Re: [PATCH] bfd/elf-hppa.h: Cleanup constants and comments

[Nick Clifton <nickc at redhat dot com>]

Hi John, Hi Helge,

> I'm think that 4 is the correct value here, because I think I read that somewhere once.
> In that case I think "2 left-shifted by this value" should show the number of bytes per table line. 
> But looking at all other usages of sh_entsize, this seems unlikely and everything is still unclear.
> So, maybe we should simply leave the comment as is, until someone finds out?

FYI - the ELF spec says that the sh_entsize field is a byte quantity.

But I agree that it would be best to leave things as they are unless someone
can prove that a change is correct and does not break anything.  So this is
what I have checked in:

diff --git a/bfd/elf-hppa.h b/bfd/elf-hppa.h
index 9f34a030cc..3b72140e5f 100644
--- a/bfd/elf-hppa.h
+++ b/bfd/elf-hppa.h
@@ -889,9 +889,11 @@ elf_hppa_fake_sections (bfd *abfd, Elf_Internal_Shdr *hdr, asection *sec)
       asection *asec;
 
 #if ARCH_SIZE == 64
-      hdr->sh_type = SHT_LOPROC + 1;
+      hdr->sh_type = SHT_PARISC_UNWIND;
 #else
-      hdr->sh_type = 1;
+      /* Note - it is not clear why this is not SHT_PARISC_UNWIND as well.
+	 Presumably it is a historical constraint, so leave it as it is.  */
+      hdr->sh_type = SHT_PROGBITS;
 #endif
       /* ?!? How are unwinds supposed to work for symbols in arbitrary
 	 sections?  Or what if we have multiple .text sections in a single
@@ -912,7 +914,10 @@ elf_hppa_fake_sections (bfd *abfd, Elf_Internal_Shdr *hdr, asection *sec)
 	    }
 	}
 
-      /* I have no idea if this is really necessary or what it means.  */
+      /* The unwind table entries are 16 bytes long, so it is not clear
+	 why this field is set to 4.  (The ELF spec says that the sh_entsize
+	 field is a byte quantity, but this is a processor specific section,
+	 so it is allowed to change the rules).  Leave as it is for now.  */
       hdr->sh_entsize = 4;
     }
   return TRUE;

Cheers
  Nick

bfd/ChangeLog
2018-08-22  Helge Deller  <deller@gmx.de>
	Nick Clifton  <nickc@redhat.com>

	* elf-hppa.h (elf_hppa_fake_sections): Use SHT_PARISC_UNWIND as
	the section type of the .PARISC.unwind section on 64-bit binaries
	and SHT_PROGBITS for 32-bit binaries.  Add a comment about it.
	Add comment about the sh_entsize value.