Re: [PATCH 5.10 017/130] x86/insn: Add an insn_decode() API

Florian Fainelli
2022-07-12T23:04:44Z

On 7/12/22 11:37, Greg Kroah-Hartman wrote:
> From: Borislav Petkov <bp@suse.de>
>
> commit 93281c4a96572a34504244969b938e035204778d upstream.
>
> 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 <bp@suse.de>
> Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
> Link: https://lkml.kernel.org/r/20210304174237.31945-5-bp@alien8.de
> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> ---
> 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
>
> --- 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)
> --- a/arch/x86/lib/insn.c
> +++ b/arch/x86/lib/insn.c
> @@ -13,6 +13,9 @@
> #include <asm/inat.h> /*__ignore_sync_check__ */
> #include <asm/insn.h> /* __ignore_sync_check__ */
>
> +#include <linux/errno.h>
> +#include <linux/kconfig.h>
> +
> #include <asm/emulate_prefix.h> /* __ignore_sync_check__ */
>
> /* Verify next sizeof(t) bytes can be on the same instruction */
> @@ -97,8 +100,12 @@ static void insn_get_emulate_prefix(stru
> * 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;
> @@ -106,7 +113,7 @@ void insn_get_prefixes(struct insn *insn
> int i, nb;
>
> if (prefixes->got)
> - return;
> + return 0;
>
> insn_get_emulate_prefix(insn);
>
> @@ -217,8 +224,10 @@ vex_end:
>
> prefixes->got = 1;
>
> + return 0;
> +
> err_out:
> - return;
> + return -ENODATA;
> }
>
> /**
> @@ -230,16 +239,25 @@ err_out:
> * 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);
> @@ -254,9 +272,13 @@ 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 -EINVAL;
> + }
> + /* VEX has only 1 byte for opcode */
> + goto end;
> }
>
> insn->attr = inat_get_opcode_attribute(op);
> @@ -267,13 +289,18 @@ 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 -EINVAL;
> + }
> end:
> opcode->got = 1;
> + return 0;
>
> err_out:
> - return;
> + return -ENODATA;
> }
>
> /**
> @@ -283,15 +310,25 @@ err_out:
> * 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);
> @@ -301,17 +338,22 @@ 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 -EINVAL;
> + }
> }
> }
>
> if (insn->x86_64 && inat_is_force64(insn->attr))
> insn->opnd_bytes = 8;
> +
> modrm->got = 1;
> + return 0;
>
> err_out:
> - return;
> + return -ENODATA;
> }
>
>
> @@ -325,11 +367,16 @@ err_out:
> 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 0;
> + }
> /*
> * For rip-relative instructions, the mod field (top 2 bits)
> * is zero and the r/m field (bottom 3 bits) is 0x5.
> @@ -343,15 +390,25 @@ 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 &&
> @@ -362,8 +419,10 @@ void insn_get_sib(struct insn *insn)
> }
> insn->sib.got = 1;
>
> + return 0;
> +
> err_out:
> - return;
> + return -ENODATA;
> }
>
>
> @@ -374,15 +433,25 @@ err_out:
> * 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:
> @@ -425,9 +494,10 @@ void insn_get_displacement(struct insn *
> }
> out:
> insn->displacement.got = 1;
> + return 0;
>
> err_out:
> - return;
> + return -ENODATA;
> }
>
> /* Decode moffset16/32/64. Return 0 if failed */
> @@ -538,20 +608,30 @@ err_out:
> }
>
> /**
> - * 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))
> @@ -604,9 +684,10 @@ void insn_get_immediate(struct insn *ins
> }
> done:
> insn->immediate.got = 1;
> + return 0;
>
> err_out:
> - return;
> + return -ENODATA;
> }
>
> /**
> @@ -615,13 +696,58 @@ err_out:
> *
> * 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;
> +
> +/* #define INSN_MODE_KERN -1 __ignore_sync_check__ mode is only valid in the kernel */
> +
> + 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;
> }
> --- 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)
> --- a/tools/arch/x86/lib/insn.c
> +++ b/tools/arch/x86/lib/insn.c
> @@ -10,10 +10,13 @@
> #else
> #include <string.h>
> #endif
> -#include "../include/asm/inat.h" /* __ignore_sync_check__ */
> -#include "../include/asm/insn.h" /* __ignore_sync_check__ */
> +#include <asm/inat.h> /* __ignore_sync_check__ */
> +#include <asm/insn.h> /* __ignore_sync_check__ */

These includes breaks the build for me with:

CC
/local/users/fainelli/buildroot/output/arm64/build/linux-custom/tools/perf/util/intel-pt-decoder/intel-pt-insn-decoder.o
In file included from util/intel-pt-decoder/intel-pt-insn-decoder.c:15:
util/intel-pt-decoder/../../../arch/x86/lib/insn.c:13:10: fatal error:
asm/inat.h: No such file or directory
#include <asm/inat.h> /* __ignore_sync_check__ */
^~~~~~~~~~~~
compilation terminated.
make[7]: *** [util/intel-pt-decoder/Build:14:
/local/users/fainelli/buildroot/output/arm64/build/linux-custom/tools/perf/util/intel-pt-decoder/intel-pt-insn-decoder.o]
Error 1
make[6]: ***
[/local/users/fainelli/buildroot/output/arm64/build/linux-custom/tools/build/Makefile.build:139:
intel-pt-decoder] Error 2
make[5]: ***
[/local/users/fainelli/buildroot/output/arm64/build/linux-custom/tools/build/Makefile.build:139:
util] Error 2
make[4]: *** [Makefile.perf:643:
/local/users/fainelli/buildroot/output/arm64/build/linux-custom/tools/perf/perf-in.o]
Error 2
make[3]: *** [Makefile.perf:229: sub-make] Error 2
make[2]: *** [Makefile:70: all] Error 2
make[1]: *** [package/pkg-generic.mk:294:
/local/users/fainelli/buildroot/output/arm64/build/linux-tools/.stamp_built]
Error 2
make: *** [Makefile:27: _all] Error 2

It looks like you would also need to back port this:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=0705ef64d1ff52b817e278ca6e28095585ff31e1
--
Florian