Messages in this thread | | | From | Huacai Chen <> | Date | Tue, 15 Nov 2022 16:25:15 +0800 | Subject | Re: [PATCH v6 1/9] LoongArch/ftrace: Add basic support |
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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.
> + > +/* > + * 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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