cmd/link: round up default start address to alignment

If the -R flag (the segment alignment) is specified but the -T
flag (start address) is not, currently the default start address
may be under-aligned, and some math in the linker may be broken.
Round up the start address to align it.

Fixes #62064.

Change-Id: I3b98c9d0cf7d3cd944b9436a36808899d2e52572
Reviewed-on: https://go-review.googlesource.com/c/go/+/527822
Run-TryBot: Cherry Mui <cherryyz@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

14 files changed, 85 insertions, 76 deletions

diff --git a/src/cmd/link/elf_test.go b/src/cmd/link/elf_test.go
index d662145847..902ce28b10 100644
--- a/src/cmd/link/elf_test.go
+++ b/src/cmd/link/elf_test.go
@@ -498,3 +498,28 @@ func TestIssue51939(t *testing.T) {
 		}
 	}
 }
+
+func TestFlagR(t *testing.T) {
+	// Test that using the -R flag to specify a (large) alignment generates
+	// a working binary.
+	// (Test only on ELF for now. The alignment allowed differs from platform
+	// to platform.)
+	testenv.MustHaveGoBuild(t)
+	t.Parallel()
+	tmpdir := t.TempDir()
+	src := filepath.Join(tmpdir, "x.go")
+	if err := os.WriteFile(src, []byte(goSource), 0444); err != nil {
+		t.Fatal(err)
+	}
+	exe := filepath.Join(tmpdir, "x.exe")
+
+	cmd := testenv.Command(t, testenv.GoToolPath(t), "build", "-ldflags=-R=0x100000", "-o", exe, src)
+	if out, err := cmd.CombinedOutput(); err != nil {
+		t.Fatalf("build failed: %v, output:\n%s", err, out)
+	}
+
+	cmd = testenv.Command(t, exe)
+	if out, err := cmd.CombinedOutput(); err != nil {
+		t.Errorf("executable failed to run: %v\n%s", err, out)
+	}
+}
diff --git a/src/cmd/link/internal/amd64/obj.go b/src/cmd/link/internal/amd64/obj.go
index b99cdbc356..3a6141b909 100644
--- a/src/cmd/link/internal/amd64/obj.go
+++ b/src/cmd/link/internal/amd64/obj.go
@@ -86,13 +86,12 @@ func archinit(ctxt *ld.Link) {
 
 	case objabi.Hplan9: /* plan 9 */
 		ld.HEADR = 32 + 8
-
-		if *ld.FlagTextAddr == -1 {
-			*ld.FlagTextAddr = 0x200000 + int64(ld.HEADR)
-		}
 		if *ld.FlagRound == -1 {
 			*ld.FlagRound = 0x200000
 		}
+		if *ld.FlagTextAddr == -1 {
+			*ld.FlagTextAddr = ld.Rnd(0x200000, *ld.FlagRound) + int64(ld.HEADR)
+		}
 
 	case objabi.Hdarwin: /* apple MACH */
 		ld.HEADR = ld.INITIAL_MACHO_HEADR
@@ -100,7 +99,7 @@ func archinit(ctxt *ld.Link) {
 			*ld.FlagRound = 4096
 		}
 		if *ld.FlagTextAddr == -1 {
-			*ld.FlagTextAddr = 0x1000000 + int64(ld.HEADR)
+			*ld.FlagTextAddr = ld.Rnd(0x1000000, *ld.FlagRound) + int64(ld.HEADR)
 		}
 
 	case objabi.Hlinux, /* elf64 executable */
@@ -112,12 +111,12 @@ func archinit(ctxt *ld.Link) {
 		ld.Elfinit(ctxt)
 
 		ld.HEADR = ld.ELFRESERVE
-		if *ld.FlagTextAddr == -1 {
-			*ld.FlagTextAddr = (1 << 22) + int64(ld.HEADR)
-		}
 		if *ld.FlagRound == -1 {
 			*ld.FlagRound = 4096
 		}
+		if *ld.FlagTextAddr == -1 {
+			*ld.FlagTextAddr = ld.Rnd(1<<22, *ld.FlagRound) + int64(ld.HEADR)
+		}
 
 	case objabi.Hwindows: /* PE executable */
 		// ld.HEADR, ld.FlagTextAddr, ld.FlagRound are set in ld.Peinit
diff --git a/src/cmd/link/internal/arm/obj.go b/src/cmd/link/internal/arm/obj.go
index 52fd5b6523..3a1830ce10 100644
--- a/src/cmd/link/internal/arm/obj.go
+++ b/src/cmd/link/internal/arm/obj.go
@@ -84,13 +84,12 @@ func archinit(ctxt *ld.Link) {
 
 	case objabi.Hplan9: /* plan 9 */
 		ld.HEADR = 32
-
-		if *ld.FlagTextAddr == -1 {
-			*ld.FlagTextAddr = 4128
-		}
 		if *ld.FlagRound == -1 {
 			*ld.FlagRound = 4096
 		}
+		if *ld.FlagTextAddr == -1 {
+			*ld.FlagTextAddr = ld.Rnd(4096, *ld.FlagRound) + int64(ld.HEADR)
+		}
 
 	case objabi.Hlinux, /* arm elf */
 		objabi.Hfreebsd,
@@ -100,12 +99,12 @@ func archinit(ctxt *ld.Link) {
 		// with dynamic linking
 		ld.Elfinit(ctxt)
 		ld.HEADR = ld.ELFRESERVE
-		if *ld.FlagTextAddr == -1 {
-			*ld.FlagTextAddr = 0x10000 + int64(ld.HEADR)
-		}
 		if *ld.FlagRound == -1 {
 			*ld.FlagRound = 0x10000
 		}
+		if *ld.FlagTextAddr == -1 {
+			*ld.FlagTextAddr = ld.Rnd(0x10000, *ld.FlagRound) + int64(ld.HEADR)
+		}
 
 	case objabi.Hwindows: /* PE executable */
 		// ld.HEADR, ld.FlagTextAddr, ld.FlagRound are set in ld.Peinit
diff --git a/src/cmd/link/internal/arm64/obj.go b/src/cmd/link/internal/arm64/obj.go
index 34b693ed6c..3d358155ba 100644
--- a/src/cmd/link/internal/arm64/obj.go
+++ b/src/cmd/link/internal/arm64/obj.go
@@ -86,13 +86,12 @@ func archinit(ctxt *ld.Link) {
 
 	case objabi.Hplan9: /* plan 9 */
 		ld.HEADR = 32
-
-		if *ld.FlagTextAddr == -1 {
-			*ld.FlagTextAddr = 4096 + int64(ld.HEADR)
-		}
 		if *ld.FlagRound == -1 {
 			*ld.FlagRound = 4096
 		}
+		if *ld.FlagTextAddr == -1 {
+			*ld.FlagTextAddr = ld.Rnd(4096, *ld.FlagRound) + int64(ld.HEADR)
+		}
 
 	case objabi.Hlinux, /* arm64 elf */
 		objabi.Hfreebsd,
@@ -100,21 +99,21 @@ func archinit(ctxt *ld.Link) {
 		objabi.Hopenbsd:
 		ld.Elfinit(ctxt)
 		ld.HEADR = ld.ELFRESERVE
-		if *ld.FlagTextAddr == -1 {
-			*ld.FlagTextAddr = 0x10000 + int64(ld.HEADR)
-		}
 		if *ld.FlagRound == -1 {
 			*ld.FlagRound = 0x10000
 		}
+		if *ld.FlagTextAddr == -1 {
+			*ld.FlagTextAddr = ld.Rnd(0x10000, *ld.FlagRound) + int64(ld.HEADR)
+		}
 
 	case objabi.Hdarwin: /* apple MACH */
 		ld.HEADR = ld.INITIAL_MACHO_HEADR
-		if *ld.FlagTextAddr == -1 {
-			*ld.FlagTextAddr = 1<<32 + int64(ld.HEADR)
-		}
 		if *ld.FlagRound == -1 {
 			*ld.FlagRound = 16384 // 16K page alignment
 		}
+		if *ld.FlagTextAddr == -1 {
+			*ld.FlagTextAddr = ld.Rnd(1<<32, *ld.FlagRound) + int64(ld.HEADR)
+		}
 
 	case objabi.Hwindows: /* PE executable */
 		// ld.HEADR, ld.FlagTextAddr, ld.FlagRound are set in ld.Peinit
diff --git a/src/cmd/link/internal/ld/main.go b/src/cmd/link/internal/ld/main.go
index aa6c00ce88..b978cfc7d4 100644
--- a/src/cmd/link/internal/ld/main.go
+++ b/src/cmd/link/internal/ld/main.go
@@ -98,7 +98,7 @@ var (
 	FlagDebugTextSize = flag.Int("debugtextsize", 0, "debug text section max size")
 	flagDebugNosplit  = flag.Bool("debugnosplit", false, "dump nosplit call graph")
 	FlagStrictDups    = flag.Int("strictdups", 0, "sanity check duplicate symbol contents during object file reading (1=warn 2=err).")
-	FlagRound         = flag.Int("R", -1, "set address rounding `quantum`")
+	FlagRound         = flag.Int64("R", -1, "set address rounding `quantum`")
 	FlagTextAddr      = flag.Int64("T", -1, "set the start address of text symbols")
 	flagEntrySymbol   = flag.String("E", "", "set `entry` symbol name")
 	flagPruneWeakMap  = flag.Bool("pruneweakmap", true, "prune weak mapinit refs")
diff --git a/src/cmd/link/internal/ld/pe.go b/src/cmd/link/internal/ld/pe.go
index 1502b3eb39..a2c5a99e8e 100644
--- a/src/cmd/link/internal/ld/pe.go
+++ b/src/cmd/link/internal/ld/pe.go
@@ -1149,11 +1149,11 @@ func Peinit(ctxt *Link) {
 	}
 
 	HEADR = PEFILEHEADR
-	if *FlagTextAddr == -1 {
-		*FlagTextAddr = PEBASE + int64(PESECTHEADR)
-	}
 	if *FlagRound == -1 {
-		*FlagRound = int(PESECTALIGN)
+		*FlagRound = PESECTALIGN
+	}
+	if *FlagTextAddr == -1 {
+		*FlagTextAddr = Rnd(PEBASE, *FlagRound) + int64(PESECTHEADR)
 	}
 }
 
diff --git a/src/cmd/link/internal/ld/xcoff.go b/src/cmd/link/internal/ld/xcoff.go
index 158a86f61d..1e4a85a12e 100644
--- a/src/cmd/link/internal/ld/xcoff.go
+++ b/src/cmd/link/internal/ld/xcoff.go
@@ -544,15 +544,14 @@ func Xcoffinit(ctxt *Link) {
 	xfile.dynLibraries = make(map[string]int)
 
 	HEADR = int32(Rnd(XCOFFHDRRESERVE, XCOFFSECTALIGN))
-	if *FlagTextAddr != -1 {
-		Errorf(nil, "-T not available on AIX")
-	}
-	*FlagTextAddr = XCOFFTEXTBASE + int64(HEADR)
 	if *FlagRound != -1 {
 		Errorf(nil, "-R not available on AIX")
 	}
-	*FlagRound = int(XCOFFSECTALIGN)
-
+	*FlagRound = XCOFFSECTALIGN
+	if *FlagTextAddr != -1 {
+		Errorf(nil, "-T not available on AIX")
+	}
+	*FlagTextAddr = Rnd(XCOFFTEXTBASE, *FlagRound) + int64(HEADR)
 }
 
 // SYMBOL TABLE
diff --git a/src/cmd/link/internal/loong64/obj.go b/src/cmd/link/internal/loong64/obj.go
index fd193a2445..b68ed494f6 100644
--- a/src/cmd/link/internal/loong64/obj.go
+++ b/src/cmd/link/internal/loong64/obj.go
@@ -53,11 +53,11 @@ func archinit(ctxt *ld.Link) {
 	case objabi.Hlinux: /* loong64 elf */
 		ld.Elfinit(ctxt)
 		ld.HEADR = ld.ELFRESERVE
-		if *ld.FlagTextAddr == -1 {
-			*ld.FlagTextAddr = 0x10000 + int64(ld.HEADR)
-		}
 		if *ld.FlagRound == -1 {
 			*ld.FlagRound = 0x10000
 		}
+		if *ld.FlagTextAddr == -1 {
+			*ld.FlagTextAddr = ld.Rnd(0x10000, *ld.FlagRound) + int64(ld.HEADR)
+		}
 	}
 }
diff --git a/src/cmd/link/internal/mips/obj.go b/src/cmd/link/internal/mips/obj.go
index 1caddac6be..e07ee0b208 100644
--- a/src/cmd/link/internal/mips/obj.go
+++ b/src/cmd/link/internal/mips/obj.go
@@ -91,12 +91,12 @@ func archinit(ctxt *ld.Link) {
 	case objabi.Hlinux: /* mips elf */
 		ld.Elfinit(ctxt)
 		ld.HEADR = ld.ELFRESERVE
-		if *ld.FlagTextAddr == -1 {
-			*ld.FlagTextAddr = 0x10000 + int64(ld.HEADR)
-		}
 		if *ld.FlagRound == -1 {
 			*ld.FlagRound = 0x10000
 		}
+		if *ld.FlagTextAddr == -1 {
+			*ld.FlagTextAddr = ld.Rnd(0x10000, *ld.FlagRound) + int64(ld.HEADR)
+		}
 	}
 }
 
diff --git a/src/cmd/link/internal/mips64/obj.go b/src/cmd/link/internal/mips64/obj.go
index 7fb19e92ac..193ad1f271 100644
--- a/src/cmd/link/internal/mips64/obj.go
+++ b/src/cmd/link/internal/mips64/obj.go
@@ -88,24 +88,23 @@ func archinit(ctxt *ld.Link) {
 
 	case objabi.Hplan9: /* plan 9 */
 		ld.HEADR = 32
-
-		if *ld.FlagTextAddr == -1 {
-			*ld.FlagTextAddr = 16*1024 + int64(ld.HEADR)
-		}
 		if *ld.FlagRound == -1 {
 			*ld.FlagRound = 16 * 1024
 		}
+		if *ld.FlagTextAddr == -1 {
+			*ld.FlagTextAddr = ld.Rnd(16*1024, *ld.FlagRound) + int64(ld.HEADR)
+		}
 
 	case objabi.Hlinux, /* mips64 elf */
 		objabi.Hopenbsd:
 		ld.Elfinit(ctxt)
 		ld.HEADR = ld.ELFRESERVE
-		if *ld.FlagTextAddr == -1 {
-			*ld.FlagTextAddr = 0x10000 + int64(ld.HEADR)
-		}
 		if *ld.FlagRound == -1 {
 			*ld.FlagRound = 0x10000
 		}
+		if *ld.FlagTextAddr == -1 {
+			*ld.FlagTextAddr = ld.Rnd(0x10000, *ld.FlagRound) + int64(ld.HEADR)
+		}
 	}
 
 	dynSymCount = 0
diff --git a/src/cmd/link/internal/ppc64/obj.go b/src/cmd/link/internal/ppc64/obj.go
index 7de0f8eac6..703c8ec2e8 100644
--- a/src/cmd/link/internal/ppc64/obj.go
+++ b/src/cmd/link/internal/ppc64/obj.go
@@ -92,24 +92,23 @@ func archinit(ctxt *ld.Link) {
 
 	case objabi.Hplan9: /* plan 9 */
 		ld.HEADR = 32
-
-		if *ld.FlagTextAddr == -1 {
-			*ld.FlagTextAddr = 4128
-		}
 		if *ld.FlagRound == -1 {
 			*ld.FlagRound = 4096
 		}
+		if *ld.FlagTextAddr == -1 {
+			*ld.FlagTextAddr = ld.Rnd(4096, *ld.FlagRound) + int64(ld.HEADR)
+		}
 
 	case objabi.Hlinux, /* ppc64 elf */
 		objabi.Hopenbsd:
 		ld.Elfinit(ctxt)
 		ld.HEADR = ld.ELFRESERVE
-		if *ld.FlagTextAddr == -1 {
-			*ld.FlagTextAddr = 0x10000 + int64(ld.HEADR)
-		}
 		if *ld.FlagRound == -1 {
 			*ld.FlagRound = 0x10000
 		}
+		if *ld.FlagTextAddr == -1 {
+			*ld.FlagTextAddr = ld.Rnd(0x10000, *ld.FlagRound) + int64(ld.HEADR)
+		}
 
 	case objabi.Haix:
 		ld.Xcoffinit(ctxt)
diff --git a/src/cmd/link/internal/riscv64/obj.go b/src/cmd/link/internal/riscv64/obj.go
index 1532d29366..a18e8369fd 100644
--- a/src/cmd/link/internal/riscv64/obj.go
+++ b/src/cmd/link/internal/riscv64/obj.go
@@ -60,12 +60,12 @@ func archinit(ctxt *ld.Link) {
 	case objabi.Hlinux, objabi.Hfreebsd:
 		ld.Elfinit(ctxt)
 		ld.HEADR = ld.ELFRESERVE
-		if *ld.FlagTextAddr == -1 {
-			*ld.FlagTextAddr = 0x10000 + int64(ld.HEADR)
-		}
 		if *ld.FlagRound == -1 {
 			*ld.FlagRound = 0x10000
 		}
+		if *ld.FlagTextAddr == -1 {
+			*ld.FlagTextAddr = ld.Rnd(0x10000, *ld.FlagRound) + int64(ld.HEADR)
+		}
 	default:
 		ld.Exitf("unknown -H option: %v", ctxt.HeadType)
 	}
diff --git a/src/cmd/link/internal/s390x/obj.go b/src/cmd/link/internal/s390x/obj.go
index c2386fb9e9..76aa962a82 100644
--- a/src/cmd/link/internal/s390x/obj.go
+++ b/src/cmd/link/internal/s390x/obj.go
@@ -81,11 +81,11 @@ func archinit(ctxt *ld.Link) {
 	case objabi.Hlinux: // s390x ELF
 		ld.Elfinit(ctxt)
 		ld.HEADR = ld.ELFRESERVE
-		if *ld.FlagTextAddr == -1 {
-			*ld.FlagTextAddr = 0x10000 + int64(ld.HEADR)
-		}
 		if *ld.FlagRound == -1 {
 			*ld.FlagRound = 0x10000
 		}
+		if *ld.FlagTextAddr == -1 {
+			*ld.FlagTextAddr = ld.Rnd(0x10000, *ld.FlagRound) + int64(ld.HEADR)
+		}
 	}
 }
diff --git a/src/cmd/link/internal/x86/obj.go b/src/cmd/link/internal/x86/obj.go
index 6ccb8e093f..4336f01ea3 100644
--- a/src/cmd/link/internal/x86/obj.go
+++ b/src/cmd/link/internal/x86/obj.go
@@ -82,21 +82,11 @@ func archinit(ctxt *ld.Link) {
 
 	case objabi.Hplan9: /* plan 9 */
 		ld.HEADR = 32
-
-		if *ld.FlagTextAddr == -1 {
-			*ld.FlagTextAddr = 4096 + int64(ld.HEADR)
-		}
 		if *ld.FlagRound == -1 {
 			*ld.FlagRound = 4096
 		}
-
-	case objabi.Hdarwin: /* apple MACH */
-		ld.HEADR = ld.INITIAL_MACHO_HEADR
 		if *ld.FlagTextAddr == -1 {
-			*ld.FlagTextAddr = 4096 + int64(ld.HEADR)
-		}
-		if *ld.FlagRound == -1 {
-			*ld.FlagRound = 4096
+			*ld.FlagTextAddr = ld.Rnd(4096, *ld.FlagRound) + int64(ld.HEADR)
 		}
 
 	case objabi.Hlinux, /* elf32 executable */
@@ -106,12 +96,12 @@ func archinit(ctxt *ld.Link) {
 		ld.Elfinit(ctxt)
 
 		ld.HEADR = ld.ELFRESERVE
-		if *ld.FlagTextAddr == -1 {
-			*ld.FlagTextAddr = 0x08048000 + int64(ld.HEADR)
-		}
 		if *ld.FlagRound == -1 {
 			*ld.FlagRound = 4096
 		}
+		if *ld.FlagTextAddr == -1 {
+			*ld.FlagTextAddr = ld.Rnd(0x08048000, *ld.FlagRound) + int64(ld.HEADR)
+		}
 
 	case objabi.Hwindows: /* PE executable */
 		// ld.HEADR, ld.FlagTextAddr, ld.FlagRound are set in ld.Peinit