Re: dl_iterate_phdr(3) needs clarification

[Yubin Ruan <ablacktshirt-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

Hi Florian,

On Sat, Sep 16, 2017 at 10:15:19AM +0200, Florian Weimer wrote:
> On 09/16/2017 05:00 PM, Yubin Ruan wrote:
> >diff --git a/man3/dl_iterate_phdr.3 b/man3/dl_iterate_phdr.3
> >index b5b75e8..35107da 100644
> >--- a/man3/dl_iterate_phdr.3
> >+++ b/man3/dl_iterate_phdr.3
> >@@ -121,10 +121,9 @@ header files.)
> >  .PP
> >  The
> >  .I dlpi_addr
> >-field indicates the base address of the shared object
> >-(i.e., the difference between the virtual memory address of
> >-the shared object and the offset of that object in the file
> >-from which it was loaded).
> >+field indicates the base address that is mapped at runtime.
> >+For an executable this field is always 0 and for a shared
> >+object it is the address where the shared object is mapped.
> 
> The part about executables is not true.  The most common case probably is
> PIE executables.  You see this if you compile the modified test program with
> -fpie -pie on a recent enough toolchain.

-fpie only affect address of PT_LOAD. The one inidcated by `dlpi_addr' is
always 0 for an executable. Yes there is indeed some confusion, see [1].

Yubin

[1]: https://stackoverflow.com/questions/8875876/getting-the-elf-header-of-the-main-executable
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