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Date:   Mon, 28 Dec 2020 10:15:10 +0900
From:   Masami Hiramatsu <mhiramat@kernel.org>
To:     Borislav Petkov <bp@alien8.de>
Cc:     Andy Lutomirski <luto@amacapital.net>, X86 ML <x86@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v1 03/19] x86/insn: Add an insn_decode() API
Message-Id: <20201228101510.49082d470ed328d81486ef04@kernel.org>
In-Reply-To: <20201223174233.28638-4-bp@alien8.de>
References: <20201223174233.28638-1-bp@alien8.de>
        <20201223174233.28638-4-bp@alien8.de>
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Hi,

On Wed, 23 Dec 2020 18:42:17 +0100
Borislav Petkov <bp@alien8.de> wrote:

> From: Borislav Petkov <bp@suse.de>
> 
> Users of the instruction decoder should use this to decode instruction
> bytes. For that, have insn*() helpers return an int value to denote
> success/failure. When there's an error fetching the next insn byte and
> the insn falls short, return -ENODATA to denote that.

-ENODATA sounds good to me :)

Acked-by: Masami Hiramatsu <mhiramat@kernel.org>

BTW, insn_decode() can return -EINVAL if !insn_complete(), is that OK?

> 
> While at it, make insn_get_opcode() more stricter as to whether what has
> seen so far is a valid insn and if not.
> 
> Copy linux/kconfig.h for the tools-version of the decoder so that it can
> use IS_ENABLED().

I think tools clone code must not use INSN_MODE_KERN because the tools may
not use kernel Kconfig.

Hmm, this may be better to make a different patch to introduce a NOSYNC tag
for sync checker in the tools. Something like;

> +int insn_decode(struct insn *insn, const void *kaddr, int buf_len, enum insn_mode m)
> +{
> +	int ret;
> +
> +	if (m == INSN_MODE_KERN)
		return -EINVAL;	/* NOSYNC */
> +	else
> +		insn_init(insn, kaddr, buf_len, m == INSN_MODE_64);
> +

Then we can simple file list for sync-check.sh.

Thank you,

> 
> Signed-off-by: Borislav Petkov <bp@suse.de>
> ---
>  arch/x86/include/asm/insn.h       |  24 ++-
>  arch/x86/lib/insn.c               | 239 +++++++++++++++++++++++-------
>  tools/arch/x86/include/asm/insn.h |  24 ++-
>  tools/arch/x86/lib/insn.c         | 239 +++++++++++++++++++++++-------
>  tools/include/linux/kconfig.h     |  73 +++++++++
>  5 files changed, 475 insertions(+), 124 deletions(-)
>  create mode 100644 tools/include/linux/kconfig.h
> 
> diff --git a/arch/x86/include/asm/insn.h b/arch/x86/include/asm/insn.h
> index a8c3d284fa46..088aa90e9158 100644
> --- a/arch/x86/include/asm/insn.h
> +++ b/arch/x86/include/asm/insn.h
> @@ -87,13 +87,23 @@ struct insn {
>  #define X86_VEX_M_MAX	0x1f			/* VEX3.M Maximum value */
>  
>  extern void insn_init(struct insn *insn, const void *kaddr, int buf_len, int x86_64);
> -extern void insn_get_prefixes(struct insn *insn);
> -extern void insn_get_opcode(struct insn *insn);
> -extern void insn_get_modrm(struct insn *insn);
> -extern void insn_get_sib(struct insn *insn);
> -extern void insn_get_displacement(struct insn *insn);
> -extern void insn_get_immediate(struct insn *insn);
> -extern void insn_get_length(struct insn *insn);
> +extern int insn_get_prefixes(struct insn *insn);
> +extern int insn_get_opcode(struct insn *insn);
> +extern int insn_get_modrm(struct insn *insn);
> +extern int insn_get_sib(struct insn *insn);
> +extern int insn_get_displacement(struct insn *insn);
> +extern int insn_get_immediate(struct insn *insn);
> +extern int insn_get_length(struct insn *insn);
> +
> +enum insn_mode {
> +	INSN_MODE_32,
> +	INSN_MODE_64,
> +	/* Mode is determined by the current kernel build. */
> +	INSN_MODE_KERN,
> +	INSN_NUM_MODES,
> +};
> +
> +extern int insn_decode(struct insn *insn, const void *kaddr, int buf_len, enum insn_mode m);
>  
>  /* Attribute will be determined after getting ModRM (for opcode groups) */
>  static inline void insn_get_attribute(struct insn *insn)
> diff --git a/arch/x86/lib/insn.c b/arch/x86/lib/insn.c
> index 1ba994862b56..b373aadcdd02 100644
> --- a/arch/x86/lib/insn.c
> +++ b/arch/x86/lib/insn.c
> @@ -13,6 +13,9 @@
>  #include <asm/inat.h>
>  #include <asm/insn.h>
>  
> +#include <linux/errno.h>
> +#include <linux/kconfig.h>
> +
>  #include <asm/emulate_prefix.h>
>  
>  /* Verify next sizeof(t) bytes can be on the same instruction */
> @@ -80,12 +83,15 @@ static int __insn_get_emulate_prefix(struct insn *insn,
>  	return 1;
>  
>  err_out:
> -	return 0;
> +	return -ENODATA;
>  }
>  
>  static void insn_get_emulate_prefix(struct insn *insn)
>  {
> -	if (__insn_get_emulate_prefix(insn, xen_prefix, sizeof(xen_prefix)))
> +	int ret;
> +
> +	ret = __insn_get_emulate_prefix(insn, xen_prefix, sizeof(xen_prefix));
> +	if (ret > 0)
>  		return;
>  
>  	__insn_get_emulate_prefix(insn, kvm_prefix, sizeof(kvm_prefix));
> @@ -98,8 +104,12 @@ static void insn_get_emulate_prefix(struct insn *insn)
>   * Populates the @insn->prefixes bitmap, and updates @insn->next_byte
>   * to point to the (first) opcode.  No effect if @insn->prefixes.got
>   * is already set.
> + *
> + * * Returns:
> + * 0:  on success
> + * < 0: on error
>   */
> -void insn_get_prefixes(struct insn *insn)
> +int insn_get_prefixes(struct insn *insn)
>  {
>  	struct insn_field *prefixes = &insn->prefixes;
>  	insn_attr_t attr;
> @@ -107,7 +117,7 @@ void insn_get_prefixes(struct insn *insn)
>  	int i, nb;
>  
>  	if (prefixes->got)
> -		return;
> +		return 0;
>  
>  	insn_get_emulate_prefix(insn);
>  
> @@ -218,8 +228,10 @@ void insn_get_prefixes(struct insn *insn)
>  
>  	prefixes->got = 1;
>  
> +	return 0;
> +
>  err_out:
> -	return;
> +	return -ENODATA;
>  }
>  
>  /**
> @@ -231,16 +243,25 @@ void insn_get_prefixes(struct insn *insn)
>   * If necessary, first collects any preceding (prefix) bytes.
>   * Sets @insn->opcode.value = opcode1.  No effect if @insn->opcode.got
>   * is already 1.
> + *
> + * Returns:
> + * 0:  on success
> + * < 0: on error
>   */
> -void insn_get_opcode(struct insn *insn)
> +int insn_get_opcode(struct insn *insn)
>  {
>  	struct insn_field *opcode = &insn->opcode;
> +	int pfx_id, ret;
>  	insn_byte_t op;
> -	int pfx_id;
> +
>  	if (opcode->got)
> -		return;
> -	if (!insn->prefixes.got)
> -		insn_get_prefixes(insn);
> +		return 0;
> +
> +	if (!insn->prefixes.got) {
> +		ret = insn_get_prefixes(insn);
> +		if (ret)
> +			return ret;
> +	}
>  
>  	/* Get first opcode */
>  	op = get_next(insn_byte_t, insn);
> @@ -255,9 +276,13 @@ void insn_get_opcode(struct insn *insn)
>  		insn->attr = inat_get_avx_attribute(op, m, p);
>  		if ((inat_must_evex(insn->attr) && !insn_is_evex(insn)) ||
>  		    (!inat_accept_vex(insn->attr) &&
> -		     !inat_is_group(insn->attr)))
> -			insn->attr = 0;	/* This instruction is bad */
> -		goto end;	/* VEX has only 1 byte for opcode */
> +		     !inat_is_group(insn->attr))) {
> +			/* This instruction is bad */
> +			insn->attr = 0;
> +			return 1;
> +		}
> +		/* VEX has only 1 byte for opcode */
> +		goto end;
>  	}
>  
>  	insn->attr = inat_get_opcode_attribute(op);
> @@ -268,13 +293,18 @@ void insn_get_opcode(struct insn *insn)
>  		pfx_id = insn_last_prefix_id(insn);
>  		insn->attr = inat_get_escape_attribute(op, pfx_id, insn->attr);
>  	}
> -	if (inat_must_vex(insn->attr))
> -		insn->attr = 0;	/* This instruction is bad */
> +
> +	if (inat_must_vex(insn->attr)) {
> +		/* This instruction is bad */
> +		insn->attr = 0;
> +		return 1;
> +	}
>  end:
>  	opcode->got = 1;
> +	return 0;
>  
>  err_out:
> -	return;
> +	return -ENODATA;
>  }
>  
>  /**
> @@ -284,15 +314,25 @@ void insn_get_opcode(struct insn *insn)
>   * Populates @insn->modrm and updates @insn->next_byte to point past the
>   * ModRM byte, if any.  If necessary, first collects the preceding bytes
>   * (prefixes and opcode(s)).  No effect if @insn->modrm.got is already 1.
> + *
> + * Returns:
> + * 0:  on success
> + * < 0: on error
>   */
> -void insn_get_modrm(struct insn *insn)
> +int insn_get_modrm(struct insn *insn)
>  {
>  	struct insn_field *modrm = &insn->modrm;
>  	insn_byte_t pfx_id, mod;
> +	int ret;
> +
>  	if (modrm->got)
> -		return;
> -	if (!insn->opcode.got)
> -		insn_get_opcode(insn);
> +		return 0;
> +
> +	if (!insn->opcode.got) {
> +		ret = insn_get_opcode(insn);
> +		if (ret)
> +			return ret;
> +	}
>  
>  	if (inat_has_modrm(insn->attr)) {
>  		mod = get_next(insn_byte_t, insn);
> @@ -302,17 +342,22 @@ void insn_get_modrm(struct insn *insn)
>  			pfx_id = insn_last_prefix_id(insn);
>  			insn->attr = inat_get_group_attribute(mod, pfx_id,
>  							      insn->attr);
> -			if (insn_is_avx(insn) && !inat_accept_vex(insn->attr))
> -				insn->attr = 0;	/* This is bad */
> +			if (insn_is_avx(insn) && !inat_accept_vex(insn->attr)) {
> +				/* Bad insn */
> +				insn->attr = 0;
> +				return 1;
> +			}
>  		}
>  	}
>  
>  	if (insn->x86_64 && inat_is_force64(insn->attr))
>  		insn->opnd_bytes = 8;
> +
>  	modrm->got = 1;
> +	return 0;
>  
>  err_out:
> -	return;
> +	return -ENODATA;
>  }
>  
>  
> @@ -326,11 +371,16 @@ void insn_get_modrm(struct insn *insn)
>  int insn_rip_relative(struct insn *insn)
>  {
>  	struct insn_field *modrm = &insn->modrm;
> +	int ret;
>  
>  	if (!insn->x86_64)
>  		return 0;
> -	if (!modrm->got)
> -		insn_get_modrm(insn);
> +
> +	if (!modrm->got) {
> +		ret = insn_get_modrm(insn);
> +		if (ret)
> +			return ret;
> +	}
>  	/*
>  	 * For rip-relative instructions, the mod field (top 2 bits)
>  	 * is zero and the r/m field (bottom 3 bits) is 0x5.
> @@ -344,15 +394,25 @@ int insn_rip_relative(struct insn *insn)
>   *
>   * If necessary, first collects the instruction up to and including the
>   * ModRM byte.
> + *
> + * Returns:
> + * 0: if decoding succeeded
> + * < 0: otherwise.
>   */
> -void insn_get_sib(struct insn *insn)
> +int insn_get_sib(struct insn *insn)
>  {
>  	insn_byte_t modrm;
> +	int ret;
>  
>  	if (insn->sib.got)
> -		return;
> -	if (!insn->modrm.got)
> -		insn_get_modrm(insn);
> +		return 0;
> +
> +	if (!insn->modrm.got) {
> +		ret = insn_get_modrm(insn);
> +		if (ret)
> +			return ret;
> +	}
> +
>  	if (insn->modrm.nbytes) {
>  		modrm = (insn_byte_t)insn->modrm.value;
>  		if (insn->addr_bytes != 2 &&
> @@ -363,8 +423,10 @@ void insn_get_sib(struct insn *insn)
>  	}
>  	insn->sib.got = 1;
>  
> +	return 0;
> +
>  err_out:
> -	return;
> +	return -ENODATA;
>  }
>  
>  
> @@ -375,15 +437,25 @@ void insn_get_sib(struct insn *insn)
>   * If necessary, first collects the instruction up to and including the
>   * SIB byte.
>   * Displacement value is sign-expanded.
> + *
> + * * Returns:
> + * 0: if decoding succeeded
> + * < 0: otherwise.
>   */
> -void insn_get_displacement(struct insn *insn)
> +int insn_get_displacement(struct insn *insn)
>  {
>  	insn_byte_t mod, rm, base;
> +	int ret;
>  
>  	if (insn->displacement.got)
> -		return;
> -	if (!insn->sib.got)
> -		insn_get_sib(insn);
> +		return 0;
> +
> +	if (!insn->sib.got) {
> +		ret = insn_get_sib(insn);
> +		if (ret)
> +			return ret;
> +	}
> +
>  	if (insn->modrm.nbytes) {
>  		/*
>  		 * Interpreting the modrm byte:
> @@ -426,12 +498,13 @@ void insn_get_displacement(struct insn *insn)
>  	}
>  out:
>  	insn->displacement.got = 1;
> +	return 0;
>  
>  err_out:
> -	return;
> +	return -ENODATA;
>  }
>  
> -/* Decode moffset16/32/64. Return 0 if failed */
> +/* Decode moffset16/32/64. Return a negative value if failed. */
>  static int __get_moffset(struct insn *insn)
>  {
>  	switch (insn->addr_bytes) {
> @@ -457,10 +530,10 @@ static int __get_moffset(struct insn *insn)
>  	return 1;
>  
>  err_out:
> -	return 0;
> +	return -ENODATA;
>  }
>  
> -/* Decode imm v32(Iz). Return 0 if failed */
> +/* Decode imm v32(Iz). Return a negative value if failed. */
>  static int __get_immv32(struct insn *insn)
>  {
>  	switch (insn->opnd_bytes) {
> @@ -480,10 +553,10 @@ static int __get_immv32(struct insn *insn)
>  	return 1;
>  
>  err_out:
> -	return 0;
> +	return -ENODATA;
>  }
>  
> -/* Decode imm v64(Iv/Ov), Return 0 if failed */
> +/* Decode imm v64(Iv/Ov). Return a negative value if failed. */
>  static int __get_immv(struct insn *insn)
>  {
>  	switch (insn->opnd_bytes) {
> @@ -507,11 +580,12 @@ static int __get_immv(struct insn *insn)
>  	insn->immediate1.got = insn->immediate2.got = 1;
>  
>  	return 1;
> +
>  err_out:
> -	return 0;
> +	return -ENODATA;
>  }
>  
> -/* Decode ptr16:16/32(Ap) */
> +/* Decode ptr16:16/32(Ap). Return a negative value if failed. */
>  static int __get_immptr(struct insn *insn)
>  {
>  	switch (insn->opnd_bytes) {
> @@ -534,25 +608,36 @@ static int __get_immptr(struct insn *insn)
>  	insn->immediate1.got = insn->immediate2.got = 1;
>  
>  	return 1;
> +
>  err_out:
> -	return 0;
> +	return -ENODATA;
>  }
>  
>  /**
> - * insn_get_immediate() - Get the immediates of instruction
> + * insn_get_immediate() - Get the immediate in an instruction
>   * @insn:	&struct insn containing instruction
>   *
>   * If necessary, first collects the instruction up to and including the
>   * displacement bytes.
>   * Basically, most of immediates are sign-expanded. Unsigned-value can be
> - * get by bit masking with ((1 << (nbytes * 8)) - 1)
> + * computed by bit masking with ((1 << (nbytes * 8)) - 1)
> + *
> + * Returns:
> + * 0:  on success
> + * < 0: on error
>   */
> -void insn_get_immediate(struct insn *insn)
> +int insn_get_immediate(struct insn *insn)
>  {
> +	int ret;
> +
>  	if (insn->immediate.got)
> -		return;
> -	if (!insn->displacement.got)
> -		insn_get_displacement(insn);
> +		return 0;
> +
> +	if (!insn->displacement.got) {
> +		ret = insn_get_displacement(insn);
> +		if (ret)
> +			return ret;
> +	}
>  
>  	if (inat_has_moffset(insn->attr)) {
>  		if (!__get_moffset(insn))
> @@ -605,9 +690,10 @@ void insn_get_immediate(struct insn *insn)
>  	}
>  done:
>  	insn->immediate.got = 1;
> +	return 0;
>  
>  err_out:
> -	return;
> +	return -ENODATA;
>  }
>  
>  /**
> @@ -616,13 +702,56 @@ void insn_get_immediate(struct insn *insn)
>   *
>   * If necessary, first collects the instruction up to and including the
>   * immediates bytes.
> - */
> -void insn_get_length(struct insn *insn)
> + *
> + * Returns:
> + *  - 0 on success
> + *  - < 0 on error
> +*/
> +int insn_get_length(struct insn *insn)
>  {
> +	int ret;
> +
>  	if (insn->length)
> -		return;
> -	if (!insn->immediate.got)
> -		insn_get_immediate(insn);
> +		return 0;
> +
> +	if (!insn->immediate.got) {
> +		ret = insn_get_immediate(insn);
> +		if (ret)
> +			return ret;
> +	}
> +
>  	insn->length = (unsigned char)((unsigned long)insn->next_byte
>  				     - (unsigned long)insn->kaddr);
> +
> +	return 0;
> +}
> +
> +/**
> + * insn_decode() - Decode an x86 instruction
> + * @insn:	&struct insn to be initialized
> + * @kaddr:	address (in kernel memory) of instruction (or copy thereof)
> + * @buf_len:	length of the insn buffer at @kaddr
> + * @m:		insn mode, see enum insn_mode
> + *
> + * Returns:
> + * 0: if decoding succeeded
> + * < 0: otherwise.
> + */
> +int insn_decode(struct insn *insn, const void *kaddr, int buf_len, enum insn_mode m)
> +{
> +	int ret;
> +
> +	if (m == INSN_MODE_KERN)
> +		insn_init(insn, kaddr, buf_len, IS_ENABLED(CONFIG_X86_64));
> +	else
> +		insn_init(insn, kaddr, buf_len, m == INSN_MODE_64);
> +
> +	ret = insn_get_length(insn);
> +	if (ret)
> +		return ret;
> +
> +	if (insn_complete(insn))
> +		return 0;
> +
> +	return -EINVAL;
>  }
> diff --git a/tools/arch/x86/include/asm/insn.h b/tools/arch/x86/include/asm/insn.h
> index 52c6262e6bfd..ed43bf01ebcc 100644
> --- a/tools/arch/x86/include/asm/insn.h
> +++ b/tools/arch/x86/include/asm/insn.h
> @@ -87,13 +87,23 @@ struct insn {
>  #define X86_VEX_M_MAX	0x1f			/* VEX3.M Maximum value */
>  
>  extern void insn_init(struct insn *insn, const void *kaddr, int buf_len, int x86_64);
> -extern void insn_get_prefixes(struct insn *insn);
> -extern void insn_get_opcode(struct insn *insn);
> -extern void insn_get_modrm(struct insn *insn);
> -extern void insn_get_sib(struct insn *insn);
> -extern void insn_get_displacement(struct insn *insn);
> -extern void insn_get_immediate(struct insn *insn);
> -extern void insn_get_length(struct insn *insn);
> +extern int insn_get_prefixes(struct insn *insn);
> +extern int insn_get_opcode(struct insn *insn);
> +extern int insn_get_modrm(struct insn *insn);
> +extern int insn_get_sib(struct insn *insn);
> +extern int insn_get_displacement(struct insn *insn);
> +extern int insn_get_immediate(struct insn *insn);
> +extern int insn_get_length(struct insn *insn);
> +
> +enum insn_mode {
> +	INSN_MODE_32,
> +	INSN_MODE_64,
> +	/* Mode is determined by the current kernel build. */
> +	INSN_MODE_KERN,
> +	INSN_NUM_MODES,
> +};
> +
> +extern int insn_decode(struct insn *insn, const void *kaddr, int buf_len, enum insn_mode m);
>  
>  /* Attribute will be determined after getting ModRM (for opcode groups) */
>  static inline void insn_get_attribute(struct insn *insn)
> diff --git a/tools/arch/x86/lib/insn.c b/tools/arch/x86/lib/insn.c
> index f3277d6e4ef2..a2f9d9e177f2 100644
> --- a/tools/arch/x86/lib/insn.c
> +++ b/tools/arch/x86/lib/insn.c
> @@ -13,6 +13,9 @@
>  #include "../include/asm/inat.h"
>  #include "../include/asm/insn.h"
>  
> +#include <linux/errno.h>
> +#include <linux/kconfig.h>
> +
>  #include "../include/asm/emulate_prefix.h"
>  
>  /* Verify next sizeof(t) bytes can be on the same instruction */
> @@ -80,12 +83,15 @@ static int __insn_get_emulate_prefix(struct insn *insn,
>  	return 1;
>  
>  err_out:
> -	return 0;
> +	return -ENODATA;
>  }
>  
>  static void insn_get_emulate_prefix(struct insn *insn)
>  {
> -	if (__insn_get_emulate_prefix(insn, xen_prefix, sizeof(xen_prefix)))
> +	int ret;
> +
> +	ret = __insn_get_emulate_prefix(insn, xen_prefix, sizeof(xen_prefix));
> +	if (ret > 0)
>  		return;
>  
>  	__insn_get_emulate_prefix(insn, kvm_prefix, sizeof(kvm_prefix));
> @@ -98,8 +104,12 @@ static void insn_get_emulate_prefix(struct insn *insn)
>   * Populates the @insn->prefixes bitmap, and updates @insn->next_byte
>   * to point to the (first) opcode.  No effect if @insn->prefixes.got
>   * is already set.
> + *
> + * * Returns:
> + * 0:  on success
> + * < 0: on error
>   */
> -void insn_get_prefixes(struct insn *insn)
> +int insn_get_prefixes(struct insn *insn)
>  {
>  	struct insn_field *prefixes = &insn->prefixes;
>  	insn_attr_t attr;
> @@ -107,7 +117,7 @@ void insn_get_prefixes(struct insn *insn)
>  	int i, nb;
>  
>  	if (prefixes->got)
> -		return;
> +		return 0;
>  
>  	insn_get_emulate_prefix(insn);
>  
> @@ -218,8 +228,10 @@ void insn_get_prefixes(struct insn *insn)
>  
>  	prefixes->got = 1;
>  
> +	return 0;
> +
>  err_out:
> -	return;
> +	return -ENODATA;
>  }
>  
>  /**
> @@ -231,16 +243,25 @@ void insn_get_prefixes(struct insn *insn)
>   * If necessary, first collects any preceding (prefix) bytes.
>   * Sets @insn->opcode.value = opcode1.  No effect if @insn->opcode.got
>   * is already 1.
> + *
> + * Returns:
> + * 0:  on success
> + * < 0: on error
>   */
> -void insn_get_opcode(struct insn *insn)
> +int insn_get_opcode(struct insn *insn)
>  {
>  	struct insn_field *opcode = &insn->opcode;
> +	int pfx_id, ret;
>  	insn_byte_t op;
> -	int pfx_id;
> +
>  	if (opcode->got)
> -		return;
> -	if (!insn->prefixes.got)
> -		insn_get_prefixes(insn);
> +		return 0;
> +
> +	if (!insn->prefixes.got) {
> +		ret = insn_get_prefixes(insn);
> +		if (ret)
> +			return ret;
> +	}
>  
>  	/* Get first opcode */
>  	op = get_next(insn_byte_t, insn);
> @@ -255,9 +276,13 @@ void insn_get_opcode(struct insn *insn)
>  		insn->attr = inat_get_avx_attribute(op, m, p);
>  		if ((inat_must_evex(insn->attr) && !insn_is_evex(insn)) ||
>  		    (!inat_accept_vex(insn->attr) &&
> -		     !inat_is_group(insn->attr)))
> -			insn->attr = 0;	/* This instruction is bad */
> -		goto end;	/* VEX has only 1 byte for opcode */
> +		     !inat_is_group(insn->attr))) {
> +			/* This instruction is bad */
> +			insn->attr = 0;
> +			return 1;
> +		}
> +		/* VEX has only 1 byte for opcode */
> +		goto end;
>  	}
>  
>  	insn->attr = inat_get_opcode_attribute(op);
> @@ -268,13 +293,18 @@ void insn_get_opcode(struct insn *insn)
>  		pfx_id = insn_last_prefix_id(insn);
>  		insn->attr = inat_get_escape_attribute(op, pfx_id, insn->attr);
>  	}
> -	if (inat_must_vex(insn->attr))
> -		insn->attr = 0;	/* This instruction is bad */
> +
> +	if (inat_must_vex(insn->attr)) {
> +		/* This instruction is bad */
> +		insn->attr = 0;
> +		return 1;
> +	}
>  end:
>  	opcode->got = 1;
> +	return 0;
>  
>  err_out:
> -	return;
> +	return -ENODATA;
>  }
>  
>  /**
> @@ -284,15 +314,25 @@ void insn_get_opcode(struct insn *insn)
>   * Populates @insn->modrm and updates @insn->next_byte to point past the
>   * ModRM byte, if any.  If necessary, first collects the preceding bytes
>   * (prefixes and opcode(s)).  No effect if @insn->modrm.got is already 1.
> + *
> + * Returns:
> + * 0:  on success
> + * < 0: on error
>   */
> -void insn_get_modrm(struct insn *insn)
> +int insn_get_modrm(struct insn *insn)
>  {
>  	struct insn_field *modrm = &insn->modrm;
>  	insn_byte_t pfx_id, mod;
> +	int ret;
> +
>  	if (modrm->got)
> -		return;
> -	if (!insn->opcode.got)
> -		insn_get_opcode(insn);
> +		return 0;
> +
> +	if (!insn->opcode.got) {
> +		ret = insn_get_opcode(insn);
> +		if (ret)
> +			return ret;
> +	}
>  
>  	if (inat_has_modrm(insn->attr)) {
>  		mod = get_next(insn_byte_t, insn);
> @@ -302,17 +342,22 @@ void insn_get_modrm(struct insn *insn)
>  			pfx_id = insn_last_prefix_id(insn);
>  			insn->attr = inat_get_group_attribute(mod, pfx_id,
>  							      insn->attr);
> -			if (insn_is_avx(insn) && !inat_accept_vex(insn->attr))
> -				insn->attr = 0;	/* This is bad */
> +			if (insn_is_avx(insn) && !inat_accept_vex(insn->attr)) {
> +				/* Bad insn */
> +				insn->attr = 0;
> +				return 1;
> +			}
>  		}
>  	}
>  
>  	if (insn->x86_64 && inat_is_force64(insn->attr))
>  		insn->opnd_bytes = 8;
> +
>  	modrm->got = 1;
> +	return 0;
>  
>  err_out:
> -	return;
> +	return -ENODATA;
>  }
>  
>  
> @@ -326,11 +371,16 @@ void insn_get_modrm(struct insn *insn)
>  int insn_rip_relative(struct insn *insn)
>  {
>  	struct insn_field *modrm = &insn->modrm;
> +	int ret;
>  
>  	if (!insn->x86_64)
>  		return 0;
> -	if (!modrm->got)
> -		insn_get_modrm(insn);
> +
> +	if (!modrm->got) {
> +		ret = insn_get_modrm(insn);
> +		if (ret)
> +			return ret;
> +	}
>  	/*
>  	 * For rip-relative instructions, the mod field (top 2 bits)
>  	 * is zero and the r/m field (bottom 3 bits) is 0x5.
> @@ -344,15 +394,25 @@ int insn_rip_relative(struct insn *insn)
>   *
>   * If necessary, first collects the instruction up to and including the
>   * ModRM byte.
> + *
> + * Returns:
> + * 0: if decoding succeeded
> + * < 0: otherwise.
>   */
> -void insn_get_sib(struct insn *insn)
> +int insn_get_sib(struct insn *insn)
>  {
>  	insn_byte_t modrm;
> +	int ret;
>  
>  	if (insn->sib.got)
> -		return;
> -	if (!insn->modrm.got)
> -		insn_get_modrm(insn);
> +		return 0;
> +
> +	if (!insn->modrm.got) {
> +		ret = insn_get_modrm(insn);
> +		if (ret)
> +			return ret;
> +	}
> +
>  	if (insn->modrm.nbytes) {
>  		modrm = (insn_byte_t)insn->modrm.value;
>  		if (insn->addr_bytes != 2 &&
> @@ -363,8 +423,10 @@ void insn_get_sib(struct insn *insn)
>  	}
>  	insn->sib.got = 1;
>  
> +	return 0;
> +
>  err_out:
> -	return;
> +	return -ENODATA;
>  }
>  
>  
> @@ -375,15 +437,25 @@ void insn_get_sib(struct insn *insn)
>   * If necessary, first collects the instruction up to and including the
>   * SIB byte.
>   * Displacement value is sign-expanded.
> + *
> + * * Returns:
> + * 0: if decoding succeeded
> + * < 0: otherwise.
>   */
> -void insn_get_displacement(struct insn *insn)
> +int insn_get_displacement(struct insn *insn)
>  {
>  	insn_byte_t mod, rm, base;
> +	int ret;
>  
>  	if (insn->displacement.got)
> -		return;
> -	if (!insn->sib.got)
> -		insn_get_sib(insn);
> +		return 0;
> +
> +	if (!insn->sib.got) {
> +		ret = insn_get_sib(insn);
> +		if (ret)
> +			return ret;
> +	}
> +
>  	if (insn->modrm.nbytes) {
>  		/*
>  		 * Interpreting the modrm byte:
> @@ -426,12 +498,13 @@ void insn_get_displacement(struct insn *insn)
>  	}
>  out:
>  	insn->displacement.got = 1;
> +	return 0;
>  
>  err_out:
> -	return;
> +	return -ENODATA;
>  }
>  
> -/* Decode moffset16/32/64. Return 0 if failed */
> +/* Decode moffset16/32/64. Return a negative value if failed. */
>  static int __get_moffset(struct insn *insn)
>  {
>  	switch (insn->addr_bytes) {
> @@ -457,10 +530,10 @@ static int __get_moffset(struct insn *insn)
>  	return 1;
>  
>  err_out:
> -	return 0;
> +	return -ENODATA;
>  }
>  
> -/* Decode imm v32(Iz). Return 0 if failed */
> +/* Decode imm v32(Iz). Return a negative value if failed. */
>  static int __get_immv32(struct insn *insn)
>  {
>  	switch (insn->opnd_bytes) {
> @@ -480,10 +553,10 @@ static int __get_immv32(struct insn *insn)
>  	return 1;
>  
>  err_out:
> -	return 0;
> +	return -ENODATA;
>  }
>  
> -/* Decode imm v64(Iv/Ov), Return 0 if failed */
> +/* Decode imm v64(Iv/Ov). Return a negative value if failed. */
>  static int __get_immv(struct insn *insn)
>  {
>  	switch (insn->opnd_bytes) {
> @@ -507,11 +580,12 @@ static int __get_immv(struct insn *insn)
>  	insn->immediate1.got = insn->immediate2.got = 1;
>  
>  	return 1;
> +
>  err_out:
> -	return 0;
> +	return -ENODATA;
>  }
>  
> -/* Decode ptr16:16/32(Ap) */
> +/* Decode ptr16:16/32(Ap). Return a negative value if failed. */
>  static int __get_immptr(struct insn *insn)
>  {
>  	switch (insn->opnd_bytes) {
> @@ -534,25 +608,36 @@ static int __get_immptr(struct insn *insn)
>  	insn->immediate1.got = insn->immediate2.got = 1;
>  
>  	return 1;
> +
>  err_out:
> -	return 0;
> +	return -ENODATA;
>  }
>  
>  /**
> - * insn_get_immediate() - Get the immediates of instruction
> + * insn_get_immediate() - Get the immediate in an instruction
>   * @insn:	&struct insn containing instruction
>   *
>   * If necessary, first collects the instruction up to and including the
>   * displacement bytes.
>   * Basically, most of immediates are sign-expanded. Unsigned-value can be
> - * get by bit masking with ((1 << (nbytes * 8)) - 1)
> + * computed by bit masking with ((1 << (nbytes * 8)) - 1)
> + *
> + * Returns:
> + * 0:  on success
> + * < 0: on error
>   */
> -void insn_get_immediate(struct insn *insn)
> +int insn_get_immediate(struct insn *insn)
>  {
> +	int ret;
> +
>  	if (insn->immediate.got)
> -		return;
> -	if (!insn->displacement.got)
> -		insn_get_displacement(insn);
> +		return 0;
> +
> +	if (!insn->displacement.got) {
> +		ret = insn_get_displacement(insn);
> +		if (ret)
> +			return ret;
> +	}
>  
>  	if (inat_has_moffset(insn->attr)) {
>  		if (!__get_moffset(insn))
> @@ -605,9 +690,10 @@ void insn_get_immediate(struct insn *insn)
>  	}
>  done:
>  	insn->immediate.got = 1;
> +	return 0;
>  
>  err_out:
> -	return;
> +	return -ENODATA;
>  }
>  
>  /**
> @@ -616,13 +702,56 @@ void insn_get_immediate(struct insn *insn)
>   *
>   * If necessary, first collects the instruction up to and including the
>   * immediates bytes.
> - */
> -void insn_get_length(struct insn *insn)
> + *
> + * Returns:
> + *  - 0 on success
> + *  - < 0 on error
> +*/
> +int insn_get_length(struct insn *insn)
>  {
> +	int ret;
> +
>  	if (insn->length)
> -		return;
> -	if (!insn->immediate.got)
> -		insn_get_immediate(insn);
> +		return 0;
> +
> +	if (!insn->immediate.got) {
> +		ret = insn_get_immediate(insn);
> +		if (ret)
> +			return ret;
> +	}
> +
>  	insn->length = (unsigned char)((unsigned long)insn->next_byte
>  				     - (unsigned long)insn->kaddr);
> +
> +	return 0;
> +}
> +
> +/**
> + * insn_decode() - Decode an x86 instruction
> + * @insn:	&struct insn to be initialized
> + * @kaddr:	address (in kernel memory) of instruction (or copy thereof)
> + * @buf_len:	length of the insn buffer at @kaddr
> + * @m:		insn mode, see enum insn_mode
> + *
> + * Returns:
> + * 0: if decoding succeeded
> + * < 0: otherwise.
> + */
> +int insn_decode(struct insn *insn, const void *kaddr, int buf_len, enum insn_mode m)
> +{
> +	int ret;
> +
> +	if (m == INSN_MODE_KERN)
> +		insn_init(insn, kaddr, buf_len, IS_ENABLED(CONFIG_X86_64));
> +	else
> +		insn_init(insn, kaddr, buf_len, m == INSN_MODE_64);
> +
> +	ret = insn_get_length(insn);
> +	if (ret)
> +		return ret;
> +
> +	if (insn_complete(insn))
> +		return 0;
> +
> +	return -EINVAL;
>  }
> diff --git a/tools/include/linux/kconfig.h b/tools/include/linux/kconfig.h
> new file mode 100644
> index 000000000000..1555a0c4f345
> --- /dev/null
> +++ b/tools/include/linux/kconfig.h
> @@ -0,0 +1,73 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _TOOLS_LINUX_KCONFIG_H
> +#define _TOOLS_LINUX_KCONFIG_H
> +
> +/* CONFIG_CC_VERSION_TEXT (Do not delete this comment. See help in Kconfig) */
> +
> +#ifdef CONFIG_CPU_BIG_ENDIAN
> +#define __BIG_ENDIAN 4321
> +#else
> +#define __LITTLE_ENDIAN 1234
> +#endif
> +
> +#define __ARG_PLACEHOLDER_1 0,
> +#define __take_second_arg(__ignored, val, ...) val
> +
> +/*
> + * The use of "&&" / "||" is limited in certain expressions.
> + * The following enable to calculate "and" / "or" with macro expansion only.
> + */
> +#define __and(x, y)			___and(x, y)
> +#define ___and(x, y)			____and(__ARG_PLACEHOLDER_##x, y)
> +#define ____and(arg1_or_junk, y)	__take_second_arg(arg1_or_junk y, 0)
> +
> +#define __or(x, y)			___or(x, y)
> +#define ___or(x, y)			____or(__ARG_PLACEHOLDER_##x, y)
> +#define ____or(arg1_or_junk, y)		__take_second_arg(arg1_or_junk 1, y)
> +
> +/*
> + * Helper macros to use CONFIG_ options in C/CPP expressions. Note that
> + * these only work with boolean and tristate options.
> + */
> +
> +/*
> + * Getting something that works in C and CPP for an arg that may or may
> + * not be defined is tricky.  Here, if we have "#define CONFIG_BOOGER 1"
> + * we match on the placeholder define, insert the "0," for arg1 and generate
> + * the triplet (0, 1, 0).  Then the last step cherry picks the 2nd arg (a one).
> + * When CONFIG_BOOGER is not defined, we generate a (... 1, 0) pair, and when
> + * the last step cherry picks the 2nd arg, we get a zero.
> + */
> +#define __is_defined(x)			___is_defined(x)
> +#define ___is_defined(val)		____is_defined(__ARG_PLACEHOLDER_##val)
> +#define ____is_defined(arg1_or_junk)	__take_second_arg(arg1_or_junk 1, 0)
> +
> +/*
> + * IS_BUILTIN(CONFIG_FOO) evaluates to 1 if CONFIG_FOO is set to 'y', 0
> + * otherwise. For boolean options, this is equivalent to
> + * IS_ENABLED(CONFIG_FOO).
> + */
> +#define IS_BUILTIN(option) __is_defined(option)
> +
> +/*
> + * IS_MODULE(CONFIG_FOO) evaluates to 1 if CONFIG_FOO is set to 'm', 0
> + * otherwise.
> + */
> +#define IS_MODULE(option) __is_defined(option##_MODULE)
> +
> +/*
> + * IS_REACHABLE(CONFIG_FOO) evaluates to 1 if the currently compiled
> + * code can call a function defined in code compiled based on CONFIG_FOO.
> + * This is similar to IS_ENABLED(), but returns false when invoked from
> + * built-in code when CONFIG_FOO is set to 'm'.
> + */
> +#define IS_REACHABLE(option) __or(IS_BUILTIN(option), \
> +				__and(IS_MODULE(option), __is_defined(MODULE)))
> +
> +/*
> + * IS_ENABLED(CONFIG_FOO) evaluates to 1 if CONFIG_FOO is set to 'y' or 'm',
> + * 0 otherwise.
> + */
> +#define IS_ENABLED(option) __or(IS_BUILTIN(option), IS_MODULE(option))
> +
> +#endif /* _TOOLS_LINUX_KCONFIG_H */
> -- 
> 2.29.2
> 


-- 
Masami Hiramatsu <mhiramat@kernel.org>