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From:   Joerg Roedel <joro@8bytes.org>
To:     x86@kernel.org
Cc:     Joerg Roedel <joro@8bytes.org>, Joerg Roedel <jroedel@suse.de>,
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Subject: [PATCH 1/3] x86/sev-es: Introduce from_syscall_gap() helper
Date:   Wed, 17 Feb 2021 13:01:41 +0100
Message-Id: <20210217120143.6106-2-joro@8bytes.org>
In-Reply-To: <20210217120143.6106-1-joro@8bytes.org>
References: <20210217120143.6106-1-joro@8bytes.org>
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From: Joerg Roedel <jroedel@suse.de>

Introduce a helper to check whether an exception came from the syscall
gap and use it in the SEV-ES code

Fixes: 315562c9af3d5 ("x86/sev-es: Adjust #VC IST Stack on entering NMI handler")
Cc: stable@vger.kernel.org # 5.10+
Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
 arch/x86/include/asm/ptrace.h | 8 ++++++++
 arch/x86/kernel/traps.c       | 3 +--
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/ptrace.h b/arch/x86/include/asm/ptrace.h
index d8324a236696..14854b2c4944 100644
--- a/arch/x86/include/asm/ptrace.h
+++ b/arch/x86/include/asm/ptrace.h
@@ -94,6 +94,8 @@ struct pt_regs {
 #include <asm/paravirt_types.h>
 #endif
 
+#include <asm/proto.h>
+
 struct cpuinfo_x86;
 struct task_struct;
 
@@ -175,6 +177,12 @@ static inline bool any_64bit_mode(struct pt_regs *regs)
 #ifdef CONFIG_X86_64
 #define current_user_stack_pointer()	current_pt_regs()->sp
 #define compat_user_stack_pointer()	current_pt_regs()->sp
+
+static inline bool from_syscall_gap(struct pt_regs *regs)
+{
+	return (regs->ip >= (unsigned long)entry_SYSCALL_64 &&
+		regs->ip <  (unsigned long)entry_SYSCALL_64_safe_stack);
+}
 #endif
 
 static inline unsigned long kernel_stack_pointer(struct pt_regs *regs)
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 7f5aec758f0e..b4f2b4e9066d 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -694,8 +694,7 @@ asmlinkage __visible noinstr struct pt_regs *vc_switch_off_ist(struct pt_regs *r
 	 * In the SYSCALL entry path the RSP value comes from user-space - don't
 	 * trust it and switch to the current kernel stack
 	 */
-	if (regs->ip >= (unsigned long)entry_SYSCALL_64 &&
-	    regs->ip <  (unsigned long)entry_SYSCALL_64_safe_stack) {
+	if (from_syscall_gap(regs)) {
 		sp = this_cpu_read(cpu_current_top_of_stack);
 		goto sync;
 	}
-- 
2.30.0