[PATCH v13 08/10] arm64: Add trampoline code for kretprobes
David Long
dave.long at linaro.org
Sun Jun 12 21:23:58 PDT 2016
On 06/07/2016 06:38 AM, Masami Hiramatsu wrote:
> 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?)
Yes, and adding the trampoline support before making use of it seemed OK
to me even if it wasn't strictly necessary.
>
> 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
>>
>
>
Thanks,
-dl
More information about the linux-arm-kernel
mailing list