linux-kernel - [PATCH entry v2 4/6] x86/entry/32: Fix #MC and #DB wiring on x86

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Date:   Fri,  3 Jul 2020 10:02:56 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     x86@...nel.org
Cc:     Andrew Cooper <andrew.cooper3@...rix.com>,
        Juergen Gross <jgross@...e.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Naresh Kamboju <naresh.kamboju@...aro.org>
Subject: [PATCH entry v2 4/6] x86/entry/32: Fix #MC and #DB wiring on x86_32

DEFINE_IDTENTRY_MCE and DEFINE_IDTENTRY_DEBUG were wired up as non-RAW
on x86_32, but the code expected them to be RAW.

Get rid of all the macro indirection for them on 32-bit and just use
DECLARE_IDTENTRY_RAW and DEFINE_IDTENTRY_RAW directly.

Also add a warning to make sure that we only hit the _kernel paths
in kernel mode.

Reported-by: Naresh Kamboju <naresh.kamboju@...aro.org>
Signed-off-by: Andy Lutomirski <luto@...nel.org>
---
 arch/x86/include/asm/idtentry.h | 23 +++++++++++++----------
 arch/x86/kernel/cpu/mce/core.c  |  4 +++-
 arch/x86/kernel/traps.c         |  2 +-
 3 files changed, 17 insertions(+), 12 deletions(-)

diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h
index 94333ac3092b..eeac6dc2adaa 100644
--- a/arch/x86/include/asm/idtentry.h
+++ b/arch/x86/include/asm/idtentry.h
@@ -353,10 +353,6 @@ static __always_inline void __##func(struct pt_regs *regs)
 
 #else	/* CONFIG_X86_64 */
 
-/* Maps to a regular IDTENTRY on 32bit for now */
-# define DECLARE_IDTENTRY_IST		DECLARE_IDTENTRY
-# define DEFINE_IDTENTRY_IST		DEFINE_IDTENTRY
-
 /**
  * DECLARE_IDTENTRY_DF - Declare functions for double fault 32bit variant
  * @vector:	Vector number (ignored for C)
@@ -387,16 +383,18 @@ __visible noinstr void func(struct pt_regs *regs,			\
 #endif	/* !CONFIG_X86_64 */
 
 /* C-Code mapping */
+#define DECLARE_IDTENTRY_NMI		DECLARE_IDTENTRY_RAW
+#define DEFINE_IDTENTRY_NMI		DEFINE_IDTENTRY_RAW
+
+#ifdef CONFIG_X86_64
 #define DECLARE_IDTENTRY_MCE		DECLARE_IDTENTRY_IST
 #define DEFINE_IDTENTRY_MCE		DEFINE_IDTENTRY_IST
 #define DEFINE_IDTENTRY_MCE_USER	DEFINE_IDTENTRY_NOIST
 
-#define DECLARE_IDTENTRY_NMI		DECLARE_IDTENTRY_RAW
-#define DEFINE_IDTENTRY_NMI		DEFINE_IDTENTRY_RAW
-
 #define DECLARE_IDTENTRY_DEBUG		DECLARE_IDTENTRY_IST
 #define DEFINE_IDTENTRY_DEBUG		DEFINE_IDTENTRY_IST
 #define DEFINE_IDTENTRY_DEBUG_USER	DEFINE_IDTENTRY_NOIST
+#endif
 
 #else /* !__ASSEMBLY__ */
 
@@ -443,9 +441,6 @@ __visible noinstr void func(struct pt_regs *regs,			\
 # define DECLARE_IDTENTRY_MCE(vector, func)				\
 	DECLARE_IDTENTRY(vector, func)
 
-# define DECLARE_IDTENTRY_DEBUG(vector, func)				\
-	DECLARE_IDTENTRY(vector, func)
-
 /* No ASM emitted for DF as this goes through a C shim */
 # define DECLARE_IDTENTRY_DF(vector, func)
 
@@ -549,7 +544,11 @@ DECLARE_IDTENTRY_RAW(X86_TRAP_BP,		exc_int3);
 DECLARE_IDTENTRY_RAW_ERRORCODE(X86_TRAP_PF,	exc_page_fault);
 
 #ifdef CONFIG_X86_MCE
+#ifdef CONFIG_X86_64
 DECLARE_IDTENTRY_MCE(X86_TRAP_MC,	exc_machine_check);
+#else
+DECLARE_IDTENTRY_RAW(X86_TRAP_MC,	exc_machine_check);
+#endif
 #endif
 
 /* NMI */
@@ -559,7 +558,11 @@ DECLARE_IDTENTRY_RAW(X86_TRAP_NMI,	xenpv_exc_nmi);
 #endif
 
 /* #DB */
+#ifdef CONFIG_X86_64
 DECLARE_IDTENTRY_DEBUG(X86_TRAP_DB,	exc_debug);
+#else
+DECLARE_IDTENTRY_RAW(X86_TRAP_DB,	exc_debug);
+#endif
 #ifdef CONFIG_XEN_PV
 DECLARE_IDTENTRY_RAW(X86_TRAP_DB,	xenpv_exc_debug);
 #endif
diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index ce9120c4f740..a6a90b5d7c83 100644
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -1901,6 +1901,8 @@ void (*machine_check_vector)(struct pt_regs *) = unexpected_machine_check;
 
 static __always_inline void exc_machine_check_kernel(struct pt_regs *regs)
 {
+	WARN_ON_ONCE(user_mode(regs));
+
 	/*
 	 * Only required when from kernel mode. See
 	 * mce_check_crashing_cpu() for details.
@@ -1954,7 +1956,7 @@ DEFINE_IDTENTRY_MCE_USER(exc_machine_check)
 }
 #else
 /* 32bit unified entry point */
-DEFINE_IDTENTRY_MCE(exc_machine_check)
+DEFINE_IDTENTRY_RAW(exc_machine_check)
 {
 	unsigned long dr7;
 
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index c17f9b57171f..6ed8cc5fbe8f 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -925,7 +925,7 @@ DEFINE_IDTENTRY_DEBUG_USER(exc_debug)
 }
 #else
 /* 32 bit does not have separate entry points. */
-DEFINE_IDTENTRY_DEBUG(exc_debug)
+DEFINE_IDTENTRY_RAW(exc_debug)
 {
 	unsigned long dr6, dr7;
 
-- 
2.25.4