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From: Paul Walmsley <paul.walmsley@sifive.com>
To: Vincent Chen <vincent.chen@sifive.com>
Cc: linux-riscv@lists.infradead.org, palmer@sifive.com,
	linux-kernel@vger.kernel.org, aou@eecs.berkeley.edu
Subject: Re: [PATCH 3/4] riscv: Correct the handling of unexpected ebreak in do_trap_break()
Date: Fri, 4 Oct 2019 11:28:23 -0700 (PDT)
Message-ID: <alpine.DEB.2.21.9999.1910041126420.15827@viisi.sifive.com> (raw)
In-Reply-To: <1569199517-5884-4-git-send-email-vincent.chen@sifive.com>

On Mon, 23 Sep 2019, Vincent Chen wrote:

> 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>

Thanks, queued the following for v5.4-rc.


- Paul

From: Vincent Chen <vincent.chen@sifive.com>
Date: Mon, 23 Sep 2019 08:45:16 +0800
Subject: [PATCH] riscv: Correct the handling of unexpected ebreak in
 do_trap_break()

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>
---
 arch/riscv/kernel/traps.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
index 82f42a55451e..93742df9067f 100644
--- 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
-- 
2.23.0


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  parent reply index

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-23  0:45 [PATCH 0/4] riscv: correct the do_trap_break() Vincent Chen
2019-09-23  0:45 ` [PATCH 1/4] riscv: avoid kernel hangs when trapped in BUG() Vincent Chen
2019-09-27 22:25   ` Christoph Hellwig
2019-10-04 18:26   ` Paul Walmsley
2019-09-23  0:45 ` [PATCH 2/4] rsicv: avoid sending a SIGTRAP to a user thread trapped in WARN() Vincent Chen
2019-09-27 22:27   ` Christoph Hellwig
2019-09-27 22:56   ` Christoph Hellwig
2019-09-30  0:22     ` Vincent Chen
2019-10-04 18:26   ` Paul Walmsley
2019-09-23  0:45 ` [PATCH 3/4] riscv: Correct the handling of unexpected ebreak in do_trap_break() Vincent Chen
2019-09-27 22:43   ` Christoph Hellwig
2019-10-04 18:28   ` Paul Walmsley [this message]
2019-09-23  0:45 ` [PATCH 4/4] riscv: remove the switch statement " Vincent Chen
2019-09-27 22:47   ` Christoph Hellwig
2019-10-07 16:08     ` Paul Walmsley
2019-10-07 16:10       ` Christoph Hellwig
2019-10-07 16:30         ` Paul Walmsley
2019-10-08  0:14           ` Vincent Chen
2019-10-08 17:07             ` Paul Walmsley
2019-10-09 22:26         ` Paul Walmsley

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