ld: fix and simplify ELF symbol generation

I started looking at this code because the nm in GNU
binutils was ignoring the first symbol in the .symtab
section.  Apparently, the System V ABI reserves the
first entry and requires all fields inside to be set
to zero.

The list of changes is as follows:

  ? reserve the first symbol entry (as noted above)
  ? fix the section indices for .data and .bss symbols
  ? factor out common code for Elf32 and Elf64
  ? remove the special case for elfsymo in [568]l/asm.c:/^asmb
  ? add the "etext" symbol in 6l
  ? add static symbols

R=rsc
CC=golang-dev
http://codereview.appspot.com/4524075

Committer: Russ Cox <rsc@golang.org>

2 files changed, 33 insertions, 48 deletions

diff --git a/src/cmd/ld/lib.h b/src/cmd/ld/lib.h
index f69f5a35d..dfd18fbff 100644
--- a/src/cmd/ld/lib.h
+++ b/src/cmd/ld/lib.h
@@ -186,8 +186,7 @@ vlong	addsize(Sym*, Sym*);
 vlong	adduint8(Sym*, uint8);
 vlong	adduint16(Sym*, uint16);
 void	asmsym(void);
-void	asmelfsym32(void);
-void	asmelfsym64(void);
+void	asmelfsym(void);
 void	asmplan9sym(void);
 void	strnput(char*, int);
 void	dodata(void);
diff --git a/src/cmd/ld/symtab.c b/src/cmd/ld/symtab.c
index da698fcc0..e3093b2aa 100644
--- a/src/cmd/ld/symtab.c
+++ b/src/cmd/ld/symtab.c
@@ -61,49 +61,35 @@ putelfstr(char *s)
 }
 
 void
-putelfsym64(Sym *x, char *s, int t, vlong addr, vlong size, int ver, Sym *go)
+putelfsyment(int off, vlong addr, vlong size, int info, int shndx)
 {
-	int bind, type, shndx, stroff;
-	
-	bind = STB_GLOBAL;
-	switch(t) {
-	default:
-		return;
-	case 'T':
-		type = STT_FUNC;
-		shndx = elftextsh + 0;
-		break;
-	case 'D':
-		type = STT_OBJECT;
-		shndx = elftextsh + 1;
+	switch(thechar) {
+	case '6':
+		LPUT(off);
+		cput(info);
+		cput(0);
+		WPUT(shndx);
+		VPUT(addr);
+		VPUT(size);
+		symsize += ELF64SYMSIZE;
 		break;
-	case 'B':
-		type = STT_OBJECT;
-		shndx = elftextsh + 2;
+	default:
+		LPUT(off);
+		LPUT(addr);
+		LPUT(size);
+		cput(info);
+		cput(0);
+		WPUT(shndx);
+		symsize += ELF32SYMSIZE;
 		break;
 	}
-	
-	stroff = putelfstr(s);
-	LPUT(stroff);	// string
-	cput((bind<<4)|(type&0xF));
-	cput(0);
-	WPUT(shndx);
-	VPUT(addr);
-	VPUT(size);
 }
 
 void
-asmelfsym64(void)
+putelfsym(Sym *x, char *s, int t, vlong addr, vlong size, int ver, Sym *go)
 {
-	genasmsym(putelfsym64);
-}
+	int bind, type, shndx, off;
 
-void
-putelfsym32(Sym *x, char *s, int t, vlong addr, vlong size, int ver, Sym *go)
-{
-	int bind, type, shndx, stroff;
-	
-	bind = STB_GLOBAL;
 	switch(t) {
 	default:
 		return;
@@ -113,27 +99,27 @@ putelfsym32(Sym *x, char *s, int t, vlong addr, vlong size, int ver, Sym *go)
 		break;
 	case 'D':
 		type = STT_OBJECT;
-		shndx = elftextsh + 1;
+		if((x->type&~SSUB) == SRODATA)
+			shndx = elftextsh + 1;
+		else
+			shndx = elftextsh + 2;
 		break;
 	case 'B':
 		type = STT_OBJECT;
-		shndx = elftextsh + 2;
+		shndx = elftextsh + 3;
 		break;
 	}
-	
-	stroff = putelfstr(s);
-	LPUT(stroff);	// string
-	LPUT(addr);
-	LPUT(size);
-	cput((bind<<4)|(type&0xF));
-	cput(0);
-	WPUT(shndx);
+	bind = ver ? STB_LOCAL : STB_GLOBAL;
+	off = putelfstr(s);
+	putelfsyment(off, addr, size, (bind<<4)|(type&0xf), shndx);
 }
 
 void
-asmelfsym32(void)
+asmelfsym(void)
 {
-	genasmsym(putelfsym32);
+	// the first symbol entry is reserved
+	putelfsyment(0, 0, 0, (STB_LOCAL<<4)|STT_NOTYPE, 0);
+	genasmsym(putelfsym);
 }
 
 void