sh: Add support for DWARF GNU extensions

Also, remove the "fix" to DW_CFA_def_cfa_register where we reset the
frame's cfa_offset to 0. This action is incorrect when handling
DW_CFA_def_cfa_register as the DWARF spec specifically states that the
previous contents of cfa_offset should be used with the new
register. The reason that I thought cfa_offset should be reset to 0 was
because it was being assigned a bogus value prior to executing the
DW_CFA_def_cfa_register op. It turns out that the bogus cfa_offset value
came from interpreting .cfi_escape pseudo-ops (those used by the GNU
extensions) as CFA_DW_def_cfa ops.

Signed-off-by: Matt Fleming <matt@console-pimps.org>

1 files changed, 13 insertions, 1 deletions

diff --git a/arch/sh/kernel/dwarf.c b/arch/sh/kernel/dwarf.c
index 44e674ed2871..5fd6e604816d 100644
--- a/arch/sh/kernel/dwarf.c
+++ b/arch/sh/kernel/dwarf.c
@@ -429,7 +429,6 @@ static int dwarf_cfa_execute_insns(unsigned char *insn_start,
                         count = dwarf_read_uleb128(current_insn,
                                                    &frame->cfa_register);
                         current_insn += count;
-                        frame->cfa_offset = 0;
                         frame->flags |= DWARF_FRAME_CFA_REG_OFFSET;
                         break;
                 case DW_CFA_def_cfa_offset:
@@ -465,6 +464,19 @@ static int dwarf_cfa_execute_insns(unsigned char *insn_start,
                         frame->regs[reg].flags |= DWARF_REG_OFFSET;
                         frame->regs[reg].addr = offset;
                         break;
+                case DW_CFA_GNU_args_size:
+                        count = dwarf_read_uleb128(current_insn, &offset);
+                        current_insn += count;
+                        break;
+                case DW_CFA_GNU_negative_offset_extended:
+                        count = dwarf_read_uleb128(current_insn, &reg);
+                        current_insn += count;
+                        count = dwarf_read_uleb128(current_insn, &offset);
+                        offset *= cie->data_alignment_factor;
+                        dwarf_frame_alloc_regs(frame, reg);
+                        frame->regs[reg].flags |= DWARF_REG_OFFSET;
+                        frame->regs[reg].addr = -offset;
+                        break;
                 default:
                         pr_debug("unhandled DWARF instruction 0x%x\n", insn);
                         break;