From: "tip-bot2 for Masami Hiramatsu (Google)" <tip-bot2@linutronix.de>
To: linux-tip-commits@vger.kernel.org
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>,
Ingo Molnar <mingo@kernel.org>,
Adrian Hunter <adrian.hunter@intel.com>,
"H. Peter Anvin" <hpa@zytor.com>,
Peter Zijlstra <peterz@infradead.org>,
x86@kernel.org, linux-kernel@vger.kernel.org
Subject: [tip: x86/asm] x86/insn: Stop decoding i64 instructions in x86-64 mode at opcode
Date: Tue, 06 May 2025 10:35:31 -0000 [thread overview]
Message-ID: <174652773170.406.15067062455529942136.tip-bot2@tip-bot2> (raw)
In-Reply-To: <174580490000.388420.5225447607417115496.stgit@devnote2>
The following commit has been merged into the x86/asm branch of tip:
Commit-ID: 4b626015e1bf119cd31d7e62f9bd9eb1412fce7b
Gitweb: https://git.kernel.org/tip/4b626015e1bf119cd31d7e62f9bd9eb1412fce7b
Author: Masami Hiramatsu (Google) <mhiramat@kernel.org>
AuthorDate: Mon, 28 Apr 2025 10:48:20 +09:00
Committer: Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 06 May 2025 12:03:16 +02:00
x86/insn: Stop decoding i64 instructions in x86-64 mode at opcode
In commit 2e044911be75 ("x86/traps: Decode 0xEA instructions as #UD")
FineIBT starts using 0xEA as an invalid instruction like UD2. But
insn decoder always returns the length of "0xea" instruction as 7
because it does not check the (i64) superscript.
The x86 instruction decoder should also decode 0xEA on x86-64 as
a one-byte invalid instruction by decoding the "(i64)" superscript tag.
This stops decoding instruction which has (i64) but does not have (o64)
superscript in 64-bit mode at opcode and skips other fields.
With this change, insn_decoder_test says 0xea is 1 byte length if
x86-64 (-y option means 64-bit):
$ printf "0:\tea\t\n" | insn_decoder_test -y -v
insn_decoder_test: success: Decoded and checked 1 instructions
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/174580490000.388420.5225447607417115496.stgit@devnote2
---
arch/x86/include/asm/inat.h | 6 ++++++
arch/x86/lib/insn.c | 7 ++++++-
arch/x86/lib/x86-opcode-map.txt | 6 +++---
arch/x86/tools/gen-insn-attr-x86.awk | 7 +++++++
tools/arch/x86/include/asm/inat.h | 6 ++++++
tools/arch/x86/lib/insn.c | 7 ++++++-
tools/arch/x86/lib/x86-opcode-map.txt | 6 +++---
tools/arch/x86/tools/gen-insn-attr-x86.awk | 7 +++++++
8 files changed, 44 insertions(+), 8 deletions(-)
diff --git a/arch/x86/include/asm/inat.h b/arch/x86/include/asm/inat.h
index 53e4015..97f3417 100644
--- a/arch/x86/include/asm/inat.h
+++ b/arch/x86/include/asm/inat.h
@@ -82,6 +82,7 @@
#define INAT_NO_REX2 (1 << (INAT_FLAG_OFFS + 8))
#define INAT_REX2_VARIANT (1 << (INAT_FLAG_OFFS + 9))
#define INAT_EVEX_SCALABLE (1 << (INAT_FLAG_OFFS + 10))
+#define INAT_INV64 (1 << (INAT_FLAG_OFFS + 11))
/* Attribute making macros for attribute tables */
#define INAT_MAKE_PREFIX(pfx) (pfx << INAT_PFX_OFFS)
#define INAT_MAKE_ESCAPE(esc) (esc << INAT_ESC_OFFS)
@@ -242,4 +243,9 @@ static inline int inat_evex_scalable(insn_attr_t attr)
{
return attr & INAT_EVEX_SCALABLE;
}
+
+static inline int inat_is_invalid64(insn_attr_t attr)
+{
+ return attr & INAT_INV64;
+}
#endif
diff --git a/arch/x86/lib/insn.c b/arch/x86/lib/insn.c
index 6ffb931..149a57e 100644
--- a/arch/x86/lib/insn.c
+++ b/arch/x86/lib/insn.c
@@ -324,6 +324,11 @@ int insn_get_opcode(struct insn *insn)
}
insn->attr = inat_get_opcode_attribute(op);
+ if (insn->x86_64 && inat_is_invalid64(insn->attr)) {
+ /* This instruction is invalid, like UD2. Stop decoding. */
+ insn->attr &= INAT_INV64;
+ }
+
while (inat_is_escape(insn->attr)) {
/* Get escaped opcode */
op = get_next(insn_byte_t, insn);
@@ -337,6 +342,7 @@ int insn_get_opcode(struct insn *insn)
insn->attr = 0;
return -EINVAL;
}
+
end:
opcode->got = 1;
return 0;
@@ -658,7 +664,6 @@ int insn_get_immediate(struct insn *insn)
}
if (!inat_has_immediate(insn->attr))
- /* no immediates */
goto done;
switch (inat_immediate_size(insn->attr)) {
diff --git a/arch/x86/lib/x86-opcode-map.txt b/arch/x86/lib/x86-opcode-map.txt
index cd3fd51..262f7ca 100644
--- a/arch/x86/lib/x86-opcode-map.txt
+++ b/arch/x86/lib/x86-opcode-map.txt
@@ -147,7 +147,7 @@ AVXcode:
# 0x60 - 0x6f
60: PUSHA/PUSHAD (i64)
61: POPA/POPAD (i64)
-62: BOUND Gv,Ma (i64) | EVEX (Prefix)
+62: BOUND Gv,Ma (i64) | EVEX (Prefix),(o64)
63: ARPL Ew,Gw (i64) | MOVSXD Gv,Ev (o64)
64: SEG=FS (Prefix)
65: SEG=GS (Prefix)
@@ -253,8 +253,8 @@ c0: Grp2 Eb,Ib (1A)
c1: Grp2 Ev,Ib (1A)
c2: RETN Iw (f64)
c3: RETN
-c4: LES Gz,Mp (i64) | VEX+2byte (Prefix)
-c5: LDS Gz,Mp (i64) | VEX+1byte (Prefix)
+c4: LES Gz,Mp (i64) | VEX+2byte (Prefix),(o64)
+c5: LDS Gz,Mp (i64) | VEX+1byte (Prefix),(o64)
c6: Grp11A Eb,Ib (1A)
c7: Grp11B Ev,Iz (1A)
c8: ENTER Iw,Ib
diff --git a/arch/x86/tools/gen-insn-attr-x86.awk b/arch/x86/tools/gen-insn-attr-x86.awk
index 5770c80..2c19d7f 100644
--- a/arch/x86/tools/gen-insn-attr-x86.awk
+++ b/arch/x86/tools/gen-insn-attr-x86.awk
@@ -64,6 +64,8 @@ BEGIN {
modrm_expr = "^([CDEGMNPQRSUVW/][a-z]+|NTA|T[012])"
force64_expr = "\\([df]64\\)"
+ invalid64_expr = "\\(i64\\)"
+ only64_expr = "\\(o64\\)"
rex_expr = "^((REX(\\.[XRWB]+)+)|(REX$))"
rex2_expr = "\\(REX2\\)"
no_rex2_expr = "\\(!REX2\\)"
@@ -319,6 +321,11 @@ function convert_operands(count,opnd, i,j,imm,mod)
if (match(ext, force64_expr))
flags = add_flags(flags, "INAT_FORCE64")
+ # check invalid in 64-bit (and no only64)
+ if (match(ext, invalid64_expr) &&
+ !match($0, only64_expr))
+ flags = add_flags(flags, "INAT_INV64")
+
# check REX2 not allowed
if (match(ext, no_rex2_expr))
flags = add_flags(flags, "INAT_NO_REX2")
diff --git a/tools/arch/x86/include/asm/inat.h b/tools/arch/x86/include/asm/inat.h
index 253690e..183aa66 100644
--- a/tools/arch/x86/include/asm/inat.h
+++ b/tools/arch/x86/include/asm/inat.h
@@ -82,6 +82,7 @@
#define INAT_NO_REX2 (1 << (INAT_FLAG_OFFS + 8))
#define INAT_REX2_VARIANT (1 << (INAT_FLAG_OFFS + 9))
#define INAT_EVEX_SCALABLE (1 << (INAT_FLAG_OFFS + 10))
+#define INAT_INV64 (1 << (INAT_FLAG_OFFS + 11))
/* Attribute making macros for attribute tables */
#define INAT_MAKE_PREFIX(pfx) (pfx << INAT_PFX_OFFS)
#define INAT_MAKE_ESCAPE(esc) (esc << INAT_ESC_OFFS)
@@ -242,4 +243,9 @@ static inline int inat_evex_scalable(insn_attr_t attr)
{
return attr & INAT_EVEX_SCALABLE;
}
+
+static inline int inat_is_invalid64(insn_attr_t attr)
+{
+ return attr & INAT_INV64;
+}
#endif
diff --git a/tools/arch/x86/lib/insn.c b/tools/arch/x86/lib/insn.c
index e91d4c4..bce69c6 100644
--- a/tools/arch/x86/lib/insn.c
+++ b/tools/arch/x86/lib/insn.c
@@ -324,6 +324,11 @@ int insn_get_opcode(struct insn *insn)
}
insn->attr = inat_get_opcode_attribute(op);
+ if (insn->x86_64 && inat_is_invalid64(insn->attr)) {
+ /* This instruction is invalid, like UD2. Stop decoding. */
+ insn->attr &= INAT_INV64;
+ }
+
while (inat_is_escape(insn->attr)) {
/* Get escaped opcode */
op = get_next(insn_byte_t, insn);
@@ -337,6 +342,7 @@ int insn_get_opcode(struct insn *insn)
insn->attr = 0;
return -EINVAL;
}
+
end:
opcode->got = 1;
return 0;
@@ -658,7 +664,6 @@ int insn_get_immediate(struct insn *insn)
}
if (!inat_has_immediate(insn->attr))
- /* no immediates */
goto done;
switch (inat_immediate_size(insn->attr)) {
diff --git a/tools/arch/x86/lib/x86-opcode-map.txt b/tools/arch/x86/lib/x86-opcode-map.txt
index cd3fd51..262f7ca 100644
--- a/tools/arch/x86/lib/x86-opcode-map.txt
+++ b/tools/arch/x86/lib/x86-opcode-map.txt
@@ -147,7 +147,7 @@ AVXcode:
# 0x60 - 0x6f
60: PUSHA/PUSHAD (i64)
61: POPA/POPAD (i64)
-62: BOUND Gv,Ma (i64) | EVEX (Prefix)
+62: BOUND Gv,Ma (i64) | EVEX (Prefix),(o64)
63: ARPL Ew,Gw (i64) | MOVSXD Gv,Ev (o64)
64: SEG=FS (Prefix)
65: SEG=GS (Prefix)
@@ -253,8 +253,8 @@ c0: Grp2 Eb,Ib (1A)
c1: Grp2 Ev,Ib (1A)
c2: RETN Iw (f64)
c3: RETN
-c4: LES Gz,Mp (i64) | VEX+2byte (Prefix)
-c5: LDS Gz,Mp (i64) | VEX+1byte (Prefix)
+c4: LES Gz,Mp (i64) | VEX+2byte (Prefix),(o64)
+c5: LDS Gz,Mp (i64) | VEX+1byte (Prefix),(o64)
c6: Grp11A Eb,Ib (1A)
c7: Grp11B Ev,Iz (1A)
c8: ENTER Iw,Ib
diff --git a/tools/arch/x86/tools/gen-insn-attr-x86.awk b/tools/arch/x86/tools/gen-insn-attr-x86.awk
index 5770c80..2c19d7f 100644
--- a/tools/arch/x86/tools/gen-insn-attr-x86.awk
+++ b/tools/arch/x86/tools/gen-insn-attr-x86.awk
@@ -64,6 +64,8 @@ BEGIN {
modrm_expr = "^([CDEGMNPQRSUVW/][a-z]+|NTA|T[012])"
force64_expr = "\\([df]64\\)"
+ invalid64_expr = "\\(i64\\)"
+ only64_expr = "\\(o64\\)"
rex_expr = "^((REX(\\.[XRWB]+)+)|(REX$))"
rex2_expr = "\\(REX2\\)"
no_rex2_expr = "\\(!REX2\\)"
@@ -319,6 +321,11 @@ function convert_operands(count,opnd, i,j,imm,mod)
if (match(ext, force64_expr))
flags = add_flags(flags, "INAT_FORCE64")
+ # check invalid in 64-bit (and no only64)
+ if (match(ext, invalid64_expr) &&
+ !match($0, only64_expr))
+ flags = add_flags(flags, "INAT_INV64")
+
# check REX2 not allowed
if (match(ext, no_rex2_expr))
flags = add_flags(flags, "INAT_NO_REX2")
prev parent reply other threads:[~2025-05-06 10:35 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-04-28 1:48 [PATCH 0/2] x86: Fix insn decoder to support 0xEA as UD Masami Hiramatsu (Google)
2025-04-28 1:48 ` [PATCH 1/2] x86: Fix opcode map (!REX2) superscript tags Masami Hiramatsu (Google)
2025-05-06 10:35 ` [tip: x86/asm] x86/insn: " tip-bot2 for Masami Hiramatsu (Google)
2025-04-28 1:48 ` [PATCH 2/2] x86: Stop decoding i64 instructions in x86-64 mode at opcode Masami Hiramatsu (Google)
2025-04-29 8:50 ` Peter Zijlstra
2025-05-06 10:35 ` tip-bot2 for Masami Hiramatsu (Google) [this message]
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