Re: [PATCH v5 00/17] powerpc: Core ftrace rework, support for ftrace direct and bpf trampolines

From: Masahiro Yamada
Date: Wed Oct 09 2024 - 12:09:12 EST

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On Mon, Sep 16, 2024 at 5:57 AM Hari Bathini <hbathini@xxxxxxxxxxxxx> wrote:
>
> This is v5 of the series posted here:
> https://lore.kernel.org/all/cover.1720942106.git.naveen@xxxxxxxxxx/
>
> 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 ~10%
> in null_syscall benchmark (NR_LOOPS=10000000) 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.
>
> 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():
> https://lore.kernel.org/all/172474280311.31690.1489687786264785049.b4-ty@xxxxxxxxxxxxxx/

It is getting better.

I attached a diff for improvements.

Also, please run 'shellcheck' and eliminate
as many warnings as you can.

$ shellcheck arch/powerpc/tools/ftrace-gen-ool-stubs.sh

In arch/powerpc/tools/ftrace-gen-ool-stubs.sh line 19:
num_ool_stubs_text=$(${OBJDUMP} -r -j __patchable_function_entries
${vmlinux_o} |

^----------^ SC2086 (info): Double quote to prevent globbing and word
splitting.

Did you mean:
num_ool_stubs_text=$(${OBJDUMP} -r -j __patchable_function_entries
"${vmlinux_o}" |

In arch/powerpc/tools/ftrace-gen-ool-stubs.sh line 20:
grep -v ".init.text" | grep "${RELOCATION}" | wc -l)
^------------------^
SC2126 (style): Consider using 'grep -c' instead of 'grep|wc -l'.

In arch/powerpc/tools/ftrace-gen-ool-stubs.sh line 21:
num_ool_stubs_inittext=$(${OBJDUMP} -r -j __patchable_function_entries
${vmlinux_o} |

^----------^ SC2086 (info): Double quote to prevent globbing and word
splitting.

Did you mean:
num_ool_stubs_inittext=$(${OBJDUMP} -r -j __patchable_function_entries
"${vmlinux_o}" |

In arch/powerpc/tools/ftrace-gen-ool-stubs.sh line 22:
grep ".init.text" | grep "${RELOCATION}" | wc -l)
^------------------^
SC2126 (style): Consider using 'grep -c' instead of 'grep|wc -l'.

In arch/powerpc/tools/ftrace-gen-ool-stubs.sh line 25:
if [ ${num_ool_stubs_text} -gt ${num_ool_stubs_text_builtin} ]; then
^-------------------^ SC2086 (info): Double quote to prevent
globbing and word splitting.
^---------------------------^ SC2086
(info): Double quote to prevent globbing and word splitting.

Did you mean:
if [ "${num_ool_stubs_text}" -gt "${num_ool_stubs_text_builtin}" ]; then

In arch/powerpc/tools/ftrace-gen-ool-stubs.sh line 26:
num_ool_stubs_text_end=$(expr ${num_ool_stubs_text} -
${num_ool_stubs_text_builtin})
^--^ SC2003 (style): expr is
antiquated. Consider rewriting this using $((..)), ${} or [[ ]].
^-------------------^ SC2086
(info): Double quote to prevent globbing and word splitting.

^---------------------------^ SC2086 (info): Double quote to prevent
globbing and word splitting.

Did you mean:
num_ool_stubs_text_end=$(expr "${num_ool_stubs_text}" -
"${num_ool_stubs_text_builtin}")

In arch/powerpc/tools/ftrace-gen-ool-stubs.sh line 31:
cat > ${arch_vmlinux_S} <<EOF
^---------------^ SC2086 (info): Double quote to prevent
globbing and word splitting.

Did you mean:
cat > "${arch_vmlinux_S}" <<EOF

For more information:
https://www.shellcheck.net/wiki/SC2086 -- Double quote to prevent globbing ...
https://www.shellcheck.net/wiki/SC2003 -- expr is antiquated. Consider rewr...
https://www.shellcheck.net/wiki/SC2126 -- Consider using 'grep -c' instead ...

> Changelog v5:
> * Intermediate files named .vmlinux.arch.* instead of .arch.vmlinux.*
> * Fixed ftrace stack tracer failure due to inadvertent use of
> 'add r7, r3, MCOUNT_INSN_SIZE' instruction instead of
> 'addi r7, r3, MCOUNT_INSN_SIZE'
> * Fixed build error for !CONFIG_MODULES case.
> * .vmlinux.arch.* files compiled under arch/powerpc/tools
> * Made sure .vmlinux.arch.* files are cleaned with `make clean`
> * num_ool_stubs_text_end used for setting up ftrace_ool_stub_text_end
> set to zero instead of computing to some random negative value when
> not required.
> * Resolved checkpatch.pl warnings.
> * Dropped RFC tag.
>
> 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 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/Kbuild | 2 +-
> arch/powerpc/Kconfig | 23 +-
> arch/powerpc/Makefile | 8 +
> arch/powerpc/Makefile.postlink | 8 +
> arch/powerpc/include/asm/ftrace.h | 33 +-
> 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 | 298 ++++++-
> arch/powerpc/kernel/trace/ftrace_64_pg.c | 69 +-
> arch/powerpc/kernel/trace/ftrace_entry.S | 244 ++++--
> arch/powerpc/kernel/vmlinux.lds.S | 3 +-
> arch/powerpc/net/bpf_jit.h | 12 +
> arch/powerpc/net/bpf_jit_comp.c | 847 +++++++++++++++++++-
> arch/powerpc/net/bpf_jit_comp32.c | 7 +-
> arch/powerpc/net/bpf_jit_comp64.c | 68 +-
> arch/powerpc/tools/Makefile | 12 +
> arch/powerpc/tools/ftrace-gen-ool-stubs.sh | 52 ++
> arch/powerpc/tools/ftrace_check.sh | 50 ++
> 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 | 7 +
> scripts/link-vmlinux.sh | 7 +-
> 30 files changed, 2098 insertions(+), 200 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
>
> --
> 2.46.0
>

--
Best Regards
Masahiro Yamada
From 0e96689efc977542a47e815a78892833e0305d79 Mon Sep 17 00:00:00 2001
From: Masahiro Yamada <masahiroy@xxxxxxxxxx>
Date: Wed, 9 Oct 2024 23:37:47 +0900
Subject: [PATCH] fixup

Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx>
---
arch/Kconfig | 2 +-
arch/powerpc/Kconfig | 5 ++---
arch/powerpc/tools/.gitignore | 2 ++
arch/powerpc/tools/Makefile | 7 ++-----
arch/powerpc/tools/ftrace-gen-ool-stubs.sh | 5 ++---
scripts/Makefile.vmlinux | 4 ++--
scripts/link-vmlinux.sh | 2 +-
7 files changed, 12 insertions(+), 15 deletions(-)
create mode 100644 arch/powerpc/tools/.gitignore

diff --git a/arch/Kconfig b/arch/Kconfig
index 87806750cf4e..a1538927c8c1 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -1685,7 +1685,7 @@ config ARCH_NEED_CMPXCHG_1_EMU
bool

config ARCH_WANTS_PRE_LINK_VMLINUX
- def_bool n
+ bool
help
An architecture can select this if it provides arch/<arch>/tools/Makefile
with .arch.vmlinux.o target to be linked into vmlinux.
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 8a31f61f1b34..c85470b24118 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -575,13 +575,12 @@ config ARCH_USING_PATCHABLE_FUNCTION_ENTRY

config PPC_FTRACE_OUT_OF_LINE
def_bool PPC64 && ARCH_USING_PATCHABLE_FUNCTION_ENTRY
- depends on PPC64
select ARCH_WANTS_PRE_LINK_VMLINUX

config PPC_FTRACE_OUT_OF_LINE_NUM_RESERVE
int "Number of ftrace out-of-line stubs to reserve within .text"
- default 32768 if PPC_FTRACE_OUT_OF_LINE
- default 0
+ depends on PPC_FTRACE_OUT_OF_LINE
+ default 32768
help
Number of stubs to reserve for use by ftrace. This space is
reserved within .text, and is distinct from any additional space
diff --git a/arch/powerpc/tools/.gitignore b/arch/powerpc/tools/.gitignore
new file mode 100644
index 000000000000..ec380a14a09a
--- /dev/null
+++ b/arch/powerpc/tools/.gitignore
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+/vmlinux.arch.S
diff --git a/arch/powerpc/tools/Makefile b/arch/powerpc/tools/Makefile
index 9eeb6edf02fe..96dbbc4f3e66 100644
--- a/arch/powerpc/tools/Makefile
+++ b/arch/powerpc/tools/Makefile
@@ -3,10 +3,7 @@
quiet_cmd_gen_ftrace_ool_stubs = GEN $@
cmd_gen_ftrace_ool_stubs = $< $(CONFIG_PPC_FTRACE_OUT_OF_LINE_NUM_RESERVE) vmlinux.o $@

-$(obj)/.vmlinux.arch.S: $(src)/ftrace-gen-ool-stubs.sh vmlinux.o FORCE
+$(obj)/vmlinux.arch.S: $(src)/ftrace-gen-ool-stubs.sh vmlinux.o FORCE
$(call if_changed,gen_ftrace_ool_stubs)

-$(obj)/.vmlinux.arch.o: $(obj)/.vmlinux.arch.S FORCE
- $(call if_changed_rule,as_o_S)
-
-clean-files += .vmlinux.arch.S .vmlinux.arch.o
+targets += vmlinux.arch.S
diff --git a/arch/powerpc/tools/ftrace-gen-ool-stubs.sh b/arch/powerpc/tools/ftrace-gen-ool-stubs.sh
index 33f5ae4bace5..c69b375309bc 100755
--- a/arch/powerpc/tools/ftrace-gen-ool-stubs.sh
+++ b/arch/powerpc/tools/ftrace-gen-ool-stubs.sh
@@ -10,16 +10,15 @@ is_enabled() {

vmlinux_o=${2}
arch_vmlinux_S=${3}
-arch_vmlinux_o=$(dirname ${arch_vmlinux_S})/$(basename ${arch_vmlinux_S} .S).o

RELOCATION=R_PPC64_ADDR64
if is_enabled CONFIG_PPC32; then
RELOCATION=R_PPC_ADDR32
fi

-num_ool_stubs_text=$(${CROSS_COMPILE}objdump -r -j __patchable_function_entries ${vmlinux_o} |
+num_ool_stubs_text=$(${OBJDUMP} -r -j __patchable_function_entries ${vmlinux_o} |
grep -v ".init.text" | grep "${RELOCATION}" | wc -l)
-num_ool_stubs_inittext=$(${CROSS_COMPILE}objdump -r -j __patchable_function_entries ${vmlinux_o} |
+num_ool_stubs_inittext=$(${OBJDUMP} -r -j __patchable_function_entries ${vmlinux_o} |
grep ".init.text" | grep "${RELOCATION}" | wc -l)

num_ool_stubs_text_builtin=${1}
diff --git a/scripts/Makefile.vmlinux b/scripts/Makefile.vmlinux
index 8f08117f4a48..dddad554e912 100644
--- a/scripts/Makefile.vmlinux
+++ b/scripts/Makefile.vmlinux
@@ -23,9 +23,9 @@ vmlinux: .vmlinux.export.o
endif

ifdef CONFIG_ARCH_WANTS_PRE_LINK_VMLINUX
-vmlinux: arch/$(SRCARCH)/tools/.vmlinux.arch.o
+vmlinux: arch/$(SRCARCH)/tools/vmlinux.arch.o

-arch/$(SRCARCH)/tools/.vmlinux.arch.o: vmlinux.o
+arch/$(SRCARCH)/tools/vmlinux.arch.o: vmlinux.o FORCE
$(Q)$(MAKE) $(build)=arch/$(SRCARCH)/tools $@
endif

diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index 33c1aa8dd468..7acf4e31e51c 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -200,7 +200,7 @@ ${MAKE} -f "${srctree}/scripts/Makefile.build" obj=init init/version-timestamp.o

arch_vmlinux_o=""
if is_enabled CONFIG_ARCH_WANTS_PRE_LINK_VMLINUX; then
- arch_vmlinux_o=arch/${SRCARCH}/tools/.vmlinux.arch.o
+ arch_vmlinux_o=arch/${SRCARCH}/tools/vmlinux.arch.o
fi

btf_vmlinux_bin_o=
--
2.43.0

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