Add -r option to 6l/8l/5l.

This permits more flexibility with cgo and swig in cases where
the program is run on a machine other than the one on which it
is built.  Rather than storing the absolute path to the shared
library in the DT_NEEDED entry, we can store just the name,
and let the dynamic linker find it using DT_RUNPATH or the
LD_LIBRARY_PATH environment variable.

R=rsc
CC=golang-dev
https://golang.org/cl/223068

src/cmd/5l/asm.c

@@ -322,6 +322,8 @@ doelf(void)
 		elfwritedynentsym(s, DT_REL, lookup(".rel", 0));
 		elfwritedynentsymsize(s, DT_RELSZ, lookup(".rel", 0));
 		elfwritedynent(s, DT_RELENT, ELF32RELSIZE);
+		if(rpath)
+			elfwritedynent(s, DT_RUNPATH, addstring(dynstr, rpath));
 		elfwritedynent(s, DT_NULL, 0);
 	}
 }

src/cmd/5l/doc.go

@@ -23,6 +23,8 @@ Options new in this version:
 -L dir1,dir2,..
 	Search for libraries (package files) in the comma-separated list of directories.
 	The default is the single location $GOROOT/pkg/$GOOS_arm.
+-r dir1:dir2:...
+	Set the dynamic linker search path when using ELF.
 -V
 	Print the linker version.
 

src/cmd/5l/l.h

@@ -333,6 +333,7 @@ EXTERN	Oprang	thumboprange[ALAST];
 EXTERN	char*	outfile;
 EXTERN	int32	pc;
 EXTERN	uchar	repop[ALAST];
+EXTERN	char*	rpath;
 EXTERN	uint32	stroffset;
 EXTERN	int32	symsize;
 EXTERN	Prog*	textp;

src/cmd/5l/obj.c

@@ -81,7 +81,7 @@ linkername[] =
 void
 usage(void)
 {
-	fprint(2, "usage: 5l [-E entry] [-H head] [-L dir] [-T text] [-D data] [-R rnd] [-o out] main.5\n");
+	fprint(2, "usage: 5l [-E entry] [-H head] [-L dir] [-T text] [-D data] [-R rnd] [-r path] [-o out] main.5\n");
 	errorexit();
 }
 
@@ -128,6 +128,9 @@ main(int argc, char *argv[])
 	case 'R':
 		INITRND = atolwhex(EARGF(usage()));
 		break;
+	case 'r':
+		rpath = EARGF(usage());
+		break;
 	case 'H':
 		HEADTYPE = atolwhex(EARGF(usage()));
 		/* do something about setting INITTEXT */

src/cmd/6l/asm.c

@@ -408,6 +408,8 @@ doelf(void)
 		elfwritedynentsym(s, DT_RELA, lookup(".rela", 0));
 		elfwritedynentsymsize(s, DT_RELASZ, lookup(".rela", 0));
 		elfwritedynent(s, DT_RELAENT, ELF64RELASIZE);
+		if(rpath)
+			elfwritedynent(s, DT_RUNPATH, addstring(dynstr, rpath));
 		elfwritedynent(s, DT_NULL, 0);
 	}
 }

src/cmd/6l/doc.go

@@ -35,6 +35,8 @@ Options new in this version:
 -L dir1,dir2,..
 	Search for libraries (package files) in the comma-separated list of directories.
 	The default is the single location $GOROOT/pkg/$GOOS_amd64.
+-r dir1:dir2:...
+	Set the dynamic linker search path when using ELF.
 -V
 	Print the linker version.
 

src/cmd/6l/l.h

@@ -330,6 +330,7 @@ EXTERN	int	nerrors;
 EXTERN	char*	noname;
 EXTERN	char*	outfile;
 EXTERN	vlong	pc;
+EXTERN	char*	rpath;
 EXTERN	int32	spsize;
 EXTERN	Sym*	symlist;
 EXTERN	int32	symsize;

src/cmd/6l/obj.c

@@ -76,7 +76,7 @@ isobjfile(char *f)
 void
 usage(void)
 {
-	fprint(2, "usage: 6l [-options] [-E entry] [-H head] [-L dir] [-T text] [-R rnd] [-o out] main.6\n");
+	fprint(2, "usage: 6l [-options] [-E entry] [-H head] [-L dir] [-T text] [-R rnd] [-r path] [-o out] main.6\n");
 	exits("usage");
 }
 
@@ -126,6 +126,9 @@ main(int argc, char *argv[])
 	case 'R':
 		INITRND = atolwhex(EARGF(usage()));
 		break;
+	case 'r':
+		rpath = EARGF(usage());
+		break;
 	case 'x':	/* produce export table */
 		doexp = 1;
 		if(argv[1] != nil && argv[1][0] != '-' && !isobjfile(argv[1]))

src/cmd/8l/asm.c

@@ -398,6 +398,8 @@ doelf(void)
 		elfwritedynentsym(s, DT_REL, lookup(".rel", 0));
 		elfwritedynentsymsize(s, DT_RELSZ, lookup(".rel", 0));
 		elfwritedynent(s, DT_RELENT, ELF32RELSIZE);
+		if(rpath)
+			elfwritedynent(s, DT_RUNPATH, addstring(dynstr, rpath));
 		elfwritedynent(s, DT_NULL, 0);
 	}
 }

src/cmd/8l/doc.go

@@ -32,6 +32,8 @@ Options new in this version:
 -L dir1,dir2,..
 	Search for libraries (package files) in the comma-separated list of directories.
 	The default is the single location $GOROOT/pkg/$GOOS_386.
+-r dir1:dir2:...
+	Set the dynamic linker search path when using ELF.
 -V
 	Print the linker version.
 

src/cmd/8l/l.h

@@ -295,6 +295,7 @@ EXTERN	int	maxop;
 EXTERN	int	nerrors;
 EXTERN	char*	noname;
 EXTERN	int32	pc;
+EXTERN	char*	rpath;
 EXTERN	int32	spsize;
 EXTERN	Sym*	symlist;
 EXTERN	int32	symsize;

src/cmd/8l/obj.c

@@ -81,7 +81,7 @@ isobjfile(char *f)
 void
 usage(void)
 {
-	fprint(2, "usage: 8l [-options] [-E entry] [-H head] [-L dir] [-T text] [-R rnd] [-o out] main.8\n");
+	fprint(2, "usage: 8l [-options] [-E entry] [-H head] [-L dir] [-T text] [-R rnd] [-r path] [-o out] main.8\n");
 	exits("usage");
 }
 
@@ -131,6 +131,8 @@ main(int argc, char *argv[])
 	case 'R':
 		INITRND = atolwhex(EARGF(usage()));
 		break;
+	case 'r':
+		rpath = EARGF(usage());
 		break;
 	case 'x':	/* produce export table */
 		doexp = 1;