[PATCH 8/9] gas: Check for overflow on return column in version 1 CIE DWARF

[Andrew Burgess]

In version 1 of DWARF CIE format, the return register column is just a
single byte.  For targets with large numbers of DWARF registers, any
use of a register with a high number for the return column
will (currently) silently overflow giving incorrect DWARF.

This commit adds an error when the overflow occurs.

gas/ChangeLog:

	* dw2gencfi.c (output_cie): Error on return column overflow.
	* testsuite/gas/riscv/cie-rtn-col-1.d: New file.
	* testsuite/gas/riscv/cie-rtn-col-3.d: New file.
	* testsuite/gas/riscv/cie-rtn-col.s: New file.

Change-Id: I1809f739ba7771737ec012807f0260e1a3ed5e64
---
 gas/ChangeLog                           |  7 +++++++
 gas/dw2gencfi.c                         |  7 ++++++-
 gas/testsuite/gas/riscv/cie-rtn-col-1.d |  3 +++
 gas/testsuite/gas/riscv/cie-rtn-col-3.d | 17 +++++++++++++++++
 gas/testsuite/gas/riscv/cie-rtn-col.s   |  3 +++
 5 files changed, 36 insertions(+), 1 deletion(-)
 create mode 100644 gas/testsuite/gas/riscv/cie-rtn-col-1.d
 create mode 100644 gas/testsuite/gas/riscv/cie-rtn-col-3.d
 create mode 100644 gas/testsuite/gas/riscv/cie-rtn-col.s

diff --git a/gas/dw2gencfi.c b/gas/dw2gencfi.c
index e27253db8ee..4c19987dfcf 100644
--- a/gas/dw2gencfi.c
+++ b/gas/dw2gencfi.c
@@ -1887,7 +1887,12 @@ output_cie (struct cie_entry *cie, bfd_boolean eh_frame, int align)
   out_uleb128 (DWARF2_LINE_MIN_INSN_LENGTH);	/* Code alignment.  */
   out_sleb128 (DWARF2_CIE_DATA_ALIGNMENT);	/* Data alignment.  */
   if (flag_dwarf_cie_version == 1)		/* Return column.  */
-    out_one (cie->return_column);
+    {
+      if ((cie->return_column & 0xff) != cie->return_column)
+        as_bad (_("return column number %d overflows in CIE version 1"),
+                cie->return_column);
+      out_one (cie->return_column);
+    }
   else
     out_uleb128 (cie->return_column);
   if (eh_frame)
diff --git a/gas/testsuite/gas/riscv/cie-rtn-col-1.d b/gas/testsuite/gas/riscv/cie-rtn-col-1.d
new file mode 100644
index 00000000000..dba9c0d3811
--- /dev/null
+++ b/gas/testsuite/gas/riscv/cie-rtn-col-1.d
@@ -0,0 +1,3 @@
+#as: --gdwarf-cie-version=1
+#source: cie-rtn-col.s
+#error: return column number 4929 overflows in CIE version 1
diff --git a/gas/testsuite/gas/riscv/cie-rtn-col-3.d b/gas/testsuite/gas/riscv/cie-rtn-col-3.d
new file mode 100644
index 00000000000..a1d71e1a940
--- /dev/null
+++ b/gas/testsuite/gas/riscv/cie-rtn-col-3.d
@@ -0,0 +1,17 @@
+#objdump: --dwarf=frames
+#as: --gdwarf-cie-version=3
+#source: cie-rtn-col.s
+
+.*:     file format elf.*-.*riscv
+
+Contents of the .* section:
+
+
+00000000 [a-zA-Z0-9]+ [a-zA-Z0-9]+ CIE
+  Version:               3
+  Augmentation:          .*
+  Code alignment factor: .*
+  Data alignment factor: .*
+  Return address column: 4929
+  Augmentation data:     .*
+#...
diff --git a/gas/testsuite/gas/riscv/cie-rtn-col.s b/gas/testsuite/gas/riscv/cie-rtn-col.s
new file mode 100644
index 00000000000..ca8774f1bcc
--- /dev/null
+++ b/gas/testsuite/gas/riscv/cie-rtn-col.s
@@ -0,0 +1,3 @@
+        .cfi_startproc
+        .cfi_return_column mepc
+        .cfi_endproc
-- 
2.14.5