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From: Andrew Turner <andrew@FreeBSD.org>
Date: Fri, 7 Oct 2016 16:17:51 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r306812 - head/sys/boot/common
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Author: andrew
Date: Fri Oct  7 16:17:51 2016
New Revision: 306812
URL: https://svnweb.freebsd.org/changeset/base/306812

Log:
  The bootloader self relocation code was slightly wrong for the
  R_AARCH64_RELATIVE relocation found on arm64. It would try to add the
  contents of the memory location being relocated to the base address and
  the relocation addend. This worked when the contents was zero, however
  this now seems to be set to the value of the addend so we add this twice.
  Fix this by just setting the memory to the computed value.
  
  Reviewed by:	emaste
  MFC after:	1 week
  Sponsored by:	DARPA, AFRL
  Differential Revision:	https://reviews.freebsd.org/D8177

Modified:
  head/sys/boot/common/self_reloc.c

Modified: head/sys/boot/common/self_reloc.c
==============================================================================
--- head/sys/boot/common/self_reloc.c	Fri Oct  7 15:42:20 2016	(r306811)
+++ head/sys/boot/common/self_reloc.c	Fri Oct  7 16:17:51 2016	(r306812)
@@ -108,12 +108,18 @@ self_reloc(Elf_Addr baseaddr, ElfW_Dyn *
 			break;
 
 		case RELOC_TYPE_RELATIVE:
-			/* Address relative to the base address. */
 			newaddr = (Elf_Addr *)(rel->r_offset + baseaddr);
-			*newaddr += baseaddr;
-			/* Add the addend when the ABI uses them */ 
 #ifdef ELF_RELA
-			*newaddr += rel->r_addend;
+			/*
+			 * For R_AARCH64_RELATIVE we need to calculate the
+			 * delta between the address we are run from and the
+			 * address we are linked at. As the latter is 0 we
+			 * just use the address we are run from for this.
+			 */
+			*newaddr = baseaddr + rel->r_addend;
+#else
+			/* Address relative to the base address. */
+			*newaddr += baseaddr;
 #endif
 			break;
 		default: