On 09.07.2025 12:01, Jens Remus wrote:
> On 08.07.2025 03:22, Steven Rostedt wrote:
>> From: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
>> diff --git a/kernel/unwind/user.c b/kernel/unwind/user.c
>> static int unwind_user_next(struct unwind_user_state *state)
>> {
>> - /* no implementation yet */
>> + struct unwind_user_frame *frame;
>> + unsigned long cfa = 0, fp, ra = 0;
>> + unsigned int shift;
>> +
>> + if (state->done)
>> + return -EINVAL;
>> +
>> + if (fp_state(state))
>> + frame = &fp_frame;
>> + else
>> + goto done;
>> +
>> + if (frame->use_fp) {
>> + if (state->fp < state->sp)
The initial check above is correct. I got the logic wrong. Sorry for
the fuss! Do not change the check to what I came up with yesterday:
> if (state->fp <= state->sp)
>
Below s390 particularity, that FP may be equal to FP in any frame,
is only allowed with the initial check.
> I meanwhile came to the conclusion that for architectures, such as s390,
> where SP at function entry == SP at call site, the FP may be equal to
> the SP. At least for the brief period where the FP has been setup and
> stack allocation did not yet take place. For most architectures this
> can probably only occur in the topmost frame. For s390 the FP is setup
> after static stack allocation, so --fno-omit-frame-pointer would enforce
> FP==SP in any frame that does not perform dynamic stack allocation.
>
>> + goto done;
>> + cfa = state->fp;
>> + } else {
>> + cfa = state->sp;
>> + }
Regards,
Jens
--
Jens Remus
Linux on Z Development (D3303)
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jremus@xxxxxxxxxx
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