runtime/cgo: avoid taking the address of crosscall2 in code

Currently, set_crosscall2 takes the address of crosscall2 without using the GOT, which, on some architectures, results in a PC-relative relocation (e.g. R_AARCH64_ADR_PREL_PG_HI21 on ARM64) to the crosscall2 symbol. But crosscall2 is dynamically exported, so the C linker thinks it may bind to a symbol from a different DSO. Some C linker may not like a PC-relative relocation to such a symbol. Using a local trampoline to avoid taking the address of a dynamically exported symbol. It may be possible to not dynamically export crosscall2. But this CL is safer for backport. Later we may remove the trampolines after unexport crosscall2, if they are not needed. Fixes #62556. Change-Id: Id28457f65ef121d3f87d8189803abc65ed453283 Reviewed-on: https://go-review.googlesource.com/c/go/+/533535 LUCI-TryBot-Result: Go LUCI <[email protected]> Reviewed-by: Ian Lance Taylor <[email protected]>
golang · Oct 12, 2023 · 872d718 · 872d718
1 parent 3b0fc5a
commit 872d718
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Showing 11 changed files with 92 additions and 10 deletions.
diff --git a/src/cmd/cgo/internal/testcarchive/carchive_test.go b/src/cmd/cgo/internal/testcarchive/carchive_test.go
@@ -1365,3 +1365,35 @@ func TestDeepStack(t *testing.T) {
 		t.Error(err)
 	}
 }
+
+func TestSharedObject(t *testing.T) {
+	// Test that we can put a Go c-archive into a C shared object.
+	globalSkip(t)
+	testenv.MustHaveGoBuild(t)
+	testenv.MustHaveCGO(t)
+	testenv.MustHaveBuildMode(t, "c-archive")
+
+	t.Parallel()
+
+	if !testWork {
+		defer func() {
+			os.Remove("libgo_s.a")
+			os.Remove("libgo_s.h")
+			os.Remove("libgo_s.so")
+		}()
+	}
+
+	cmd := exec.Command("go", "build", "-buildmode=c-archive", "-o", "libgo_s.a", "./libgo")
+	out, err := cmd.CombinedOutput()
+	t.Logf("%v\n%s", cmd.Args, out)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	ccArgs := append(cc, "-shared", "-o", "libgo_s.so", "libgo_s.a")
+	out, err = exec.Command(ccArgs[0], ccArgs[1:]...).CombinedOutput()
+	t.Logf("%v\n%s", ccArgs, out)
+	if err != nil {
+		t.Fatal(err)
+	}
+}
diff --git a/src/runtime/cgo/asm_386.s b/src/runtime/cgo/asm_386.s
@@ -6,12 +6,17 @@
 
 // Set the x_crosscall2_ptr C function pointer variable point to crosscall2.
 // It's such a pointer chain: _crosscall2_ptr -> x_crosscall2_ptr -> crosscall2
+// Use a local trampoline, to avoid taking the address of a dynamically exported
+// function.
 TEXT ·set_crosscall2(SB),NOSPLIT,$0-0
 	MOVL	_crosscall2_ptr(SB), AX
-	MOVL	$crosscall2(SB), BX
+	MOVL	$crosscall2_trampoline<>(SB), BX
 	MOVL	BX, (AX)
 	RET
 
+TEXT crosscall2_trampoline<>(SB),NOSPLIT,$0-0
+	JMP	crosscall2(SB)
+
 // Called by C code generated by cmd/cgo.
 // func crosscall2(fn, a unsafe.Pointer, n int32, ctxt uintptr)
 // Saves C callee-saved registers and calls cgocallback with three arguments.

diff --git a/src/runtime/cgo/asm_amd64.s b/src/runtime/cgo/asm_amd64.s
@@ -7,12 +7,17 @@
 
 // Set the x_crosscall2_ptr C function pointer variable point to crosscall2.
 // It's such a pointer chain: _crosscall2_ptr -> x_crosscall2_ptr -> crosscall2
+// Use a local trampoline, to avoid taking the address of a dynamically exported
+// function.
 TEXT ·set_crosscall2(SB),NOSPLIT,$0-0
 	MOVQ	_crosscall2_ptr(SB), AX
-	MOVQ	$crosscall2(SB), BX
+	MOVQ	$crosscall2_trampoline<>(SB), BX
 	MOVQ	BX, (AX)
 	RET
 
+TEXT crosscall2_trampoline<>(SB),NOSPLIT,$0-0
+	JMP	crosscall2(SB)
+
 // Called by C code generated by cmd/cgo.
 // func crosscall2(fn, a unsafe.Pointer, n int32, ctxt uintptr)
 // Saves C callee-saved registers and calls cgocallback with three arguments.

diff --git a/src/runtime/cgo/asm_arm.s b/src/runtime/cgo/asm_arm.s
@@ -6,12 +6,17 @@
 
 // Set the x_crosscall2_ptr C function pointer variable point to crosscall2.
 // It's such a pointer chain: _crosscall2_ptr -> x_crosscall2_ptr -> crosscall2
+// Use a local trampoline, to avoid taking the address of a dynamically exported
+// function.
 TEXT ·set_crosscall2(SB),NOSPLIT,$0-0
 	MOVW	_crosscall2_ptr(SB), R1
-	MOVW	$crosscall2(SB), R2
+	MOVW	$crosscall2_trampoline<>(SB), R2
 	MOVW	R2, (R1)
 	RET
 
+TEXT crosscall2_trampoline<>(SB),NOSPLIT,$0-0
+	JMP	crosscall2(SB)
+
 // Called by C code generated by cmd/cgo.
 // func crosscall2(fn, a unsafe.Pointer, n int32, ctxt uintptr)
 // Saves C callee-saved registers and calls cgocallback with three arguments.

diff --git a/src/runtime/cgo/asm_arm64.s b/src/runtime/cgo/asm_arm64.s
@@ -7,12 +7,17 @@
 
 // Set the x_crosscall2_ptr C function pointer variable point to crosscall2.
 // It's such a pointer chain: _crosscall2_ptr -> x_crosscall2_ptr -> crosscall2
+// Use a local trampoline, to avoid taking the address of a dynamically exported
+// function.
 TEXT ·set_crosscall2(SB),NOSPLIT,$0-0
 	MOVD	_crosscall2_ptr(SB), R1
-	MOVD	$crosscall2(SB), R2
+	MOVD	$crosscall2_trampoline<>(SB), R2
 	MOVD	R2, (R1)
 	RET
 
+TEXT crosscall2_trampoline<>(SB),NOSPLIT,$0-0
+	JMP	crosscall2(SB)
+
 // Called by C code generated by cmd/cgo.
 // func crosscall2(fn, a unsafe.Pointer, n int32, ctxt uintptr)
 // Saves C callee-saved registers and calls cgocallback with three arguments.

diff --git a/src/runtime/cgo/asm_loong64.s b/src/runtime/cgo/asm_loong64.s
@@ -7,12 +7,17 @@
 
 // Set the x_crosscall2_ptr C function pointer variable point to crosscall2.
 // It's such a pointer chain: _crosscall2_ptr -> x_crosscall2_ptr -> crosscall2
+// Use a local trampoline, to avoid taking the address of a dynamically exported
+// function.
 TEXT ·set_crosscall2(SB),NOSPLIT,$0-0
 	MOVV	_crosscall2_ptr(SB), R5
-	MOVV	$crosscall2(SB), R6
+	MOVV	$crosscall2_trampoline<>(SB), R6
 	MOVV	R6, (R5)
 	RET
 
+TEXT crosscall2_trampoline<>(SB),NOSPLIT,$0-0
+	JMP	crosscall2(SB)
+
 // Called by C code generated by cmd/cgo.
 // func crosscall2(fn, a unsafe.Pointer, n int32, ctxt uintptr)
 // Saves C callee-saved registers and calls cgocallback with three arguments.

diff --git a/src/runtime/cgo/asm_mips64x.s b/src/runtime/cgo/asm_mips64x.s
@@ -8,12 +8,17 @@
 
 // Set the x_crosscall2_ptr C function pointer variable point to crosscall2.
 // It's such a pointer chain: _crosscall2_ptr -> x_crosscall2_ptr -> crosscall2
+// Use a local trampoline, to avoid taking the address of a dynamically exported
+// function.
 TEXT ·set_crosscall2(SB),NOSPLIT,$0-0
 	MOVV	_crosscall2_ptr(SB), R5
-	MOVV	$crosscall2(SB), R6
+	MOVV	$crosscall2_trampoline<>(SB), R6
 	MOVV	R6, (R5)
 	RET
 
+TEXT crosscall2_trampoline<>(SB),NOSPLIT,$0-0
+	JMP	crosscall2(SB)
+
 // Called by C code generated by cmd/cgo.
 // func crosscall2(fn, a unsafe.Pointer, n int32, ctxt uintptr)
 // Saves C callee-saved registers and calls cgocallback with three arguments.

diff --git a/src/runtime/cgo/asm_mipsx.s b/src/runtime/cgo/asm_mipsx.s
@@ -8,12 +8,17 @@
 
 // Set the x_crosscall2_ptr C function pointer variable point to crosscall2.
 // It's such a pointer chain: _crosscall2_ptr -> x_crosscall2_ptr -> crosscall2
+// Use a local trampoline, to avoid taking the address of a dynamically exported
+// function.
 TEXT ·set_crosscall2(SB),NOSPLIT,$0-0
 	MOVW	_crosscall2_ptr(SB), R5
-	MOVW	$crosscall2(SB), R6
+	MOVW	$crosscall2_trampoline<>(SB), R6
 	MOVW	R6, (R5)
 	RET
 
+TEXT crosscall2_trampoline<>(SB),NOSPLIT,$0-0
+	JMP	crosscall2(SB)
+
 // Called by C code generated by cmd/cgo.
 // func crosscall2(fn, a unsafe.Pointer, n int32, ctxt uintptr)
 // Saves C callee-saved registers and calls cgocallback with three arguments.

diff --git a/src/runtime/cgo/asm_ppc64x.s b/src/runtime/cgo/asm_ppc64x.s
@@ -16,7 +16,9 @@
 DEFINE_PPC64X_FUNCDESC(_crosscall2<>, crosscall2)
 #define CROSSCALL2_FPTR $_crosscall2<>(SB)
 #else
-#define CROSSCALL2_FPTR $crosscall2(SB)
+// Use a local trampoline, to avoid taking the address of a dynamically exported
+// function.
+#define CROSSCALL2_FPTR $crosscall2_trampoline<>(SB)
 #endif
 
 // Set the x_crosscall2_ptr C function pointer variable point to crosscall2.
@@ -27,6 +29,9 @@ TEXT ·set_crosscall2(SB),NOSPLIT,$0-0
 	MOVD	R6, (R5)
 	RET
 
+TEXT crosscall2_trampoline<>(SB),NOSPLIT,$0-0
+	JMP	crosscall2(SB)
+
 // Called by C code generated by cmd/cgo.
 // func crosscall2(fn, a unsafe.Pointer, n int32, ctxt uintptr)
 // Saves C callee-saved registers and calls cgocallback with three arguments.

diff --git a/src/runtime/cgo/asm_riscv64.s b/src/runtime/cgo/asm_riscv64.s
@@ -6,12 +6,17 @@
 
 // Set the x_crosscall2_ptr C function pointer variable point to crosscall2.
 // It's such a pointer chain: _crosscall2_ptr -> x_crosscall2_ptr -> crosscall2
+// Use a local trampoline, to avoid taking the address of a dynamically exported
+// function.
 TEXT ·set_crosscall2(SB),NOSPLIT,$0-0
 	MOV	_crosscall2_ptr(SB), X7
-	MOV	$crosscall2(SB), X8
+	MOV	$crosscall2_trampoline<>(SB), X8
 	MOV	X8, (X7)
 	RET
 
+TEXT crosscall2_trampoline<>(SB),NOSPLIT,$0-0
+	JMP	crosscall2(SB)
+
 // Called by C code generated by cmd/cgo.
 // func crosscall2(fn, a unsafe.Pointer, n int32, ctxt uintptr)
 // Saves C callee-saved registers and calls cgocallback with three arguments.

diff --git a/src/runtime/cgo/asm_s390x.s b/src/runtime/cgo/asm_s390x.s
@@ -6,12 +6,17 @@
 
 // Set the x_crosscall2_ptr C function pointer variable point to crosscall2.
 // It's such a pointer chain: _crosscall2_ptr -> x_crosscall2_ptr -> crosscall2
+// Use a local trampoline, to avoid taking the address of a dynamically exported
+// function.
 TEXT ·set_crosscall2(SB),NOSPLIT,$0-0
 	MOVD	_crosscall2_ptr(SB), R1
-	MOVD	$crosscall2(SB), R2
+	MOVD	$crosscall2_trampoline<>(SB), R2
 	MOVD	R2, (R1)
 	RET
 
+TEXT crosscall2_trampoline<>(SB),NOSPLIT,$0-0
+	JMP	crosscall2(SB)
+
 // Called by C code generated by cmd/cgo.
 // func crosscall2(fn, a unsafe.Pointer, n int32, ctxt uintptr)
 // Saves C callee-saved registers and calls cgocallback with three arguments.