This allows enabling branch broadcast for Perf hosted sessions (the option is currently only available for the sysfs interface). Hopefully this could be useful for testing the decode in perf, for example does a determinisitic run with branch broadcast enabled look the same as with it disabled? It could also be used for scenarios like OpenJ9's support for JIT code:
java -Xjit:perfTool hello.java
Currently this is not working and you get the usual errors of a missing DSO, but branch broadcast would have to be enabled anyway before working through this next issue:
CS ETM Trace: Debug data not found for address 0xffff7b94b058 in /tmp/perf-29360.map
Address range support in Perf for branch broadcast has also not been added here, but could be added later.
The documentation has been refactored slightly to allow updates to be made that link the Perf format arguments with the existing documentation.
For Suzuki's comment, I will do it as a separate change that converts all the other hard coded values to a more consistent sysreg.h style:
nit: While at this, please could you change the hard coded value to ETM4_CFG_BIT_RETSTK ?
Changes since v1:
* Added Leo's reviewed by on patch 3 * Fix bracket styling * Add documentation
Applies on top of coresight/next efa56eddf5d5c. But this docs fix is also required to get the links to work: https://marc.info/?l=linux-doc&m=164139331923986&w=2
Also available at: https://gitlab.arm.com/linux-arm/linux-jc/-/tree/james-branch-broadcast-v2
James Clark (6): coresight: Add config flag to enable branch broadcast coresight: Fail to open with return stacks if they are unavailable perf cs-etm: Update deduction of TRCCONFIGR register for branch broadcast Documentation: coresight: Turn numbered subsections into real subsections Documentation: coresight: Link config options to existing documentation Documentation: coresight: Expand branch broadcast documentation
.../coresight/coresight-etm4x-reference.rst | 14 ++++- Documentation/trace/coresight/coresight.rst | 56 +++++++++++++++++-- .../hwtracing/coresight/coresight-etm-perf.c | 2 + .../coresight/coresight-etm4x-core.c | 23 ++++++-- include/linux/coresight-pmu.h | 2 + tools/include/linux/coresight-pmu.h | 2 + tools/perf/arch/arm/util/cs-etm.c | 3 + 7 files changed, 92 insertions(+), 10 deletions(-)