RFC powerpc: Core ftrace rework, support for ftrace direct and bpf trampolines

This is v4 of the series posted here:
http://lkml.kernel.org/r/[email protected]

This series reworks core ftrace support on powerpc to have the function profiling sequence moved out of line. This enables us to have a single nop at kernel function entry virtually eliminating effect of the function tracer when it is not enabled. The function profile sequence is moved out of line and is allocated at two separate places depending on a new config option.

For 64-bit powerpc, the function profiling sequence is also updated to include an additional instruction 'mtlr r0' after the usual two-instruction sequence to fix link stack imbalance (return address predictor) when ftrace is enabled. This showed an improvement of ~22% in null_syscall benchmark on a Power 10 system with ftrace enabled.

Finally, support for ftrace direct calls is added based on support for DYNAMIC_FTRACE_WITH_CALL_OPS. BPF Trampoline support is added atop this.

Support for ftrace direct calls is added for 32-bit powerpc. There is some code to enable bpf trampolines for 32-bit powerpc, but it is not complete and will need to be pursued separately.

This is marked RFC so that this can get more testing. Patches 1 to 10 are independent of this series and can go in separately though. Rest of the patches depend on the series from Benjamin Gray adding support for patch_uint() and patch_ulong():
http://lkml.kernel.org/r/[email protected]

Changelog v4:
- Patches 1, 10 and 13 are new.
- Address review comments from Nick. Numerous changes throughout the patch series.
- Extend support for ftrace ool to vmlinux text up to 64MB (patch 13).
- Address remaining TODOs in support for BPF Trampolines.
- Update synchronization when patching instructions during trampoline attach/detach.

- Naveen

Naveen N Rao (17):
powerpc/trace: Account for -fpatchable-function-entry support by
toolchain
powerpc/kprobes: Use ftrace to determine if a probe is at function
entry
powerpc64/ftrace: Nop out additional 'std' instruction emitted by gcc

    v5.x

powerpc32/ftrace: Unify 32-bit and 64-bit ftrace entry code powerpc/module_64: Convert #ifdef to IS_ENABLED() powerpc/ftrace: Remove pointer to struct module from dyn_arch_ftrace powerpc/ftrace: Skip instruction patching if the instructions are the
same
powerpc/ftrace: Move ftrace stub used for init text before _einittext powerpc64/bpf: Fold bpf_jit_emit_func_call_hlp() into
bpf_jit_emit_func_call_rel()
powerpc/ftrace: Add a postlink script to validate function tracer
kbuild: Add generic hook for architectures to use before the final
vmlinux link
powerpc64/ftrace: Move ftrace sequence out of line powerpc64/ftrace: Support .text larger than 32MB with out-of-line
stubs
powerpc/ftrace: Add support for DYNAMIC_FTRACE_WITH_CALL_OPS powerpc/ftrace: Add support for DYNAMIC_FTRACE_WITH_DIRECT_CALLS samples/ftrace: Add support for ftrace direct samples on powerpc powerpc64/bpf: Add support for bpf trampolines

 arch/Kconfig                                |   6 +
 arch/powerpc/Kconfig                        |  23 +-
 arch/powerpc/Makefile                       |   8 +
 arch/powerpc/Makefile.postlink              |   8 +
 arch/powerpc/include/asm/ftrace.h           |  32 +-
 arch/powerpc/include/asm/module.h           |   5 +
 arch/powerpc/include/asm/ppc-opcode.h       |  14 +
 arch/powerpc/kernel/asm-offsets.c           |  11 +
 arch/powerpc/kernel/kprobes.c               |  18 +-
 arch/powerpc/kernel/module_64.c             |  66 +-
 arch/powerpc/kernel/trace/Makefile          |  11 +-
 arch/powerpc/kernel/trace/ftrace.c          | 295 ++++++-
 arch/powerpc/kernel/trace/ftrace_64_pg.c    |  69 +-
 arch/powerpc/kernel/trace/ftrace_entry.S    | 246 ++++--
 arch/powerpc/kernel/vmlinux.lds.S           |   3 +-
 arch/powerpc/net/bpf_jit.h                  |  12 +
 arch/powerpc/net/bpf_jit_comp.c             | 842 +++++++++++++++++++-
 arch/powerpc/net/bpf_jit_comp32.c           |   7 +-
 arch/powerpc/net/bpf_jit_comp64.c           |  68 +-
 arch/powerpc/tools/Makefile                 |  10 +
 arch/powerpc/tools/ftrace-gen-ool-stubs.sh  |  52 ++
 arch/powerpc/tools/ftrace_check.sh          |  45 ++
 samples/ftrace/ftrace-direct-modify.c       |  85 +-
 samples/ftrace/ftrace-direct-multi-modify.c | 101 ++-
 samples/ftrace/ftrace-direct-multi.c        |  79 +-
 samples/ftrace/ftrace-direct-too.c          |  83 +-
 samples/ftrace/ftrace-direct.c              |  69 +-
 scripts/Makefile.vmlinux                    |   8 +
 scripts/link-vmlinux.sh                     |  11 +-
 29 files changed, 2083 insertions(+), 204 deletions(-)
 create mode 100644 arch/powerpc/tools/Makefile
 create mode 100755 arch/powerpc/tools/ftrace-gen-ool-stubs.sh
 create mode 100755 arch/powerpc/tools/ftrace_check.sh

base-commit: 582b0e554593e530b1386eacafee6c412c5673cc
prerequisite-patch-id: a1d50e589288239d5a8b1c1f354cd4737057c9d3
prerequisite-patch-id: da4142d56880861bd0ad7ad7087c9e2670a2ee54
prerequisite-patch-id: 609d292e054b2396b603890522a940fa0bdfb6d8
prerequisite-patch-id: 6f7213fb77b1260defbf43be0e47bff9c80054cc
prerequisite-patch-id: ad3b71bf071ae4ba1bee5b087e61a2055772a74f

2.45.2