[PW_SID:1155929] riscv: kprobes: simulate nop and c.nop instructions by linux-riscv-bot · Pull Request #2576 · linux-riscv/linux

linux-riscv-bot · 2026-09-02T09:57:01Z

PR for series 1155929 applied to workflow__riscv__fixes

Name: riscv: kprobes: simulate nop and c.nop instructions
URL: https://patchwork.kernel.org/project/linux-riscv/list/?series=1155929
Version: 3

A kprobe or uprobe placed on a nop currently replays the instruction out-of-line: the breakpoint trap runs the probe handler and redirects execution to a copy of the instruction sitting in an XOL slot, and a second breakpoint appended after the copy traps again to finish the hit. That costs an extra exception round-trip per hit; for uprobes the slot runs in user mode, so the re-trap is a full kernel<->userspace round-trip. nop and c.nop have no architectural effect, so the replay can be replaced by simply advancing the program counter when handling the initial breakpoint, completing every hit within a single trap. arm64 does the same in its probe-decode path, which is also shared between kprobes and uprobes; see commit ac4ad5c ("arm64: insn: Simulate nop instruction for better uprobe performance"). riscv_probe_decode_insn() is shared by kprobes and uprobes, so the simulation applies to both. It primarily matters for uprobes on USDT probe sites: under the SystemTap SDT ABI (sys/sdt.h, parsed by libbpf), the recorded probe location is by construction a plain nop or c.nop, the same case that motivated the arm64 series. Measured on QEMU (RISC-V virt, emulated): for a uprobe on a USDT style nop site the per-hit cost drops by roughly 80 percent; for a kprobe on a nop by roughly 40 percent. On real arm64 hardware the referenced commit measured ~2x. Compile tested on RISC-V, and verified with the RISC-V kprobes KUnit test which now covers nop and c.nop. Signed-off-by: Xiaofeng Yuan <yuanxiaofeng@eswincomputing.com> Signed-off-by: Linux RISC-V bot <linux.riscv.bot@gmail.com>

Extend the RISC-V kprobes KUnit test with test_kprobes_nop and test_kprobes_c_nop, covering both the 32-bit nop and the compressed c.nop simulation paths. Signed-off-by: Xiaofeng Yuan <yuanxiaofeng@eswincomputing.com> Signed-off-by: Linux RISC-V bot <linux.riscv.bot@gmail.com>

linux-riscv-bot · 2026-09-02T14:37:41Z

Patch 1: "[v3,1/2] riscv: kprobes: simulate nop and c.nop instructions"
build-rv32-defconfig
Desc: Builds riscv32 defconfig
Duration: 141.73 seconds
Result: PASS

linux-riscv-bot · 2026-09-02T15:03:58Z

Patch 1: "[v3,1/2] riscv: kprobes: simulate nop and c.nop instructions"
build-rv64-clang-allmodconfig
Desc: Builds riscv64 allmodconfig with Clang, and checks for errors and added warnings
Duration: 1575.72 seconds
Result: PASS

linux-riscv-bot · 2026-09-02T15:34:21Z

Patch 1: "[v3,1/2] riscv: kprobes: simulate nop and c.nop instructions"
build-rv64-gcc-allmodconfig
Desc: Builds riscv64 allmodconfig with GCC, and checks for errors and added warnings
Duration: 1820.37 seconds
Result: PASS

linux-riscv-bot · 2026-09-02T15:34:51Z

Patch 1: "[v3,1/2] riscv: kprobes: simulate nop and c.nop instructions"
build-rv64-nommu-k210-defconfig
Desc: Builds riscv64 defconfig with NOMMU for K210
Duration: 26.44 seconds
Result: PASS

linux-riscv-bot · 2026-09-02T15:35:20Z

Patch 1: "[v3,1/2] riscv: kprobes: simulate nop and c.nop instructions"
build-rv64-nommu-k210-virt
Desc: Builds riscv64 defconfig with NOMMU for the virt platform
Duration: 27.64 seconds
Result: PASS

linux-riscv-bot · 2026-09-02T15:35:24Z

Patch 1: "[v3,1/2] riscv: kprobes: simulate nop and c.nop instructions"
checkpatch
Desc: Runs checkpatch.pl on the patch
Duration: 1.41 seconds
Result: PASS

linux-riscv-bot · 2026-09-02T15:36:58Z

Patch 1: "[v3,1/2] riscv: kprobes: simulate nop and c.nop instructions"
dtb-warn-rv64
Desc: Checks for Device Tree warnings/errors
Duration: 92.19 seconds
Result: PASS

linux-riscv-bot · 2026-09-02T15:37:01Z

Patch 1: "[v3,1/2] riscv: kprobes: simulate nop and c.nop instructions"
header-inline
Desc: Detects static functions without inline keyword in header files
Duration: 0.65 seconds
Result: PASS

linux-riscv-bot · 2026-09-02T15:37:03Z

Patch 1: "[v3,1/2] riscv: kprobes: simulate nop and c.nop instructions"
kdoc
Desc: Detects for kdoc errors
Duration: 0.83 seconds
Result: PASS

linux-riscv-bot · 2026-09-02T15:37:06Z

Patch 1: "[v3,1/2] riscv: kprobes: simulate nop and c.nop instructions"
module-param
Desc: Detect module_param changes
Duration: 0.28 seconds
Result: PASS

linux-riscv-bot · 2026-09-02T15:37:07Z

Patch 1: "[v3,1/2] riscv: kprobes: simulate nop and c.nop instructions"
verify-fixes
Desc: Verifies that the Fixes: tags exist
Duration: 0.24 seconds
Result: PASS

linux-riscv-bot · 2026-09-02T15:37:10Z

Patch 1: "[v3,1/2] riscv: kprobes: simulate nop and c.nop instructions"
verify-signedoff
Desc: Verifies that Signed-off-by: tags are correct
Duration: 0.32 seconds
Result: PASS

linux-riscv-bot · 2026-09-02T15:39:47Z

Patch 2: "[v3,2/2] riscv: kprobes: add nop and c.nop to the KUnit test"
build-rv32-defconfig
Desc: Builds riscv32 defconfig
Duration: 142.01 seconds
Result: PASS

linux-riscv-bot · 2026-09-02T15:59:34Z

Patch 2: "[v3,2/2] riscv: kprobes: add nop and c.nop to the KUnit test"
build-rv64-clang-allmodconfig
Desc: Builds riscv64 allmodconfig with Clang, and checks for errors and added warnings
Duration: 1184.34 seconds
Result: PASS

linux-riscv-bot · 2026-09-02T16:24:43Z

Patch 2: "[v3,2/2] riscv: kprobes: add nop and c.nop to the KUnit test"
build-rv64-gcc-allmodconfig
Desc: Builds riscv64 allmodconfig with GCC, and checks for errors and added warnings
Duration: 1507.60 seconds
Result: PASS

linux-riscv-bot · 2026-09-02T16:25:12Z

Patch 2: "[v3,2/2] riscv: kprobes: add nop and c.nop to the KUnit test"
build-rv64-nommu-k210-defconfig
Desc: Builds riscv64 defconfig with NOMMU for K210
Duration: 26.47 seconds
Result: PASS

linux-riscv-bot · 2026-09-02T16:25:41Z

Patch 2: "[v3,2/2] riscv: kprobes: add nop and c.nop to the KUnit test"
build-rv64-nommu-k210-virt
Desc: Builds riscv64 defconfig with NOMMU for the virt platform
Duration: 27.66 seconds
Result: PASS

linux-riscv-bot · 2026-09-02T16:25:44Z

Patch 2: "[v3,2/2] riscv: kprobes: add nop and c.nop to the KUnit test"
checkpatch
Desc: Runs checkpatch.pl on the patch
Duration: 0.77 seconds
Result: PASS

linux-riscv-bot · 2026-09-02T16:27:16Z

Patch 2: "[v3,2/2] riscv: kprobes: add nop and c.nop to the KUnit test"
dtb-warn-rv64
Desc: Checks for Device Tree warnings/errors
Duration: 91.05 seconds
Result: PASS

linux-riscv-bot · 2026-09-02T16:27:19Z

Patch 2: "[v3,2/2] riscv: kprobes: add nop and c.nop to the KUnit test"
header-inline
Desc: Detects static functions without inline keyword in header files
Duration: 0.23 seconds
Result: PASS

linux-riscv-bot · 2026-09-02T16:27:23Z

Patch 2: "[v3,2/2] riscv: kprobes: add nop and c.nop to the KUnit test"
kdoc
Desc: Detects for kdoc errors
Duration: 0.81 seconds
Result: PASS

linux-riscv-bot · 2026-09-02T16:27:25Z

Patch 2: "[v3,2/2] riscv: kprobes: add nop and c.nop to the KUnit test"
module-param
Desc: Detect module_param changes
Duration: 0.25 seconds
Result: PASS

linux-riscv-bot · 2026-09-02T16:27:28Z

Patch 2: "[v3,2/2] riscv: kprobes: add nop and c.nop to the KUnit test"
verify-fixes
Desc: Verifies that the Fixes: tags exist
Duration: 0.22 seconds
Result: PASS

linux-riscv-bot · 2026-09-02T16:27:30Z

Patch 2: "[v3,2/2] riscv: kprobes: add nop and c.nop to the KUnit test"
verify-signedoff
Desc: Verifies that Signed-off-by: tags are correct
Duration: 0.30 seconds
Result: PASS

Linux RISC-V bot and others added 3 commits September 2, 2026 05:24

Adding CI files

9ed823f

linux-riscv-bot force-pushed the workflow__riscv__fixes branch from 9ed823f to a54e736 Compare September 2, 2026 20:29

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