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Date: Thu, 28 Aug 2014 18:51:15 +0900
From: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To: Wang Nan <wangnan0@...wei.com>
Cc: Russell King <linux@....linux.org.uk>,
"David A. Long" <dave.long@...aro.org>,
Jon Medhurst <tixy@...aro.org>,
Taras Kondratiuk <taras.kondratiuk@...aro.org>,
Ben Dooks <ben.dooks@...ethink.co.uk>,
Ananth N Mavinakayanahalli <ananth@...ibm.com>,
Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
"David S. Miller" <davem@...emloft.net>,
Will Deacon <will.deacon@....com>,
Pei Feiyue <peifeiyue@...wei.com>,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 1/3] ARM: probes: check stack operation when decoding
(2014/08/27 22:02), Wang Nan wrote:
> 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.
OK, reviewed. but since I'm not so sure about arm32 ISA,
I need help from ARM32 maintainer to ack this.
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Thank you,
>
> Signed-off-by: Wang Nan <wangnan0@...wei.com>
> Cc: Russell King <linux@....linux.org.uk>
> Cc: "David A. Long" <dave.long@...aro.org>
> Cc: Jon Medhurst <tixy@...aro.org>
> Cc: Taras Kondratiuk <taras.kondratiuk@...aro.org>
> Cc: Ben Dooks <ben.dooks@...ethink.co.uk>
> Cc: Ananth N Mavinakayanahalli <ananth@...ibm.com>
> Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
> Cc: Will Deacon <will.deacon@....com>
>
> ---
> 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. */
>
--
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@...achi.com
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