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Re: ARM long branch stub: thumb

On 20.02.2009 16:23, Richard Earnshaw wrote:
On Fri, 2009-02-20 at 15:15 +0100, Christophe LYON wrote:

 static const bfd_vma elf32_arm_stub_long_branch_v4t_thumb_arm[] =
   {
-    0x4e03b540,         /* push {r6, lr} */
-                        /* ldr  r6, [pc, #12] */
-    0x473046fe,         /* mov  lr, pc */
-                        /* bx   r6 */
-    0xe8bd4040,         /* pop  {r6, pc} */
-    0xe12fff1e,         /* bx   lr */
-    0x00000000,         /* dcd  R_ARM_ABS32(X) */
+    0x46c04778,         /* bx   pc */
+                        /* nop   */
+    0xe51ff004,         /* ldr   pc, [pc, #-4] */
+    0x00000000,         /* dcd   R_ARM_ABS32(X) */
   };


Unless I've missed a correction going on elsewhere, this isn't going to
work for BE-8 mode. The rules for manipulating thumb and ARM opcodes are
different (swap-16 and swap-32 respectively), and the code has to know
what instructions are at each address (the old code wouldn't have that
problem as it was all Thumb code).

Damned!

If I look at arm_build_one_stub, I can see that only put_arm_insn is use, whatever the stub being encoded. So there is a problem with any stub using thumb, isn't it?

Christophe.

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