From dbe3ba3018ec1fc53ea0d0adf0f687f5d438039d Mon Sep 17 00:00:00 2001 From: Qing Zhang Date: Sat, 10 Dec 2022 22:40:15 +0800 Subject: [PATCH] LoongArch/ftrace: Add basic support This patch contains basic ftrace support for LoongArch. Specifically, function tracer (HAVE_FUNCTION_TRACER), function graph tracer (HAVE_ FUNCTION_GRAPH_TRACER) are implemented following the instructions in Documentation/trace/ftrace-design.txt. Use `-pg` makes stub like a child function `void _mcount(void *ra)`. Thus, it can be seen store RA and alloc stack before `call _mcount`. Find `alloc stack` at first, and then find `store RA`. Note that the functions in both inst.c and time.c should not be hooked with the compiler's -pg option: to prevent infinite self-referencing for the former, and to ignore early setup stuff for the latter. Co-developed-by: Jinyang He Signed-off-by: Jinyang He Signed-off-by: Qing Zhang Signed-off-by: Huacai Chen --- arch/loongarch/Kconfig | 2 + arch/loongarch/include/asm/ftrace.h | 21 ++++++++ arch/loongarch/kernel/Makefile | 8 ++++ arch/loongarch/kernel/ftrace.c | 73 ++++++++++++++++++++++++++++ arch/loongarch/kernel/mcount.S | 96 +++++++++++++++++++++++++++++++++++++ 5 files changed, 200 insertions(+) create mode 100644 arch/loongarch/include/asm/ftrace.h create mode 100644 arch/loongarch/kernel/ftrace.c create mode 100644 arch/loongarch/kernel/mcount.S diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig index 28d827c..72a41e0 100644 --- a/arch/loongarch/Kconfig +++ b/arch/loongarch/Kconfig @@ -90,6 +90,8 @@ config LOONGARCH select HAVE_EBPF_JIT select HAVE_EXIT_THREAD select HAVE_FAST_GUP + select HAVE_FUNCTION_GRAPH_TRACER + select HAVE_FUNCTION_TRACER select HAVE_GENERIC_VDSO select HAVE_IOREMAP_PROT select HAVE_IRQ_EXIT_ON_IRQ_STACK diff --git a/arch/loongarch/include/asm/ftrace.h b/arch/loongarch/include/asm/ftrace.h new file mode 100644 index 0000000..c3f5cde --- /dev/null +++ b/arch/loongarch/include/asm/ftrace.h @@ -0,0 +1,21 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Copyright (C) 2022 Loongson Technology Corporation Limited + */ + +#ifndef _ASM_LOONGARCH_FTRACE_H +#define _ASM_LOONGARCH_FTRACE_H + +#ifdef CONFIG_FUNCTION_TRACER + +#define MCOUNT_INSN_SIZE 4 /* sizeof mcount call */ + +#ifndef __ASSEMBLY__ +#define mcount _mcount +extern void _mcount(void); +extern void prepare_ftrace_return(unsigned long self_addr, unsigned long callsite_sp, unsigned long old); +#endif /* __ASSEMBLY__ */ + +#endif /* CONFIG_FUNCTION_TRACER */ + +#endif /* _ASM_LOONGARCH_FTRACE_H */ diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile index 8674453..3f71bce 100644 --- a/arch/loongarch/kernel/Makefile +++ b/arch/loongarch/kernel/Makefile @@ -15,6 +15,14 @@ obj-$(CONFIG_EFI) += efi.o obj-$(CONFIG_CPU_HAS_FPU) += fpu.o +ifdef CONFIG_FUNCTION_TRACER +obj-y += mcount.o ftrace.o +CFLAGS_REMOVE_ftrace.o = $(CC_FLAGS_FTRACE) +CFLAGS_REMOVE_inst.o = $(CC_FLAGS_FTRACE) +CFLAGS_REMOVE_time.o = $(CC_FLAGS_FTRACE) +CFLAGS_REMOVE_perf_event.o = $(CC_FLAGS_FTRACE) +endif + obj-$(CONFIG_MODULES) += module.o module-sections.o obj-$(CONFIG_STACKTRACE) += stacktrace.o diff --git a/arch/loongarch/kernel/ftrace.c b/arch/loongarch/kernel/ftrace.c new file mode 100644 index 0000000..8c3ec1b --- /dev/null +++ b/arch/loongarch/kernel/ftrace.c @@ -0,0 +1,73 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 2022 Loongson Technology Corporation Limited + */ + +#include +#include +#include +#include + +#include +#include +#include +#include +#include +#include + +#include + +#ifdef CONFIG_FUNCTION_GRAPH_TRACER + +/* + * As `call _mcount` follows LoongArch psABI, ra-saved operation and + * stack operation can be found before this insn. + */ + +static int ftrace_get_parent_ra_addr(unsigned long insn_addr, int *ra_off) +{ + int limit = 32; + union loongarch_instruction *insn; + + insn = (union loongarch_instruction *)insn_addr; + + do { + insn--; + limit--; + + if (is_ra_save_ins(insn)) + *ra_off = -((1 << 12) - insn->reg2i12_format.immediate); + + } while (!is_stack_alloc_ins(insn) && limit); + + if (!limit) + return -EINVAL; + + return 0; +} + +void prepare_ftrace_return(unsigned long self_addr, + unsigned long callsite_sp, unsigned long old) +{ + int ra_off; + unsigned long return_hooker = (unsigned long)&return_to_handler; + + if (unlikely(ftrace_graph_is_dead())) + return; + + if (unlikely(atomic_read(¤t->tracing_graph_pause))) + return; + + if (ftrace_get_parent_ra_addr(self_addr, &ra_off)) + goto out; + + if (!function_graph_enter(old, self_addr, 0, NULL)) + *(unsigned long *)(callsite_sp + ra_off) = return_hooker; + + return; + +out: + ftrace_graph_stop(); + WARN_ON(1); +} +#endif /* CONFIG_FUNCTION_GRAPH_TRACER */ diff --git a/arch/loongarch/kernel/mcount.S b/arch/loongarch/kernel/mcount.S new file mode 100644 index 0000000..8cdc156 --- /dev/null +++ b/arch/loongarch/kernel/mcount.S @@ -0,0 +1,96 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * LoongArch specific _mcount support + * + * Copyright (C) 2022 Loongson Technology Corporation Limited + */ + +#include +#include +#include +#include + + .text + +#define MCOUNT_S0_OFFSET (0) +#define MCOUNT_RA_OFFSET (SZREG) +#define MCOUNT_STACK_SIZE (2 * SZREG) + + .macro MCOUNT_SAVE_REGS + PTR_ADDI sp, sp, -MCOUNT_STACK_SIZE + PTR_S s0, sp, MCOUNT_S0_OFFSET + PTR_S ra, sp, MCOUNT_RA_OFFSET + move s0, a0 + .endm + + .macro MCOUNT_RESTORE_REGS + move a0, s0 + PTR_L ra, sp, MCOUNT_RA_OFFSET + PTR_L s0, sp, MCOUNT_S0_OFFSET + PTR_ADDI sp, sp, MCOUNT_STACK_SIZE + .endm + +SYM_FUNC_START(_mcount) + la.pcrel t1, ftrace_stub + la.pcrel t2, ftrace_trace_function /* Prepare t2 for (1) */ + PTR_L t2, t2, 0 + beq t1, t2, fgraph_trace + + MCOUNT_SAVE_REGS + + move a0, ra /* arg0: self return address */ + move a1, s0 /* arg1: parent's return address */ + jirl ra, t2, 0 /* (1) call *ftrace_trace_function */ + + MCOUNT_RESTORE_REGS + +fgraph_trace: +#ifdef CONFIG_FUNCTION_GRAPH_TRACER + la.pcrel t1, ftrace_stub + la.pcrel t3, ftrace_graph_return + PTR_L t3, t3, 0 + bne t1, t3, ftrace_graph_caller + la.pcrel t1, ftrace_graph_entry_stub + la.pcrel t3, ftrace_graph_entry + PTR_L t3, t3, 0 + bne t1, t3, ftrace_graph_caller +#endif + +SYM_INNER_LABEL(ftrace_stub, SYM_L_GLOBAL) + jr ra +#ifdef CONFIG_FUNCTION_GRAPH_TRACER +SYM_INNER_LABEL(ftrace_graph_func, SYM_L_GLOBAL) + bl ftrace_stub +#endif +SYM_FUNC_END(_mcount) +EXPORT_SYMBOL(_mcount) + +#ifdef CONFIG_FUNCTION_GRAPH_TRACER +SYM_FUNC_START(ftrace_graph_caller) + MCOUNT_SAVE_REGS + + PTR_ADDI a0, ra, -4 /* arg0: Callsite self return addr */ + PTR_ADDI a1, sp, MCOUNT_STACK_SIZE /* arg1: Callsite sp */ + move a2, s0 /* arg2: Callsite parent ra */ + bl prepare_ftrace_return + + MCOUNT_RESTORE_REGS + jr ra +SYM_FUNC_END(ftrace_graph_caller) + +SYM_FUNC_START(return_to_handler) + PTR_ADDI sp, sp, -2 * SZREG + PTR_S a0, sp, 0 + PTR_S a1, sp, SZREG + + bl ftrace_return_to_handler + + /* Restore the real parent address: a0 -> ra */ + move ra, a0 + + PTR_L a0, sp, 0 + PTR_L a1, sp, SZREG + PTR_ADDI sp, sp, 2 * SZREG + jr ra +SYM_FUNC_END(return_to_handler) +#endif /* CONFIG_FUNCTION_GRAPH_TRACER */ -- 2.7.4