Re: Need help with assembly code

[Samuel Thibault]

Hello,

Svante Signell, le lun. 29 nov. 2021 18:40:48 +0100, a ecrit:
> I've been working lately with on how to port valgrind to GNU/Hurd, and found 
> out
> that this is not a trivial task.

It is indeed very far from a trivial task. I'd rather recommend to port
gcc's lsan support, it will be most probably much easier to port.

> Seems like one have to make a suitable mix of linux and darwin code
> (and to some extent freebsd/solaris code).

Also it'd need a fair amount of code to reimplement the basic posixish
needs of valgrind in terms of the Hurd RPCs.

> .macro DO_SYSCALL
>         /* establish stack frame */
>         push    %ebp
>         mov     %esp, %ebp
>         subl    $$8, %esp       /* 16-byte align stack */
>         
> L_$0_1: /* Even though we can't take a signal until the
>            __pthread_sigmask completes, start the range early.
>            If eip is in the range [1,2), the syscall hasn't been started yet 
> */
> 
>         /* Set the signal mask which should be current during the syscall. */
>         /* Set up for __pthread_sigmask(SIG_SETMASK, sysmask, postmask) */
>         pushl   20(%ebp)
>         pushl   16(%ebp)
>         pushl   $$VKI_SIG_SETMASK
>         pushl   $$0xcafebabe    /* totally fake return address */
>         movl    $$__NR___pthread_sigmask, %eax
>         int     $$0x80  /* should be sysenter? */
>         jc      L_$0_7  /* __pthread_sigmask failed */
>         addl    $$16,%esp

Mach doesn't use int 0x80 but an lcall. See for instance
glibc/sysdeps/mach/i386/syscall.S

Samuel