Re: [musl] [PATCH] dl_iterate_phdr: return empty string for the name of the main program

[Rich Felker <dalias@libc.org>]

On Mon, Apr 11, 2022 at 08:24:21AM -0400, Jeffrey Walton wrote:
> On Mon, Apr 4, 2022 at 11:57 PM Michael Forney <mforney@mforney.org> wrote:
> >
> > On 2022-04-04, Colin Cross <ccross@google.com> wrote:
> > > The glibc man page for dl_iterate_phdr states:
> > > The first object visited by callback is the main program.   For  the  main
> > > program,  the
> > > dlpi_name field will be an empty string.
> > >
> > > This is relied upon by the LLVM ASAN runtime:
> > > https://github.com/llvm/llvm-project/blob/72ec2f76396fe5de5397bfb898993fdb22e2b0da/compiler-rt/lib/asan/asan_linux.cpp#L135
> > >
> > > Without this patch, running a binary that has been instrumented with
> > > ASAN fails with:
> > > ==4156919==ASan runtime does not come first in initial library list; you
> > > should either link runtime to your application or manually preload it with
> > > LD_PRELOAD.
> > >
> > > Use a constant empty string instead of the DSO name field for the first
> > > entry in the DSO list.
> >
> > I believe glibc is the exception here, not musl. When I looked at
> > this, every other operating system I tried used the program name for
> > the first object.
> 
> I may be splitting hairs, but the dl_iterate_phdr(3) man page does not
> say a program is returned during the enumeration. It says shared
> objects are returned.

You are. The intent, actual practice -- and absolute necessity for
this function to serve its purpose, which includes admiting the
implementation of exception handling -- is that it be included. And in
this context, the (dynamic linked) program *is* a shared object.

Rich