cmd/link: don't count tbss section in TestFlagD

TestFlagD looks for a data-like section at the lowest address.
On OpenBSD, the .tbss section matches the current condition, which
has address 0, causing the test fail. Don't count TLS sections.

Also, print the section name on error.

Fixes golang#75444.

Change-Id: Ic0aa1a2bb7c6bd5c0023d4482405a482095ff68b
Reviewed-on: https://go-review.googlesource.com/c/go/+/703375
Reviewed-by: Michael Pratt <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>

Author: cherrymui

src/cmd/link/elf_test.go

@@ -627,30 +627,30 @@ func testFlagD(t *testing.T, dataAddr string, roundQuantum string, expectedAddr
 	defer ef.Close()
 
 	// Find the first data-related section to verify segment placement
-	var firstDataSectionAddr uint64
-	var found bool = false
+	var firstDataSection *elf.Section
 	for _, sec := range ef.Sections {
 		if sec.Type == elf.SHT_PROGBITS || sec.Type == elf.SHT_NOBITS {
 			// These sections are writable, allocated at runtime, but not executable
+			// nor TLS.
 			isWrite := sec.Flags&elf.SHF_WRITE != 0
 			isExec := sec.Flags&elf.SHF_EXECINSTR != 0
 			isAlloc := sec.Flags&elf.SHF_ALLOC != 0
+			isTLS := sec.Flags&elf.SHF_TLS != 0
 
-			if isWrite && !isExec && isAlloc {
-				addrLower := sec.Addr < firstDataSectionAddr
-				if !found || addrLower {
-					firstDataSectionAddr = sec.Addr
-					found = true
+			if isWrite && !isExec && isAlloc && !isTLS {
+				if firstDataSection == nil || sec.Addr < firstDataSection.Addr {
+					firstDataSection = sec
 				}
 			}
 		}
 	}
 
-	if !found {
+	if firstDataSection == nil {
 		t.Fatalf("can't find any writable data sections")
 	}
-	if firstDataSectionAddr != expectedAddr {
-		t.Errorf("data section starts at 0x%x, expected 0x%x", firstDataSectionAddr, expectedAddr)
+	if firstDataSection.Addr != expectedAddr {
+		t.Errorf("data section starts at 0x%x for section %s, expected 0x%x",
+			firstDataSection.Addr, firstDataSection.Name, expectedAddr)
 	}
 }