Fixes PR122.

* src/vm/jit/arm/md.c (md_jit_method_patch_address): Fixed for corner case with
large displacements.

diff --git a/src/vm/jit/arm/md.c b/src/vm/jit/arm/md.c
index 30df98d484ba893b04a6925ec15d4c3b7ff2de6b..e4549a1b7a67bfd8eb8bc8c305adf67c5e63b658 100644 (file)
--- a/src/vm/jit/arm/md.c
+++ b/src/vm/jit/arm/md.c
@@ -142,20 +142,41 @@ void *md_jit_method_patch_address(void *pv, void *ra, void *mptr)
        /* Case: We loaded from base REG_PV with positive offset. */
 
        else if (M_MEM_GET_Rbase(mcode) == REG_PV && (mcode & 0x00800000) == 0x00800000) {
-               /* We loaded from REG_METHODPTR with a larger displacement */
+               /* We loaded with a larger displacement. Normally this means we loaded
+                  from REG_METHODPTR. However there is a corner case if we loaded
+                  from the data segment at an address aligned to 12 bit, which leads to a
+                  zero (positive) displacement for the last instruction. */
 
                mcode = pc[-1];
 
                /* check for "ADD IP, FP, #??, ROTL 12" */
 
-               if ((mcode & 0xffffff00) == 0xe28bca00)
+               if ((mcode & 0xffffff00) == 0xe28bca00) {
+                       /* We loaded from REG_METHODPTR with a larger displacement. */
+
+                       assert(mptr != NULL);
+                       disp += (int32_t) ((mcode & 0x00ff) << 12);
+                       pa = ((uint8_t *) mptr) + disp;
+               }
+
+               /* check for "SUB IP, IP, #??, ROTL 12" (corner case) */
+
+               else if ((mcode & 0xffffff00) == 0xe24cca00 && disp == 0) {
+                       /* We loaded from data segment with a larger displacement aligned to 12 bit. */
+
                        disp += (int32_t) ((mcode & 0x00ff) << 12);
-               else
+                       pa = ((uint8_t *) pv) - disp;
+               }
+
+               /* Case is not covered, something is severely wrong. */
+
+               else {
                        vm_abort_disassemble(pc - 1, 4, "md_jit_method_patch_address: unknown instruction %x", mcode);
 
-               /* we loaded from REG_METHODPTR */
+                       /* Keep compiler happy. */
 
-               pa = ((uint8_t *) mptr) + disp;
+                       pa = NULL;
+               }
        }
 
        /* Case is not covered, something is severely wrong. */