Re: [PATCH v12 07/10] arm64: kprobes instruction simulation support

[David Long <dave.long@linaro.org>]

On 05/18/2016 09:52 PM, Huang Shijie wrote:
> On Wed, Apr 27, 2016 at 02:53:02PM -0400, David Long wrote:
>> From: Sandeepa Prabhu <sandeepa.s.prabhu@gmail.com>
>>
>> Kprobes needs simulation of instructions that cannot be stepped
>> from a different memory location, e.g.: those instructions
>> that uses PC-relative addressing. In simulation, the behaviour
>> of the instruction is implemented using a copy of pt_regs.
>>
>> The following instruction categories are simulated:
>>   - All branching instructions(conditional, register, and immediate)
>>   - Literal access instructions(load-literal, adr/adrp)
>>
>> Conditional execution is limited to branching instructions in
>> ARM v8. If conditions at PSTATE do not match the condition fields
>> of opcode, the instruction is effectively NOP.
>>
>> Thanks to Will Cohen for assorted suggested changes.
>>
>> Signed-off-by: Sandeepa Prabhu <sandeepa.s.prabhu@gmail.com>
>> Signed-off-by: William Cohen <wcohen@redhat.com>
>> Signed-off-by: David A. Long <dave.long@linaro.org>
>> ---
>>   arch/arm64/include/asm/insn.h            |   1 +
>>   arch/arm64/include/asm/probes.h          |   5 +-
>>   arch/arm64/kernel/Makefile               |   3 +-
>>   arch/arm64/kernel/insn.c                 |   1 +
>>   arch/arm64/kernel/kprobes-arm64.c        |  29 ++++
>>   arch/arm64/kernel/kprobes.c              |  32 ++++-
>>   arch/arm64/kernel/probes-simulate-insn.c | 218 +++++++++++++++++++++++++++++++
>>   arch/arm64/kernel/probes-simulate-insn.h |  28 ++++
>>   8 files changed, 311 insertions(+), 6 deletions(-)
>>   create mode 100644 arch/arm64/kernel/probes-simulate-insn.c
>>   create mode 100644 arch/arm64/kernel/probes-simulate-insn.h
>>
>> diff --git a/arch/arm64/include/asm/insn.h b/arch/arm64/include/asm/insn.h
>> index b9567a1..26cee10 100644
>> --- a/arch/arm64/include/asm/insn.h
>> +++ b/arch/arm64/include/asm/insn.h
>> @@ -410,6 +410,7 @@ u32 aarch32_insn_mcr_extract_crm(u32 insn);
>>
>>   typedef bool (pstate_check_t)(unsigned long);
>>   extern pstate_check_t * const opcode_condition_checks[16];
>> +
>>   #endif /* __ASSEMBLY__ */
>>
>>   #endif	/* __ASM_INSN_H */
>> diff --git a/arch/arm64/include/asm/probes.h b/arch/arm64/include/asm/probes.h
>> index c5fcbe6..d524f7d 100644
>> --- a/arch/arm64/include/asm/probes.h
>> +++ b/arch/arm64/include/asm/probes.h
>> @@ -15,11 +15,12 @@
>>   #ifndef _ARM_PROBES_H
>>   #define _ARM_PROBES_H
>>
>> +#include <asm/opcodes.h>
>> +
>>   struct kprobe;
>>   struct arch_specific_insn;
>>
>>   typedef u32 kprobe_opcode_t;
>> -typedef unsigned long (kprobes_pstate_check_t)(unsigned long);
>>   typedef void (kprobes_handler_t) (u32 opcode, long addr, struct pt_regs *);
>>
>>   enum pc_restore_type {
>> @@ -35,7 +36,7 @@ struct kprobe_pc_restore {
>>   /* architecture specific copy of original instruction */
>>   struct arch_specific_insn {
>>   	kprobe_opcode_t *insn;
>> -	kprobes_pstate_check_t *pstate_cc;
>> +	pstate_check_t *pstate_cc;
>>   	kprobes_handler_t *handler;
>>   	/* restore address after step xol */
>>   	struct kprobe_pc_restore restore;
>> diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
>> index 8816de2..43bf6cc 100644
>> --- a/arch/arm64/kernel/Makefile
>> +++ b/arch/arm64/kernel/Makefile
>> @@ -37,7 +37,8 @@ arm64-obj-$(CONFIG_CPU_PM)		+= sleep.o suspend.o
>>   arm64-obj-$(CONFIG_CPU_IDLE)		+= cpuidle.o
>>   arm64-obj-$(CONFIG_JUMP_LABEL)		+= jump_label.o
>>   arm64-obj-$(CONFIG_KGDB)		+= kgdb.o
>> -arm64-obj-$(CONFIG_KPROBES)		+= kprobes.o kprobes-arm64.o
>> +arm64-obj-$(CONFIG_KPROBES)		+= kprobes.o kprobes-arm64.o		\
>> +					   probes-simulate-insn.o
>>   arm64-obj-$(CONFIG_EFI)			+= efi.o efi-entry.stub.o
>>   arm64-obj-$(CONFIG_PCI)			+= pci.o
>>   arm64-obj-$(CONFIG_ARMV8_DEPRECATED)	+= armv8_deprecated.o
>> diff --git a/arch/arm64/kernel/insn.c b/arch/arm64/kernel/insn.c
>> index f79e72e..bb2738c 100644
>> --- a/arch/arm64/kernel/insn.c
>> +++ b/arch/arm64/kernel/insn.c
>> @@ -30,6 +30,7 @@
>>   #include <asm/cacheflush.h>
>>   #include <asm/debug-monitors.h>
>>   #include <asm/fixmap.h>
>> +#include <asm/opcodes.h>
>>   #include <asm/insn.h>
>>
>>   #define AARCH64_INSN_SF_BIT	BIT(31)
>> diff --git a/arch/arm64/kernel/kprobes-arm64.c b/arch/arm64/kernel/kprobes-arm64.c
>> index e07727a..487238a 100644
>> --- a/arch/arm64/kernel/kprobes-arm64.c
>> +++ b/arch/arm64/kernel/kprobes-arm64.c
>> @@ -21,6 +21,7 @@
>>   #include <asm/sections.h>
>>
>>   #include "kprobes-arm64.h"
>> +#include "probes-simulate-insn.h"
>>
>>   static bool __kprobes aarch64_insn_is_steppable(u32 insn)
>>   {
>> @@ -62,8 +63,36 @@ arm_probe_decode_insn(kprobe_opcode_t insn, struct arch_specific_insn *asi)
>>   	 */
>>   	if (aarch64_insn_is_steppable(insn))
>>   		return INSN_GOOD;
>> +
>> +	if (aarch64_insn_is_bcond(insn)) {
>> +		asi->handler = simulate_b_cond;
>> +	} else if (aarch64_insn_is_cbz(insn) ||
>> +	    aarch64_insn_is_cbnz(insn)) {
>> +		asi->handler = simulate_cbz_cbnz;
>> +	} else if (aarch64_insn_is_tbz(insn) ||
>> +	    aarch64_insn_is_tbnz(insn)) {
>> +		asi->handler = simulate_tbz_tbnz;
>> +	} else if (aarch64_insn_is_adr_adrp(insn))
>> +		asi->handler = simulate_adr_adrp;
>> +	else if (aarch64_insn_is_b(insn) ||
>> +	    aarch64_insn_is_bl(insn))
>> +		asi->handler = simulate_b_bl;
>
> For the same codingstyle, we'd better add more "{}" here and below.
>
> thanks
> Huang Shijie
>
>> +	else if (aarch64_insn_is_br(insn) ||
>> +	    aarch64_insn_is_blr(insn) ||
>> +	    aarch64_insn_is_ret(insn))
>> +		asi->handler = simulate_br_blr_ret;
>> +	else if (aarch64_insn_is_ldr_lit(insn))
>> +		asi->handler = simulate_ldr_literal;
>> +	else if (aarch64_insn_is_ldrsw_lit(insn))
>> +		asi->handler = simulate_ldrsw_literal;
>>   	else
>> +		/*
>> +		 * Instruction cannot be stepped out-of-line and we don't
>> +		 * (yet) simulate it.
>> +		 */
>>   		return INSN_REJECTED;
>> +
>> +	return INSN_GOOD_NO_SLOT;
>>   }
>

I've made this change for the next version of the patch.

Thanks,
-dl