Re: Problem with libpthread of uClibc

[Ian Lance Taylor <iant at google dot com>]

Nitin Garg <nitingarg98@gmail.com> writes:

> We are using ARM Cortex-A9 processor. The toolchain is gcc-4.0.0 with
> uClibc-0.9.30 and the kernel is 2.6.28.
>
> Using this toolchain when we build any application like "Hello World"
> and link it against pthread lib, the application does a segmentation
> fault when executed on target and gives "Illegal instruction" error
> message.
>
> I debugged the problem and it came out to be that "swp" instructions
> were disabled on the cortex-a9. The SWP instruction has been
> deprecated starting with the ARMv6 architecture. On newer ARMv7
> processors, this instruction is disabled by default but it can be
> enabled by bit 10 in the System Control register. We can also build
> the kernel with CONFIG_OABI_COMPAT enabled.
>
> The real problem seems to be in the linuxthreads of uClibc where "swp"
> is being used for locks.
> Shall this not be replaced with ldrex/strex for ARMv7 onwards?

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Actually I'm not sure there is any gcc issue here at all.  gcc 4.0.0 is
fairly old.

Ian