Messages in this thread | | | From | Huacai Chen <> | Date | Mon, 14 Nov 2022 14:50:28 +0800 | Subject | Re: [PATCH v2 3/5] LoongArch: Add kretprobe support |
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On Mon, Nov 14, 2022 at 2:11 PM Jinyang He <hejinyang@loongson.cn> wrote: > > On 2022/11/14 下午12:43, Huacai Chen wrote: > > > Hi, Tiezhu and Jinyang, > > > > On Wed, Sep 28, 2022 at 8:50 AM Tiezhu Yang <yangtiezhu@loongson.cn> wrote: > >> Use the generic kretprobe trampoline handler to add kretprobe > >> support for LoongArch. > >> > >> Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn> > >> --- > >> arch/loongarch/Kconfig | 1 + > >> arch/loongarch/kernel/Makefile | 2 +- > >> arch/loongarch/kernel/kprobes.c | 24 ++++++++ > >> arch/loongarch/kernel/kprobes_trampoline.S | 97 ++++++++++++++++++++++++++++++ > >> 4 files changed, 123 insertions(+), 1 deletion(-) > >> create mode 100644 arch/loongarch/kernel/kprobes_trampoline.S > >> > >> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig > >> index 8debd70..877be6a 100644 > >> --- a/arch/loongarch/Kconfig > >> +++ b/arch/loongarch/Kconfig > >> @@ -95,6 +95,7 @@ config LOONGARCH > >> select HAVE_IRQ_EXIT_ON_IRQ_STACK > >> select HAVE_IRQ_TIME_ACCOUNTING > >> select HAVE_KPROBES > >> + select HAVE_KRETPROBES > >> select HAVE_MOD_ARCH_SPECIFIC > >> select HAVE_NMI > >> select HAVE_PCI > >> diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile > >> index ff98d8a..48f50607 100644 > >> --- a/arch/loongarch/kernel/Makefile > >> +++ b/arch/loongarch/kernel/Makefile > >> @@ -33,6 +33,6 @@ obj-$(CONFIG_UNWINDER_PROLOGUE) += unwind_prologue.o > >> > >> obj-$(CONFIG_PERF_EVENTS) += perf_event.o perf_regs.o > >> > >> -obj-$(CONFIG_KPROBES) += kprobes.o > >> +obj-$(CONFIG_KPROBES) += kprobes.o kprobes_trampoline.o > >> > >> CPPFLAGS_vmlinux.lds := $(KBUILD_CFLAGS) > >> diff --git a/arch/loongarch/kernel/kprobes.c b/arch/loongarch/kernel/kprobes.c > >> index c11f6e0..ca3f1dc 100644 > >> --- a/arch/loongarch/kernel/kprobes.c > >> +++ b/arch/loongarch/kernel/kprobes.c > >> @@ -306,6 +306,30 @@ int __init arch_populate_kprobe_blacklist(void) > >> (unsigned long)__irqentry_text_end); > >> } > >> > >> +/* Called from __kretprobe_trampoline */ > >> +void __used *trampoline_probe_handler(struct pt_regs *regs) > >> +{ > >> + return (void *)kretprobe_trampoline_handler(regs, NULL); > >> +} > >> +NOKPROBE_SYMBOL(trampoline_probe_handler); > >> + > >> +void arch_prepare_kretprobe(struct kretprobe_instance *ri, > >> + struct pt_regs *regs) > >> +{ > >> + ri->ret_addr = (kprobe_opcode_t *)regs->regs[1]; > >> + ri->fp = NULL; > >> + > >> + /* Replace the return addr with trampoline addr */ > >> + regs->regs[1] = (unsigned long)&__kretprobe_trampoline; > >> +} > >> +NOKPROBE_SYMBOL(arch_prepare_kretprobe); > >> + > >> +int arch_trampoline_kprobe(struct kprobe *p) > >> +{ > >> + return 0; > >> +} > >> +NOKPROBE_SYMBOL(arch_trampoline_kprobe); > >> + > >> int __init arch_init_kprobes(void) > >> { > >> return 0; > >> diff --git a/arch/loongarch/kernel/kprobes_trampoline.S b/arch/loongarch/kernel/kprobes_trampoline.S > >> new file mode 100644 > >> index 0000000..9888ab8 > >> --- /dev/null > >> +++ b/arch/loongarch/kernel/kprobes_trampoline.S > >> @@ -0,0 +1,97 @@ > >> +/* SPDX-License-Identifier: GPL-2.0+ */ > >> +#include <linux/linkage.h> > >> +#include <asm/stackframe.h> > >> + > >> + .text > >> + > >> + .macro save_all_base_regs > >> + cfi_st zero, PT_R0 > >> + cfi_st ra, PT_R1 > >> + cfi_st tp, PT_R2 > >> + cfi_st a0, PT_R4 > >> + cfi_st a1, PT_R5 > >> + cfi_st a2, PT_R6 > >> + cfi_st a3, PT_R7 > >> + cfi_st a4, PT_R8 > >> + cfi_st a5, PT_R9 > >> + cfi_st a6, PT_R10 > >> + cfi_st a7, PT_R11 > >> + cfi_st t0, PT_R12 > >> + cfi_st t1, PT_R13 > >> + cfi_st t2, PT_R14 > >> + cfi_st t3, PT_R15 > >> + cfi_st t4, PT_R16 > >> + cfi_st t5, PT_R17 > >> + cfi_st t6, PT_R18 > >> + cfi_st t7, PT_R19 > >> + cfi_st t8, PT_R20 > >> + cfi_st u0, PT_R21 > >> + cfi_st fp, PT_R22 > >> + cfi_st s0, PT_R23 > >> + cfi_st s1, PT_R24 > >> + cfi_st s2, PT_R25 > >> + cfi_st s3, PT_R26 > >> + cfi_st s4, PT_R27 > >> + cfi_st s5, PT_R28 > >> + cfi_st s6, PT_R29 > >> + cfi_st s7, PT_R30 > >> + cfi_st s8, PT_R31 > >> + addi.d t0, sp, PT_SIZE > >> + LONG_S t0, sp, PT_R3 > >> + csrrd t0, LOONGARCH_CSR_CRMD > >> + andi t0, t0, 0x7 /* extract bit[1:0] PLV, bit[2] IE */ > >> + LONG_S t0, sp, PT_PRMD > >> + .endm > >> + > >> + .macro restore_all_base_regs > >> + cfi_ld zero, PT_R0 > >> + cfi_ld tp, PT_R2 > >> + cfi_ld a0, PT_R4 > >> + cfi_ld a1, PT_R5 > >> + cfi_ld a2, PT_R6 > >> + cfi_ld a3, PT_R7 > >> + cfi_ld a4, PT_R8 > >> + cfi_ld a5, PT_R9 > >> + cfi_ld a6, PT_R10 > >> + cfi_ld a7, PT_R11 > >> + cfi_ld t0, PT_R12 > >> + cfi_ld t1, PT_R13 > >> + cfi_ld t2, PT_R14 > >> + cfi_ld t3, PT_R15 > >> + cfi_ld t4, PT_R16 > >> + cfi_ld t5, PT_R17 > >> + cfi_ld t6, PT_R18 > >> + cfi_ld t7, PT_R19 > >> + cfi_ld t8, PT_R20 > >> + cfi_ld u0, PT_R21 > >> + cfi_ld fp, PT_R22 > >> + cfi_ld s0, PT_R23 > >> + cfi_ld s1, PT_R24 > >> + cfi_ld s2, PT_R25 > >> + cfi_ld s3, PT_R26 > >> + cfi_ld s4, PT_R27 > >> + cfi_ld s5, PT_R28 > >> + cfi_ld s6, PT_R29 > >> + cfi_ld s7, PT_R30 > >> + cfi_ld s8, PT_R31 > >> + LONG_L t0, sp, PT_PRMD > >> + li.d t1, 0x7 /* mask bit[1:0] PLV, bit[2] IE */ > >> + csrxchg t0, t1, LOONGARCH_CSR_CRMD > >> + .endm > > Do you think we need to save and restore all regs here? > > > > Huacai > > Hi, Huacai, > > > Note that it is not function context. In the original kprobe design, it is > triggered by 'break' and then trap into exception with all pt_regs saved. > The all pt_regs will be visible to the user. So I think in this version > we should also support all regs to user. BTW, due to all exceptions is > trapped by 'break' something in pt_regs is not needed, like estat, > badvaddr and so on. OK, but I still have some questions: 1, Why $r0 need save/restore? 2, Why save $r1 but not restore? 3, What is the purpose of CRMD magic?
Huacai > > > Thanks, > > Jinyang > > >> + > >> +SYM_CODE_START(__kretprobe_trampoline) > >> + addi.d sp, sp, -PT_SIZE > >> + save_all_base_regs > >> + > >> + move a0, sp /* pt_regs */ > >> + > >> + bl trampoline_probe_handler > >> + > >> + /* use the result as the return-address */ > >> + move ra, a0 > >> + > >> + restore_all_base_regs > >> + addi.d sp, sp, PT_SIZE > >> + > >> + jr ra > >> +SYM_CODE_END(__kretprobe_trampoline) > >> -- > >> 2.1.0 > >> > >> >
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