Re: [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.

All of this is also true for the other PowerPC ABIs, fwiw (both 32-bit
and 64-bit; the offset of the LR save slot isn't the same in all ABIs).


Segher