ARM: 8124/1: don't enter kgdb when userspace executes a kgdb break instruction

The kgdb breakpoint hooks (kgdb_brk_fn and kgdb_compiled_brk_fn)
should only be entered when a kgdb break instruction is executed
from the kernel. Otherwise, if kgdb is enabled, a userspace program
can cause the kernel to drop into the debugger by executing either
KGDB_BREAKINST or KGDB_COMPILED_BREAK.

Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Omar Sandoval <osandov@osandov.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 4 insertions, 0 deletions

diff --git a/arch/arm/kernel/kgdb.c b/arch/arm/kernel/kgdb.c
index 778c2f7024ff..a74b53c1b7df 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
 };