[llvm] r333997 - [MC][ARM] Add range checking for Thumb2 resolved fixups.

[Peter Smith via llvm-commits]

Author: psmith
Date: Tue Jun  5 03:00:56 2018
New Revision: 333997

URL: http://llvm.org/viewvc/llvm-project?rev=333997&view=rev
Log:
[MC][ARM] Add range checking for Thumb2 resolved fixups.

When the branch target of a Thumb2 unconditional or conditonal branch is
resolved at assembly time, no range checking is performed on the result
leading to incorrect immediates. This change adds a range check:
+- 16 Megabytes for unconditional branches, +- 1 Megabyte for the
conditional branch.

Differential Revision: https://reviews.llvm.org/D46306


Added:
    llvm/trunk/test/MC/ARM/thumb2-branch-ranges.s
Modified:
    llvm/trunk/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.cpp

Modified: llvm/trunk/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.cpp?rev=333997&r1=333996&r2=333997&view=diff
==============================================================================
--- llvm/trunk/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.cpp (original)
+++ llvm/trunk/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.cpp Tue Jun  5 03:00:56 2018
@@ -487,6 +487,11 @@ unsigned ARMAsmBackend::adjustFixupValue
     return 0xffffff & ((Value - 8) >> 2);
   case ARM::fixup_t2_uncondbranch: {
     Value = Value - 4;
+    if (!isInt<25>(Value)) {
+      Ctx.reportError(Fixup.getLoc(), "Relocation out of range");
+      return 0;
+    }
+
     Value >>= 1; // Low bit is not encoded.
 
     uint32_t out = 0;
@@ -506,6 +511,11 @@ unsigned ARMAsmBackend::adjustFixupValue
   }
   case ARM::fixup_t2_condbranch: {
     Value = Value - 4;
+    if (!isInt<21>(Value)) {
+      Ctx.reportError(Fixup.getLoc(), "Relocation out of range");
+      return 0;
+    }
+
     Value >>= 1; // Low bit is not encoded.
 
     uint64_t out = 0;

Added: llvm/trunk/test/MC/ARM/thumb2-branch-ranges.s
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/MC/ARM/thumb2-branch-ranges.s?rev=333997&view=auto
==============================================================================
--- llvm/trunk/test/MC/ARM/thumb2-branch-ranges.s (added)
+++ llvm/trunk/test/MC/ARM/thumb2-branch-ranges.s Tue Jun  5 03:00:56 2018
@@ -0,0 +1,96 @@
+@ RUN: not llvm-mc %s -triple thumbv7-linux-gnueabi -filetype=obj -o /dev/null 2>&1 | FileCheck %s
+
+// Thumb2 unconditional branch has a range of +- 16 Megabytes. The
+// conditional branch has a range of +- 1 Megabyte. We should give
+// an error message if we evaluate the expression at assembly
+// time and it is out of range.
+
+        .syntax unified
+        .thumb
+        b.w end
+        .space 0xfffffe
+end:
+        b.w end2
+        .space 0xfffffe
+        .global end2
+end2:
+
+// branch to arm function uses relocation
+        b.w end3
+        .space 0x1000000
+        .global end3
+        .type end3, %function
+        .arm
+end3:   bx lr
+        .thumb
+
+// branch to thumb function is resolved at assembly time
+// CHECK-NOT: error
+// CHECK: [[@LINE+2]]:{{[0-9]}}: error: Relocation out of range
+// CHECK-LABEL: b.w end4
+        b.w end4
+        .space 0x1000000
+        .thumb_func
+end4:
+
+        beq.w end5
+        .space 0xffffc
+end5:
+
+// conditional branch to arm function uses relocation
+        beq.w end6
+        .arm
+        .type end6, %function
+        .space 0x100000
+end6:   bx lr
+        .thumb
+
+// conditional branch to thumb function resolved at assembly time
+// CHECK-NOT: error
+// CHECK: [[@LINE+2]]:{{[0-9]}}: error: Relocation out of range
+// CHECK-LABEL: beq.w end7
+        beq.w end7
+        .space 0x100000
+end7:
+
+start:
+        .space 0xfffffc
+        b.w start
+
+        .arm
+        .global start2
+        .type start2, %function
+start2:
+        .space 0x1000000
+        .thumb
+// branch to arm function uses relocation
+        b.w start2
+
+start3:
+        .space 0x1000000
+// branch to thumb function resolved at assembly time
+// CHECK-NOT: error
+// CHECK: [[@LINE+2]]:{{[0-9]}}: error: Relocation out of range
+// CHECK-LABEL: b.w start3
+        b.w start3
+
+start4:
+        .space 0xffffc
+        b.w start4
+
+        .arm
+        .global start5
+        .type start5, %function
+start5:
+        .space 0x100000
+        .thumb
+// conditional branch to arm function uses relocation
+        beq.w start5
+
+start6:
+        .space 0x100000
+// branch to thumb function resolved at assembly time
+// CHECK-NOT: error
+// CHECK: [[@LINE+2]]:{{[0-9]}}: error: Relocation out of range
+// CHECK-LABEL: beq.w start6
+        beq.w start6