linux-kernel - [PATCH v3 1/3] xtensa: add trap handler for division by zero

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Date:   Tue, 17 May 2022 03:44:56 -0700
From:   Max Filippov <jcmvbkbc@...il.com>
To:     linux-xtensa@...ux-xtensa.org
Cc:     Chris Zankel <chris@...kel.net>, linux-kernel@...r.kernel.org,
        Max Filippov <jcmvbkbc@...il.com>
Subject: [PATCH v3 1/3] xtensa: add trap handler for division by zero

Add c-level handler for the division by zero exception and kill the task
if it was thrown from the kernel space or send SIGFPE otherwise.

Signed-off-by: Max Filippov <jcmvbkbc@...il.com>
---
 arch/xtensa/kernel/traps.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/xtensa/kernel/traps.c b/arch/xtensa/kernel/traps.c
index 138a86fbe9d7..24d11b44fa57 100644
--- a/arch/xtensa/kernel/traps.c
+++ b/arch/xtensa/kernel/traps.c
@@ -49,6 +49,7 @@
  */
 
 static void do_illegal_instruction(struct pt_regs *regs);
+static void do_div0(struct pt_regs *regs);
 static void do_interrupt(struct pt_regs *regs);
 #if XTENSA_FAKE_NMI
 static void do_nmi(struct pt_regs *regs);
@@ -95,7 +96,7 @@ static dispatch_init_table_t __initdata dispatch_init_table[] = {
 #ifdef SUPPORT_WINDOWED
 { EXCCAUSE_ALLOCA,		USER|KRNL, fast_alloca },
 #endif
-/* EXCCAUSE_INTEGER_DIVIDE_BY_ZERO unhandled */
+{ EXCCAUSE_INTEGER_DIVIDE_BY_ZERO, 0,	   do_div0 },
 /* EXCCAUSE_PRIVILEGED unhandled */
 #if XCHAL_UNALIGNED_LOAD_EXCEPTION || XCHAL_UNALIGNED_STORE_EXCEPTION
 #ifdef CONFIG_XTENSA_UNALIGNED_USER
@@ -307,6 +308,11 @@ static void do_illegal_instruction(struct pt_regs *regs)
 	force_sig(SIGILL);
 }
 
+static void do_div0(struct pt_regs *regs)
+{
+	__die_if_kernel("Unhandled division by 0 in kernel", regs, SIGKILL);
+	force_sig_fault(SIGFPE, FPE_INTDIV, (void __user *)regs->pc);
+}
 
 /*
  * Handle unaligned memory accesses from user space. Kill task.
-- 
2.30.2