Author: gonzo
Date: Thu Oct 22 05:07:25 2020
New Revision: 366924
URL: https://svnweb.freebsd.org/changeset/base/366924
Log:
[hwpmc] Fix call chain capture for ARM64
Use ELR register value instead of LR for PMC_TRAPFRAME_TO_PC macro since
it's the former that indicates PC if the interrupted execution thread.
This fixes a bug where pmcstat lost the leaf function of the call chain
and started with the second function in the chain.
Although this change is an improvement over the previous logic there is still
posibility for incomplete data: if the leaf function does not have stack
variables and does not call any other functions compiler would not generate
a stack frame for it and the FP value would point to the caller's frame, so
instead of the actual "caller1 -> caller2 -> leaf" chain only
"caller1 -> leaf" would be captured.
Sponsored by: Ampere Computing
Submitted by: Klara, Inc.
Modified:
head/sys/arm64/include/pmc_mdep.h
Modified: head/sys/arm64/include/pmc_mdep.h
==============================================================================
--- head/sys/arm64/include/pmc_mdep.h Thu Oct 22 04:49:14 2020
(r366923)
+++ head/sys/arm64/include/pmc_mdep.h Thu Oct 22 05:07:25 2020
(r366924)
@@ -54,7 +54,7 @@ union pmc_md_pmc {
((S) >= (START) && (S) < (END))
#define PMC_IN_KERNEL(va) INKERNEL((va))
#define PMC_IN_USERSPACE(va) ((va) <= VM_MAXUSER_ADDRESS)
-#define PMC_TRAPFRAME_TO_PC(TF) ((TF)->tf_lr)
+#define PMC_TRAPFRAME_TO_PC(TF) ((TF)->tf_elr)
#define PMC_TRAPFRAME_TO_FP(TF) ((TF)->tf_x[29])
/*
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