[PATCH v13 08/10] arm64: Add trampoline code for kretprobes
Masami Hiramatsu
mhiramat at kernel.org
Tue Jun 7 03:38:12 PDT 2016
On Thu, 2 Jun 2016 23:26:22 -0400
David Long <dave.long at linaro.org> wrote:
> From: William Cohen <wcohen at redhat.com>
>
> The trampoline code is used by kretprobes to capture a return from a probed
> function. This is done by saving the registers, calling the handler, and
> restoring the registers. The code then returns to the original saved caller
> return address. It is necessary to do this directly instead of using a
> software breakpoint because the code used in processing that breakpoint
> could itself be kprobe'd and cause a problematic reentry into the debug
> exception handler.
OK, I think we had discussed why this was not included to the next patch.
(Not like to merge patches from different person?)
Acked-by: Masami Hiramatsu <mhiramat at kernel.org>
Thanks,
> Signed-off-by: William Cohen <wcohen at redhat.com>
> Signed-off-by: David A. Long <dave.long at linaro.org>
> ---
> arch/arm64/include/asm/kprobes.h | 2 +
> arch/arm64/kernel/Makefile | 1 +
> arch/arm64/kernel/asm-offsets.c | 11 +++++
> arch/arm64/kernel/kprobes.c | 5 ++
> arch/arm64/kernel/kprobes_trampoline.S | 85 ++++++++++++++++++++++++++++++++++
> 5 files changed, 104 insertions(+)
> create mode 100644 arch/arm64/kernel/kprobes_trampoline.S
>
> diff --git a/arch/arm64/include/asm/kprobes.h b/arch/arm64/include/asm/kprobes.h
> index 79c9511..61b4915 100644
> --- a/arch/arm64/include/asm/kprobes.h
> +++ b/arch/arm64/include/asm/kprobes.h
> @@ -56,5 +56,7 @@ int kprobe_exceptions_notify(struct notifier_block *self,
> unsigned long val, void *data);
> int kprobe_breakpoint_handler(struct pt_regs *regs, unsigned int esr);
> int kprobe_single_step_handler(struct pt_regs *regs, unsigned int esr);
> +void kretprobe_trampoline(void);
> +void __kprobes *trampoline_probe_handler(struct pt_regs *regs);
>
> #endif /* _ARM_KPROBES_H */
> diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
> index 46724a1..75751b7 100644
> --- a/arch/arm64/kernel/Makefile
> +++ b/arch/arm64/kernel/Makefile
> @@ -38,6 +38,7 @@ arm64-obj-$(CONFIG_CPU_IDLE) += cpuidle.o
> arm64-obj-$(CONFIG_JUMP_LABEL) += jump_label.o
> arm64-obj-$(CONFIG_KGDB) += kgdb.o
> arm64-obj-$(CONFIG_KPROBES) += kprobes.o kprobes-arm64.o \
> + kprobes_trampoline.o \
> probes-simulate-insn.o
> arm64-obj-$(CONFIG_EFI) += efi.o efi-entry.stub.o
> arm64-obj-$(CONFIG_PCI) += pci.o
> diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
> index f8e5d47..03dfa27 100644
> --- a/arch/arm64/kernel/asm-offsets.c
> +++ b/arch/arm64/kernel/asm-offsets.c
> @@ -51,6 +51,17 @@ int main(void)
> DEFINE(S_X5, offsetof(struct pt_regs, regs[5]));
> DEFINE(S_X6, offsetof(struct pt_regs, regs[6]));
> DEFINE(S_X7, offsetof(struct pt_regs, regs[7]));
> + DEFINE(S_X8, offsetof(struct pt_regs, regs[8]));
> + DEFINE(S_X10, offsetof(struct pt_regs, regs[10]));
> + DEFINE(S_X12, offsetof(struct pt_regs, regs[12]));
> + DEFINE(S_X14, offsetof(struct pt_regs, regs[14]));
> + DEFINE(S_X16, offsetof(struct pt_regs, regs[16]));
> + DEFINE(S_X18, offsetof(struct pt_regs, regs[18]));
> + DEFINE(S_X20, offsetof(struct pt_regs, regs[20]));
> + DEFINE(S_X22, offsetof(struct pt_regs, regs[22]));
> + DEFINE(S_X24, offsetof(struct pt_regs, regs[24]));
> + DEFINE(S_X26, offsetof(struct pt_regs, regs[26]));
> + DEFINE(S_X28, offsetof(struct pt_regs, regs[28]));
> DEFINE(S_LR, offsetof(struct pt_regs, regs[30]));
> DEFINE(S_SP, offsetof(struct pt_regs, sp));
> #ifdef CONFIG_COMPAT
> diff --git a/arch/arm64/kernel/kprobes.c b/arch/arm64/kernel/kprobes.c
> index 9d0ad47..b35f76f 100644
> --- a/arch/arm64/kernel/kprobes.c
> +++ b/arch/arm64/kernel/kprobes.c
> @@ -575,6 +575,11 @@ bool arch_within_kprobe_blacklist(unsigned long addr)
> return false;
> }
>
> +void __kprobes __used *trampoline_probe_handler(struct pt_regs *regs)
> +{
> + return NULL;
> +}
> +
> int __init arch_init_kprobes(void)
> {
> return 0;
> diff --git a/arch/arm64/kernel/kprobes_trampoline.S b/arch/arm64/kernel/kprobes_trampoline.S
> new file mode 100644
> index 0000000..ba37d85
> --- /dev/null
> +++ b/arch/arm64/kernel/kprobes_trampoline.S
> @@ -0,0 +1,85 @@
> +/*
> + * trampoline entry and return code for kretprobes.
> + */
> +
> +#include <linux/linkage.h>
> +#include <asm/asm-offsets.h>
> +#include <asm/assembler.h>
> +
> + .text
> +
> +.macro save_all_base_regs
> + stp x0, x1, [sp, #S_X0]
> + stp x2, x3, [sp, #S_X2]
> + stp x4, x5, [sp, #S_X4]
> + stp x6, x7, [sp, #S_X6]
> + stp x8, x9, [sp, #S_X8]
> + stp x10, x11, [sp, #S_X10]
> + stp x12, x13, [sp, #S_X12]
> + stp x14, x15, [sp, #S_X14]
> + stp x16, x17, [sp, #S_X16]
> + stp x18, x19, [sp, #S_X18]
> + stp x20, x21, [sp, #S_X20]
> + stp x22, x23, [sp, #S_X22]
> + stp x24, x25, [sp, #S_X24]
> + stp x26, x27, [sp, #S_X26]
> + stp x28, x29, [sp, #S_X28]
> + add x0, sp, #S_FRAME_SIZE
> + stp lr, x0, [sp, #S_LR]
> +/*
> + * Construct a useful saved PSTATE
> + */
> + mrs x0, nzcv
> + and x0, x0, #(PSR_N_BIT | PSR_Z_BIT | PSR_C_BIT | PSR_V_BIT)
> + mrs x1, daif
> + and x1, x1, #(PSR_D_BIT | PSR_A_BIT | PSR_I_BIT | PSR_F_BIT)
> + orr x0, x0, x1
> + mrs x1, CurrentEL
> + and x1, x1, #(3 << 2)
> + orr x0, x1, x0
> + mrs x1, SPSel
> + and x1, x1, #1
> + orr x0, x1, x0
> + str x0, [sp, #S_PSTATE]
> +.endm
> +
> +.macro restore_all_base_regs
> + ldr x0, [sp, #S_PSTATE]
> + and x0, x0, #(PSR_N_BIT | PSR_Z_BIT | PSR_C_BIT | PSR_V_BIT)
> + msr nzcv, x0
> + ldp x0, x1, [sp, #S_X0]
> + ldp x2, x3, [sp, #S_X2]
> + ldp x4, x5, [sp, #S_X4]
> + ldp x6, x7, [sp, #S_X6]
> + ldp x8, x9, [sp, #S_X8]
> + ldp x10, x11, [sp, #S_X10]
> + ldp x12, x13, [sp, #S_X12]
> + ldp x14, x15, [sp, #S_X14]
> + ldp x16, x17, [sp, #S_X16]
> + ldp x18, x19, [sp, #S_X18]
> + ldp x20, x21, [sp, #S_X20]
> + ldp x22, x23, [sp, #S_X22]
> + ldp x24, x25, [sp, #S_X24]
> + ldp x26, x27, [sp, #S_X26]
> + ldp x28, x29, [sp, #S_X28]
> +.endm
> +
> +ENTRY(kretprobe_trampoline)
> +
> + sub sp, sp, #S_FRAME_SIZE
> +
> + save_all_base_regs
> +
> + mov x0, sp
> + bl trampoline_probe_handler
> + /* Replace trampoline address in lr with actual
> + orig_ret_addr return address. */
> + mov lr, x0
> +
> + restore_all_base_regs
> +
> + add sp, sp, #S_FRAME_SIZE
> +
> + ret
> +
> +ENDPROC(kretprobe_trampoline)
> --
> 2.5.0
>
--
Masami Hiramatsu <mhiramat at kernel.org>
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