cmd/internal/dwarf: update to DWARF4, emit frame_base

In preparation for CL 41770, upgrade .debug_info to DWARF4, and emit
DW_AT_frame_base on subprograms. This should make no semantic
difference.

Also fix a long-standing bug/inconsistency in puttattr: it didn't
add the addend to ref_addrs. Previously this didn't matter because it
was only used for types, but now it's used for section offsets into
symbols that have multiple entries.

RELNOTE=yes

Change-Id: Ib10654ac92edfa29c5167c44133648151d70cf76
Reviewed-on: https://go-review.googlesource.com/44210
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>

diff --git a/src/cmd/internal/dwarf/dwarf.go b/src/cmd/internal/dwarf/dwarf.go
index 2974bf50921d4818d982348f13b2dac977c5a86c..a617c389f92ab7e1a477272515f072b4ed56fbb2 100644 (file)
--- a/src/cmd/internal/dwarf/dwarf.go
+++ b/src/cmd/internal/dwarf/dwarf.go
@@ -255,7 +255,7 @@ var abbrevs = [DW_NABRV]dwAbbrev{
                        {DW_AT_language, DW_FORM_data1},
                        {DW_AT_low_pc, DW_FORM_addr},
                        {DW_AT_high_pc, DW_FORM_addr},
-                       {DW_AT_stmt_list, DW_FORM_data4},
+                       {DW_AT_stmt_list, DW_FORM_sec_offset},
                        {DW_AT_comp_dir, DW_FORM_string},
                        {DW_AT_producer, DW_FORM_string},
                },
@@ -269,6 +269,7 @@ var abbrevs = [DW_NABRV]dwAbbrev{
                        {DW_AT_name, DW_FORM_string},
                        {DW_AT_low_pc, DW_FORM_addr},
                        {DW_AT_high_pc, DW_FORM_addr},
+                       {DW_AT_frame_base, DW_FORM_block1},
                        {DW_AT_external, DW_FORM_flag},
                },
        },
@@ -306,13 +307,12 @@ var abbrevs = [DW_NABRV]dwAbbrev{
                        {DW_AT_type, DW_FORM_ref_addr},
                },
        },
-
        /* LEXICAL_BLOCK_RANGES */
        {
                DW_TAG_lexical_block,
                DW_CHILDREN_yes,
                []dwAttrForm{
-                       {DW_AT_ranges, DW_FORM_data4}, // replace with DW_FORM_sec_offset in DWARFv4.
+                       {DW_AT_ranges, DW_FORM_sec_offset},
                },
        },
 
@@ -634,14 +634,15 @@ func putattr(ctxt Context, s Sym, abbrev int, form int, cls int, value int64, da
                        ctxt.AddInt(s, 1, 0)
                }
 
-       // In DWARF 3 the ref_addr is always 32 bits, unless emitting a large
+       // As of DWARF 3 the ref_addr is always 32 bits, unless emitting a large
        // (> 4 GB of debug info aka "64-bit") unit, which we don't implement.
        case DW_FORM_ref_addr: // reference to a DIE in the .info section
+               fallthrough
+       case DW_FORM_sec_offset: // offset into a DWARF section other than .info
                if data == nil {
                        return fmt.Errorf("dwarf: null reference in %d", abbrev)
-               } else {
-                       ctxt.AddSectionOffset(s, 4, data, 0)
                }
+               ctxt.AddSectionOffset(s, 4, data, value)
 
        case DW_FORM_ref1, // reference within the compilation unit
                DW_FORM_ref2,      // reference
@@ -687,7 +688,8 @@ func PutFunc(ctxt Context, s, ranges Sym, name string, external bool, startPC Sy
        Uleb128put(ctxt, s, DW_ABRV_FUNCTION)
        putattr(ctxt, s, DW_ABRV_FUNCTION, DW_FORM_string, DW_CLS_STRING, int64(len(name)), name)
        putattr(ctxt, s, DW_ABRV_FUNCTION, DW_FORM_addr, DW_CLS_ADDRESS, 0, startPC)
-       putattr(ctxt, s, DW_ABRV_FUNCTION, DW_FORM_addr, DW_CLS_ADDRESS, size+ctxt.SymValue(startPC), startPC)
+       putattr(ctxt, s, DW_ABRV_FUNCTION, DW_FORM_addr, DW_CLS_ADDRESS, size, startPC)
+       putattr(ctxt, s, DW_ABRV_FUNCTION, DW_FORM_block1, DW_CLS_BLOCK, 1, []byte{DW_OP_call_frame_cfa})
        var ev int64
        if external {
                ev = 1
@@ -722,7 +724,7 @@ func putscope(ctxt Context, s, ranges Sym, startPC Sym, curscope int32, scopes [
                        putattr(ctxt, s, DW_ABRV_LEXICAL_BLOCK_SIMPLE, DW_FORM_addr, DW_CLS_ADDRESS, scope.Ranges[0].End, startPC)
                } else {
                        Uleb128put(ctxt, s, DW_ABRV_LEXICAL_BLOCK_RANGES)
-                       putattr(ctxt, s, DW_ABRV_LEXICAL_BLOCK_RANGES, DW_FORM_data4, DW_CLS_PTR, ranges.Len(), ranges)
+                       putattr(ctxt, s, DW_ABRV_LEXICAL_BLOCK_RANGES, DW_FORM_sec_offset, DW_CLS_PTR, ranges.Len(), ranges)
 
                        ctxt.AddAddress(ranges, nil, -1)
                        ctxt.AddAddress(ranges, startPC, 0)

diff --git a/src/cmd/internal/dwarf/dwarf_defs.go b/src/cmd/internal/dwarf/dwarf_defs.go
index d1870b579f81e355c3427bc18bd9281dcea334dc..da238b7e9a44508ab9478d48e307e91181998d2b 100644 (file)
--- a/src/cmd/internal/dwarf/dwarf_defs.go
+++ b/src/cmd/internal/dwarf/dwarf_defs.go
@@ -212,6 +212,11 @@ const (
        DW_FORM_ref8      = 0x14 // reference
        DW_FORM_ref_udata = 0x15 // reference
        DW_FORM_indirect  = 0x16 // (see Section 7.5.3)
+       // Dwarf4
+       DW_FORM_sec_offset   = 0x17 // lineptr, loclistptr, macptr, rangelistptr
+       DW_FORM_exprloc      = 0x18 // exprloc
+       DW_FORM_flag_present = 0x19 // flag
+       DW_FORM_ref_sig8     = 0x20 // reference
 )
 
 // Table 24 (#operands, notes)

diff --git a/src/cmd/link/internal/ld/dwarf.go b/src/cmd/link/internal/ld/dwarf.go
index c705bf3ba55401f84046bb026341c118e282d4a8..ba8ace54c81fd34f4b0b4dbb845af52e74ddfafd 100644 (file)
--- a/src/cmd/link/internal/ld/dwarf.go
+++ b/src/cmd/link/internal/ld/dwarf.go
@@ -1348,7 +1348,7 @@ func writeinfo(ctxt *Link, syms []*Symbol, funcs []*Symbol) []*Symbol {
                // Fields marked with (*) must be changed for 64-bit dwarf
                // This must match COMPUNITHEADERSIZE above.
                Adduint32(ctxt, s, 0) // unit_length (*), will be filled in later.
-               Adduint16(ctxt, s, 3) // dwarf version (appendix F)
+               Adduint16(ctxt, s, 4) // dwarf version (appendix F)
 
                // debug_abbrev_offset (*)
                adddwarfref(ctxt, s, abbrevsym, 4)