From: Russell King <rmk+lkml@arm.linux.org.uk>
To: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: "Rosendahl Viktor (Nokia-D/Helsinki)"
<Viktor.Rosendahl@nokia.com>,
ext Tony Lindgren <tony@atomide.com>,
"Moiseichuk Leonid (Nokia-D/Helsinki)"
<leonid.moiseichuk@nokia.com>,
"Kallioinen Juha (Nokia-D/Helsinki)" <juha.kallioinen@nokia.com>,
Siarhei Siamashka <siarhei.siamashka@nokia.com>,
Eero Tamminen <eero.tamminen@nokia.com>,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.arm.linux.org.uk
Subject: Re: [PATCH] ARM fix syscall trace return value
Date: Tue, 17 Feb 2009 19:02:53 +0000 [thread overview]
Message-ID: <20090217190253.GA10322@flint.arm.linux.org.uk> (raw)
In-Reply-To: <20090217181805.GA15788@Krystal>
On Tue, Feb 17, 2009 at 01:18:05PM -0500, Mathieu Desnoyers wrote:
> I am currently finding core bugs in the Linux kernel implementation of
> the ARM architecture. :-( e.g. return value not being sent to the
> syscall_trace function upon exit (upon which LTTng depends). (patch
> below)
Well then how can strace work? The fact of the matter is that strace
can and does work, and so I suspect that the problem is not in the
kernel but whatever "LTTng" is trying to do.
> BTW, the patch below applies to 2.6.29-rc4.
And is wrong.
> Index: linux-omap-2.6/arch/arm/kernel/entry-common.S
> ===================================================================
> --- linux-omap-2.6.orig/arch/arm/kernel/entry-common.S 2009-02-17 16:58:14.000000000 +0000
> +++ linux-omap-2.6/arch/arm/kernel/entry-common.S 2009-02-17 17:24:33.000000000 +0000
> @@ -89,6 +89,7 @@
> mov why, #1
> tst r1, #_TIF_SYSCALL_TRACE @ are we tracing syscalls?
> beq ret_slow_syscall
> + mov r2, #0 @ fork returns 0 to the child
This may be incorrect.
> mov r1, sp
> mov r0, #1 @ trace exit [IP = 1]
> bl syscall_trace
> @@ -292,7 +293,7 @@
>
> __sys_trace_return:
> str r0, [sp, #S_R0 + S_OFF]! @ save returned r0
> - mov r2, scno
> + mov r2, r0
This part is wrong. 'r2' *is* the syscall number.
The place to get the return value is by reading the registers, r0 to be
exact. No other method is supported.
--
Russell King
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/
maintainer of:
next prev parent reply other threads:[~2009-02-17 19:04 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-02-17 18:18 [PATCH] ARM fix syscall trace return value Mathieu Desnoyers
2009-02-17 19:02 ` Russell King [this message]
2009-02-17 19:22 ` Viktor Rosendahl
2009-02-17 19:30 ` Mathieu Desnoyers
2009-02-17 19:40 ` Russell King
2009-02-17 20:08 ` Mathieu Desnoyers
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