Re: [PATCH v2 2/3] ARM: kprobes: collects stack consumption for store instructions

Jon Medhurst (Tixy)
2014-11-20T15:22:20Z

On Tue, 2014-11-18 at 14:19 +0800, Wang Nan wrote:
> This patch use previous introduced checker on store instructions,
> record stack consumption informations to arch_probes_insn.

The above sentence has some grammar issues, can I suggest...

"This patch uses the previously introduced checker functionality on
store instructions to record their stack consumption information to
arch_probes_insn."

Hope you don't mind me correcting things like this.

> With such
> information, kprobe opt can decide how much stack needs to be
> protected.
>
> v1 -> v2:
> - Bugfix and code improvements following Tixy's suggestion. See:
> http://www.spinics.net/lists/arm-kernel/msg372912.html
>
> v2 -> v3:
> - Totaly reconstructed following Tixy' instruction. See:
> https://lkml.org/lkml/2014/10/27/662 .
> Add his SOB.

As I mentioned in other patch, the version summary shouldn't go in the
commit message.

> Signed-off-by: Wang Nan <wangnan0@huawei.com>
> Signed-off-by: Jon Medhurst <tixy@linaro.org>
> ---

Apart from one error in the decoding tables, all my comments below are
minor things about comments and formatting. So with those fixed, your
next (perhaps final) version of this patch can add

Reviewed-by: Jon Medhurst <tixy@linaro.org>

Thanks for your work on this. And I'm glad you managed to come up with
fairly straightforward decoding tables, I was a bit worried that my
suggestion to use those might turn out impractical.

> arch/arm/include/asm/probes.h | 1 +
> arch/arm/kernel/Makefile | 6 +-
> arch/arm/kernel/kprobes-arm.c | 3 +-
> arch/arm/kernel/kprobes-thumb.c | 5 +-
> arch/arm/kernel/kprobes.c | 2 +-
> arch/arm/kernel/probes-checkers-arm.c | 99 ++++++++++++++++++++++++++++
> arch/arm/kernel/probes-checkers-common.c | 87 +++++++++++++++++++++++++
> arch/arm/kernel/probes-checkers-thumb.c | 108 +++++++++++++++++++++++++++++++
> arch/arm/kernel/probes-checkers.h | 54 ++++++++++++++++
> arch/arm/kernel/probes.c | 10 +++
> 10 files changed, 368 insertions(+), 7 deletions(-)
> create mode 100644 arch/arm/kernel/probes-checkers-arm.c
> create mode 100644 arch/arm/kernel/probes-checkers-common.c
> create mode 100644 arch/arm/kernel/probes-checkers-thumb.c
> create mode 100644 arch/arm/kernel/probes-checkers.h
>
> diff --git a/arch/arm/include/asm/probes.h b/arch/arm/include/asm/probes.h
> index 806cfe6..ccf9af3 100644
> --- a/arch/arm/include/asm/probes.h
> +++ b/arch/arm/include/asm/probes.h
> @@ -38,6 +38,7 @@ struct arch_probes_insn {
> probes_check_cc *insn_check_cc;
> probes_insn_singlestep_t *insn_singlestep;
> probes_insn_fn_t *insn_fn;
> + int stack_space;
> };
>
> #endif
> diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
> index 38ddd9f..45aed4b 100644
> --- a/arch/arm/kernel/Makefile
> +++ b/arch/arm/kernel/Makefile
> @@ -52,11 +52,11 @@ obj-$(CONFIG_FUNCTION_GRAPH_TRACER) += ftrace.o insn.o
> obj-$(CONFIG_JUMP_LABEL) += jump_label.o insn.o patch.o
> obj-$(CONFIG_KEXEC) += machine_kexec.o relocate_kernel.o
> obj-$(CONFIG_UPROBES) += probes.o probes-arm.o uprobes.o uprobes-arm.o
> -obj-$(CONFIG_KPROBES) += probes.o kprobes.o kprobes-common.o patch.o
> +obj-$(CONFIG_KPROBES) += probes.o kprobes.o kprobes-common.o patch.o probes-checkers-common.o
> ifdef CONFIG_THUMB2_KERNEL
> -obj-$(CONFIG_KPROBES) += kprobes-thumb.o probes-thumb.o
> +obj-$(CONFIG_KPROBES) += kprobes-thumb.o probes-thumb.o probes-checkers-thumb.o
> else
> -obj-$(CONFIG_KPROBES) += kprobes-arm.o probes-arm.o
> +obj-$(CONFIG_KPROBES) += kprobes-arm.o probes-arm.o probes-checkers-arm.o
> endif
> obj-$(CONFIG_ARM_KPROBES_TEST) += test-kprobes.o
> test-kprobes-objs := kprobes-test.o
> diff --git a/arch/arm/kernel/kprobes-arm.c b/arch/arm/kernel/kprobes-arm.c
> index 5a81275..56f78ce 100644
> --- a/arch/arm/kernel/kprobes-arm.c
> +++ b/arch/arm/kernel/kprobes-arm.c
> @@ -64,6 +64,7 @@
>
> #include "kprobes.h"
> #include "probes-arm.h"
> +#include "probes-checkers.h"
>
> #if __LINUX_ARM_ARCH__ >= 6
> #define BLX(reg) "blx "reg" \n\t"
> @@ -342,4 +343,4 @@ const union decode_action kprobes_arm_actions[NUM_PROBES_ARM_ACTIONS] = {
> [PROBES_LDMSTM] = {.decoder = kprobe_decode_ldmstm}
> };
>
> -const struct decode_checker *kprobes_arm_checkers[] = {NULL};
> +const struct decode_checker *kprobes_arm_checkers[] = {arm_stack_checker, NULL};
> diff --git a/arch/arm/kernel/kprobes-thumb.c b/arch/arm/kernel/kprobes-thumb.c
> index b8ba7d2..dbfd3ca 100644
> --- a/arch/arm/kernel/kprobes-thumb.c
> +++ b/arch/arm/kernel/kprobes-thumb.c
> @@ -15,6 +15,7 @@
>
> #include "kprobes.h"
> #include "probes-thumb.h"
> +#include "probes-checkers.h"
>
> /* These emulation encodings are functionally equivalent... */
> #define t32_emulate_rd8rn16rm0ra12_noflags \
> @@ -665,5 +666,5 @@ const union decode_action kprobes_t32_actions[NUM_PROBES_T32_ACTIONS] = {
> .handler = t32_emulate_rdlo12rdhi8rn16rm0_noflags},
> };
>
> -const struct decode_checker *kprobes_t32_checkers[] = {NULL};
> -const struct decode_checker *kprobes_t16_checkers[] = {NULL};
> +const struct decode_checker *kprobes_t32_checkers[] = {t32_stack_checker, NULL};
> +const struct decode_checker *kprobes_t16_checkers[] = {t16_stack_checker, NULL};
> diff --git a/arch/arm/kernel/kprobes.c b/arch/arm/kernel/kprobes.c
> index f114a3f..d7bee4b 100644
> --- a/arch/arm/kernel/kprobes.c
> +++ b/arch/arm/kernel/kprobes.c
> @@ -94,7 +94,7 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
> p->opcode = insn;
> p->ainsn.insn = tmp_insn;
>
> - switch ((*decode_insn)(insn, &p->ainsn, true, actions, NULL)) {
> + switch ((*decode_insn)(insn, &p->ainsn, true, actions, checkers)) {
> case INSN_REJECTED: /* not supported */
> return -EINVAL;
>
> diff --git a/arch/arm/kernel/probes-checkers-arm.c b/arch/arm/kernel/probes-checkers-arm.c
> new file mode 100644
> index 0000000..b6e0bdf
> --- /dev/null
> +++ b/arch/arm/kernel/probes-checkers-arm.c
> @@ -0,0 +1,99 @@
> +/*
> + * arch/arm/kernel/probes-checkers-arm.c
> + *
> + * Copyright (C) 2014 Huawei Inc.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + * General Public License for more details.
> + */
> +
> +#include <linux/kernel.h>
> +#include "probes.h"
> +#include "probes-arm.h"
> +#include "probes-checkers.h"
> +
> +static enum probes_insn __kprobes arm_check_stack(probes_opcode_t insn,
> + struct arch_probes_insn *asi,
> + const struct decode_header *h)
> +{
> + /*
> + * PROBES_LDRSTRD, PROBES_LDMSTM, PROBES_STORE,
> + * PROBES_STORE_EXTRA may get here. Simply mark all normal
> + * insns as STACK_USE_NONE.
> + */
> + static const union decode_item table[] = {
> + /*
> + * 'str{,d,b,h}, rx, [sp, ry]' should be marked as UNKNOWN

We are also checking for when ry==sp so the above comment should be
replaced with something like...

* 'str{,d,b,h}, rx, [ry, rz]' should be marked as UNKNOWN
* if ry or rz is sp

Or probably best to use the naming convention for registers that is
closer to what ARM documentation uses...

* 'STR{,D,B,H}, Rt, [Rn, Rm]' should be marked as UNKNOWN
* if Rn or Rm is SP

> + *
> + * x
> + * STR (register) cccc 011x x0x0 xxxx xxxx xxxx xxxx xxxx
> + * STRB (register) cccc 011x x1x0 xxxx xxxx xxxx xxxx xxxx
> + */
> + DECODE_OR (0x0e10000f, 0x0600000d),
> + DECODE_OR (0x0e1f0000, 0x060d0000),
> +
> + /*
> + * x
> + * STRD (register) cccc 000x x0x0 xxxx xxxx xxxx 1111 xxxx
> + * STRH (register) cccc 000x x0x0 xxxx xxxx xxxx 1011 xxxx
> + */
> + DECODE_OR (0x0e5000bf, 0x000000bd),
> + DECODE_CUSTOM (0x0e5f00b0, 0x000d00b0, STACK_USE_UNKNOWN),
> +
> + /*
> + * For PROBES_LDMSTMDX, only stmdx sp, [...] need to examine

Think PROBES_LDMSTMDX should be PROBES_LDMSTM as that is what the enum
is called.

> + *
> + * Bit B/A (bit 24) encodes arithmetic operation order. 1 means
> + * before, 0 means after.
> + * Bit I/D (bit 23) encodes arithmetic operation. 1 means
> + * increment, 0 means decrement.
> + *
> + * So:
> + * B I
> + * / /
> + * A D | Rn |
> + * stmdx sp, [...] cccc 100x 00x0 xxxx xxxx xxxx xxxx xxxx
> + */
> + DECODE_CUSTOM (0x0edf0000, 0x080d0000, STACK_USE_STMDX),
> +
> + /* P U W | Rn | Rt | imm12 |*/
> + /* STR (immediate) cccc 010x x0x0 1101 xxxx xxxx xxxx xxxx */
> + /* STRB (immediate) cccc 010x x1x0 1101 xxxx xxxx xxxx xxxx */
> + /* P U W | Rn | Rt |imm4| |imm4|*/
> + /* STRD (immediate) cccc 000x x1x0 1101 xxxx xxxx 1111 xxxx */
> + /* STRH (immediate) cccc 000x x1x0 1101 xxxx xxxx 1011 xxxx */
> + /*
> + * index = (P == '1'); add = (U == '1').
> + * Above insns with:
> + * index == 0 (str{,d,h} rx, [sp], #+/-imm) or
> + * add == 1 (str{,d,h} rx, [sp, #+<imm>])
> + * should be STACK_USE_NONE.
> + * Only str{,b,d,h} rx,[sp,#-n] (P == 1 and U == 0) are
> + * required to be examined.
> + */
> + /* str{,b} rx,[sp,#-n] cccc 0101 0xx0 1101 xxxx xxxx xxxx xxxx */
> + DECODE_CUSTOM (0x0f9f0000, 0x050d0000, STACK_USE_FIXED_XXX),
> +
> + /* str{d,h}rx,[sp,#-n] cccc 0001 01x0 1101 xxxx xxxx 1x11 xxxx */
> + DECODE_CUSTOM (0x0fdf0000, 0x014d0000, STACK_USE_FIXED_X0X),

The above should also be checking the value of bits 4,5 and 7, i.e. be

DECODE_CUSTOM (0x0fdf00b0, 0x014d00b0, STACK_USE_FIXED_X0X),

> +
> + /* fall through */
> + DECODE_CUSTOM (0, 0, STACK_USE_NONE),
> + DECODE_END
> + };
> +
> + return probes_decode_insn(insn, asi, table, false, false, stack_check_actions, NULL);
> +}
> +
> +const struct decode_checker arm_stack_checker[NUM_PROBES_ARM_ACTIONS] = {
> + [PROBES_LDRSTRD] = {.checker = arm_check_stack},
> + [PROBES_STORE_EXTRA] = {.checker = arm_check_stack},
> + [PROBES_STORE] = {.checker = arm_check_stack},
> + [PROBES_LDMSTM] = {.checker = arm_check_stack},
> +};
> diff --git a/arch/arm/kernel/probes-checkers-common.c b/arch/arm/kernel/probes-checkers-common.c
> new file mode 100644
> index 0000000..e46f844
> --- /dev/null
> +++ b/arch/arm/kernel/probes-checkers-common.c
> @@ -0,0 +1,87 @@
> +/*
> + * arch/arm/kernel/probes-checkers-common.c
> + *
> + * Copyright (C) 2014 Huawei Inc.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + * General Public License for more details.
> + */
> +
> +#include <linux/kernel.h>
> +#include "probes.h"
> +#include "probes-arm.h"
> +#include "probes-checkers.h"
> +
> +enum probes_insn checker_stack_use_none(probes_opcode_t insn,
> + struct arch_probes_insn *asi,
> + const struct decode_header *h)
> +{
> + asi->stack_space = 0;
> + return INSN_GOOD_NO_SLOT;
> +}
> +
> +enum probes_insn checker_stack_use_unknown(probes_opcode_t insn,
> + struct arch_probes_insn *asi,
> + const struct decode_header *h)
> +{
> + asi->stack_space = -1;
> + return INSN_GOOD_NO_SLOT;
> +}
> +
> +#ifdef CONFIG_THUMB2_KERNEL
> +enum probes_insn checker_stack_use_imm_0xx(probes_opcode_t insn,
> + struct arch_probes_insn *asi,
> + const struct decode_header *h)
> +{
> + int imm = insn & 0xff;
> + asi->stack_space = imm;
> + return INSN_GOOD_NO_SLOT;
> +}
> +#else
> +enum probes_insn checker_stack_use_imm_x0x(probes_opcode_t insn,
> + struct arch_probes_insn *asi,
> + const struct decode_header *h)
> +{
> + int imm = ((insn & 0xf00) >> 4) + (insn & 0xf);
> + asi->stack_space = imm;
> + return INSN_GOOD_NO_SLOT;
> +}
> +#endif
> +
> +enum probes_insn checker_stack_use_imm_xxx(probes_opcode_t insn,
> + struct arch_probes_insn *asi,
> + const struct decode_header *h)
> +{
> + int imm = insn & 0xfff;
> + asi->stack_space = imm;
> + return INSN_GOOD_NO_SLOT;
> +}
> +
> +enum probes_insn checker_stack_use_stmdx(probes_opcode_t insn,
> + struct arch_probes_insn *asi,
> + const struct decode_header *h)
> +{
> + unsigned int reglist = insn & 0xffff;
> + int pbit = insn & (1 << 24);
> + asi->stack_space = (hweight32(reglist) - (!pbit ? 1 : 0)) * 4;
> +
> + return INSN_GOOD_NO_SLOT;
> +}
> +
> +const union decode_action stack_check_actions[] = {
> + [STACK_USE_NONE] = {.decoder = checker_stack_use_none},
> + [STACK_USE_UNKNOWN] = {.decoder = checker_stack_use_unknown},
> +#ifdef CONFIG_THUMB2_KERNEL
> + [STACK_USE_FIXED_0XX] = {.decoder = checker_stack_use_imm_0xx},
> +#else
> + [STACK_USE_FIXED_X0X] = {.decoder = checker_stack_use_imm_x0x},
> +#endif
> + [STACK_USE_FIXED_XXX] = {.decoder = checker_stack_use_imm_xxx},
> + [STACK_USE_STMDX] = {.decoder = checker_stack_use_stmdx},
> +};
> diff --git a/arch/arm/kernel/probes-checkers-thumb.c b/arch/arm/kernel/probes-checkers-thumb.c
> new file mode 100644
> index 0000000..f5732c0
> --- /dev/null
> +++ b/arch/arm/kernel/probes-checkers-thumb.c
> @@ -0,0 +1,108 @@
> +/*
> + * arch/arm/kernel/probes-checkers-arm.c
> + *
> + * Copyright (C) 2014 Huawei Inc.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + * General Public License for more details.
> + */
> +
> +#include <linux/kernel.h>
> +#include "probes.h"
> +#include "probes-thumb.h"
> +#include "probes-checkers.h"
> +
> +static enum probes_insn __kprobes t32_check_stack(probes_opcode_t insn,
> + struct arch_probes_insn *asi,
> + const struct decode_header *h)
> +{
> + /*
> + * PROBES_T32_LDMSTM, PROBES_T32_LDRDSTRD and PROBES_T32_LDRSTR
> + * may get here. Simply mark all normal insns as STACK_USE_NONE.
> + */
> + static const union decode_item table[] = {
> +
> + /*
> + * First, filter out all ldr insns to make our life easier.
> + * Following load insns may come here:
> + * LDM, LDRD, LDR.
> + * In T32 encoding, bit 20 is enough for distinguishing
> + * load and store. All load insns have this bit set, when
> + * all store insns have this bit clear.
> + */
> + DECODE_CUSTOM (0x00100000, 0x00100000, STACK_USE_NONE),
> +
> + /*
> + * Mark all 'str{,b,h}, rx, [ra, ab]' as STACK_USE_UNKNOWN

There's a typo above, s/ab/rb/ ^^

> + * if ra or rb is sp. T32 doesn't encode STRD.
> + */
> + /* | Rn | Rt | | Rm |*/
> + /* STR (register) 1111 1000 0100 xxxx xxxx 0000 00xx xxxx */
> + /* STRB (register) 1111 1000 0000 xxxx xxxx 0000 00xx xxxx */
> + /* STRH (register) 1111 1000 0010 xxxx xxxx 0000 00xx xxxx */
> + /* INVALID INSN 1111 1000 0110 xxxx xxxx 0000 00xx xxxx */
> + /* By Introducing INVALID INSN, bit 21 and 22 can be ignore. */

Another typo, s/ignore/ignored/ ^^^^^^

> + DECODE_OR (0xff9f0fc0, 0xf80d0000),
> + DECODE_CUSTOM (0xff900fcf, 0xf800000d, STACK_USE_UNKNOWN),
> +
> +
> + /* | Rn | Rt | PUW| imm8 |*/
> + /* STR (imm 8) 1111 1000 0100 xxxx xxxx 110x xxxx xxxx */
> + /* STRB (imm 8) 1111 1000 0000 xxxx xxxx 110x xxxx xxxx */
> + /* STRH (imm 8) 1111 1000 0010 xxxx xxxx 110x xxxx xxxx */
> + /* INVALID INSN 1111 1000 0110 xxxx xxxx 110x xxxx xxxx */
> + /* Only consider U == 0 and P == 1: strx rx, [sp, #-<imm>] */
> + DECODE_CUSTOM (0xff9f0e00, 0xf80d0c00, STACK_USE_FIXED_0XX),
> +
> + /* For str{,b,h} (imm 12), offset is always positive, so ignore them. */
> +
> + /* P U W | Rn | Rt | Rt2| imm8 |*/
> + /* STRD (immediate) 1110 1001 01x0 1101 xxxx xxxx xxxx xxxx */
> + /* Only consider U == 0 and P == 1 */
> + DECODE_CUSTOM (0xffdf0000, 0xe94d0000, STACK_USE_FIXED_0XX),
> +
> + /* | Rn | */
> + /* STMDB 1110 1001 00x0 1101 xxxx xxxx xxxx xxxx */
> + DECODE_CUSTOM (0xffdf0000, 0xe94d0000, STACK_USE_STMDX),
> +
> + /* fall through */
> + DECODE_CUSTOM (0, 0, STACK_USE_NONE),
> + DECODE_END
> + };
> +
> + return probes_decode_insn(insn, asi, table, false, false, stack_check_actions, NULL);
> +}
> +
> +const struct decode_checker t32_stack_checker[NUM_PROBES_T32_ACTIONS] = {
> + [PROBES_T32_LDMSTM] = {.checker = t32_check_stack},
> + [PROBES_T32_LDRDSTRD] = {.checker = t32_check_stack},
> + [PROBES_T32_LDRSTR] = {.checker = t32_check_stack},
> +};
> +
> +/*
> + * See following comments. This insn must be 'push'.
> + */
> +static enum probes_insn __kprobes t16_check_stack(probes_opcode_t insn,
> + struct arch_probes_insn *asi,
> + const struct decode_header *h)
> +{
> + unsigned int reglist = insn & 0x1ff;
> + asi->stack_space = hweight32(reglist) * 4;
> + return INSN_GOOD;
> +}
> +
> +/*
> + * T16 encoding is simple: only push insn is possible to use extra

Above comment doesn't quite make sense to me, how about something
like...

* T16 encoding is simple: only the push insn can need extra stack space

> + * Other insns, like str, can only use r0-r7 as Rn.
> + */
> +const struct decode_checker t16_stack_checker[NUM_PROBES_T16_ACTIONS] = {
> + [PROBES_T16_PUSH] = {.checker = t16_check_stack},
> +};
> +
> +

Those blank lines at end of the file aren't needed. (I only noticed that
because "git am" warned about them as whitespace errors.)

> diff --git a/arch/arm/kernel/probes-checkers.h b/arch/arm/kernel/probes-checkers.h
> new file mode 100644
> index 0000000..69e8171
> --- /dev/null
> +++ b/arch/arm/kernel/probes-checkers.h
> @@ -0,0 +1,54 @@
> +/*
> + * arch/arm/kernel/probes-checkers-common.c
> + *
> + * Copyright (C) 2014 Huawei Inc.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + * General Public License for more details.
> + */
> +#ifndef _ARM_KERNEL_PROBES_CHECKERS_H
> +#define _ARM_KERNEL_PROBES_CHECKERS_H
> +
> +#include <linux/kernel.h>
> +#include <linux/types.h>
> +#include "probes.h"
> +
> +extern probes_check_t checker_stack_use_none;
> +extern probes_check_t checker_stack_use_unknown;
> +#ifdef CONFIG_THUMB2_KERNEL
> +extern probes_check_t checker_stack_use_imm_0xx;
> +#else
> +extern probes_check_t checker_stack_use_imm_x0x;
> +#endif
> +extern probes_check_t checker_stack_use_imm_xxx;
> +extern probes_check_t checker_stack_use_stmdx;
> +
> +enum {
> + STACK_USE_NONE,
> + STACK_USE_UNKNOWN,
> +#ifdef CONFIG_THUMB2_KERNEL
> + STACK_USE_FIXED_0XX,
> +#else
> + STACK_USE_FIXED_X0X,
> +#endif
> + STACK_USE_FIXED_XXX,
> + STACK_USE_STMDX,
> + NUM_STACK_USE_TYPES
> +};
> +
> +extern const union decode_action stack_check_actions[];
> +
> +#ifndef CONFIG_THUMB2_KERNEL
> +extern const struct decode_checker arm_stack_checker[];
> +#else
> +#endif
> +extern const struct decode_checker t32_stack_checker[];
> +extern const struct decode_checker t16_stack_checker[];
> +#endif
> +
> diff --git a/arch/arm/kernel/probes.c b/arch/arm/kernel/probes.c
> index 02598da..9cd42c9 100644
> --- a/arch/arm/kernel/probes.c
> +++ b/arch/arm/kernel/probes.c
> @@ -425,6 +425,16 @@ probes_decode_insn(probes_opcode_t insn, struct arch_probes_insn *asi,
> */
> probes_opcode_t origin_insn = insn;
>
> + /*
> + * stack_space is initialized to 0 here. Checker functions
> + * should update is value if they find this is a stack store
> + * instruction: positive value means bytes of stack usage,
> + * negitive value means unable to determine stack usage
> + * statically. For instruction doesn't store to stack, checker
> + * do nothing with it.
> + */
> + asi->stack_space = 0;
> +
> if (emulate)
> insn = prepare_emulated_insn(insn, asi, thumb);
>

Thanks

--
Tixy