Patch is attached. Thank you!
On Sat, May 25, 2019 at 2:30 AM Khem Raj <raj.k...@gmail.com> wrote:
> On Fri, May 24, 2019 at 6:58 PM Shane Peelar <lookatyouhac...@gmail.com>
> wrote:
> >
> > Great! Would you be willing to accept a patch that makes arch-x86_64.c
> handle that condition like the other arches?
> >
>
> yes certainly.
>
> > -Shane
> >
> > On Fri, May 24, 2019 at 12:27 PM Khem Raj <raj.k...@gmail.com> wrote:
> >>
> >>
> >>
> >> On 5/24/19 8:10 AM, Shane Peelar wrote:
> >> > 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.
> >> > |||||||
> >> > |||||||
> >>
> >> It seems ok to me.
> >>
> >> >
> >> > On Fri, May 24, 2019 at 12:08 AM Khem Raj <raj.k...@gmail.com
> >> > <mailto: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>
> >> > > <mailto: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
> >> > > >
> >> > >
> >> >
>
From 2cc1d58caaba994855516b50d5af057854c94fe8 Mon Sep 17 00:00:00 2001
From: Shane Peelar <lookatyouhac...@gmail.com>
Date: Sat, 25 May 2019 08:45:45 -0400
Subject: [PATCH] arch-x86_64.c: Make assert conditional
Make the assert in arch_prelink a condition instead of an assert,
keeping things consistent with the other arches. This makes
prelink not bail out on `-fno-plt` executables.
Signed-off-by: Shane Peelar <lookatyouhac...@gmail.com>
---
src/arch-x86_64.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/src/arch-x86_64.c b/src/arch-x86_64.c
index 2f6c551..aa739e6 100644
--- a/src/arch-x86_64.c
+++ b/src/arch-x86_64.c
@@ -418,7 +418,8 @@ x86_64_arch_prelink (struct prelink_info *info)
".plt"))
break;
- assert (i < dso->ehdr.e_shnum);
+ if (i == dso->ehdr.e_shnum)
+ return 0;
data = dso->shdr[i].sh_addr + 0x16;
write_le64 (dso, dso->info[DT_PLTGOT] + 8, data);
}
--
2.21.0
--
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