Messages in this thread | | | Subject | Re: [PATCH v2 3/5] LoongArch: Add kretprobe support | From | Jinyang He <> | Date | Mon, 14 Nov 2022 14:11:13 +0800 |
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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.
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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