[PATCH v2] ld: warn about PE base relocations to sections above .reloc

[Jan Beulich]

Due to a bogus linker script, or perhaps because a section doesn't get
placed by a linker script while default placement puts it too high up,
sections can end up above .reloc. Since the process of determining its
contents (and hence its size) happens before final section placement,
relocations needed for such sections would no longer point at the
correct address in the final binary. Warn about this (down the road this
may want to become an error, unless size determination and content
creation for .reloc would get decoupled).

Two of the testcases would actually trigger the warning, because .reloc
gets placed at 0 without mentioning it in their linker scripts. Extend
the two scripts accordingly.

ld/
2021-03-XX  Jan Beulich  <jbeulich@suse.com>

	* pe-dll.c (generate_reloc): Warn when relocated entry is above
	.reloc.
	* testsuite/ld-scripts/pr14962.t, testsuite/ld-scripts/weak.t:
	Place .reloc section.
---
v2: Wrap string literal in _().

--- a/ld/pe-dll.c
+++ b/ld/pe-dll.c
@@ -1627,6 +1627,15 @@ generate_reloc (bfd *abfd, struct bfd_li
 		  reloc_data[total_relocs].vma = sec_vma + relocs[i]->address;
 		  reloc_data[total_relocs].idx = total_relocs;
 
+		  /* Since we're only about to determine .reloc's size,
+		     subsequent output section VMA calculations will shift up
+		     sections at this or higher addresses.  Relocations for
+		     such sections would hence end up not being correct.  */
+		  if (reloc_data[total_relocs].vma
+		      >= reloc_s->output_section->vma)
+		    einfo (_("%P: base relocation for section `%s' above "
+			     ".reloc section\n"), s->output_section->name);
+
 #define BITS_AND_SHIFT(bits, shift) (bits * 1000 | shift)
 
 		  switch BITS_AND_SHIFT (relocs[i]->howto->bitsize,
--- a/ld/testsuite/ld-scripts/pr14962.t
+++ b/ld/testsuite/ld-scripts/pr14962.t
@@ -5,5 +5,6 @@ SECTIONS
   .text : { *(.text .pr) }
   .data : { *(.data .rw) }
   .bss : { *(.bss) }
+  .reloc : { *(.reloc) }
   /DISCARD/ : { *(*) }
 }
--- a/ld/testsuite/ld-scripts/weak.t
+++ b/ld/testsuite/ld-scripts/weak.t
@@ -6,6 +6,9 @@ SECTIONS
   .data 0x2000 : {
     tmpdir/weak2.o(.data)
   }
+  .reloc : {
+     *(.reloc)
+  }
   /DISCARD/ : {
     *(*)
   }