cmd/internal/ld: reserve space for package list note when -buildmode=shared

This makes the intermediate object file a little bigger but it doesn't waste
any space in the final shared library.

Fixes #10691

Change-Id: Ic51a571d60291f1ac2dad1b50dba4679643168ae
Reviewed-on: https://go-review.googlesource.com/9710
Reviewed-by: Ian Lance Taylor <iant@golang.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/src/cmd/6l/obj.go b/src/cmd/6l/obj.go
index ba3580ef5f..9e6dc60e2d 100644
--- a/src/cmd/6l/obj.go
+++ b/src/cmd/6l/obj.go
@@ -169,6 +169,14 @@ func archinit() {
 		ld.Elfinit()
 
 		ld.HEADR = ld.ELFRESERVE
+		if ld.Buildmode == ld.BuildmodeShared {
+			// When building a shared library we write a package list
+			// note that can get quite large. The external linker will
+			// re-layout all the sections anyway, so making this larger
+			// just wastes a little space in the intermediate object
+			// file, not the final shared library.
+			ld.HEADR *= 3
+		}
 		if ld.INITTEXT == -1 {
 			ld.INITTEXT = (1 << 22) + int64(ld.HEADR)
 		}