PR ld/22966: Fix n64 MIPS `.got.plt' range checks

The addressable signed 32-bit range for n64 MIPS `.got.plt' references
is from 0xffffffff7fff8000 to 0x7fff7fff, due to how the composition of
an LUI and an LD instruction works for address calculation in the 64-bit
addressing mode, such as when CP0.Status.UX=1.

We currently have a range check in `mips_finish_exec_plt', however it is
not correct as it verifies that the `.got.plt' start address referred is
between 0xffffffff80000000 and 0x7fffffff.  It is also implemented as an
assertion rather than a proper error message despite that the situation
can be triggered by user input.  Additionally there is no check made for
individual `.got.plt' entries referred even though they can be out of
range while the `.got.plt' start address is not.

Fix all these problems and use the correct range for the check, limiting
it to n64 output files, and then issue a proper error message both in
`mips_finish_exec_plt' and in `_bfd_mips_elf_finish_dynamic_symbol',
suggesting the use of the `-Ttext-segment=...' option that will often
work and with the default linker scripts in particular.  Add suitable
tests covering boundary cases.

	bfd/
	PR ld/22966
	* elfxx-mips.c (_bfd_mips_elf_finish_dynamic_symbol): Verify the
	`.got.plt' entry referred is in range.
	(mips_finish_exec_plt): Correct the range check for `.got.plt'
	start.  Replace the assertion used for that with a proper error
	message.

	ld/
	PR ld/22966
	* testsuite/ld-mips-elf/n64-plt-1.dd: New test.
	* testsuite/ld-mips-elf/n64-plt-1.gd: New test.
	* testsuite/ld-mips-elf/n64-plt-2.ed: New test.
	* testsuite/ld-mips-elf/n64-plt-3.ed: New test.
	* testsuite/ld-mips-elf/n64-plt-4.dd: New test.
	* testsuite/ld-mips-elf/n64-plt-4.gd: New test.
	* testsuite/ld-mips-elf/n64-plt-1.ld: New test linker script.
	* testsuite/ld-mips-elf/n64-plt-2.ld: New test linker script.
	* testsuite/ld-mips-elf/n64-plt-3.ld: New test linker script.
	* testsuite/ld-mips-elf/n64-plt-4.ld: New test linker script.
	* testsuite/ld-mips-elf/n64-plt.s: New test source.
	* testsuite/ld-mips-elf/n64-plt-lib.s: New test source.
	* testsuite/ld-mips-elf/mips-elf.exp: Run the new tests.

2 files changed, 38 insertions, 2 deletions

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index b812fdc..d12dc99 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,5 +1,14 @@
 2018-06-19  Maciej W. Rozycki  <macro@mips.com>
 
+	PR ld/22966
+	* elfxx-mips.c (_bfd_mips_elf_finish_dynamic_symbol): Verify the
+	`.got.plt' entry referred is in range.
+	(mips_finish_exec_plt): Correct the range check for `.got.plt'
+	start.  Replace the assertion used for that with a proper error
+	message.
+
+2018-06-19  Maciej W. Rozycki  <macro@mips.com>
+
 	* elfxx-mips.c (_bfd_mips_elf_finish_dynamic_symbol): Fix
 	formatting.
 
diff --git a/bfd/elfxx-mips.c b/bfd/elfxx-mips.c
index d25f4ff..844750eb 100644
--- a/bfd/elfxx-mips.c
+++ b/bfd/elfxx-mips.c
@@ -10602,6 +10602,22 @@ _bfd_mips_elf_finish_dynamic_symbol (bfd *output_bfd,
       got_address_high = ((got_address + 0x8000) >> 16) & 0xffff;
       got_address_low = got_address & 0xffff;
 
+      /* The PLT sequence is not safe for N64 if .got.plt entry's address
+	 cannot be loaded in two instructions.  */
+      if (ABI_64_P (output_bfd)
+	  && ((got_address + 0x80008000) & ~(bfd_vma) 0xffffffff) != 0)
+	{
+	  _bfd_error_handler
+	    /* xgettext:c-format */
+	    (_("%pB: `%pA' entry VMA of %#" PRIx64 " outside the 32-bit range "
+	       "supported; consider using `-Ttext-segment=...'"),
+	     output_bfd,
+	     htab->root.sgotplt->output_section,
+	     (int64_t) got_address);
+	  bfd_set_error (bfd_error_no_error);
+	  return FALSE;
+	}
+
       /* Initially point the .got.plt entry at the PLT header.  */
       loc = (htab->root.sgotplt->contents
 	     + got_index * MIPS_ELF_GOT_SIZE (dynobj));
@@ -11246,8 +11262,19 @@ mips_finish_exec_plt (bfd *output_bfd, struct bfd_link_info *info)
 
   /* The PLT sequence is not safe for N64 if .got.plt's address can
      not be loaded in two instructions.  */
-  BFD_ASSERT ((gotplt_value & ~(bfd_vma) 0x7fffffff) == 0
-	      || ~(gotplt_value | 0x7fffffff) == 0);
+  if (ABI_64_P (output_bfd)
+      && ((gotplt_value + 0x80008000) & ~(bfd_vma) 0xffffffff) != 0)
+    {
+      _bfd_error_handler
+	/* xgettext:c-format */
+	(_("%pB: `%pA' start VMA of %#" PRIx64 " outside the 32-bit range "
+	   "supported; consider using `-Ttext-segment=...'"),
+	 output_bfd,
+	 htab->root.sgotplt->output_section,
+	 (int64_t) gotplt_value);
+      bfd_set_error (bfd_error_no_error);
+      return FALSE;
+    }
 
   /* Install the PLT header.  */
   loc = htab->root.splt->contents;