linux-kernel - [PATCH 1/3] x86: allow kernel exception fixup for divide errors (#DE)

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Date:	Tue, 24 Aug 2010 14:10:27 +0300
From:	Avi Kivity <avi@...hat.com>
To:	x86@...nel.org, kvm@...r.kernel.org,
	Marcelo Tosatti <mtosatti@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 1/3] x86: allow kernel exception fixup for divide errors (#DE)

KVM wants to emulate the DIV and IDIV instructions by executing them natively;
this can cause a #DE to be raised.

Allow the exception handling mechanism to process #DE exceptions so KVM can
catch and process them.

Signed-off-by: Avi Kivity <avi@...hat.com>
---
 arch/x86/kernel/traps.c |   10 +++++++++-
 1 files changed, 9 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 725ef4d..dd313cf 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -205,7 +205,8 @@ dotraplinkage void do_##name(struct pt_regs *regs, long error_code)	\
 	do_trap(trapnr, signr, str, regs, error_code, &info);		\
 }
 
-DO_ERROR_INFO(0, SIGFPE, "divide error", divide_error, FPE_INTDIV, regs->ip)
+static DO_ERROR_INFO(0, SIGFPE, "divide error", divide_error_user,
+		     FPE_INTDIV, regs->ip)
 DO_ERROR(4, SIGSEGV, "overflow", overflow)
 DO_ERROR(5, SIGSEGV, "bounds", bounds)
 DO_ERROR_INFO(6, SIGILL, "invalid opcode", invalid_op, ILL_ILLOPN, regs->ip)
@@ -217,6 +218,13 @@ DO_ERROR(12, SIGBUS, "stack segment", stack_segment)
 #endif
 DO_ERROR_INFO(17, SIGBUS, "alignment check", alignment_check, BUS_ADRALN, 0)
 
+dotraplinkage void do_divide_error(struct pt_regs *regs, long error_code)
+{
+	if (!user_mode_vm(regs) && fixup_exception(regs))
+		return;
+	do_divide_error_user(regs, error_code);
+}
+
 #ifdef CONFIG_X86_64
 /* Runs on IST stack */
 dotraplinkage void do_stack_segment(struct pt_regs *regs, long error_code)
-- 
1.7.1

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