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SubjectRe: [PATCH v2] On ppc64le we HAVE_RELIABLE_STACKTRACE
On Mon, Mar 05, 2018 at 05:49:28PM +0100, Torsten Duwe wrote:
> The "Power Architecture 64-Bit ELF V2 ABI" says in section 2.3.2.3:
>
> [...] There are several rules that must be adhered to in order to ensure
> reliable and consistent call chain backtracing:
>
> * Before a function calls any other function, it shall establish its
> own stack frame, whose size shall be a multiple of 16 bytes.
>
> – In instances where a function’s prologue creates a stack frame, the
> back-chain word of the stack frame shall be updated atomically with
> the value of the stack pointer (r1) when a back chain is implemented.
> (This must be supported as default by all ELF V2 ABI-compliant
> environments.)
> [...]
> – The function shall save the link register that contains its return
> address in the LR save doubleword of its caller’s stack frame before
> calling another function.
>
> To me this sounds like the equivalent of HAVE_RELIABLE_STACKTRACE.
> This patch may be unneccessarily limited to ppc64le, but OTOH the only
> user of this flag so far is livepatching, which is only implemented on
> PPCs with 64-LE, a.k.a. ELF ABI v2.
>
> This change also implements save_stack_trace_tsk_reliable() for ppc64
> that checks for the above conditions, where possible.
>
> Signed-off-by: Torsten Duwe <duwe@suse.de>

This doesn't seem to address some of my previous concerns:

- Bailing on interrupt/exception frames

- Function graph tracing return address conversion

- kretprobes return address conversion

--
Josh

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