Re: [PATCH v2 0/9] ARM: remove set_fs callers and implementation

From: Russell King - ARM Linux admin
Date: Sat Sep 19 2020 - 04:19:17 EST

On Fri, Sep 18, 2020 at 02:46:15PM +0200, Arnd Bergmann wrote:
> Hi Christoph, Russell,
> Here is an updated series for removing set_fs() from arch/arm,
> based on the previous feedback.
> I have tested the oabi-compat changes using the LTP tests for the three
> modified syscalls using an Armv7 kernel and a Debian 5 OABI user space,
> and I have lightly tested the get_kernel_nofault infrastructure by
> loading the test_lockup.ko module after setting CONFIG_DEBUG_SPINLOCK.

I'm not too keen on always saving the syscall number, but for the gain
of getting rid of set_fs() I think it's worth it. However...

I think there are some things to check - what value do you end up
with as the first number in /proc/self/syscall when you do:

strace cat /proc/self/syscall


It should be 3, not 0x900003. I suspect you're getting the latter
with these changes. IIRC, task_thread_info(task)->syscall needs to
be the value _without_ the offset, otherwise tracing will break.

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