[PATCH v5 1/3] ARM: probes: check stack operation when decoding
From: Wang Nan
Date: Wed Aug 27 2014 - 09:16:12 EST
This patch improves arm instruction decoder, allows it check whether an
instruction is a stack store operation. This information is important
for kprobe optimization.
For normal str instruction, this patch add a series of _SP_STACK
register indicator in the decoder to test the base and offset register
in ldr <Rt>, [<Rn>, <Rm>] against sp.
For stm instruction, it check sp register in instruction specific
decoder.
Signed-off-by: Wang Nan <wangnan0@xxxxxxxxxx>
Cc: Russell King <linux@xxxxxxxxxxxxxxxx>
Cc: "David A. Long" <dave.long@xxxxxxxxxx>
Cc: Jon Medhurst <tixy@xxxxxxxxxx>
Cc: Taras Kondratiuk <taras.kondratiuk@xxxxxxxxxx>
Cc: Ben Dooks <ben.dooks@xxxxxxxxxxxxxxx>
Cc: Ananth N Mavinakayanahalli <ananth@xxxxxxxxxx>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@xxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
---
arch/arm/include/asm/probes.h | 1 +
arch/arm/kernel/kprobes-common.c | 4 ++++
arch/arm/kernel/probes-arm.c | 4 ++--
arch/arm/kernel/probes-thumb.c | 6 +++---
arch/arm/kernel/probes.c | 20 ++++++++++++++++++--
arch/arm/kernel/probes.h | 6 ++++++
6 files changed, 34 insertions(+), 7 deletions(-)
diff --git a/arch/arm/include/asm/probes.h b/arch/arm/include/asm/probes.h
index 806cfe6..3f6912c 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;
+ bool is_stack_operation;
};
#endif
diff --git a/arch/arm/kernel/kprobes-common.c b/arch/arm/kernel/kprobes-common.c
index 0bf5d64..4e8b918 100644
--- a/arch/arm/kernel/kprobes-common.c
+++ b/arch/arm/kernel/kprobes-common.c
@@ -133,6 +133,10 @@ kprobe_decode_ldmstm(probes_opcode_t insn, struct arch_probes_insn *asi,
int is_ldm = insn & 0x100000;
int rn = (insn >> 16) & 0xf;
+ /* whether this is a push instruction? */
+ if ((rn == 0xd) && (!is_ldm))
+ asi->is_stack_operation = true;
+
if (rn <= 12 && (reglist & 0xe000) == 0) {
/* Instruction only uses registers in the range R0..R12 */
handler = emulate_generic_r0_12_noflags;
diff --git a/arch/arm/kernel/probes-arm.c b/arch/arm/kernel/probes-arm.c
index 8eaef81..5c187ba 100644
--- a/arch/arm/kernel/probes-arm.c
+++ b/arch/arm/kernel/probes-arm.c
@@ -577,7 +577,7 @@ static const union decode_item arm_cccc_01xx_table[] = {
/* STR (immediate) cccc 010x x0x0 xxxx xxxx xxxx xxxx xxxx */
/* STRB (immediate) cccc 010x x1x0 xxxx xxxx xxxx xxxx xxxx */
DECODE_EMULATEX (0x0e100000, 0x04000000, PROBES_STORE,
- REGS(NOPCWB, ANY, 0, 0, 0)),
+ REGS(NOPCWB_SP_STACK, ANY, 0, 0, 0)),
/* LDR (immediate) cccc 010x x0x1 xxxx xxxx xxxx xxxx xxxx */
/* LDRB (immediate) cccc 010x x1x1 xxxx xxxx xxxx xxxx xxxx */
@@ -587,7 +587,7 @@ static const union decode_item arm_cccc_01xx_table[] = {
/* STR (register) cccc 011x x0x0 xxxx xxxx xxxx xxxx xxxx */
/* STRB (register) cccc 011x x1x0 xxxx xxxx xxxx xxxx xxxx */
DECODE_EMULATEX (0x0e100000, 0x06000000, PROBES_STORE,
- REGS(NOPCWB, ANY, 0, 0, NOPC)),
+ REGS(NOPCWB_SP_STACK, ANY, 0, 0, NOPC_SP_STACK)),
/* LDR (register) cccc 011x x0x1 xxxx xxxx xxxx xxxx xxxx */
/* LDRB (register) cccc 011x x1x1 xxxx xxxx xxxx xxxx xxxx */
diff --git a/arch/arm/kernel/probes-thumb.c b/arch/arm/kernel/probes-thumb.c
index 4131351..d0d30d8 100644
--- a/arch/arm/kernel/probes-thumb.c
+++ b/arch/arm/kernel/probes-thumb.c
@@ -54,7 +54,7 @@ static const union decode_item t32_table_1110_100x_x1xx[] = {
/* STRD (immediate) 1110 1001 x1x0 xxxx xxxx xxxx xxxx xxxx */
/* LDRD (immediate) 1110 1001 x1x1 xxxx xxxx xxxx xxxx xxxx */
DECODE_EMULATEX (0xff400000, 0xe9400000, PROBES_T32_LDRDSTRD,
- REGS(NOPCWB, NOSPPC, NOSPPC, 0, 0)),
+ REGS(NOPCWB_SP_STACK, NOSPPC, NOSPPC, 0, 0)),
/* TBB 1110 1000 1101 xxxx xxxx xxxx 0000 xxxx */
/* TBH 1110 1000 1101 xxxx xxxx xxxx 0001 xxxx */
@@ -345,12 +345,12 @@ static const union decode_item t32_table_1111_100x[] = {
/* STR (immediate) 1111 1000 1100 xxxx xxxx xxxx xxxx xxxx */
/* LDR (immediate) 1111 1000 1101 xxxx xxxx xxxx xxxx xxxx */
DECODE_EMULATEX (0xffe00000, 0xf8c00000, PROBES_T32_LDRSTR,
- REGS(NOPCX, ANY, 0, 0, 0)),
+ REGS(NOPCX_SP_STACK, ANY, 0, 0, 0)),
/* STR (register) 1111 1000 0100 xxxx xxxx 0000 00xx xxxx */
/* LDR (register) 1111 1000 0101 xxxx xxxx 0000 00xx xxxx */
DECODE_EMULATEX (0xffe00fc0, 0xf8400000, PROBES_T32_LDRSTR,
- REGS(NOPCX, ANY, 0, 0, NOSPPC)),
+ REGS(NOPCX_SP_STACK, ANY, 0, 0, NOSPPC)),
/* LDRB (literal) 1111 1000 x001 1111 xxxx xxxx xxxx xxxx */
/* LDRSB (literal) 1111 1001 x001 1111 xxxx xxxx xxxx xxxx */
diff --git a/arch/arm/kernel/probes.c b/arch/arm/kernel/probes.c
index 1c77b8d..f811cac 100644
--- a/arch/arm/kernel/probes.c
+++ b/arch/arm/kernel/probes.c
@@ -258,7 +258,9 @@ set_emulated_insn(probes_opcode_t insn, struct arch_probes_insn *asi,
* non-zero value, the corresponding nibble in pinsn is validated and modified
* according to the type.
*/
-static bool __kprobes decode_regs(probes_opcode_t *pinsn, u32 regs, bool modify)
+static bool __kprobes decode_regs(probes_opcode_t *pinsn,
+ struct arch_probes_insn *asi,
+ u32 regs, bool modify)
{
probes_opcode_t insn = *pinsn;
probes_opcode_t mask = 0xf; /* Start at least significant nibble */
@@ -307,11 +309,14 @@ static bool __kprobes decode_regs(probes_opcode_t *pinsn, u32 regs, bool modify)
goto reject;
break;
+ case REG_TYPE_NOPCWB_SP_STACK:
case REG_TYPE_NOPCWB:
if (!is_writeback(insn))
break; /* No writeback, so any register is OK */
/* fall through... */
+ case REG_TYPE_NOPC_SP_STACK:
case REG_TYPE_NOPC:
+ case REG_TYPE_NOPCX_SP_STACK:
case REG_TYPE_NOPCX:
/* Reject PC (R15) */
if (((insn ^ 0xffffffff) & mask) == 0)
@@ -319,6 +324,15 @@ static bool __kprobes decode_regs(probes_opcode_t *pinsn, u32 regs, bool modify)
break;
}
+ /* check stack operation */
+ switch (regs & 0xf) {
+ case REG_TYPE_NOPCWB_SP_STACK:
+ case REG_TYPE_NOPC_SP_STACK:
+ case REG_TYPE_NOPCX_SP_STACK:
+ if (((insn ^ 0xdddddddd) & mask) == 0)
+ asi->is_stack_operation = true;
+ }
+
/* Replace value of nibble with new register number... */
insn &= ~mask;
insn |= new_bits & mask;
@@ -394,6 +408,8 @@ probes_decode_insn(probes_opcode_t insn, struct arch_probes_insn *asi,
const struct decode_header *next;
bool matched = false;
+ asi->is_stack_operation = false;
+
if (emulate)
insn = prepare_emulated_insn(insn, asi, thumb);
@@ -410,7 +426,7 @@ probes_decode_insn(probes_opcode_t insn, struct arch_probes_insn *asi,
if (!matched && (insn & h->mask.bits) != h->value.bits)
continue;
- if (!decode_regs(&insn, regs, emulate))
+ if (!decode_regs(&insn, asi, regs, emulate))
return INSN_REJECTED;
switch (type) {
diff --git a/arch/arm/kernel/probes.h b/arch/arm/kernel/probes.h
index dba9f24..568fd01 100644
--- a/arch/arm/kernel/probes.h
+++ b/arch/arm/kernel/probes.h
@@ -278,13 +278,19 @@ enum decode_reg_type {
REG_TYPE_NOSP, /* Register must not be SP */
REG_TYPE_NOSPPC, /* Register must not be SP or PC */
REG_TYPE_NOPC, /* Register must not be PC */
+ REG_TYPE_NOPC_SP_STACK, /* REG_TYPE_NOPC and if this reg is sp
+ then this is a stack operation */
REG_TYPE_NOPCWB, /* No PC if load/store write-back flag also set */
+ REG_TYPE_NOPCWB_SP_STACK, /* REG_TYPE_NOPCWB and, if this reg is sp
+ then this is a stack operation */
/* The following types are used when the encoding for PC indicates
* another instruction form. This distiction only matters for test
* case coverage checks.
*/
REG_TYPE_NOPCX, /* Register must not be PC */
+ REG_TYPE_NOPCX_SP_STACK, /* REG_TYPE_NOPCX and if this reg is sp
+ then this is a stack operation */
REG_TYPE_NOSPPCX, /* Register must not be SP or PC */
/* Alias to allow '0' arg to be used in REGS macro. */
--
1.8.4
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