runtime: identify special functions by flag instead of address

When there are plugins, there may not be a unique copy of runtime
functions like goexit, mcall, etc.  So identifying them by entry
address is problematic.  Instead, keep track of each special function
using a field in the symbol table.  That way, multiple copies of
the same runtime function will be treated identically.

Fixes #24351
Fixes #23133

Change-Id: Iea3232df8a6af68509769d9ca618f530cc0f84fd
Reviewed-on: https://go-review.googlesource.com/100739
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

1 files changed, 30 insertions, 3 deletions

diff --git a/src/runtime/symtab.go b/src/runtime/symtab.go
index 7d7c363b5b..91a8f8eb05 100644
--- a/src/runtime/symtab.go
+++ b/src/runtime/symtab.go
@@ -133,7 +133,7 @@ again:
 		}
 		se.pcExpander.init(ncallers[0], se.wasPanic)
 		ncallers = ncallers[1:]
-		se.wasPanic = se.pcExpander.funcInfo.valid() && se.pcExpander.funcInfo.entry == sigpanicPC
+		se.wasPanic = se.pcExpander.funcInfo.valid() && se.pcExpander.funcInfo.funcID == funcID_sigpanic
 		if se.skip > 0 {
 			for ; se.skip > 0; se.skip-- {
 				se.pcExpander.next()
@@ -349,6 +349,35 @@ const (
 	_ArgsSizeUnknown            = -0x80000000
 )
 
+// A FuncID identifies particular functions that need to be treated
+// specially by the runtime.
+// Note that in some situations involving plugins, there may be multiple
+// copies of a particular special runtime function.
+// Note: this list must match the list in cmd/internal/objabi/funcid.go.
+type funcID uint32
+
+const (
+	funcID_normal funcID = iota // not a special function
+	funcID_goexit
+	funcID_jmpdefer
+	funcID_mcall
+	funcID_morestack
+	funcID_mstart
+	funcID_rt0_go
+	funcID_asmcgocall
+	funcID_sigpanic
+	funcID_runfinq
+	funcID_bgsweep
+	funcID_forcegchelper
+	funcID_timerproc
+	funcID_gcBgMarkWorker
+	funcID_systemstack_switch
+	funcID_systemstack
+	funcID_cgocallback_gofunc
+	funcID_gogo
+	funcID_externalthreadhandler
+)
+
 // moduledata records information about the layout of the executable
 // image. It is written by the linker. Any changes here must be
 // matched changes to the code in cmd/internal/ld/symtab.go:symtab.
@@ -648,7 +677,6 @@ func findfunc(pc uintptr) funcInfo {
 		idx = uint32(len(datap.ftab) - 1)
 	}
 	if pc < datap.ftab[idx].entry {
-
 		// With multiple text sections, the idx might reference a function address that
 		// is higher than the pc being searched, so search backward until the matching address is found.
 
@@ -659,7 +687,6 @@ func findfunc(pc uintptr) funcInfo {
 			throw("findfunc: bad findfunctab entry idx")
 		}
 	} else {
-
 		// linear search to find func with pc >= entry.
 		for datap.ftab[idx+1].entry <= pc {
 			idx++