Pad Go symbol table out to page boundary when linking dynamically.

This avoids a crash when using cgo where glibc's malloc thinks
that it can use some of the memory following the symbol table.
This fails because the symbol table is mapped read-only, which
affects the whole page.

R=rsc
CC=golang-dev
https://golang.org/cl/1616042

src/cmd/5l/asm.c

@@ -532,6 +532,8 @@ asmb(void)
 			asmthumbmap();
 		if(dlm)
 			asmdyn();
+		if(!debug['s'])
+			strnput("", INITRND-(8+symsize+lcsize)%INITRND);
 		cflush();
 		seek(cout, symo, 0);
 		lputl(symsize);
@@ -679,8 +681,8 @@ asmb(void)
 			ph->off = symo;
 			ph->vaddr = symdatva;
 			ph->paddr = symdatva;
-			ph->filesz = 8+symsize+lcsize;
-			ph->memsz = 8+symsize+lcsize;
+			ph->filesz = rnd(8+symsize+lcsize, INITRND);
+			ph->memsz = rnd(8+symsize+lcsize, INITRND);
 			ph->align = INITRND;
 		}
 

src/cmd/6l/asm.c

@@ -620,6 +620,8 @@ asmb(void)
 			asmlc();
 		if(dlm)
 			asmdyn();
+		if(!debug['s'])
+			strnput("", INITRND-(8+symsize+lcsize)%INITRND);
 		cflush();
 		seek(cout, symo, 0);
 		lputl(symsize);
@@ -753,8 +755,8 @@ asmb(void)
 			ph->off = symo;
 			ph->vaddr = symdatva;
 			ph->paddr = symdatva;
-			ph->filesz = 8+symsize+lcsize;
-			ph->memsz = 8+symsize+lcsize;
+			ph->filesz = rnd(8+symsize+lcsize, INITRND);
+			ph->memsz = rnd(8+symsize+lcsize, INITRND);
 			ph->align = INITRND;
 		}
 

src/cmd/8l/asm.c

@@ -642,7 +642,7 @@ asmb(void)
 			asmlc();
 		if(dlm)
 			asmdyn();
-		if(HEADTYPE == 10)
+		if(HEADTYPE == 10 || (iself && !debug['s']))
 			strnput("", INITRND-(8+symsize+lcsize)%INITRND);
 		cflush();
 		seek(cout, symo, 0);
@@ -884,8 +884,8 @@ asmb(void)
 			ph->off = symo;
 			ph->vaddr = symdatva;
 			ph->paddr = symdatva;
-			ph->filesz = 8+symsize+lcsize;
-			ph->memsz = 8+symsize+lcsize;
+			ph->filesz = rnd(8+symsize+lcsize, INITRND);
+			ph->memsz = rnd(8+symsize+lcsize, INITRND);
 			ph->align = INITRND;
 		}