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cmd/link: add runtime.text.N symbols to Mach-O symbol table

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On Darwin/ARM64 when external linking, for very large text we
split it into multiple sections. For each section (other than the
first) we create runtime.text.N marker symbols. In CL 316050 I
forgot to add those symbols to the symbol table. This CL does it.

It doesn't actually matter for program execution. But we add them
on ELF when splitting text sections, so we do it here as well.
Also, this makes it easier to tell if we split text sections.

Change-Id: Ida7f8e9431867881e5ee2bc1a2129eeaf83cb878
Reviewed-on: https://go-review.googlesource.com/c/go/+/353209
Trust: Cherry Mui <cherryyz@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>
This commit is contained in:
Cherry Mui 2021-09-29 16:47:12 -04:00
parent d4aed7e42c
commit 9112d296e8
2 changed files with 22 additions and 4 deletions
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18
src/cmd/link/internal/ld/ld_test.go
View File

@ -5,6 +5,7 @@
package ld
import (
"bytes"
"debug/pe"
"fmt"
"internal/testenv"
@ -154,13 +155,22 @@ func TestLargeTextSectionSplitting(t *testing.T) {
// is arbitrary; we just need something sufficiently large that uses
// external linking.
exe := filepath.Join(dir, "go.exe")
out, eerr := exec.Command(testenv.GoToolPath(t), "build", "-o", exe, "-ldflags=-linkmode=external -debugtextsize=1048576", "cmd/go").CombinedOutput()
if eerr != nil {
t.Fatalf("build failure: %s\n%s\n", eerr, string(out))
out, err := exec.Command(testenv.GoToolPath(t), "build", "-o", exe, "-ldflags=-linkmode=external -debugtextsize=1048576", "cmd/go").CombinedOutput()
if err != nil {
t.Fatalf("build failure: %s\n%s\n", err, string(out))
}
// Check that we did split text sections.
out, err = exec.Command(testenv.GoToolPath(t), "tool", "nm", exe).CombinedOutput()
if err != nil {
t.Fatalf("nm failure: %s\n%s\n", err, string(out))
}
if !bytes.Contains(out, []byte("runtime.text.1")) {
t.Errorf("runtime.text.1 not found, text section not split?")
}
// Result should be runnable.
_, err := exec.Command(exe, "version").CombinedOutput()
_, err = exec.Command(exe, "version").CombinedOutput()
if err != nil {
t.Fatal(err)
}

8
src/cmd/link/internal/ld/macho.go
View File

@ -897,6 +897,14 @@ func collectmachosyms(ctxt *Link) {
if ldr.SymType(s) == sym.STEXT {
addsym(s)
}
for n := range Segtext.Sections[1:] {
s := ldr.Lookup(fmt.Sprintf("runtime.text.%d", n+1), 0)
if s != 0 {
addsym(s)
} else {
break
}
}
s = ldr.Lookup("runtime.etext", 0)
if ldr.SymType(s) == sym.STEXT {
addsym(s)