On Thu, Mar 4, 2021 at 9:56 AM Borislav Petkov wrote:
>
> From: Borislav Petkov
>
> 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.
>
> 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().
>
> Also, cast the INSN_MODE_KERN dummy define value to (enum insn_mode)
> for tools use of the decoder because perf tool builds with -Werror and
> errors out with -Werror=sign-compare otherwise.
>
> Signed-off-by: Borislav Petkov
> Acked-by: Masami Hiramatsu
> ---
> arch/x86/include/asm/insn.h | 24 +++-
> arch/x86/lib/insn.c | 216 +++--
> tools/arch/x86/include/asm/insn.h | 24 +++-
> tools/arch/x86/lib/insn.c | 222 +++---
> tools/include/linux/kconfig.h | 73 ++
> 5 files changed, 452 insertions(+), 107 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 93f84600ac2c..de9fe760c1e7 100644
> --- a/arch/x86/include/asm/insn.h
> +++ b/arch/x86/include/asm/insn.h
> @@ -132,13 +132,23 @@ 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 ed1e0335aa14..bb58004497f8 100644
> --- a/arch/x86/lib/insn.c
> +++ b/arch/x86/lib/insn.c
> @@ -14,6 +14,9 @@
> #include /*__ignore_sync_check__ */
> #include /* __ignore_sync_check__ */
>
> +#include
> +#include
> +
> #include /* __ignore_sync_check__ */
>
> #define leXX_to_cpu(t, r) \
> @@ -112,8 +115,12 @@ 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 = >prefixes;
> insn_attr_t attr;
> @@ -121,7 +128,7 @@ void insn_get_prefixes(struct insn *insn)
> int i, nb;
>
> if (prefixes->got)
> - return;
> + return 0;
>
> insn_get_emulate_prefix(insn);
>
> @@ -231,8 +238,10 @@ void insn_get_prefixes(struct insn *insn)
>
> prefixes->got = 1;
>
> + return 0;
> +
> err_out:
> - return;
> + return -ENODATA;
> }
>
> /**
> @@ -244,16 +253,25 @@ 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 = >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 =
