Unbreak ptrace on x86_64

The asm code was calling __tls_get_addr in order to set errno to 0
before the system call and that was trashing registers holding the
syscall arguments. Don't bother setting errno to 0 anymore (the
in-tree users are careful to set that themselves when appropriate).
While here, declare it properly as a weak symbol. At this point we
could just drop the hand-written assembly.

Proxies-to-x86_64-dfly: Antonio Huete Jimenez, Jan Lentfer
Dragonfly-bug: http://bugs.dragonflybsd.org/issue1571

diff --git a/lib/libc/x86_64/sys/ptrace.S b/lib/libc/x86_64/sys/ptrace.S
index 5246112..4c92b35 100644 (file)
--- a/lib/libc/x86_64/sys/ptrace.S
+++ b/lib/libc/x86_64/sys/ptrace.S
@@ -40,34 +40,20 @@
 #include <machine/asm.h>
 #include "SYS.h"
 
-ENTRY(ptrace)
-#ifdef PIC
-#  ifdef __thread
-       movq    PIC_GOT(CNAME(errno)),%rax
-#  else
-       pushq   %rdi
-       leaq    errno@TLSGD(%rip),%rdi
-       call    __tls_get_addr@PLT
-       popq    %rdi
-#  endif
-#else
-#  ifdef __thread
-       leaq    CNAME(errno)(%rip),%rax
-#  else
-       movq    errno@GOTTPOFF(%rip),%rax
-       addq    %fs:0,%rax
-#  endif
-#endif
-       movl    $0,(%rax)
-       mov     $SYS_ptrace,%eax
+       .weak   _ptrace
+       .set    _ptrace,__sys_ptrace
+       .weak   ptrace
+       .set    ptrace,__sys_ptrace
+ENTRY(__sys_ptrace)
+       mov     $SYS_ptrace,%rax
        KERNCALL
-       jb      err
-       ret
-err:
+       jb      1f
+       retq
+1:
 #ifdef PIC
        movq    PIC_GOT(HIDENAME(cerror)),%rdx
        jmp     *%rdx
 #else
        jmp     HIDENAME(cerror)
 #endif
-END(ptrace)
+END(__sys_ptrace)