Stowage/go
2
0
Fork 0
mirror of https://github.com/golang/go.git synced 2025-12-08 06:10:04 +00:00
Code Issues Projects Releases Packages Wiki Activity

cmd/asm, cmd/link, runtime: introduce FuncInfo flag bits

Browse source 
The runtime traceback code has its own definition of which functions
mark the top frame of a stack, separate from the TOPFRAME bits that
exist in the assembly and are passed along in DWARF information.
It's error-prone and redundant to have two different sources of truth.
This CL provides the actual TOPFRAME bits to the runtime, so that
the runtime can use those bits instead of reinventing its own category.

This CL also adds a new bit, SPWRITE, which marks functions that
write directly to SP (anything but adding and subtracting constants).
Such functions must stop a traceback, because the traceback has no
way to rederive the SP on entry. Again, the runtime has its own definition
which is mostly correct, but also missing some functions. During ordinary
goroutine context switches, such functions do not appear on the stack,
so the incompleteness in the runtime usually doesn't matter.
But profiling signals can arrive at any moment, and the runtime may
crash during traceback if it attempts to unwind an SP-writing frame
and gets out-of-sync with the actual stack. The runtime contains code
to try to detect likely candidates but again it is incomplete.
Deriving the SPWRITE bit automatically from the actual assembly code
provides the complete truth, and passing it to the runtime lets the
runtime use it.

This CL is part of a stack adding windows/arm64
support (#36439), intended to land in the Go 1.17 cycle.
This CL is, however, not windows/arm64-specific.
It is cleanup meant to make the port (and future ports) easier.

Change-Id: I227f53b23ac5b3dabfcc5e8ee3f00df4e113cf58
Reviewed-on: https://go-review.googlesource.com/c/go/+/288800
Trust: Russ Cox <rsc@golang.org>
Trust: Jason A. Donenfeld <Jason@zx2c4.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Jason A. Donenfeld <Jason@zx2c4.com>
This commit is contained in:
Russ Cox 2021-01-28 15:21:33 -05:00
parent aa0388f2ed
commit 4dd77bdc91
24 changed files with 209 additions and 101 deletions
Download patch file Download diff file Expand all files Collapse all files

23
src/cmd/internal/obj/link.go
View file

@ -454,6 +454,7 @@ type FuncInfo struct {
Locals int32
Align int32
FuncID objabi.FuncID
FuncFlag objabi.FuncFlag
Text *Prog
Autot map[*LSym]struct{}
Pcln Pcln
@ -619,10 +620,6 @@ const (
// target of an inline during compilation
AttrWasInlined
// TopFrame means that this function is an entry point and unwinders should not
// keep unwinding beyond this frame.
AttrTopFrame
// Indexed indicates this symbol has been assigned with an index (when using the
// new object file format).
AttrIndexed
@ -663,7 +660,6 @@ func (a *Attribute) NeedCtxt() bool { return a.load()&AttrNeedCtxt !=
func (a *Attribute) NoFrame() bool { return a.load()&AttrNoFrame != 0 }
func (a *Attribute) Static() bool { return a.load()&AttrStatic != 0 }
func (a *Attribute) WasInlined() bool { return a.load()&AttrWasInlined != 0 }
func (a *Attribute) TopFrame() bool { return a.load()&AttrTopFrame != 0 }
func (a *Attribute) Indexed() bool { return a.load()&AttrIndexed != 0 }
func (a *Attribute) UsedInIface() bool { return a.load()&AttrUsedInIface != 0 }
func (a *Attribute) ContentAddressable() bool { return a.load()&AttrContentAddressable != 0 }
@ -713,14 +709,13 @@ var textAttrStrings = [...]struct {
{bit: AttrNoFrame, s: "NOFRAME"},
{bit: AttrStatic, s: "STATIC"},
{bit: AttrWasInlined, s: ""},
{bit: AttrTopFrame, s: "TOPFRAME"},
{bit: AttrIndexed, s: ""},
{bit: AttrContentAddressable, s: ""},
{bit: AttrABIWrapper, s: "ABIWRAPPER"},
}
// TextAttrString formats a for printing in as part of a TEXT prog.
func (a Attribute) TextAttrString() string {
// String formats a for printing in as part of a TEXT prog.
func (a Attribute) String() string {
var s string
for _, x := range textAttrStrings {
if a&x.bit != 0 {
@ -746,6 +741,18 @@ func (a Attribute) TextAttrString() string {
return s
}
// TextAttrString formats the symbol attributes for printing in as part of a TEXT prog.
func (s *LSym) TextAttrString() string {
attr := s.Attribute.String()
if s.Func().FuncFlag&objabi.FuncFlag_TOPFRAME != 0 {
if attr != "" {
attr += "|"
}
attr += "TOPFRAME"
}
return attr
}
func (s *LSym) String() string {
return s.Name
}