Re: powerpc: step-jump-cont failure (Was: [PATCH] utrace: don't set ->ops = utrace_detached_ops lockless)

[Oleg Nesterov]

On 12/07, Jan Kratochvil wrote:
>
> On Mon, 07 Dec 2009 15:24:51 +0100, Oleg Nesterov wrote:
> > But. &raise_sigusr2 is not equal to the "actual" address of 
> > &raise_sigusr2(),
> > this value points to the "thunk" (I do not know the correct English term)
>
> ppc64 calls it "function descriptor" (GDB
> ppc64_linux_convert_from_func_ptr_addr):
>    For PPC64, a function descriptor is a TOC entry,

Thanks Jan.

> in a data section,

Yes!

Now I can't understand how this test-case could ever work on ppc.
step-jump-cont does:

        regs->nip = raise_sigusr2;      <--- points to data section
        ptrace(PTRACE_CONT);

of course, the tracee gets SIGSEGV, this section is not executable.

Oleg.