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cmd/compile: mark wrapper functions with DW_AT_trampoline

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Change DWARF generation to tag wrapper functions with the
"DW_AT_trampoline attribute". The intent is that debuggers can pick up
on this attr so as to skip through the wrapper to the eventual target.

DWARF standard allows for a couple of different possible variants of
the trampoline attr; this is the simplest variant (all it tells the
debugger is that the function is a wrapper, doesn't include a
reference to the wrapper routine).

This implementation keys off the WRAPPER LSym attribute, which is set
for method wrappers, ABI wrappers, and a selected set of runtime
assembly routines (ex: "runtime.call32").

Change-Id: Ib53e1bc56c02b86ca3ac5e7da1a541ec262726cf
Reviewed-on: https://go-review.googlesource.com/c/go/+/347352
Reviewed-by: Than McIntosh <thanm@google.com>
Run-TryBot: Than McIntosh <thanm@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Jeremy Faller <jeremy@golang.org>
This commit is contained in:
Alessandro Arzilli 2021-09-03 15:04:52 +02:00 committed by Than McIntosh
parent e4dfd788e6
commit 5b48fca1fa
2 changed files with 53 additions and 12 deletions
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61
src/cmd/internal/dwarf/dwarf.go
View File

@ -325,8 +325,10 @@ const (
DW_ABRV_COMPUNIT
DW_ABRV_COMPUNIT_TEXTLESS
DW_ABRV_FUNCTION
DW_ABRV_WRAPPER
DW_ABRV_FUNCTION_ABSTRACT
DW_ABRV_FUNCTION_CONCRETE
DW_ABRV_WRAPPER_CONCRETE
DW_ABRV_INLINED_SUBROUTINE
DW_ABRV_INLINED_SUBROUTINE_RANGES
DW_ABRV_VARIABLE
@ -455,6 +457,19 @@ var abbrevs = [DW_NABRV]dwAbbrev{
},
},
/* WRAPPER */
{
DW_TAG_subprogram,
DW_CHILDREN_yes,
[]dwAttrForm{
{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_trampoline, DW_FORM_flag},
},
},
/* FUNCTION_ABSTRACT */
{
DW_TAG_subprogram,
@ -478,6 +493,19 @@ var abbrevs = [DW_NABRV]dwAbbrev{
},
},
/* WRAPPER_CONCRETE */
{
DW_TAG_subprogram,
DW_CHILDREN_yes,
[]dwAttrForm{
{DW_AT_abstract_origin, DW_FORM_ref_addr},
{DW_AT_low_pc, DW_FORM_addr},
{DW_AT_high_pc, DW_FORM_addr},
{DW_AT_frame_base, DW_FORM_block1},
{DW_AT_trampoline, DW_FORM_flag},
},
},
/* INLINED_SUBROUTINE */
{
DW_TAG_inlined_subroutine,
@ -1329,11 +1357,14 @@ func putInlinedFunc(ctxt Context, s *FnState, callIdx int) error {
// for the function (which holds location-independent attributes such
// as name, type), then the remainder of the attributes are specific
// to this instance (location, frame base, etc).
func PutConcreteFunc(ctxt Context, s *FnState) error {
func PutConcreteFunc(ctxt Context, s *FnState, isWrapper bool) error {
if logDwarf {
ctxt.Logf("PutConcreteFunc(%v)\n", s.Info)
}
abbrev := DW_ABRV_FUNCTION_CONCRETE
if isWrapper {
abbrev = DW_ABRV_WRAPPER_CONCRETE
}
Uleb128put(ctxt, s.Info, int64(abbrev))
// Abstract origin.
@ -1346,6 +1377,10 @@ func PutConcreteFunc(ctxt Context, s *FnState) error {
// cfa / frame base
putattr(ctxt, s.Info, abbrev, DW_FORM_block1, DW_CLS_BLOCK, 1, []byte{DW_OP_call_frame_cfa})
if isWrapper {
putattr(ctxt, s.Info, abbrev, DW_FORM_flag, DW_CLS_FLAG, int64(1), 0)
}
// Scopes
if err := putPrunedScopes(ctxt, s, abbrev); err != nil {
return err
@ -1368,11 +1403,14 @@ func PutConcreteFunc(ctxt Context, s *FnState) error {
// when its containing package was compiled (hence there is no need to
// emit an abstract version for it to use as a base for inlined
// routine records).
func PutDefaultFunc(ctxt Context, s *FnState) error {
func PutDefaultFunc(ctxt Context, s *FnState, isWrapper bool) error {
if logDwarf {
ctxt.Logf("PutDefaultFunc(%v)\n", s.Info)
}
abbrev := DW_ABRV_FUNCTION
if isWrapper {
abbrev = DW_ABRV_WRAPPER
}
Uleb128put(ctxt, s.Info, int64(abbrev))
// Expand '"".' to import path.
@ -1385,13 +1423,16 @@ func PutDefaultFunc(ctxt Context, s *FnState) error {
putattr(ctxt, s.Info, abbrev, DW_FORM_addr, DW_CLS_ADDRESS, 0, s.StartPC)
putattr(ctxt, s.Info, abbrev, DW_FORM_addr, DW_CLS_ADDRESS, s.Size, s.StartPC)
putattr(ctxt, s.Info, abbrev, DW_FORM_block1, DW_CLS_BLOCK, 1, []byte{DW_OP_call_frame_cfa})
ctxt.AddFileRef(s.Info, s.Filesym)
var ev int64
if s.External {
ev = 1
if isWrapper {
putattr(ctxt, s.Info, abbrev, DW_FORM_flag, DW_CLS_FLAG, int64(1), 0)
} else {
ctxt.AddFileRef(s.Info, s.Filesym)
var ev int64
if s.External {
ev = 1
}
putattr(ctxt, s.Info, abbrev, DW_FORM_flag, DW_CLS_FLAG, ev, 0)
}
putattr(ctxt, s.Info, abbrev, DW_FORM_flag, DW_CLS_FLAG, ev, 0)
// Scopes
if err := putPrunedScopes(ctxt, s, abbrev); err != nil {
@ -1489,10 +1530,10 @@ func determineVarAbbrev(v *Var, fnabbrev int) (int, bool, bool) {
// Determine whether to use a concrete variable or regular variable DIE.
concrete := true
switch fnabbrev {
case DW_ABRV_FUNCTION:
case DW_ABRV_FUNCTION, DW_ABRV_WRAPPER:
concrete = false
break
case DW_ABRV_FUNCTION_CONCRETE:
case DW_ABRV_FUNCTION_CONCRETE, DW_ABRV_WRAPPER_CONCRETE:
// If we're emitting a concrete subprogram DIE and the variable
// in question is not part of the corresponding abstract function DIE,
// then use the default (non-concrete) abbrev for this param.

4
src/cmd/internal/obj/dwarf.go
View File

@ -378,9 +378,9 @@ func (ctxt *Link) populateDWARF(curfn interface{}, s *LSym, myimportpath string)
if err != nil {
ctxt.Diag("emitting DWARF for %s failed: %v", s.Name, err)
}
err = dwarf.PutConcreteFunc(dwctxt, fnstate)
err = dwarf.PutConcreteFunc(dwctxt, fnstate, s.Wrapper())
} else {
err = dwarf.PutDefaultFunc(dwctxt, fnstate)
err = dwarf.PutDefaultFunc(dwctxt, fnstate, s.Wrapper())
}
if err != nil {
ctxt.Diag("emitting DWARF for %s failed: %v", s.Name, err)