Currently unwinder unconditionally returns %r14 from the first frame
pointed by %r15 from pt_regs. A task could be interrupted when a function
already allocated this frame (if it needs it) for its callees or to
store local variables. In that case this frame would contain random
values from stack or values stored there by a callee. As we are only
interested in %r14 to get potential return address, skip bogus return
addresses which doesn't belong to kernel text.
This helps to avoid duplicating filtering logic in unwider users, most
of which use unwind_get_return_address() and would choke on bogus 0
address returned by it otherwise.
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
A comment in arch/s390/include/asm/unwind.h says:
> If 'first_frame' is not zero unwind_start skips unwind frames until it
> reaches the specified stack pointer.
> The end of the unwinding is indicated with unwind_done, this can be true
> right after unwind_start, e.g. with first_frame!=0 that can not be found.
> unwind_next_frame skips to the next frame.
> Once the unwind is completed unwind_error() can be used to check if there
> has been a situation where the unwinder could not correctly understand
> the tasks call chain.
With this change backchain unwinder now comply with behaviour
described. As well as matches orc unwinder implementation. Now unwinder
starts from reliable state, i.e. __unwind_start own stack frame is
taken or stack frame generated by __switch_to (ksp) - both known to be
valid. In case of pt_regs %r15 is better match for pt_regs psw, than
sometimes random "sp" caller passed.
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Consider reaching task pt_regs graceful unwinder termination. Task
pt_regs itself never contains a valid state to which a task might return
within the kernel context (user task pt_regs is a special case). Since
we already avoid printing user task pt_regs and in most cases we don't
even bother filling task pt_regs psw and r15 with something reasonable
simply skip task pt_regs altogether. With this change unwind_error() now
accurately represent whether unwinder reached task pt_regs successfully
or failed along the way.
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Currently unwinder yields 2 entries when pt_regs are met:
sp="address of pt_regs itself" ip=pt_regs->psw
sp=pt_regs->gprs[15] ip="r14 from stack frame pointed by pt_regs->gprs[15]"
And neither of those 2 states (combination of sp and ip) ever happened.
reuse_sp has been introduced by commit a1d863ac3e ("s390/unwind: fix
mixing regs and sp"). reuse_sp=true makes unwinder keen to produce the
following result, when pt_regs are given (as an arg to unwind_start):
sp=pt_regs->gprs[15] ip=pt_regs->psw
sp=pt_regs->gprs[15] ip="r14 from stack frame pointed by pt_regs->gprs[15]"
The first state is an actual state in which a task was when pt_regs were
collected. The second state is marked unreliable and is for debugging
purposes to cover the case when a task has been interrupted in between
stack frame allocation and writing back_chain - in this case r14 might
show an actual caller.
Make unwinder behaviour enabled via reuse_sp=true default and drop the
special case handling.
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
If unwinder is looking at pt_regs which is not on stack then something
went wrong and an error has to be reported rather than successful
unwinding termination.
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
- Adjust PMU device drivers registration to avoid WARN_ON and few other
perf improvements.
- Enhance tracing in vfio-ccw.
- Few stack unwinder fixes and improvements, convert get_wchan custom
stack unwinding to generic api usage.
- Fixes for mm helpers issues uncovered with tests validating architecture
page table helpers.
- Fix noexec bit handling when hardware doesn't support it.
- Fix memleak and unsigned value compared with zero bugs in crypto
code. Minor code simplification.
- Fix crash during kdump with kasan enabled kernel.
- Switch bug and alternatives from asm to asm_inline to improve inlining
decisions.
- Use 'depends on cc-option' for MARCH and TUNE options in Kconfig,
add z13s and z14 ZR1 to TUNE descriptions.
- Minor head64.S simplification.
- Fix physical to logical CPU map for SMT.
- Several cleanups in qdio code.
- Other minor cleanups and fixes all over the code.
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Merge tag 's390-5.5-1' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux
Pull s390 updates from Vasily Gorbik:
- Adjust PMU device drivers registration to avoid WARN_ON and few other
perf improvements.
- Enhance tracing in vfio-ccw.
- Few stack unwinder fixes and improvements, convert get_wchan custom
stack unwinding to generic api usage.
- Fixes for mm helpers issues uncovered with tests validating
architecture page table helpers.
- Fix noexec bit handling when hardware doesn't support it.
- Fix memleak and unsigned value compared with zero bugs in crypto
code. Minor code simplification.
- Fix crash during kdump with kasan enabled kernel.
- Switch bug and alternatives from asm to asm_inline to improve
inlining decisions.
- Use 'depends on cc-option' for MARCH and TUNE options in Kconfig, add
z13s and z14 ZR1 to TUNE descriptions.
- Minor head64.S simplification.
- Fix physical to logical CPU map for SMT.
- Several cleanups in qdio code.
- Other minor cleanups and fixes all over the code.
* tag 's390-5.5-1' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux: (41 commits)
s390/cpumf: Adjust registration of s390 PMU device drivers
s390/smp: fix physical to logical CPU map for SMT
s390/early: move access registers setup in C code
s390/head64: remove unnecessary vdso_per_cpu_data setup
s390/early: move control registers setup in C code
s390/kasan: support memcpy_real with TRACE_IRQFLAGS
s390/crypto: Fix unsigned variable compared with zero
s390/pkey: use memdup_user() to simplify code
s390/pkey: fix memory leak within _copy_apqns_from_user()
s390/disassembler: don't hide instruction addresses
s390/cpum_sf: Assign error value to err variable
s390/cpum_sf: Replace function name in debug statements
s390/cpum_sf: Use consistant debug print format for sampling
s390/unwind: drop unnecessary code around calling ftrace_graph_ret_addr()
s390: add error handling to perf_callchain_kernel
s390: always inline current_stack_pointer()
s390/mm: add mm_pxd_folded() checks to pxd_free()
s390/mm: properly clear _PAGE_NOEXEC bit when it is not supported
s390/mm: simplify page table helpers for large entries
s390/mm: make pmd/pud_bad() report large entries as bad
...
The current code around calling ftrace_graph_ret_addr() is ifdeffed and
also tests if ftrace redirection is present on stack.
ftrace_graph_ret_addr() however performs the test internally and there
is a version for !CONFIG_FUNCTION_GRAPH_TRACER as well. The unnecessary
code can thus be dropped.
Link: http://lkml.kernel.org/r/20191029143904.24051-2-mbenes@suse.cz
Signed-off-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
unwind_for_each_frame stops after the first frame if regs->gprs[15] <=
sp.
The reason is that in case regs are specified, the first frame should be
regs->psw.addr and the second frame should be sp->gprs[8]. However,
currently the second frame is regs->gprs[15], which confuses
outside_of_stack().
Fix by introducing a flag to distinguish this special case from
unwinding the interrupt handler, for which the current behavior is
appropriate.
Fixes: 78c98f9074 ("s390/unwind: introduce stack unwind API")
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Cc: stable@vger.kernel.org # v5.2+
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
When current task is interrupted in-between stack frame allocation
and backchain write instructions new stack frame backchain pointer
is left uninitialized. That invalid backchain value is passed into
outside_of_stack for sanity check. Make sure int overflow does not happen
by subtracting stack_frame size from the stack "end" rather than adding
it to "random" backchain value.
Fixes: 41b0474c1b1c ("s390/unwind: introduce stack unwind API")
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Avoid kasan false positive when current task is interrupted in-between
stack frame allocation and backchain write instructions leaving new stack
frame backchain invalid. In particular if backchain is 0 the unwinder
tries to read pt_regs from the stack and might hit kasan poisoned bytes,
leading to kasan "stack-out-of-bounds" report.
Disable kasan instrumentation of unwinder stack reads, since this
limitation couldn't be handled otherwise with current backchain unwinder
implementation.
Fixes: 78c98f9074 ("s390/unwind: introduce stack unwind API")
Reported-by: Julian Wiedmann <jwi@linux.ibm.com>
Tested-by: Benjamin Block <bblock@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Make the call chain more reliable by tagging the ftrace stack entries
with the stack pointer that is associated with the return address.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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 <schwidefsky@de.ibm.com>
Miroslav Benes