacktrace: use common arch_stack_walk infrastructure

Use common arch_stack_walk infrastructure to avoid duplicated code and
avoid taking care of the stack storage and filtering.

Common code also uses try_get_task_stack/put_task_stack when needed which
have been missing in our code, which also solves potential problem for us.

Signed-off-by: Vasily Gorbik <[email protected]>

show more ...

s390/unwind: introduce stack unwind API

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

struct unwind_state state;
u

s390/unwind: introduce stack unwind API

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 <[email protected]>

show more ...

s390/stacktrace: Remove the pointless ULONG_MAX marker

Terminating the last trace entry with ULONG_MAX is a completely pointless
exercise and none of the consumers can rely on it because it's
incons

s390/stacktrace: Remove the pointless ULONG_MAX marker

Terminating the last trace entry with ULONG_MAX is a completely pointless
exercise and none of the consumers can rely on it because it's
inconsistently implemented across architectures. In fact quite some of the
callers remove the entry and adjust stack_trace.nr_entries afterwards.

Signed-off-by: Thomas Gleixner <[email protected]>
Acked-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Alexander Potapenko <[email protected]>
Cc: Martin Schwidefsky <[email protected]>
Cc: [email protected]
Cc: Heiko Carstens <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]

show more ...

s390: kernel: add SPDX identifiers to the remaining files

It's good to have SPDX identifiers in all files to make it easier to
audit the kernel tree for correct licenses.

Update the arch/s390/kerne

s390: kernel: add SPDX identifiers to the remaining files

It's good to have SPDX identifiers in all files to make it easier to
audit the kernel tree for correct licenses.

Update the arch/s390/kernel/ files with the correct SPDX license
identifier based on the license text in the file itself. The SPDX
identifier is a legally binding shorthand, which can be used instead of
the full boiler plate text.

This work is based on a script and data from Thomas Gleixner, Philippe
Ombredanne, and Kate Stewart.

Cc: Martin Schwidefsky <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Kate Stewart <[email protected]>
Cc: Philippe Ombredanne <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Signed-off-by: Martin Schwidefsky <[email protected]>

show more ...

sched/headers: Prepare for new header dependencies before moving code to <linux/sched/debug.h>

We are going to split <linux/sched/debug.h> out of <linux/sched.h>, which
will have to be picked up fro

sched/headers: Prepare for new header dependencies before moving code to <linux/sched/debug.h>

We are going to split <linux/sched/debug.h> out of <linux/sched.h>, which
will have to be picked up from other headers and a couple of .c files.

Create a trivial placeholder <linux/sched/debug.h> file that just
maps to <linux/sched.h> to make this patch obviously correct and
bisectable.

Include the new header in the files that are going to need it.

Acked-by: Linus Torvalds <[email protected]>
Cc: Mike Galbraith <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Signed-off-by: Ingo Molnar <[email protected]>

show more ...

s390: kernel: Audit and remove any unnecessary uses of module.h

Historically a lot of these existed because we did not have
a distinction between what was modular code and what was providing
support

s390: kernel: Audit and remove any unnecessary uses of module.h

Historically a lot of these existed because we did not have
a distinction between what was modular code and what was providing
support to modules via EXPORT_SYMBOL and friends. That changed
when we forked out support for the latter into the export.h file.

This means we should be able to reduce the usage of module.h
in code that is obj-y Makefile or bool Kconfig. The advantage
in doing so is that module.h itself sources about 15 other headers;
adding significantly to what we feed cpp, and it can obscure what
headers we are effectively using.

Since module.h was the source for init.h (for __init) and for
export.h (for EXPORT_SYMBOL) we consider each change instance
for the presence of either and replace as needed. Build testing
revealed some implicit header usage that was fixed up accordingly.

Signed-off-by: Paul Gortmaker <[email protected]>
Signed-off-by: Heiko Carstens <[email protected]>
Signed-off-by: Martin Schwidefsky <[email protected]>

show more ...

s390/dumpstack: restore reliable indicator for call traces

Before merging all different stack tracers the call traces printed had
an indicator if an entry can be considered reliable or not.
Unreliab

s390/dumpstack: restore reliable indicator for call traces

Before merging all different stack tracers the call traces printed had
an indicator if an entry can be considered reliable or not.
Unreliable entries were put in braces, reliable not. Currently all
lines contain these extra braces.

This patch restores the old behaviour by adding an extra "reliable"
parameter to the callback functions. Only show_trace makes currently
use of it.

Before:
[ 0.804751] Call Trace:
[ 0.804753] ([<000000000017d0e0>] try_to_wake_up+0x318/0x5e0)
[ 0.804756] ([<0000000000161d64>] create_worker+0x174/0x1c0)

After:
[ 0.804751] Call Trace:
[ 0.804753] ([<000000000017d0e0>] try_to_wake_up+0x318/0x5e0)
[ 0.804756] [<0000000000161d64>] create_worker+0x174/0x1c0

Fixes: 758d39ebd3d5 ("s390/dumpstack: merge all four stack tracers")
Signed-off-by: Heiko Carstens <[email protected]>
Signed-off-by: Martin Schwidefsky <[email protected]>

show more ...

s390/dumpstack: merge all four stack tracers

We have four different stack tracers of which three had bugs. So it's
time to merge them to a single stack tracer which allows to specify a
call back fun

s390/dumpstack: merge all four stack tracers

We have four different stack tracers of which three had bugs. So it's
time to merge them to a single stack tracer which allows to specify a
call back function which will be called for each step.

This patch changes behavior a bit:

- the "nosched" and "in_sched_functions" check within
save_stack_trace_tsk did work only for the last stack frame within a
context. Now it considers the check for each stack frame like it
should.

- both the oprofile variant and the perf_events variant did save a
return address twice if a zero back chain was detected, which
indicates an interrupt frame. The new dump_trace function will call
the oprofile and perf_events backends with the psw address that is
contained within the corresponding pt_regs structure instead.

- the original show_trace and save_context_stack functions did already
use the psw address of the pt_regs structure if a zero back chain
was detected. However now we ignore the psw address if it is a user
space address. After all we trace the kernel stack and not the user
space stack. This way we also get rid of the garbage user space
address in case of warnings and / or panic call traces.

So this should make life easier since now there is only one stack
tracer left which we can break.

Signed-off-by: Heiko Carstens <[email protected]>
Signed-off-by: Martin Schwidefsky <[email protected]>

show more ...

s390: add current_stack_pointer() helper function

Implement current_stack_pointer() helper function and use it
everywhere, instead of having several different inline assembly
variants.

Signed-off-b

s390: add current_stack_pointer() helper function

Implement current_stack_pointer() helper function and use it
everywhere, instead of having several different inline assembly
variants.

Signed-off-by: Heiko Carstens <[email protected]>
Tested-by: Peter Oberparleiter <[email protected]>
Signed-off-by: Martin Schwidefsky <[email protected]>

show more ...

s390/stacktrace: use nosched instead of savesched parameter

Use the inversed "nosched" logic like all other architectures.

Signed-off-by: Heiko Carstens <[email protected]>
Tested-by: Peter

s390/stacktrace: use nosched instead of savesched parameter

Use the inversed "nosched" logic like all other architectures.

Signed-off-by: Heiko Carstens <[email protected]>
Tested-by: Peter Oberparleiter <[email protected]>
Signed-off-by: Martin Schwidefsky <[email protected]>

show more ...