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Commit cd7246f0 authored by Matt Fleming's avatar Matt Fleming
Browse files

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: default avatarMatt Fleming <matt@console-pimps.org>
parent b955873b

arch/sh/include/asm/dwarf.h

+4 −0
Original line number Diff line number Diff line
@@ -340,6 +340,10 @@ struct dwarf_stack { 
#define DW_CFA_lo_user		0x1c

#define DW_CFA_hi_user		0x3f



/* GNU extension opcodes  */

#define DW_CFA_GNU_args_size	0x2e

#define DW_CFA_GNU_negative_offset_extended 0x2f



/*

 * Some call frame instructions encode their operands in the opcode. We

 * need some helper functions to extract both the opcode and operands

arch/sh/kernel/dwarf.c

+13 −1
Original line number Diff line number Diff line
@@ -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;