[PATCH 2/4] ARM: kprobes: introduces checker

From: Wang Nan
Date: Sat Oct 25 2014 - 14:53:56 EST

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This patch introdces 'checker' to decoding phase, and calls checkers
when instruction decoding. This allows further analysis for specific
instructions.

Signed-off-by: Wang Nan <wangnan0@xxxxxxxxxx>
---
arch/arm/kernel/kprobes.c | 2 +-
arch/arm/kernel/kprobes.h | 3 ++-
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 +-
9 files changed, 79 insertions(+), 14 deletions(-)

diff --git a/arch/arm/kernel/kprobes.c b/arch/arm/kernel/kprobes.c
index 6d64420..3302983 100644
--- a/arch/arm/kernel/kprobes.c
+++ b/arch/arm/kernel/kprobes.c
@@ -90,7 +90,7 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
p->opcode = insn;
p->ainsn.insn = tmp_insn;

- switch ((*decode_insn)(insn, &p->ainsn, true, actions)) {
+ 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..632fe0b 100644
--- a/arch/arm/kernel/kprobes.h
+++ b/arch/arm/kernel/kprobes.h
@@ -36,7 +36,8 @@ 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

diff --git a/arch/arm/kernel/probes-arm.c b/arch/arm/kernel/probes-arm.c
index a17899f..d280e825 100644
--- a/arch/arm/kernel/probes-arm.c
+++ b/arch/arm/kernel/probes-arm.c
@@ -730,10 +730,11 @@ 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 74c7f97..185adaf 100644
--- a/arch/arm/kernel/probes-arm.h
+++ b/arch/arm/kernel/probes-arm.h
@@ -70,6 +70,7 @@ 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 ac27d63..56925e4 100644
--- a/arch/arm/kernel/probes-thumb.c
+++ b/arch/arm/kernel/probes-thumb.c
@@ -901,20 +901,22 @@ 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 f36aa21..2277744 100644
--- a/arch/arm/kernel/probes-thumb.h
+++ b/arch/arm/kernel/probes-thumb.h
@@ -95,9 +95,11 @@ 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;
--
1.8.4

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Next message: Jiri Kosina: "Linux Kernel live patching mailinglist announcement"
Previous message: Wang Nan: "[PATCH 0/4] ARM: kprobes: introduces instruction checker."
In reply to: Jon Medhurst (Tixy): "Re: [PATCH 4/4] ARM: kprobes: disallow probing stack consuming instructions"
Next in thread: Wang Nan: "[PATCH 1/4] ARM: kprobes: seprates load and store actions"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]