powerpc/livepatch: Implement reliable stack tracing for the consistency model
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.
Feel free to add other ppc variants, but so far only ppc64le got tested.
This change also implements save_stack_trace_tsk_reliable() for ppc64le
that checks for the above conditions, where possible.
Signed-off-by: Torsten Duwe <duwe@suse.de>
Signed-off-by: Nicolai Stange <nstange@suse.de>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index ebb90f0..23247fa 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -221,6 +221,7 @@
select HAVE_PERF_USER_STACK_DUMP
select HAVE_RCU_TABLE_FREE if SMP
select HAVE_REGS_AND_STACK_ACCESS_API
+ select HAVE_RELIABLE_STACKTRACE if PPC64 && CPU_LITTLE_ENDIAN
select HAVE_SYSCALL_TRACEPOINTS
select HAVE_VIRT_CPU_ACCOUNTING
select HAVE_IRQ_TIME_ACCOUNTING