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Date: Mon, 14 Nov 2022 12:43:02 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: Tiezhu Yang <yangtiezhu@...ngson.cn>
Cc: Masami Hiramatsu <mhiramat@...nel.org>, loongarch@...ts.linux.dev,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/5] LoongArch: Add kretprobe support
Hi, Tiezhu and Jinyang,
On Wed, Sep 28, 2022 at 8:50 AM Tiezhu Yang <yangtiezhu@...ngson.cn> wrote:
>
> Use the generic kretprobe trampoline handler to add kretprobe
> support for LoongArch.
>
> Signed-off-by: Tiezhu Yang <yangtiezhu@...ngson.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
> +
> +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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