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cmd/internal/obj, cmd/link: record ABIs and aliases in Go obj files

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This repurposes the "version" field of a symbol reference in the Go
object file format to be an ABI field. Currently, this is just 0 or 1
depending on whether the symbol is static (the linker turns it into a
different internal version number), so it's already only tenuously a
symbol version. We change this to be -1 for static symbols and
otherwise by the ABI number.

This also adds a separate list of ABI alias symbols to be recorded in
the object file. The ABI aliases must be a separate list and not just
part of the symbol definitions because it's possible to have a symbol
defined in one package and the alias "defined" in a different package.
For example, this can happen if a symbol is defined in assembly in one
package and stubbed in a different package. The stub triggers the
generation of the ABI alias, but in a different package from the
definition.

For #27539.

Change-Id: I015c9fe54690c027de6ef77e22b5585976a01587
Reviewed-on: https://go-review.googlesource.com/c/147157
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
This commit is contained in:
Austin Clements 2018-10-26 13:53:02 -04:00
parent 07544c7e80
commit c5718b6b26
6 changed files with 96 additions and 26 deletions
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31
src/cmd/internal/obj/link.go
View file

@ -432,7 +432,7 @@ const (
)
// Attribute is a set of symbol attributes.
type Attribute int16
type Attribute uint16
const (
AttrDuplicateOK Attribute = 1 << iota
@ -468,6 +468,13 @@ const (
// For function symbols; indicates that the specified function was the
// target of an inline during compilation
AttrWasInlined
// attrABIBase is the value at which the ABI is encoded in
// Attribute. This must be last; all bits after this are
// assumed to be an ABI value.
//
// MUST BE LAST since all bits above this comprise the ABI.
attrABIBase
)
func (a Attribute) DuplicateOK() bool { return a&AttrDuplicateOK != 0 }
@ -493,6 +500,12 @@ func (a *Attribute) Set(flag Attribute, value bool) {
}
}
func (a Attribute) ABI() ABI { return ABI(a / attrABIBase) }
func (a *Attribute) SetABI(abi ABI) {
const mask = 1 // Only one ABI bit for now.
*a = (*a &^ (mask * attrABIBase)) | Attribute(abi)*attrABIBase
}
var textAttrStrings = [...]struct {
bit Attribute
s string
@ -524,6 +537,12 @@ func (a Attribute) TextAttrString() string {
a &^= x.bit
}
}
switch a.ABI() {
case ABI0:
case ABIInternal:
s += "ABIInternal|"
a.SetABI(0) // Clear ABI so we don't print below.
}
if a != 0 {
s += fmt.Sprintf("UnknownAttribute(%d)|", a)
}
@ -606,6 +625,16 @@ type Link struct {
// state for writing objects
Text []*LSym
Data []*LSym
// ABIAliases are text symbols that should be aliased to all
// ABIs. These symbols may only be referenced and not defined
// by this object, since the need for an alias may appear in a
// different object than the definition. Hence, this
// information can't be carried in the symbol definition.
//
// TODO(austin): Replace this with ABI wrappers once the ABIs
// actually diverge.
ABIAliases []*LSym
}
func (ctxt *Link) Diag(format string, args ...interface{}) {