PIC, alignment problems with libcrypt on armv7

[Jussi Kivilinna]

Hello,

On 2016-06-29 20:44, Michael Plass wrote:
> I recently tracked down a couple of problems with libcrypt-1.7.1 in the
> context of netbsd pkgsrc on raspberry pi 2 (armv7).

Thanks for tracking and reporting these.

> 
> The details are covered in this thread:
> 
> http://mail-index.netbsd.org/tech-pkg/2016/06/29/msg017059.html
> 
> The first problem is a non-PIC reference in cipher/poly1305-armv7-neon.S
> that prevents the library from being loaded when using ASLR:

Looks correct. I need to review other armv7 assembly for similar errors.

I wonder if there is automated way to check resulting library for such
non-PIC references. If there is, such check could be incorporated to
build process and abort build if found.

> 
> ==============================
> commit 9bf37f803059304b1f46747953ef8e961c7e643b
> Author: Michael Plass <mfpnb at plass-family.net>
> Date:   Wed Jun 29 10:15:16 2016 -0700
> 
>     Remove a non-PIC reference in armv7 poly1305.
> 
> diff --git a/cipher/poly1305-armv7-neon.S b/cipher/poly1305-armv7-neon.S
> index 1134e85..e2727bd 100644
> --- a/cipher/poly1305-armv7-neon.S
> +++ b/cipher/poly1305-armv7-neon.S
> @@ -52,7 +52,7 @@ _gcry_poly1305_armv7_neon_init_ext:
>         and r2, r2, r2
>         moveq r14, #-1
>         ldmia r1!, {r2-r5}
> -       ldr r7, =.Lpoly1305_init_constants_neon
> +       adr r7, .Lpoly1305_init_constants_neon
>         mov r6, r2
>         mov r8, r2, lsr #26
>         mov r9, r3, lsr #20
> ==============================
> 
> The second problem showed up as a bus error running tests/basic.
> The problem is that ldm/stm don't deal with unaligned accesses even
> on armv7 (see http://www.heyrick.co.uk/armwiki/Unaligned_data_access).
> My workaround is to undef the gcc-defined feature symbol, but a better
> fix would be to strip out the conditional guards, since the alignment
> adjustments are needed on all versions.

I have made wrong assumption about unaligned accesses with ldm/stm.
I'll make the needed changes and add proper unaligned buffer test cases
so that these will be caught in future.

-Jussi

> ==============================
> commit 68c3274900ea129099f04892d32ccbb061ff6a72
> Author: Michael Plass <mfpnb at plass-family.net>
> Date:   Wed Jun 29 10:27:55 2016 -0700
> 
>     Avoid doing unaligned ldm/stm even on armv7 - it does not work.
> 
> diff --git a/cipher/rijndael-arm.S b/cipher/rijndael-arm.S
> index 694369d..34a9acc 100644
> --- a/cipher/rijndael-arm.S
> +++ b/cipher/rijndael-arm.S
> @@ -19,6 +19,7 @@
>   */
>  
>  #include <config.h>
> +#undef __ARM_FEATURE_UNALIGNED
>  
>  #if defined(__ARMEL__)
>  #ifdef HAVE_COMPATIBLE_GCC_ARM_PLATFORM_AS
> ==============================
> 
> 
> 
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