diff options
| author | Qing Zhang <zhangqing@loongson.cn> | 2022-12-10 22:40:15 +0800 |
|---|---|---|
| committer | Huacai Chen <chenhuacai@loongson.cn> | 2022-12-14 08:41:53 +0800 |
| commit | 4733f09d880745953b88c3358b49ad495aecd8e9 (patch) | |
| tree | c53c7531fa72b908bab436f27cfb139f63d42ea5 /arch/loongarch/Makefile | |
| parent | a0a458fbd6f2317832e2d74acdbfa2451c3f4b8f (diff) | |
LoongArch/ftrace: Add dynamic function tracer support
The compiler has inserted 2 NOPs before the regular function prologue.
T series registers are available and safe because of LoongArch's psABI.
At runtime, we can replace nop with bl to enable ftrace call and replace
bl with nop to disable ftrace call. The bl instruction requires us to
save the original RA value, so it saves RA at t0 here.
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.
1) ftrace_make_call, ftrace_make_nop (in kernel/ftrace.c)
The two functions turn each recorded call site of filtered functions
into a call to ftrace_caller or nops.
2) ftracce_update_ftrace_func (in kernel/ftrace.c)
turns the nops at ftrace_call into a call to a generic entry for
function tracers.
3) ftrace_caller (in kernel/mcount_dyn.S)
The entry where each _mcount call sites calls to once they are
filtered to be traced.
Co-developed-by: Jinyang He <hejinyang@loongson.cn>
Signed-off-by: Jinyang He <hejinyang@loongson.cn>
Signed-off-by: Qing Zhang <zhangqing@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Diffstat (limited to 'arch/loongarch/Makefile')
| -rw-r--r-- | arch/loongarch/Makefile | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/arch/loongarch/Makefile b/arch/loongarch/Makefile index 5232d8c0f9ca..4402387d2755 100644 --- a/arch/loongarch/Makefile +++ b/arch/loongarch/Makefile @@ -25,6 +25,11 @@ endif 32bit-emul = elf32loongarch 64bit-emul = elf64loongarch +ifdef CONFIG_DYNAMIC_FTRACE +KBUILD_CPPFLAGS += -DCC_USING_PATCHABLE_FUNCTION_ENTRY +CC_FLAGS_FTRACE := -fpatchable-function-entry=2 +endif + ifdef CONFIG_64BIT tool-archpref = $(64bit-tool-archpref) UTS_MACHINE := loongarch64 |