riscv: Correct the handling of unexpected ebreak in do_trap_break()

[ Upstream commit 8bb0daef64e5a92db63ad1d3bbf9e280a7b3612a ]

For the kernel space, all ebreak instructions are determined at compile
time because the kernel space debugging module is currently unsupported.
Hence, it should be treated as a bug if an ebreak instruction which does
not belong to BUG_TRAP_TYPE_WARN or BUG_TRAP_TYPE_BUG is executed in
kernel space. For the userspace, debugging module or user problem may
intentionally insert an ebreak instruction to trigger a SIGTRAP signal.
To approach the above two situations, the do_trap_break() will direct
the BUG_TRAP_TYPE_NONE ebreak exception issued in kernel space to die()
and will send a SIGTRAP to the trapped process only when the ebreak is
in userspace.

Signed-off-by: Vincent Chen <vincent.chen@sifive.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
[paul.walmsley@sifive.com: fixed checkpatch issue]
Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
index 82f42a55451ebc444c0c4f3535c3aa5c86134e44..93742df9067fb5c864139445c414273bb9cd7168 100644 (file)
--- a/arch/riscv/kernel/traps.c
+++ b/arch/riscv/kernel/traps.c
@@ -130,8 +130,6 @@ asmlinkage void do_trap_break(struct pt_regs *regs)
                type = report_bug(regs->sepc, regs);
                switch (type) {
 #ifdef CONFIG_GENERIC_BUG
-               case BUG_TRAP_TYPE_NONE:
-                       break;
                case BUG_TRAP_TYPE_WARN:
                        regs->sepc += get_break_insn_length(regs->sepc);
                        return;
@@ -140,8 +138,10 @@ asmlinkage void do_trap_break(struct pt_regs *regs)
                default:
                        die(regs, "Kernel BUG");
                }
+       } else {
+               force_sig_fault(SIGTRAP, TRAP_BRKPT,
+                               (void __user *)(regs->sepc));
        }
-       force_sig_fault(SIGTRAP, TRAP_BRKPT, (void __user *)(regs->sepc));
 }
 
 #ifdef CONFIG_GENERIC_BUG