FFI step 2: can ask for libc.so.6.

introduced explicit "data" symbol instead of etext
to mark beginning of data, so that using larger
alignment (i.e. 4MB like GNU loader) doesn't
confuse garbage collector.

split dodata into dodata and dobss in preparation
for putting the dynamic data + headers in the data
segment instead of stuffed at the beginning of the binary.

R=r
DELTA=52  (37 added, 3 deleted, 12 changed)
OCL=33610
CL=33618

src/cmd/6l/asm.c

@@ -128,7 +128,7 @@ asmb(void)
 	int32 v, magic;
 	int a, nl;
 	uchar *op1;
-	vlong vl, va, startva, fo, w, symo, hashoff;
+	vlong vl, va, startva, fo, w, symo, hashoff, dstrtab, off;
 	vlong symdatva = 0x99LL<<32;
 	Elf64Hdr *eh;
 	Elf64PHdr *ph, *pph;
@@ -431,6 +431,7 @@ asmb(void)
 		sh = newElf64SHdr("");
 
 		pph = nil;	/* silence compiler */
+		dstrtab = 0;
 
 		/* Dynamic linking sections */
 		if (!debug['d']) {	/* -d suppresses dynamic loader format */
@@ -443,7 +444,7 @@ asmb(void)
 			pph->off = ELF64HDRSIZE;
 			pph->vaddr = startva + pph->off;
 			pph->paddr = startva + pph->off;
-			pph->align = 8;
+			pph->align = INITRND;
 
 			/* interpreter */
 			ph = newElf64PHdr();
@@ -503,13 +504,19 @@ asmb(void)
 			sh->addr = startva + sh->off;
 			sh->off = startelf();
 			elf64writedynent(DT_HASH, startva+hashoff);
-			elf64writedynent(DT_STRTAB, startva+ELF64FULLHDRSIZE-STRTABSIZE);
 			elf64writedynent(DT_SYMTAB, startva);
 			elf64writedynent(DT_RELA, startva);
 			elf64writedynent(DT_RELASZ, 0);	// size of the whole rela in bytes
 			elf64writedynent(DT_RELAENT, ELF64RELASIZE);
-			elf64writedynent(DT_STRSZ, STRTABSIZE);
 			elf64writedynent(DT_SYMENT, 0);
+//			elf64writedynent(DT_NEEDED, elf64addstr("libc.so.6"));
+
+			/* make space for these now but fill them in later */
+			cflush();
+			dstrtab = seek(cout, 0, 1);
+			elf64writedynent(DT_STRTAB, -1);
+			elf64writedynent(DT_STRSZ, -1);
+
 			elf64writedynent(DT_NULL, 0);
 			sh->size = endelf() - sh->off;
 			sh->addralign = 8;
@@ -534,7 +541,7 @@ asmb(void)
 			ph->paddr = startva + ph->off;
 			ph->filesz = sh->off + sh->size - ph->off;
 			ph->memsz = ph->filesz;
-			ph->align = 8;
+			ph->align = INITRND;
 		}
 
 		ph = newElf64PHdr();
@@ -644,6 +651,17 @@ asmb(void)
 		elf64writestrtable();
 		sh->size = endelf() - sh->off;
 
+		if(dstrtab != 0) {
+			// update DT_STRTAB entry
+			cflush();
+			off = seek(cout, 0, 1);
+			seek(cout, dstrtab, 0);
+			elf64writedynent(DT_STRTAB, sh->addr);
+			elf64writedynent(DT_STRSZ, sh->size);
+			cflush();
+			seek(cout, off, 0);
+		}
+
 		/* Main header */
 		eh = getElf64Hdr();
 		eh->ident[EI_MAG0] = '\177';

src/cmd/6l/l.h

@@ -390,6 +390,7 @@ double	cputime(void);
 void	datblk(int32, int32);
 void	deadcode(void);
 void	diag(char*, ...);
+void	dobss(void);
 void	dodata(void);
 void	doinit(void);
 void	doprof1(void);

src/cmd/6l/obj.c

@@ -390,6 +390,7 @@ main(int argc, char *argv[])
 	patch();
 	follow();
 	dodata();
+	dobss();
 	dostkoff();
 	paramspace = "SP";	/* (FP) now (SP) on output */
 	if(debug['p'])

src/cmd/6l/pass.c

@@ -124,6 +124,14 @@ dodata(void)
 		}
 		datsize += u;
 	}
+}
+
+void
+dobss(void)
+{
+	int i;
+	Sym *s;
+	int32 t;
 
 	/* now the bss */
 	bsssize = 0;
@@ -137,6 +145,7 @@ dodata(void)
 		s->value = bsssize + datsize;
 		bsssize += t;
 	}
+	xdefine("data", SBSS, 0);
 	xdefine("edata", SBSS, datsize);
 	xdefine("end", SBSS, bsssize + datsize);
 }

src/cmd/ld/elf64.c

@@ -13,7 +13,7 @@ static	Elf64Hdr	hdr;
 static	Elf64PHdr	*phdr[NSECT];
 static	Elf64SHdr	*shdr[NSECT];
 static	char	*sname[NSECT];
-static	char	*str[NSECT];
+static	char	*str[20];
 
 /*
  Initialize the global variable that describes the ELF header. It will be updated as
@@ -80,15 +80,19 @@ elf64writestrtable(void)
 		diag("elf64 string table overflow");
 }
 
-void
+uint32
-e64addstr(char *name)
+elf64addstr(char *name)
 {
-	if (numstr >= NSECT) {
+	int r;
+
+	if (numstr >= nelem(str)) {
 		diag("too many elf strings");
-		return;
+		return 0;
 	}
 	str[numstr++] = strdup(name);
+	r = stroffset;
 	stroffset += strlen(name)+1;
+	return r;
 }
 
 uint32
@@ -135,11 +139,10 @@ newElf64SHdr(char *name)
 		hdr.shstrndx = hdr.shnum;
 	e = malloc(sizeof *e);
 	memset(e, 0, sizeof *e);
-	e->name = stroffset;
+	e->name = elf64addstr(name);
 	if (hdr.shnum >= NSECT) {
 		diag("too many shdrs");
 	} else {
-		e64addstr(name);
 		shdr[hdr.shnum++] = e;
 	}
 	return e;
@@ -152,7 +155,7 @@ getElf64Hdr(void)
 }
 
 uint32
-elf64writehdr()
+elf64writehdr(void)
 {
 	int i;
 

src/cmd/ld/elf64.h

@@ -274,6 +274,7 @@ Elf64PHdr	*newElf64PHdr();
 uint32	elf64writehdr(void);
 uint32	elf64writephdrs(void);
 uint32	elf64writeshdrs(void);
+uint32	elf64addstr(char*);
 void	elf64writestrtable(void);
 void	elf64writedynent(int, uint64);
 uint32	elf64_hash(uchar*);

src/pkg/runtime/mgc0.c

@@ -19,6 +19,7 @@ enum {
 	Debug = 0
 };
 
+extern byte data[];
 extern byte etext[];
 extern byte end[];
 
@@ -84,7 +85,7 @@ mark(void)
 	G *gp;
 
 	// mark data+bss
-	scanblock(0, etext, end - etext);
+	scanblock(0, data, end - data);
 
 	// mark stacks
 	for(gp=allg; gp!=nil; gp=gp->alllink) {