linux-kernel - Re: [PATCH 04/28] nios2: Exception handling

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Message-ID: <20140422105744.GA589@arch.cereza>
Date:	Tue, 22 Apr 2014 07:57:44 -0300
From:	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>
To:	Ley Foon Tan <lftan@...era.com>
Cc:	linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-doc@...r.kernel.org, lftan.linux@...il.com,
	cltang@...esourcery.com
Subject: Re: [PATCH 04/28] nios2: Exception handling

Hi Ley Foon,

On Apr 18, Ley Foon Tan wrote:
> +
> +	/* Get thread info pointer */
> +	movi	r11, %lo(0xfffff000)
> +	and	r11, sp, r11
> +	ldw	r11, TI_FLAGS(r11)
> +
> +	/* If someone is ptrace:ing us, take the long way. */
> +	BTBNZ	r11, r11, TIF_SYSCALL_TRACE, traced_system_call
> +

Are you sure this is correct? Have you tested this works correctly?

Last time I tested this, it caused the traced_system_call to be taken
for every system call. I already reported and provided a patch a few
months ago:

http://lists.rocketboards.org/pipermail/nios2-dev/2014-January/006968.html

Here's my proposed fix:

diff --git a/arch/nios2/kernel/entry.S b/arch/nios2/kernel/entry.S
index 9cf2bac..3798008 100644
--- a/arch/nios2/kernel/entry.S
+++ b/arch/nios2/kernel/entry.S
@@ -204,13 +204,10 @@ ENTRY(handle_system_call)
 	ldw	r1, %lo(sys_call_table)(r1)
 	beq	r1, r0, ret_invsyscall
 
-	/* Get thread info pointer */
-	movi	r11, %lo(0xfffff000)
-	and	r11, sp, r11
-	ldw	r11, TI_FLAGS(r11)
-
-	/* If someone is ptrace:ing us, take the long way. */
-	BTBNZ	r11, r11, TIF_SYSCALL_TRACE, traced_system_call
+	/* Check if we are being traced */
+	GET_THREAD_INFO r11
+	ldw	r11,TI_FLAGS(r11)
+	BTBNZ	r11,r11,TIF_SYSCALL_TRACE,traced_system_call
 
 	/* Execute the system call */
 	callr	r1
-- 
1.9.1

-- 
Ezequiel García, Free Electrons
Embedded Linux, Kernel and Android Engineering
http://free-electrons.com
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