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Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.98 #2 (Red Hat Linux)) id 1tmXqM-000000079le-2FmP; Mon, 24 Feb 2025 12:45:54 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 0) id 1C9CA300898; Mon, 24 Feb 2025 13:45:54 +0100 (CET) Message-ID: <20250224124200.166774696@infradead.org> User-Agent: quilt/0.66 Date: Mon, 24 Feb 2025 13:37:06 +0100 From: Peter Zijlstra To: x86@kernel.org Cc: linux-kernel@vger.kernel.org, peterz@infradead.org, alyssa.milburn@intel.com, scott.d.constable@intel.com, joao@overdrivepizza.com, andrew.cooper3@citrix.com, jpoimboe@kernel.org, jose.marchesi@oracle.com, hjl.tools@gmail.com, ndesaulniers@google.com, samitolvanen@google.com, nathan@kernel.org, ojeda@kernel.org, kees@kernel.org, alexei.starovoitov@gmail.com, mhiramat@kernel.org, jmill@asu.edu Subject: [PATCH v4 03/10] x86/traps: Decode 0xEA #UD References: <20250224123703.843199044@infradead.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" FineIBT will start using 0xEA as #UD Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Kees Cook --- arch/x86/include/asm/bug.h | 1 + arch/x86/kernel/traps.c | 20 +++++++++++++++++--- 2 files changed, 18 insertions(+), 3 deletions(-) --- a/arch/x86/include/asm/bug.h +++ b/arch/x86/include/asm/bug.h @@ -25,6 +25,7 @@ #define BUG_UD2 0xfffe #define BUG_UD1 0xfffd #define BUG_UD1_UBSAN 0xfffc +#define BUG_EA 0xffea =20 #ifdef CONFIG_GENERIC_BUG =20 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -96,6 +96,7 @@ __always_inline int is_valid_bugaddr(uns * Check for UD1 or UD2, accounting for Address Size Override Prefixes. * If it's a UD1, further decode to determine its use: * + * FineIBT: ea (bad) * UBSan{0}: 67 0f b9 00 ud1 (%eax),%eax * UBSan{10}: 67 0f b9 40 10 ud1 0x10(%eax),%eax * static_call: 0f b9 cc ud1 %esp,%ecx @@ -113,6 +114,10 @@ __always_inline int decode_bug(unsigned v =3D *(u8 *)(addr++); if (v =3D=3D INSN_ASOP) v =3D *(u8 *)(addr++); + if (v =3D=3D 0xea) { + *len =3D addr - start; + return BUG_EA; + } if (v !=3D OPCODE_ESCAPE) return BUG_NONE; =20 @@ -309,10 +314,16 @@ static noinstr bool handle_bug(struct pt =20 switch (ud_type) { case BUG_UD2: - if (report_bug(regs->ip, regs) =3D=3D BUG_TRAP_TYPE_WARN || - handle_cfi_failure(regs) =3D=3D BUG_TRAP_TYPE_WARN) { - regs->ip +=3D ud_len; + if (report_bug(regs->ip, regs) =3D=3D BUG_TRAP_TYPE_WARN) { + handled =3D true; + break; + } + fallthrough; + + case BUG_EA: + if (handle_cfi_failure(regs) =3D=3D BUG_TRAP_TYPE_WARN) { handled =3D true; + break; } break; =20 @@ -328,6 +339,9 @@ static noinstr bool handle_bug(struct pt break; } =20 + if (handled) + regs->ip +=3D ud_len; + if (regs->flags & X86_EFLAGS_IF) raw_local_irq_disable(); instrumentation_end();