[PATCH 3/4] ARM: kprobes: collects stack consumption for store instructions
From: Wang Nan
Date: Sat Oct 25 2014 - 14:56:06 EST
This patch use previous introduced checker on store instructions,
record stack consumption informations to arch_probes_insn. With such
information, kprobe opt can decide how much stack needs to be
protected.
Signed-off-by: Wang Nan <wangnan0@xxxxxxxxxx>
---
arch/arm/include/asm/probes.h | 1 +
arch/arm/kernel/kprobes.c | 15 +++++++-
arch/arm/kernel/probes-arm.c | 25 +++++++++++++
arch/arm/kernel/probes-arm.h | 1 +
arch/arm/kernel/probes-thumb.c | 80 ++++++++++++++++++++++++++++++++++++++++++
arch/arm/kernel/probes-thumb.h | 2 ++
arch/arm/kernel/probes.c | 64 +++++++++++++++++++++++++++++++++
arch/arm/kernel/probes.h | 13 +++++++
8 files changed, 200 insertions(+), 1 deletion(-)
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/kprobes.c b/arch/arm/kernel/kprobes.c
index 3302983..618531d 100644
--- a/arch/arm/kernel/kprobes.c
+++ b/arch/arm/kernel/kprobes.c
@@ -61,6 +61,16 @@ 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;
+#ifdef CONFIG_THUMB2_KERNEL
+ const struct decode_checker *t32_checkers[] =
+ {t32_stack_checker, NULL};
+ const struct decode_checker *t16_checkers[] =
+ {t16_stack_checker, NULL};
+#else
+ const struct decode_checker *arm_checkers[] =
+ {arm_stack_checker, NULL};
+#endif
if (in_exception_text(addr))
return -EINVAL;
@@ -74,9 +84,11 @@ 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 = t32_checkers;
} else {
decode_insn = thumb16_probes_decode_insn;
actions = kprobes_t16_actions;
+ checkers = t16_checkers;
}
#else /* !CONFIG_THUMB2_KERNEL */
thumb = false;
@@ -85,12 +97,13 @@ 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 = arm_checkers;
#endif
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-arm.c b/arch/arm/kernel/probes-arm.c
index d280e825..20e95c0 100644
--- a/arch/arm/kernel/probes-arm.c
+++ b/arch/arm/kernel/probes-arm.c
@@ -109,6 +109,31 @@ void __kprobes simulate_mov_ipsp(probes_opcode_t insn,
regs->uregs[12] = regs->uregs[13];
}
+enum probes_insn __kprobes chk_stack_arm_store(probes_opcode_t insn,
+ struct arch_probes_insn *asi,
+ const struct decode_header *h)
+{
+ int imm = insn & 0xfff;
+ check_insn_stack_regs(insn, asi, h, imm);
+ return INSN_GOOD;
+}
+
+enum probes_insn __kprobes chk_stack_arm_store_extra(probes_opcode_t insn,
+ struct arch_probes_insn *asi,
+ const struct decode_header *h)
+{
+ int imm = ((insn & 0xf00) >> 4) + (insn & 0xf);
+ check_insn_stack_regs(insn, asi, h, imm);
+ return INSN_GOOD;
+}
+
+const struct decode_checker arm_stack_checker[NUM_PROBES_ARM_ACTIONS] = {
+ [PROBES_STRD] = {.checker = chk_stack_arm_store_extra},
+ [PROBES_STORE_EXTRA] = {.checker = chk_stack_arm_store_extra},
+ [PROBES_STRD] = {.checker = chk_stack_arm_store},
+ [PROBES_STM] = {.checker = chk_stack_stm},
+};
+
/*
* For the instruction masking and comparisons in all the "space_*"
* functions below, Do _not_ rearrange the order of tests unless
diff --git a/arch/arm/kernel/probes-arm.h b/arch/arm/kernel/probes-arm.h
index 185adaf..4d63cf8 100644
--- a/arch/arm/kernel/probes-arm.h
+++ b/arch/arm/kernel/probes-arm.h
@@ -73,4 +73,5 @@ enum probes_insn arm_probes_decode_insn(probes_opcode_t,
const union decode_action *actions,
const struct decode_checker *checkers[]);
+extern const struct decode_checker arm_stack_checker[];
#endif
diff --git a/arch/arm/kernel/probes-thumb.c b/arch/arm/kernel/probes-thumb.c
index 56925e4..8e7c5be 100644
--- a/arch/arm/kernel/probes-thumb.c
+++ b/arch/arm/kernel/probes-thumb.c
@@ -15,6 +15,86 @@
#include "probes.h"
#include "probes-thumb.h"
+enum probes_insn __kprobes chk_stack_t32_strd(probes_opcode_t insn,
+ struct arch_probes_insn *asi,
+ const struct decode_header *h)
+{
+ int imm = insn & 0xff;
+ check_insn_stack_regs(insn, asi, h, imm);
+ return INSN_GOOD;
+}
+
+/*
+ * Note: This function doesn't process PROBES_T32_STRD.
+ */
+enum probes_insn __kprobes chk_stack_t32_check_str(probes_opcode_t insn,
+ struct arch_probes_insn *asi,
+ const struct decode_header *h)
+{
+ int rn = -1, rm = -1;
+ u32 regs = h->type_regs.bits >> DECODE_TYPE_BITS;
+ int index, add;
+
+ /* Rn is used in every cases */
+ BUG_ON((regs & 0xf0000) == 0);
+ rn = (insn & 0xf0000) >> 16;
+ if ((regs & 0xf) != 0)
+ rm = insn & 0xf;
+
+ /*
+ * Rn is not SP. Rm can't be sp in any case.
+ * So it is not a stack store.
+ */
+ if (rn != 0xd)
+ return INSN_GOOD;
+
+ /*
+ * For 'str? rx, [sp, ry]', ry can be negative. In addition,
+ * index is true in every cases, so unable to determine stack
+ * consumption.
+ */
+ if (rm != -1) {
+ asi->stack_space = -1;
+ return INSN_GOOD;
+ }
+
+ /*
+ * For 'str? rx, [sp, #+/-<imm>]', if bit 23 is set, index
+ * and add are both set. Else, index and add are determined
+ * by P bit and U bit (bit 10, 9)
+ */
+ if (insn & 0x800000)
+ index = add = 1;
+ else {
+ index = (insn & (1 << 10));
+ add = (insn &(1 << 9));
+ }
+
+ if (!index || add)
+ return INSN_GOOD;
+
+ asi->stack_space = insn & 0xff;
+ return INSN_GOOD;
+}
+
+enum probes_insn __kprobes chk_stack_t16_push(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;
+}
+
+const struct decode_checker t32_stack_checker[NUM_PROBES_T32_ACTIONS] = {
+ [PROBES_T32_STM] = {.checker = chk_stack_stm},
+ [PROBES_T32_STRD] = {.checker = chk_stack_t32_strd},
+ [PROBES_T32_STR] = {.checker = chk_stack_t32_check_str},
+};
+
+const struct decode_checker t16_stack_checker[NUM_PROBES_T16_ACTIONS] = {
+ [PROBES_T16_PUSH] = {.checker = chk_stack_t16_push},
+};
static const union decode_item t32_table_1110_100x_x0xx[] = {
/* Load/store multiple instructions */
diff --git a/arch/arm/kernel/probes-thumb.h b/arch/arm/kernel/probes-thumb.h
index 2277744..a5783d0 100644
--- a/arch/arm/kernel/probes-thumb.h
+++ b/arch/arm/kernel/probes-thumb.h
@@ -102,4 +102,6 @@ thumb32_probes_decode_insn(probes_opcode_t insn, struct arch_probes_insn *asi,
bool emulate, const union decode_action *actions,
const struct decode_checker *checkers[]);
+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..4ef4087 100644
--- a/arch/arm/kernel/probes.c
+++ b/arch/arm/kernel/probes.c
@@ -188,6 +188,25 @@ void __kprobes probes_emulate_none(probes_opcode_t opcode,
asi->insn_fn();
}
+/* ARM and Thumb can share this checker */
+enum probes_insn __kprobes chk_stack_stm(probes_opcode_t insn,
+ struct arch_probes_insn *asi,
+ const struct decode_header *h)
+{
+ unsigned int reglist = insn & 0xffff;
+ int ubit = insn & (1 << 23);
+ int pbit = insn & (1 << 24);
+ int rn = (insn >> 16) & 0xf;
+
+ /* This is stmi?, doesn't require extra stack */
+ if (ubit)
+ return INSN_GOOD;
+ /* If pbit == ubit (== 0), this is stmda, one dword is saved */
+ asi->stack_space = (rn == 0xd) ?
+ (hweight32(reglist) - ((!pbit == !ubit) ? 1 : 0)) * 4 : 0;
+ return INSN_GOOD;
+}
+
/*
* Prepare an instruction slot to receive an instruction for emulating.
* This is done by placing a subroutine return after the location where the
@@ -425,6 +444,8 @@ probes_decode_insn(probes_opcode_t insn, struct arch_probes_insn *asi,
*/
probes_opcode_t origin_insn = insn;
+ asi->stack_space = 0;
+
if (emulate)
insn = prepare_emulated_insn(insn, asi, thumb);
@@ -503,3 +524,46 @@ probes_decode_insn(probes_opcode_t insn, struct arch_probes_insn *asi,
}
}
}
+
+int __kprobes check_insn_stack_regs(probes_opcode_t insn,
+ struct arch_probes_insn *asi,
+ const struct decode_header *h,
+ int imm)
+{
+ u32 regs = h->type_regs.bits >> DECODE_TYPE_BITS;
+ int rn = -1, rm = -1, index, add;
+ asi->stack_space = 0;
+
+ if (((regs >> 16) & 0xf) != REG_TYPE_NONE)
+ rn = (insn >> 16) & 0xf;
+
+ if ((regs & 0xf) != REG_TYPE_NONE)
+ rm = insn & 0xf;
+
+ if ((rn != 13) && (rm != 13))
+ return NOT_STACK_STORE;
+
+ index = insn & (1 << 24);
+ add = insn & (1 << 23);
+
+ if (!index)
+ return NOT_STACK_STORE;
+
+ /*
+ * Even if insn is 'str r0, [sp], +<Rm>', Rm may less than 0.
+ * Therefore if both Rn and Rm are registers and !index,
+ * We are unable to determine whether it is a stack store.
+ */
+ if ((rn != -1) && (rm != -1)) {
+ asi->stack_space = -1;
+ return STACK_REG;
+ }
+
+ /* 'str(d/h) r0, [sp], #+/-<imm>' */
+ /* or 'str(d/h) r0, [sp, #+<imm>'] */
+ if (add)
+ return NOT_STACK_STORE;
+
+ asi->stack_space = imm;
+ return STACK_IMM;
+}
diff --git a/arch/arm/kernel/probes.h b/arch/arm/kernel/probes.h
index b4bf1f5..b52629c 100644
--- a/arch/arm/kernel/probes.h
+++ b/arch/arm/kernel/probes.h
@@ -413,4 +413,17 @@ probes_decode_insn(probes_opcode_t insn, struct arch_probes_insn *asi,
const union decode_action *actions,
const struct decode_checker **checkers);
+enum probes_insn __kprobes chk_stack_stm(probes_opcode_t,
+ struct arch_probes_insn *,
+ const struct decode_header *);
+
+enum {
+ NOT_STACK_STORE,
+ STACK_REG,
+ STACK_IMM,
+};
+int __kprobes check_insn_stack_regs(probes_opcode_t insn,
+ struct arch_probes_insn *asi,
+ const struct decode_header *h,
+ int imm);
#endif
--
1.8.4
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/