Messages in this thread | | | From | Huacai Chen <> | Date | Tue, 15 Nov 2022 17:04:51 +0800 | Subject | Re: [PATCH v6 1/9] LoongArch/ftrace: Add basic support |
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On Tue, Nov 15, 2022 at 4:51 PM Qing Zhang <zhangqing@loongson.cn> wrote: > > Hi, Huacai > > On 2022/11/15 下午4:25, Huacai Chen wrote: > > Hi, Qing, > > > > On Tue, Nov 15, 2022 at 10:55 AM Qing Zhang <zhangqing@loongson.cn> wrote: > >> > >> 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 open stack before `call _mcount`. > >> Find `open 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 <hejinyang@loongson.cn> > >> Signed-off-by: Jinyang He <hejinyang@loongson.cn> > >> Signed-off-by: Qing Zhang <zhangqing@loongson.cn> > >> --- > >> arch/loongarch/Kconfig | 2 + > >> arch/loongarch/Makefile | 5 ++ > >> arch/loongarch/include/asm/ftrace.h | 18 ++++++ > >> arch/loongarch/kernel/Makefile | 8 +++ > >> arch/loongarch/kernel/ftrace.c | 74 +++++++++++++++++++++++ > >> arch/loongarch/kernel/mcount.S | 94 +++++++++++++++++++++++++++++ > >> 6 files changed, 201 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 1943f840e494..92c4ec8c8527 100644 > >> --- a/arch/loongarch/Kconfig > >> +++ b/arch/loongarch/Kconfig > >> @@ -91,6 +91,8 @@ config LOONGARCH > >> select HAVE_EBPF_JIT > >> select HAVE_EXIT_THREAD > >> select HAVE_FAST_GUP > >> + select HAVE_FUNCTION_GRAPH_TRACER > > This line should be moved to another patch. > > > >> + select HAVE_FUNCTION_TRACER > >> select HAVE_GENERIC_VDSO > >> select HAVE_IOREMAP_PROT > >> select HAVE_IRQ_EXIT_ON_IRQ_STACK > >> diff --git a/arch/loongarch/Makefile b/arch/loongarch/Makefile > >> index a0fc1f9980e3..6832a8f891fd 100644 > >> --- a/arch/loongarch/Makefile > >> +++ b/arch/loongarch/Makefile > >> @@ -36,6 +36,11 @@ ifneq ($(SUBARCH),$(ARCH)) > >> endif > >> endif > >> > >> +ifdef CONFIG_DYNAMIC_FTRACE > >> +KBUILD_CPPFLAGS += -DCC_USING_PATCHABLE_FUNCTION_ENTRY > >> +CC_FLAGS_FTRACE := -fpatchable-function-entry=2 > >> +endif > >> + > >> ifdef CONFIG_64BIT > >> ld-emul = $(64bit-emul) > >> cflags-y += -mabi=lp64s > >> diff --git a/arch/loongarch/include/asm/ftrace.h b/arch/loongarch/include/asm/ftrace.h > >> new file mode 100644 > >> index 000000000000..6a3e76234618 > >> --- /dev/null > >> +++ b/arch/loongarch/include/asm/ftrace.h > >> @@ -0,0 +1,18 @@ > >> +/* SPDX-License-Identifier: GPL-2.0 */ > >> +/* > >> + * Copyright (C) 2022 Loongson Technology Corporation Limited > >> + */ > >> + > >> +#ifndef _ASM_LOONGARCH_FTRACE_H > >> +#define _ASM_LOONGARCH_FTRACE_H > >> + > >> +#ifdef CONFIG_FUNCTION_TRACER > >> +#define MCOUNT_INSN_SIZE 4 /* sizeof mcount call */ > >> + > >> +#ifndef __ASSEMBLY__ > >> +extern void _mcount(void); > >> +#define mcount _mcount > >> + > >> +#endif /* __ASSEMBLY__ */ > >> +#endif /* CONFIG_FUNCTION_TRACER */ > >> +#endif /* _ASM_LOONGARCH_FTRACE_H */ > >> diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile > >> index 86744531b100..3f71bce1c7ce 100644 > >> --- a/arch/loongarch/kernel/Makefile > >> +++ b/arch/loongarch/kernel/Makefile > >> @@ -15,6 +15,14 @@ obj-$(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 000000000000..c8ddc5f11f32 > >> --- /dev/null > >> +++ b/arch/loongarch/kernel/ftrace.c > >> @@ -0,0 +1,74 @@ > >> +// SPDX-License-Identifier: GPL-2.0 > >> +/* > >> + * Copyright (C) 2022 Loongson Technology Corporation Limited > >> + */ > >> + > >> +#include <linux/uaccess.h> > >> +#include <linux/init.h> > >> +#include <linux/ftrace.h> > >> +#include <linux/syscalls.h> > >> + > >> +#include <asm/asm.h> > >> +#include <asm/asm-offsets.h> > >> +#include <asm/cacheflush.h> > >> +#include <asm/inst.h> > >> +#include <asm/loongarch.h> > >> +#include <asm/syscall.h> > >> +#include <asm/unistd.h> > >> + > >> +#include <asm-generic/sections.h> > >> + > >> +#ifdef CONFIG_FUNCTION_GRAPH_TRACER > > This should also be moved to another patch. > > No, CONFIG_FUNCTION_GRAPH_TRACER is the basic feature, as the first > patch for non-dynamic ftrace, unless it is a separate patch, which is > obviously not necessary (Refer to the first submission of riscv and > arm64 here). But FUNCTION_GRAPH_TRACER is added until Patch-4.
Huacai > > Thanks, > - Qing > > > >> + > >> +/* > >> + * 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) > >> +{ > >> + union loongarch_instruction *insn; > >> + int limit = 32; > >> + > >> + 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 000000000000..3de7c2d7fd12 > >> --- /dev/null > >> +++ b/arch/loongarch/kernel/mcount.S > >> @@ -0,0 +1,94 @@ > >> +/* SPDX-License-Identifier: GPL-2.0 */ > >> +/* > >> + * LoongArch specific _mcount support > >> + * > >> + * Copyright (C) 2022 Loongson Technology Corporation Limited > >> + */ > >> + > >> +#include <asm/export.h> > >> +#include <asm/regdef.h> > >> +#include <asm/stackframe.h> > >> +#include <asm/ftrace.h> > >> + > >> + .text > >> + > >> +#define MCOUNT_STACK_SIZE (2 * SZREG) > >> +#define MCOUNT_S0_OFFSET (0) > >> +#define MCOUNT_RA_OFFSET (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 > > The same as above. > > > > Huacai > >> + 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 > >> + > >> + .globl ftrace_stub > >> +ftrace_stub: > >> + jr ra > >> +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 */ > >> -- > >> 2.36.0 > >> > >> >
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