[PATCH] D29586: [lsan] Enable LSan for arm Linux

[Adhemerval Zanella via Phabricator via llvm-commits]

zatrazz added a comment.

In https://reviews.llvm.org/D29586#672157, @m.ostapenko wrote:

> In https://reviews.llvm.org/D29586#668769, @m.ostapenko wrote:
>
> > In https://reviews.llvm.org/D29586#668050, @rengolin wrote:
> >
> > > You seem to be enabling it on soft and hard float. Did you test on both environments? What type of hardware did you test this?
> >
> >
> > I've tested the patch on two configurations:
> >
> > 1. Linaro Ubuntu 14.04 (Trusty) on Arndale board. It's a hard float system, right?
>
>
> Oh, things become more complicated... I see many test failures with host GCC 4.8 because fast unwinder failed to get backtraces for mallocs. This happens because **__interceptor_malloc**, compiled by GCC 4.8, didn't properly save **frame pointer register**:
>
>   00000000 <__interceptor_malloc>:
>      0:   e92d 47f0       stmdb   sp!, {r4, r5, r6, r7, r8, r9, sl, lr}
>      4:   f5ad 6d85       sub.w   sp, sp, #1064   ; 0x428
>      8:   4d29            ldr     r5, [pc, #164]  ; (b0 <__interceptor_malloc+0xb0>)
>      a:   4b2a            ldr     r3, [pc, #168]  ; (b4 <__interceptor_malloc+0xb4>)
>      c:   af04            add     r7, sp, #16
>      e:   447d            add     r5, pc
>
>
> But if compile with clang (3.3, 3.5 or trunk) or GCC 4.9, the fp is saved properly:
>
>   00000000 <__interceptor_malloc>:
>      0:   e92d4ff0        push    {r4, r5, r6, r7, r8, r9, sl, fp, lr}
>      4:   e28db01c        add     fp, sp, #28
>      8:   e24dd024        sub     sp, sp, #36     ; 0x24
>      c:   e24ddb01        sub     sp, sp, #1024   ; 0x400
>     10:   e1a08000        mov     r8, r0
>
>
> So, it seems that LSan's operability depends on what compiler is used to build it :(.


It is a know issue [1] [2] and in fact it a little more complicated, it depends on the flags used as well:
 if you mix thumb and arm code fast unwinder won't work. I am not sure which option would be better, 
but I am afraid to get a reliable stacktrack on arm (with mixed objects and function built with different compilers)
we will need to use a external unwinder (maybe libunwinder). But it will have the side-effect of making 
backtrace way slower.

[1] https://llvm.org/bugs/show_bug.cgi?id=22741
[2] https://llvm.org/bugs/show_bug.cgi?id=18505


Repository:
  rL LLVM

https://reviews.llvm.org/D29586