[PATCH v8 0/9] LoongArch: Add ftrace support

From: Qing Zhang
Date: Wed Nov 16 2022 - 03:07:31 EST


This patch series to support basic and dynamic ftrace.

1) -pg
Use `-pg` makes stub like a child function `void _mcount(void *ra)`.
Thus, it can be seen store RA and open stack before `call _mcount`.
Find `open stack` at first, and then find `store RA`.

2) -fpatchable-function-entry=2
The compiler has inserted 2 NOPs before the regular function prologue.
T series registers are available and safe because of LoongArch psABI.

At runtime, replace nop with bl to enable ftrace call and replace bl with
nop to disable ftrace call. The bl requires us to save the original RA value,
so here it saves RA at t0.
details are:

| Compiled | Disabled | Enabled |
+------------+------------------------+------------------------+
| nop | move t0, ra | move t0, ra |
| nop | nop | bl ftrace_caller |
| func_body | func_body | func_body |

The RA value will be recovered by ftrace_regs_entry, and restored into RA
before returning to the regular function prologue. When a function is not
being traced, the move t0, ra is not harmful.

performs a series of startup tests on ftrace and The test cases in selftests
has passed on LoongArch.

Changes in v2:
- Remove patch "LoongArch: ftrace: Add CALLER_ADDRx macros" there are other
better ways
Suggested by Steve:
- Add HAVE_DYNAMIC_FTRACE_WITH_ARGS support (6/10)
Suggested by Jinyang:
- Change addu16id to lu12iw and Adjust module_finalize return value (7/10)
- Use the "jr" pseudo-instruction where applicable (1/10)
- Use the "la.pcrel" instead of "la" (3/10)

Changes in v3:
Reported by Jeff:
- Fix unwind state when option func_stack_trace (10/10)

Changes in v4:
- No comments. Just resend the series.
- Rebased onto v6.0.0-rc4.

Changes in v5:
- Modify the indentation of Kconfig and small changes

Changes in v6:
Suggested by Huacai:
- Adjusting the patch Sequence
- renamed mcount-dyn.S for consistency

Changes in v7:
- delete redefinition

Changes in v8:
- remove useless macro judgment and modify the return location
- move some code to Patch-3

Qing Zhang (9):
LoongArch/ftrace: Add basic support
LoongArch/ftrace: Add recordmcount support
LoongArch/ftrace: Add dynamic function tracer support
LoongArch/ftrace: Add dynamic function graph tracer support
LoongArch/ftrace: Add HAVE_DYNAMIC_FTRACE_WITH_REGS support
LoongArch/ftrace: Add HAVE_DYNAMIC_FTRACE_WITH_ARGS support
LoongArch/ftrace: Add HAVE_FUNCTION_GRAPH_RET_ADDR_PTR support
LoongArch: modules/ftrace: Initialize PLT at load time
LoongArch: Enable CONFIG_KALLSYMS_ALL and CONFIG_DEBUG_FS

arch/loongarch/Kconfig | 7 +
arch/loongarch/Makefile | 5 +
arch/loongarch/configs/loongson3_defconfig | 2 +
arch/loongarch/include/asm/ftrace.h | 59 +++++
arch/loongarch/include/asm/inst.h | 15 ++
arch/loongarch/include/asm/module.h | 5 +-
arch/loongarch/include/asm/module.lds.h | 1 +
arch/loongarch/include/asm/unwind.h | 3 +-
arch/loongarch/kernel/Makefile | 13 +
arch/loongarch/kernel/ftrace.c | 74 ++++++
arch/loongarch/kernel/ftrace_dyn.c | 264 +++++++++++++++++++++
arch/loongarch/kernel/inst.c | 127 ++++++++++
arch/loongarch/kernel/mcount.S | 94 ++++++++
arch/loongarch/kernel/mcount_dyn.S | 154 ++++++++++++
arch/loongarch/kernel/module-sections.c | 11 +
arch/loongarch/kernel/module.c | 22 ++
arch/loongarch/kernel/unwind_guess.c | 4 +-
arch/loongarch/kernel/unwind_prologue.c | 46 +++-
scripts/recordmcount.c | 23 ++
19 files changed, 919 insertions(+), 10 deletions(-)
create mode 100644 arch/loongarch/include/asm/ftrace.h
create mode 100644 arch/loongarch/kernel/ftrace.c
create mode 100644 arch/loongarch/kernel/ftrace_dyn.c
create mode 100644 arch/loongarch/kernel/mcount.S
create mode 100644 arch/loongarch/kernel/mcount_dyn.S

--
2.36.0