I did some reading into the sources in other architectures. The closest match, arch_i386.c, makes the write conditional as you say. So do other arches, including arch_arm.c, arch_sh.c, arch-mips.c, arch-s390.c, arch-s390x.c, and arch-ia64.c.
Notably, arch-cris.c has the same assert as arch-x86_64.c instead of the conditional. The code roughly looks like follows: 1. Check for dso->info[DT_PLTGOT]. If it does not exist, return 0 2. Call addr_to_sec on dso->info[DT_PLTGOT], return 1 if error 3. Look for the section named ".plt" in the ELF. 4. If the section cannot be found, return 0 5. Otherwise, write the address of .plt + constant (dependent on arch) to got[1] In arch-x86_64.c and arch-cris.c, step (4) above is an assert: 1. Check for dso->info[DT_PLTGOT]. If it does not exist, return 0 2. Call addr_to_sec on dso->info[DT_PLTGOT], return 1 if error 3. Look for the section named ".plt" in the ELF. 4. Assert that the section was found 5. Write the address of .plt + constant (dependent on arch) to got[1] I tested out making the assert conditional and nothing seemed to break at least. On Fri, May 24, 2019 at 12:08 AM Khem Raj <raj.k...@gmail.com> wrote: > > > On 5/23/19 7:53 PM, Shane Peelar wrote: > > Any of them on the system pretty much, and yes they are also built with > > -fno-plt. > > OK, I think its better to them conditionally check for .plt section, > can you describe more of whats going on when sections are checked. > > > > > On Thu, May 23, 2019 at 9:59 PM Khem Raj <raj.k...@gmail.com > > <mailto:raj.k...@gmail.com>> wrote: > > > > > > > > On 5/23/19 8:05 AM, Shane Peelar wrote: > > > Hi Everyone @ the Yocto project, > > > > > > I'm Shane Peelar, a PhD Candidate at the University of Windsor. > > > I'm writing to you about prelink-cross, as part of the Yocto > project. > > > Specifically, I'm looking at using it with executables built using > > > `-fno-plt` under GCC. > > > I wasn't quite sure where to send this email to, so I figured I'd > > try > > > here. If there's a better place to send this, please let me know. > > > > > > Right now, prelink-cross seems to fail an assertion in > > arch-x86_64.c, > > > line 421, when > > > using it with an executable built with `-fno-plt`: > > > > > > ... > > > assert (i < dso->ehdr.e_shnum) > > > ... > > > > > > This snippet seems to be looking for the ".plt" section and, > > since it > > > can't find it, the assertion fires. This makes sense because in > > > `-fno-plt` executables, the `.plt` section is missing entirely. > > > I'm not an expert on ELF stuff, although I am learning quickly. > It > > > looks like > > > this code wants to write into GOT[1] the address of ".plt" + 0x16 > -- > > > since ".plt" doesn't > > > exist, does it make sense to just change this assert to an if > > statement > > > like so: > > > > > > ... > > > if (i < dso->ehdr.e_shnum) > > > { ... } > > > ... > > > > > > and skip over that part? Or is this a real error condition for > > > prelink-cross and it really should not continue? The executable > in > > > question is also non-PIE, if that makes a difference. > > > > > > > what shared libs is this linking to ? are they also built with > > -fno-plt ? > > > > > Thanks for your time, > > > Shane > > > > > >
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