[PATCH][Binutils][AArch64] When DF_BIND_NOW don't use TLSDESC GOT value.

[Tamar Christina]

Hi All,

When using DF_BIND_NOW on AArch64 we don't reserve the GOT slot for a TLSDESC,
but we still emitted DT_TLSDESC_GOT and DT_TLSDESC_PLT.  This caused random
memory corruption as the "special" value of (bfd_vma)-1 would be set for
dt_tlsdesc_got.

Since we don't have a value of dt_tlsdesc_got I also don't emit DT_TLSDESC_PLT
now becuase it would point to an incomplete PLT. To be able to write the PLT
entry DT_TLSDESC_GOT is needed and since we don't have one we can't write the
PLT entry either.

It is my understanding that GLIBC doesn't need these two entries when not lazy
loading.  Conversely AArch32 does not reserve neither the GOT not the PLT slot
when doing DF_BIND_NOW.

AArch32 does not need these checks because these values are initialized to 0
and so the if (...) checks don't pass, but on AArch64 these are initialized
to (bfd_vma)-1 and thus we need some extra checks.

build on native hardware and regtested on
  aarch64-none-elf, aarch64-none-elf (32 bit host),
  aarch64-none-linux-gnu, aarch64-none-linux-gnu (32 bit host)

Cross-compiled and regtested on
  aarch64-none-linux-gnu, aarch64_be-none-linux-gnu

and no issues, also fixes 3 other linker testcases.

Ok for master? and for backport to binutils-2.32?

Thanks,
Tamar

bfd/ChangeLog:

2019-04-01  Tamar Christina  <tamar.christina@arm.com>

	PR ld/24302
	* elfnn-aarch64.c (elfNN_aarch64_size_dynamic_sections): Don't emit
	DT_TLSDESC_GOT and DT_TLSDESC_PLT when DF_BIND_NOW.
	(elfNN_aarch64_finish_dynamic_sections): Don't write PLT if DF_BIND_NOW.

ld/ChangeLog:

2019-04-01  Tamar Christina  <tamar.christina@arm.com>

	PR ld/24302
	* testsuite/ld-aarch64/aarch64-elf.exp: Add new test.
	* testsuite/ld-aarch64/tls-relax-gdesc-le-now.d: New test.


The 03/29/2019 19:16, Tamar Christina wrote:
> Hi All,
> 
> I will post a slight modification on Monday after all checks finish for an small thing I noticed after sending this out.
> 
> Please hold on review until then.
> 
> Thanks,
> Tamar
> 
> > -----Original Message-----
> > From: binutils-owner@sourceware.org <binutils-owner@sourceware.org>
> > On Behalf Of Tamar Christina
> > Sent: Friday, March 29, 2019 18:58
> > To: binutils@sourceware.org
> > Cc: nd <nd@arm.com>; Richard Earnshaw <Richard.Earnshaw@arm.com>;
> > Marcus Shawcroft <Marcus.Shawcroft@arm.com>
> > Subject: [PATCH][Binutils][AArch64] When DF_BIND_NOW don't use
> > TLSDESC GOT value.
> > 
> > Hi All,
> > 
> > When using DF_BIND_NOW on AArch64 we don't reserve the GOT slot for a
> > TLSDESC, but we still emitted DT_TLSDESC_GOT and DT_TLSDESC_PLT.  This
> > caused random memory corruption as the "special" value of (bfd_vma)-1
> > would be set for dt_tlsdesc_got.
> > 
> > Since we don't have a value of dt_tlsdesc_got I also don't emit
> > DT_TLSDESC_PLT now becuase it would point to an incomplete PLT. To be
> > able to write the PLT entry DT_TLSDESC_GOT is needed and since we don't
> > have one we can't write the PLT entry either.
> > 
> > It is my understanding that GLIBC doesn't need these two entries when not
> > lazy loading.  Conversely AArch32 does not reserve neither the GOT not the
> > PLT slot when doing DF_BIND_NOW.
> > 
> > AArch32 does not need these checks because these values are initialized to 0
> > and so the if (...) checks don't pass, but on AArch64 these are initialized to
> > (bfd_vma)-1 and thus we need some extra checks.
> > 
> > build on native hardware and regtested on
> >   aarch64-none-elf, aarch64-none-elf (32 bit host),
> >   aarch64-none-linux-gnu, aarch64-none-linux-gnu (32 bit host)
> > 
> > Cross-compiled and regtested on
> >   aarch64-none-linux-gnu, aarch64_be-none-linux-gnu
> > 
> > and no issues, also fixes 3 other linker testcases.
> > 
> > Ok for master? and for backport to binutils-2.32?
> > 
> > Thanks,
> > Tamar
> > 
> > bfd/ChangeLog:
> > 
> > 2019-03-29  Tamar Christina  <tamar.christina@arm.com>
> > 
> > 	PR ld/24302
> > 	* elfnn-aarch64.c (elfNN_aarch64_size_dynamic_sections): Don't
> > emit
> > 	DT_TLSDESC_GOT and DT_TLSDESC_PLT when DF_BIND_NOW.
> > 	(elfNN_aarch64_finish_dynamic_sections): Don't write PLT if
> > DF_BIND_NOW.
> > 
> > ld/ChangeLog:
> > 
> > 2019-03-29  Tamar Christina  <tamar.christina@arm.com>
> > 
> > 	PR ld/24302
> > 	* testsuite/ld-aarch64/aarch64-elf.exp: Add new test.
> > 	* testsuite/ld-aarch64/tls-relax-gdesc-le-now.d: New test.
> > 
> > --

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