delocate: use 64-bit GOT offsets in the large memory model.

I tried to save space and use 32-bit GOT offsets since a GOT > 2GiB is
crazy. However, Clang's linker emits 64-bit relocations even for .long,
thus the four bytes following each offset get stomped. It mostly works
because the relocations are applied in order, thus the following
relocation gets stomped but is then processed and fixed. But there's
four bytes of stomp at the end which hits the module integrity hash,
which is fatal.

This could be fixed by adding four bytes of padding after the list of
offsets, but that's piling a hack on a hack. So this change just
switches to 64-bit offsets.

Change-Id: I227eec67c481d93a414fbed19aa99471f9df0f0e
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/42484
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: David Benjamin <davidben@google.com>

util/fipstools/delocate/delocate.go

@@ -1271,12 +1271,10 @@ Args:
 			changed = true
 
 			wrappers = append(wrappers, func(k func()) {
-				// While the compiler output supports 64-bit offsets in the GOT,
-				// https://refspecs.linuxbase.org/elf/x86_64-abi-0.98.pdf page 70, footnote
-				// 3 says that the GOT is limited to 32 bits. It's not clear about
-				// signed/unsigned but a GOT with more than 2^31 entries seems implausible
-				// so we save the extra space.
-				d.output.WriteString(fmt.Sprintf("\tmovsl .Lboringssl_%s_%s(%%rip), %s\n", prefix, symbol, targetReg))
+				// Even if one tries to use 32-bit GOT offsets, Clang's linker (at the time
+				// of writing) emits 64-bit relocations anyway, so the following four bytes
+				// get stomped. Thus we use 64-bit offsets.
+				d.output.WriteString(fmt.Sprintf("\tmovq .Lboringssl_%s_%s(%%rip), %s\n", prefix, symbol, targetReg))
 			})
 
 		default:
@@ -1573,11 +1571,11 @@ func transform(w stringWriter, inputs []inputFile) error {
 
 		for _, name := range sortedSet(d.gotOffsetsNeeded) {
 			w.WriteString(".Lboringssl_got_" + name + ":\n")
-			w.WriteString("\t.long " + name + "@GOT\n")
+			w.WriteString("\t.quad " + name + "@GOT\n")
 		}
 		for _, name := range sortedSet(d.gotOffOffsetsNeeded) {
 			w.WriteString(".Lboringssl_gotoff_" + name + ":\n")
-			w.WriteString("\t.long " + name + "@GOTOFF\n")
+			w.WriteString("\t.quad " + name + "@GOTOFF\n")
 		}
 	}
 

util/fipstools/delocate/testdata/x86_64-LargeMemory/out.s

@@ -13,7 +13,7 @@ BORINGSSL_bcm_text_start:
 	addq $.Lboringssl_got_delta-.L0, %rcx
         addq    %rax, %rcx
 # WAS movabsq $_Z1gv@GOTOFF, %rax
-	movsl .Lboringssl_gotoff__Z1gv(%rip), %rax
+	movq .Lboringssl_gotoff__Z1gv(%rip), %rax
         addq    %rcx, %rax
         jmpq    *%rax
 
@@ -27,7 +27,7 @@ BORINGSSL_bcm_text_start:
 	addq $.Lboringssl_got_delta-.L0$pb, %rcx
         addq    %rax, %rcx
 # WAS movabsq $h@GOT, %rax
-	movsl .Lboringssl_got_h(%rip), %rax
+	movq .Lboringssl_got_h(%rip), %rax
         movq    (%rcx,%rax), %rax
         movl    (%rax), %eax
         retq
@@ -55,9 +55,9 @@ OPENSSL_ia32cap_addr_delta:
 .Lboringssl_got_delta:
 	.quad _GLOBAL_OFFSET_TABLE_-.Lboringssl_got_delta
 .Lboringssl_got_h:
-	.long h@GOT
+	.quad h@GOT
 .Lboringssl_gotoff__Z1gv:
-	.long _Z1gv@GOTOFF
+	.quad _Z1gv@GOTOFF
 .type BORINGSSL_bcm_text_hash, @object
 .size BORINGSSL_bcm_text_hash, 64
 BORINGSSL_bcm_text_hash: