[Pkg-bluetooth-maintainers] Bug#856487: libsbc1: compiling with gcc > 4.9 causes stack corruption

[Niels Thykier]

On Mon, 17 Apr 2017 17:02:32 +0100 Paul Brook <paul at nowt.org> wrote:
> Package: libsbc1
> Version: 1.3-1+b2
> Followup-For: Bug #856487
> 
> Not a stack corruption.
> 
> This is miscompilation of sbc_analyze_4b_8s_armv6.  gcc appears to look
> into the asm function and decides that it does not clobber r3 (which the
> normal ARM ABI says is call clobbered).  The last out += out_stride ends
> up incrementing the pointer by an arbitrary amount.
> 

Hi Paul,

Many thanks for finding the bug and the solution to it.

> The attached patch works around the bug.
> 

@Bluetooth maintainers: Could you please apply the patch below for stretch?

> I'm not entirely sure whether this is a gcc bug or not, but at best it's
> surprising behavior from gcc.  I've attached a reduced testcase for the toolchain
> folks to argue over (compile with gcc -O2, tested with gcc 6.3.0-2 from
> sid).
> 
> Paul
> 

@ARM porters: I will let you be the judge of this and forward it to GCC
as necessary.  (The test case is available from:
https://bugs.debian.org/cgi-bin/bugreport.cgi?att=1;bug=856487;filename=gcc-naked-bug.c;msg=130)

Thanks,
~Niels


> diff -ur clean/sbc/sbc_primitives_armv6.c sbc-1.3/sbc/sbc_primitives_armv6.c
> --- clean/sbc/sbc_primitives_armv6.c	2013-04-30 17:19:23.000000000 +0100
> +++ sbc-1.3/sbc/sbc_primitives_armv6.c	2017-04-17 16:43:49.918809345 +0100
> @@ -102,6 +102,7 @@
>  		"pop    {r8-r11}\n"
>  		"stmia  r1, {r4, r5, r6, r7}\n"
>  		"pop    {r1, r4-r7, pc}\n"
> +        :::"r0", "r2", "r3", "ip"
>  	);
>  }
>  
> @@ -258,6 +259,7 @@
>  		"pop    {r8-r11}\n"
>  		"stmia  r1!, {r4, r5, r6, r7}\n"
>  		"pop    {r1, r4-r7, pc}\n"
> +        :::"r0", "r2", "r3", "ip"
>  	);
>  }
>