linux-kernel - [PATCH] ARM: Don't oops when userspace executes kgdb break instructions.

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Message-ID: <20140718225049.GA11937@mew.guest.dropbox.com>
Date:	Fri, 18 Jul 2014 15:51:31 -0700
From:	Omar Sandoval <osandov@...ndov.com>
To:	linux-arm-kernel@...ts.infradead.org
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH] ARM: Don't oops when userspace executes kgdb break
 instructions.

Don't break into kgdb when userspace executes the kernel break instructions
(KGDB_BREAKINST and KGDB_COMPILED_BREAK). The kernel will oops in
kgdb_handle_exception.

Signed-off-by: Omar Sandoval <osandov@...ndov.com>
---
The following program will immediately cause a kernel oops:
.globl _start
_start:
	udf	#65006	@ KGDB_BREAKINST

 arch/arm/kernel/kgdb.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/arm/kernel/kgdb.c b/arch/arm/kernel/kgdb.c
index 778c2f7..a74b53c 100644
--- a/arch/arm/kernel/kgdb.c
+++ b/arch/arm/kernel/kgdb.c
@@ -160,12 +160,16 @@ static int kgdb_compiled_brk_fn(struct pt_regs *regs, unsigned int instr)
 static struct undef_hook kgdb_brkpt_hook = {
 	.instr_mask		= 0xffffffff,
 	.instr_val		= KGDB_BREAKINST,
+	.cpsr_mask		= MODE_MASK,
+	.cpsr_val		= SVC_MODE,
 	.fn			= kgdb_brk_fn
 };
 
 static struct undef_hook kgdb_compiled_brkpt_hook = {
 	.instr_mask		= 0xffffffff,
 	.instr_val		= KGDB_COMPILED_BREAK,
+	.cpsr_mask		= MODE_MASK,
+	.cpsr_val		= SVC_MODE,
 	.fn			= kgdb_compiled_brk_fn
 };
 
-- 
2.0.1
--
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