some question about LR of task_pt_regs

Russell King - ARM Linux linux at
Mon Oct 26 03:40:36 PDT 2015

On Mon, Oct 19, 2015 at 05:55:29PM +0800, yoma sophian wrote:
> hi all:
> I use linaro toolchain which libc is compile in thumb mode and if any
> user mode program call sleep, the lr of its task_pt_regs will be 0, no
> matter how many function level I called.

It depends on the userspace code at the time that the system call is
made.  If it's setting LR to zero, then you'll read zero.  I don't
think it has anything to do with the toolchain either.  Check the
libc code around the site for the system call.

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