diff options
| author | Masami Hiramatsu (Google) <mhiramat@kernel.org> | 2025-04-28 10:48:20 +0900 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2025-05-06 12:03:16 +0200 |
| commit | 4b626015e1bf119cd31d7e62f9bd9eb1412fce7b (patch) | |
| tree | f1d3986efb8aab54a688d816f6cac1c0e15fc3b9 /arch/x86/lib/insn.c | |
| parent | ca698ec2f07873a448d53c580795c4e023c75393 (diff) | |
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
Diffstat (limited to 'arch/x86/lib/insn.c')
| -rw-r--r-- | arch/x86/lib/insn.c | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/arch/x86/lib/insn.c b/arch/x86/lib/insn.c index 6ffb931b9fb1..149a57e334ab 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)) { |