Re: [PATCH v2 1/3] ARM: kprobes: introduces checker

From: Masami Hiramatsu
Date: Thu Nov 20 2014 - 06:58:11 EST

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(2014/11/18 15:19), Wang Nan wrote:
> This patch introdces 'checker' to decoding phase, and calls checkers
> when instruction decoding. This allows further decoding for specific
> instructions.
>
> v1 -> v2:
> - kprobe checker stubs are introduced in this patch.

Hmm, could you state this patch just introduce a "stub" call of the
checker in the patch description? (not only version comment)

Other parts are OK to me.

Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>

Thank you,

>
> Signed-off-by: Wang Nan <wangnan0@xxxxxxxxxx>
> ---
> arch/arm/kernel/kprobes-arm.c | 2 ++
> arch/arm/kernel/kprobes-thumb.c | 3 +++
> arch/arm/kernel/kprobes.c | 6 ++++-
> arch/arm/kernel/kprobes.h | 7 ++++--
> arch/arm/kernel/probes-arm.c | 5 ++--
> arch/arm/kernel/probes-arm.h | 3 ++-
> arch/arm/kernel/probes-thumb.c | 10 ++++----
> arch/arm/kernel/probes-thumb.h | 6 +++--
> arch/arm/kernel/probes.c | 51 ++++++++++++++++++++++++++++++++++++++++-
> arch/arm/kernel/probes.h | 11 ++++++++-
> arch/arm/kernel/uprobes.c | 2 +-
> 11 files changed, 91 insertions(+), 15 deletions(-)
>
> diff --git a/arch/arm/kernel/kprobes-arm.c b/arch/arm/kernel/kprobes-arm.c
> index ac300c6..5a81275 100644
> --- a/arch/arm/kernel/kprobes-arm.c
> +++ b/arch/arm/kernel/kprobes-arm.c
> @@ -341,3 +341,5 @@ const union decode_action kprobes_arm_actions[NUM_PROBES_ARM_ACTIONS] = {
> [PROBES_BRANCH] = {.handler = simulate_bbl},
> [PROBES_LDMSTM] = {.decoder = kprobe_decode_ldmstm}
> };
> +
> +const struct decode_checker *kprobes_arm_checkers[] = {NULL};
> diff --git a/arch/arm/kernel/kprobes-thumb.c b/arch/arm/kernel/kprobes-thumb.c
> index 9495d7f..b8ba7d2 100644
> --- a/arch/arm/kernel/kprobes-thumb.c
> +++ b/arch/arm/kernel/kprobes-thumb.c
> @@ -664,3 +664,6 @@ const union decode_action kprobes_t32_actions[NUM_PROBES_T32_ACTIONS] = {
> [PROBES_T32_MUL_ADD_LONG] = {
> .handler = t32_emulate_rdlo12rdhi8rn16rm0_noflags},
> };
> +
> +const struct decode_checker *kprobes_t32_checkers[] = {NULL};
> +const struct decode_checker *kprobes_t16_checkers[] = {NULL};
> diff --git a/arch/arm/kernel/kprobes.c b/arch/arm/kernel/kprobes.c
> index 6d64420..f114a3f 100644
> --- a/arch/arm/kernel/kprobes.c
> +++ b/arch/arm/kernel/kprobes.c
> @@ -61,6 +61,7 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
> kprobe_decode_insn_t *decode_insn;
> const union decode_action *actions;
> int is;
> + const struct decode_checker **checkers;
>
> if (in_exception_text(addr))
> return -EINVAL;
> @@ -74,9 +75,11 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
> insn = __opcode_thumb32_compose(insn, inst2);
> decode_insn = thumb32_probes_decode_insn;
> actions = kprobes_t32_actions;
> + checkers = kprobes_t32_checkers;
> } else {
> decode_insn = thumb16_probes_decode_insn;
> actions = kprobes_t16_actions;
> + checkers = kprobes_t16_checkers;
> }
> #else /* !CONFIG_THUMB2_KERNEL */
> thumb = false;
> @@ -85,12 +88,13 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
> insn = __mem_to_opcode_arm(*p->addr);
> decode_insn = arm_probes_decode_insn;
> actions = kprobes_arm_actions;
> + checkers = kprobes_arm_checkers;
> #endif
>
> p->opcode = insn;
> p->ainsn.insn = tmp_insn;
>
> - switch ((*decode_insn)(insn, &p->ainsn, true, actions)) {
> + switch ((*decode_insn)(insn, &p->ainsn, true, actions, NULL)) {
> case INSN_REJECTED: /* not supported */
> return -EINVAL;
>
> diff --git a/arch/arm/kernel/kprobes.h b/arch/arm/kernel/kprobes.h
> index 9a2712e..05f3b40 100644
> --- a/arch/arm/kernel/kprobes.h
> +++ b/arch/arm/kernel/kprobes.h
> @@ -36,16 +36,19 @@ kprobe_decode_ldmstm(kprobe_opcode_t insn, struct arch_probes_insn *asi,
> typedef enum probes_insn (kprobe_decode_insn_t)(probes_opcode_t,
> struct arch_probes_insn *,
> bool,
> - const union decode_action *);
> + const union decode_action *,
> + const struct decode_checker *[*]);
>
> #ifdef CONFIG_THUMB2_KERNEL
>
> extern const union decode_action kprobes_t32_actions[];
> extern const union decode_action kprobes_t16_actions[];
> -
> +extern const struct decode_checker *kprobes_t32_checkers[];
> +extern const struct decode_checker *kprobes_t16_checkers[];
> #else /* !CONFIG_THUMB2_KERNEL */
>
> extern const union decode_action kprobes_arm_actions[];
> +extern const struct decode_checker *kprobes_arm_checkers[];
>
> #endif
>
> diff --git a/arch/arm/kernel/probes-arm.c b/arch/arm/kernel/probes-arm.c
> index 8eaef81..125feda 100644
> --- a/arch/arm/kernel/probes-arm.c
> +++ b/arch/arm/kernel/probes-arm.c
> @@ -725,10 +725,11 @@ static void __kprobes arm_singlestep(probes_opcode_t insn,
> */
> enum probes_insn __kprobes
> arm_probes_decode_insn(probes_opcode_t insn, struct arch_probes_insn *asi,
> - bool emulate, const union decode_action *actions)
> + bool emulate, const union decode_action *actions,
> + const struct decode_checker *checkers[])
> {
> asi->insn_singlestep = arm_singlestep;
> asi->insn_check_cc = probes_condition_checks[insn>>28];
> return probes_decode_insn(insn, asi, probes_decode_arm_table, false,
> - emulate, actions);
> + emulate, actions, checkers);
> }
> diff --git a/arch/arm/kernel/probes-arm.h b/arch/arm/kernel/probes-arm.h
> index ace6572..8b11ec4 100644
> --- a/arch/arm/kernel/probes-arm.h
> +++ b/arch/arm/kernel/probes-arm.h
> @@ -68,6 +68,7 @@ extern const union decode_item probes_decode_arm_table[];
>
> enum probes_insn arm_probes_decode_insn(probes_opcode_t,
> struct arch_probes_insn *, bool emulate,
> - const union decode_action *actions);
> + const union decode_action *actions,
> + const struct decode_checker *checkers[]);
>
> #endif
> diff --git a/arch/arm/kernel/probes-thumb.c b/arch/arm/kernel/probes-thumb.c
> index 4131351..a5022b4 100644
> --- a/arch/arm/kernel/probes-thumb.c
> +++ b/arch/arm/kernel/probes-thumb.c
> @@ -863,20 +863,22 @@ static void __kprobes thumb32_singlestep(probes_opcode_t opcode,
>
> enum probes_insn __kprobes
> thumb16_probes_decode_insn(probes_opcode_t insn, struct arch_probes_insn *asi,
> - bool emulate, const union decode_action *actions)
> + bool emulate, const union decode_action *actions,
> + const struct decode_checker *checkers[])
> {
> asi->insn_singlestep = thumb16_singlestep;
> asi->insn_check_cc = thumb_check_cc;
> return probes_decode_insn(insn, asi, probes_decode_thumb16_table, true,
> - emulate, actions);
> + emulate, actions, checkers);
> }
>
> enum probes_insn __kprobes
> thumb32_probes_decode_insn(probes_opcode_t insn, struct arch_probes_insn *asi,
> - bool emulate, const union decode_action *actions)
> + bool emulate, const union decode_action *actions,
> + const struct decode_checker *checkers[])
> {
> asi->insn_singlestep = thumb32_singlestep;
> asi->insn_check_cc = thumb_check_cc;
> return probes_decode_insn(insn, asi, probes_decode_thumb32_table, true,
> - emulate, actions);
> + emulate, actions, checkers);
> }
> diff --git a/arch/arm/kernel/probes-thumb.h b/arch/arm/kernel/probes-thumb.h
> index 7c6f6eb..ccfe3e4 100644
> --- a/arch/arm/kernel/probes-thumb.h
> +++ b/arch/arm/kernel/probes-thumb.h
> @@ -89,9 +89,11 @@ extern const union decode_item probes_decode_thumb16_table[];
>
> enum probes_insn __kprobes
> thumb16_probes_decode_insn(probes_opcode_t insn, struct arch_probes_insn *asi,
> - bool emulate, const union decode_action *actions);
> + bool emulate, const union decode_action *actions,
> + const struct decode_checker *checkers[]);
> enum probes_insn __kprobes
> thumb32_probes_decode_insn(probes_opcode_t insn, struct arch_probes_insn *asi,
> - bool emulate, const union decode_action *actions);
> + bool emulate, const union decode_action *actions,
> + const struct decode_checker *checkers[]);
>
> #endif
> diff --git a/arch/arm/kernel/probes.c b/arch/arm/kernel/probes.c
> index a8ab540..02598da 100644
> --- a/arch/arm/kernel/probes.c
> +++ b/arch/arm/kernel/probes.c
> @@ -342,6 +342,31 @@ static const int decode_struct_sizes[NUM_DECODE_TYPES] = {
> [DECODE_TYPE_REJECT] = sizeof(struct decode_reject)
> };
>
> +static int run_checkers(const struct decode_checker *checkers[],
> + int action, probes_opcode_t insn,
> + struct arch_probes_insn *asi,
> + const struct decode_header *h)
> +{
> + const struct decode_checker **p;
> +
> + if (!checkers)
> + return INSN_GOOD;
> +
> + p = checkers;
> + while (*p != NULL) {
> + int retval;
> + probes_check_t *checker_func = (*p)[action].checker;
> +
> + retval = INSN_GOOD;
> + if (checker_func)
> + retval = checker_func(insn, asi, h);
> + if (retval == INSN_REJECTED)
> + return retval;
> + p++;
> + }
> + return INSN_GOOD;
> +}
> +
> /*
> * probes_decode_insn operates on data tables in order to decode an ARM
> * architecture instruction onto which a kprobe has been placed.
> @@ -388,11 +413,17 @@ static const int decode_struct_sizes[NUM_DECODE_TYPES] = {
> int __kprobes
> probes_decode_insn(probes_opcode_t insn, struct arch_probes_insn *asi,
> const union decode_item *table, bool thumb,
> - bool emulate, const union decode_action *actions)
> + bool emulate, const union decode_action *actions,
> + const struct decode_checker *checkers[])
> {
> const struct decode_header *h = (struct decode_header *)table;
> const struct decode_header *next;
> bool matched = false;
> + /*
> + * @insn can be modified by decode_regs. Save its original
> + * value for checkers.
> + */
> + probes_opcode_t origin_insn = insn;
>
> if (emulate)
> insn = prepare_emulated_insn(insn, asi, thumb);
> @@ -422,18 +453,36 @@ probes_decode_insn(probes_opcode_t insn, struct arch_probes_insn *asi,
> }
>
> case DECODE_TYPE_CUSTOM: {
> + int err;
> struct decode_custom *d = (struct decode_custom *)h;
> + int action = d->decoder.action;
> +
> + err = run_checkers(checkers, action, origin_insn, asi, h);
> + if (err == INSN_REJECTED)
> + return INSN_REJECTED;
> return actions[d->decoder.action].decoder(insn, asi, h);
> }
>
> case DECODE_TYPE_SIMULATE: {
> + int err;
> struct decode_simulate *d = (struct decode_simulate *)h;
> + int action = d->handler.action;
> +
> + err = run_checkers(checkers, action, origin_insn, asi, h);
> + if (err == INSN_REJECTED)
> + return INSN_REJECTED;
> asi->insn_handler = actions[d->handler.action].handler;
> return INSN_GOOD_NO_SLOT;
> }
>
> case DECODE_TYPE_EMULATE: {
> + int err;
> struct decode_emulate *d = (struct decode_emulate *)h;
> + int action = d->handler.action;
> +
> + err = run_checkers(checkers, action, origin_insn, asi, h);
> + if (err == INSN_REJECTED)
> + return INSN_REJECTED;
>
> if (!emulate)
> return actions[d->handler.action].decoder(insn,
> diff --git a/arch/arm/kernel/probes.h b/arch/arm/kernel/probes.h
> index dba9f24..b4bf1f5 100644
> --- a/arch/arm/kernel/probes.h
> +++ b/arch/arm/kernel/probes.h
> @@ -314,6 +314,14 @@ union decode_action {
> probes_custom_decode_t *decoder;
> };
>
> +typedef enum probes_insn (probes_check_t)(probes_opcode_t,
> + struct arch_probes_insn *,
> + const struct decode_header *);
> +
> +struct decode_checker {
> + probes_check_t *checker;
> +};
> +
> #define DECODE_END \
> {.bits = DECODE_TYPE_END}
>
> @@ -402,6 +410,7 @@ probes_insn_handler_t probes_emulate_none;
> int __kprobes
> probes_decode_insn(probes_opcode_t insn, struct arch_probes_insn *asi,
> const union decode_item *table, bool thumb, bool emulate,
> - const union decode_action *actions);
> + const union decode_action *actions,
> + const struct decode_checker **checkers);
>
> #endif
> diff --git a/arch/arm/kernel/uprobes.c b/arch/arm/kernel/uprobes.c
> index 56adf9c..372585a 100644
> --- a/arch/arm/kernel/uprobes.c
> +++ b/arch/arm/kernel/uprobes.c
> @@ -88,7 +88,7 @@ int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm,
> auprobe->ixol[1] = __opcode_to_mem_arm(UPROBE_SS_ARM_INSN);
>
> ret = arm_probes_decode_insn(insn, &auprobe->asi, false,
> - uprobes_probes_actions);
> + uprobes_probes_actions, NULL);
> switch (ret) {
> case INSN_REJECTED:
> return -EINVAL;
>

--
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@xxxxxxxxxxx

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