[binutils-gdb] Fix ld-arm bug in encoding of blx calls jumping from thumb to arm instructions

[Nick Clifton]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=a747a286b9331adfba85a508beddaef47ea1a1c2

commit a747a286b9331adfba85a508beddaef47ea1a1c2
Author: Viorel Preoteasa <viorel.preoteasa@gmail.com>
Date:   Fri Mar 18 15:32:28 2022 +0000

    Fix ld-arm bug in encoding of blx calls jumping from thumb to arm instructions
    
            PR 28924
            * elf32-arm.c (THM_MAX_FWD_BRANCH_OFFSET): Fix definition.
            (THM2_MAX_FWD_BRANCH_OFFSET): Likewise.

Diff:
---
 bfd/ChangeLog   |  6 ++++++
 bfd/elf32-arm.c | 18 +++++++++++++++---
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 414646c84f0..6ac8b96c57a 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,9 @@
+2022-03-18  Viorel Preoteasa  <viorel.preoteasa@gmail.com>
+
+	PR 28924
+	* elf32-arm.c (THM_MAX_FWD_BRANCH_OFFSET): Fix definition.
+	(THM2_MAX_FWD_BRANCH_OFFSET): Likewise.
+
 2022-03-16  Simon Marchi  <simon.marchi@efficios.com>
 
 	* Makefile.am (ALL_MACHINES, ALL_MACHINES_CFILES):
diff --git a/bfd/elf32-arm.c b/bfd/elf32-arm.c
index 616efe60ad1..5b8f5e5a0e6 100644
--- a/bfd/elf32-arm.c
+++ b/bfd/elf32-arm.c
@@ -2536,11 +2536,23 @@ static const bfd_vma elf32_arm_nacl_plt_entry [] =
   0xea000000,		/* b	.Lplt_tail			*/
 };
 
+/* PR 28924:
+   There was a bug due to too high values of THM_MAX_FWD_BRANCH_OFFSET and
+   THM2_MAX_FWD_BRANCH_OFFSET.  The first macro concerns the case when Thumb-2
+   is not available, and second macro when Thumb-2 is available.  Among other
+   things, they affect the range of branches represented as BLX instructions
+   in Encoding T2 defined in Section A8.8.25 of the ARM Architecture
+   Reference Manual ARMv7-A and ARMv7-R edition issue C.d.  Such branches are
+   specified there to have a maximum forward offset that is a multiple of 4.
+   Previously, the respective values defined here were multiples of 2 but not
+   4 and they are included in comments for reference.  */
 #define ARM_MAX_FWD_BRANCH_OFFSET  ((((1 << 23) - 1) << 2) + 8)
-#define ARM_MAX_BWD_BRANCH_OFFSET  ((-((1 << 23) << 2)) + 8)
-#define THM_MAX_FWD_BRANCH_OFFSET  ((1 << 22) -2 + 4)
+#define ARM_MAX_BWD_BRANCH_OFFSET ((-((1 << 23) << 2)) + 8)
+#define THM_MAX_FWD_BRANCH_OFFSET   ((1 << 22) - 4 + 4)
+/* #def THM_MAX_FWD_BRANCH_OFFSET   ((1 << 22) - 2 + 4) */
 #define THM_MAX_BWD_BRANCH_OFFSET  (-(1 << 22) + 4)
-#define THM2_MAX_FWD_BRANCH_OFFSET (((1 << 24) - 2) + 4)
+#define THM2_MAX_FWD_BRANCH_OFFSET (((1 << 24) - 4) + 4)
+/* #def THM2_MAX_FWD_BRANCH_OFFSET (((1 << 24) - 2) + 4) */
 #define THM2_MAX_BWD_BRANCH_OFFSET (-(1 << 24) + 4)
 #define THM2_MAX_FWD_COND_BRANCH_OFFSET (((1 << 20) -2) + 4)
 #define THM2_MAX_BWD_COND_BRANCH_OFFSET (-(1 << 20) + 4)