musl-1.1.22 -static segfaults in __init_tls

musl-1.1.22 -static segfaults in __init_tls

[Sami Farin]

Fedora 29 Linux, gcc-8.3.1-2.fc29, x86_64 kernel 4.19.33.

$ cat musl_crash.c; musl-gcc musl_crash.c -static; ./a.out
int main(int argc, char* argv[]) {
    return 0;
}

Segmentation fault
$ gcc -static musl_crash.c; ./a.out
$

Program received signal SIGSEGV, Segmentation fault.
0x000000000040145c in __init_tls ()
(gdb) d32
Dump of assembler code from 0x40143c to 0x40147c:
   0x000000000040143c <__init_tls+12>:	xor    %ecx,%ecx
   0x000000000040143e <__init_tls+14>:	push   %rbp
   0x000000000040143f <__init_tls+15>:	xor    %edx,%edx
   0x0000000000401441 <__init_tls+17>:	mov    $0x800000,%ebp
   0x0000000000401446 <__init_tls+22>:	push   %rbx
   0x0000000000401447 <__init_tls+23>:	mov    0x18(%rdi),%r11
   0x000000000040144b <__init_tls+27>:	mov    $0x0,%ebx
   0x0000000000401450 <__init_tls+32>:	mov    0x28(%rdi),%r9
   0x0000000000401454 <__init_tls+36>:	mov    %r11,%rax
   0x0000000000401457 <__init_tls+39>:	test   %r9,%r9
   0x000000000040145a <__init_tls+42>:	je     0x4014b3 <__init_tls+131>
=> 0x000000000040145c <__init_tls+44>:	mov    (%rax),%esi
   0x000000000040145e <__init_tls+46>:	cmp    $0x6,%esi
   0x0000000000401461 <__init_tls+49>:	jne    0x401468 <__init_tls+56>
   0x0000000000401463 <__init_tls+51>:	mov    %r11,%rcx
   0x0000000000401466 <__init_tls+54>:	jmp    0x401475 <__init_tls+69>
   0x0000000000401468 <__init_tls+56>:	cmp    $0x2,%esi
   0x000000000040146b <__init_tls+59>:	jne    0x40147b <__init_tls+75>
   0x000000000040146d <__init_tls+61>:	test   %rbx,%rbx
   0x0000000000401470 <__init_tls+64>:	je     0x4014aa <__init_tls+122>
   0x0000000000401472 <__init_tls+66>:	mov    %rbx,%rcx
   0x0000000000401475 <__init_tls+69>:	sub    0x10(%rax),%rcx
   0x0000000000401479 <__init_tls+73>:	jmp    0x4014aa <__init_tls+122>
   0x000000000040147b <__init_tls+75>:	cmp    $0x7,%esi
End of assembler dump.
(gdb) p $rax
$1 = 4194368


-- 

Re: musl-1.1.22 -static segfaults in __init_tls

[Szabolcs Nagy]

* Sami Farin <hvtaifwkbgefbaei@gmail.com> [2019-04-15 12:59:17 +0200]:
> Fedora 29 Linux, gcc-8.3.1-2.fc29, x86_64 kernel 4.19.33.
> 
> $ cat musl_crash.c; musl-gcc musl_crash.c -static; ./a.out
> int main(int argc, char* argv[]) {
>     return 0;
> }
> 
> Segmentation fault

this is likely a broken binutils

if the ldflag

  -Wl,--build-id

or

  -Wl,-z,noseparate-code

fixes it then it's

https://sourceware.org/bugzilla/show_bug.cgi?id=23428

report it to fedora as it affects anything static linked.
(even with glibc if all non-executable load sections are
turned off such as the note section for build-id)

Re: musl-1.1.22 -static segfaults in __init_tls

[Sami Farin]

On Mon, Apr 15, 2019 at 15:07:37 +0200, Szabolcs Nagy wrote:
> * Sami Farin <hvtaifwkbgefbaei@gmail.com> [2019-04-15 12:59:17 +0200]:
> > Fedora 29 Linux, gcc-8.3.1-2.fc29, x86_64 kernel 4.19.33.
> > 
> > $ cat musl_crash.c; musl-gcc musl_crash.c -static; ./a.out
> > int main(int argc, char* argv[]) {
> >     return 0;
> > }
> > 
> > Segmentation fault
> 
> this is likely a broken binutils
> 
> if the ldflag
> 
>   -Wl,--build-id
> 
> or
> 
>   -Wl,-z,noseparate-code
> 
> fixes it then it's
> 
> https://sourceware.org/bugzilla/show_bug.cgi?id=23428
> 
> report it to fedora as it affects anything static linked.
> (even with glibc if all non-executable load sections are
> turned off such as the note section for build-id)

Thanks.  Both of those options you suggested generated a non-segfaulting
binary with buggy Fedora binutils.  

I applied these commits and musl-gcc generates working binaries (without
needing to pass those ldflags):
6737a6b34f4823deb7142f27b4074831a37ac1e1
d55c3e36094f06bb1fb02f5eac19fdccf1d91f7e
28a27bdbb9500797e6767f80c8128b09112aeed5
d97f1f87b31901ccdb711ec88a0ab792c31d1f60

But I'll just wait till binutils-2.31.2 is released later this year,
Fedora probably doesn't bother cherry-picking...

Make check produces now
# of expected passes		2257
# of unexpected failures	28
# of expected failures		57
# of untested testcases		6
# of unsupported tests		16

which I hope is better than Fedora 29 2.31.1-25:
# of unexpected failures	39

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