Dwarf output for 6l.

Part 1, general scaffolding and pc/lc sections.

R=rsc, r, ken2
CC=golang-dev
https://golang.org/cl/1987042

src/cmd/6l/Makefile

@@ -9,6 +9,7 @@ TARG=\
 
 OFILES=\
 	asm.$O\
+	dwarf.$O\
 	elf.$O\
 	enam.$O\
 	go.$O\
@@ -26,6 +27,7 @@ HFILES=\
 	../ld/lib.h\
 	../ld/elf.h\
 	../ld/macho.h\
+	../ld/dwarf.h\
 
 $(TARG): $(OFILES)
 	$(LD) -o $(TARG) -L"$(GOROOT)"/lib $(OFILES) -lbio -l9

src/cmd/6l/asm.c

@@ -31,6 +31,7 @@
 #include	"l.h"
 #include	"../ld/lib.h"
 #include	"../ld/elf.h"
+#include	"../ld/dwarf.h"
 #include	"../ld/macho.h"
 
 #define	Dbufslop	100
@@ -300,10 +301,9 @@ doelf(void)
 		elfstr[ElfStrGosymcounts] = addstring(shstrtab, ".gosymcounts");
 		elfstr[ElfStrGosymtab] = addstring(shstrtab, ".gosymtab");
 		elfstr[ElfStrGopclntab] = addstring(shstrtab, ".gopclntab");
-		if(debug['e']) {
                 elfstr[ElfStrSymtab] = addstring(shstrtab, ".symtab");
                 elfstr[ElfStrStrtab] = addstring(shstrtab, ".strtab");
-		}
+                dwarfaddshstrings(shstrtab);
 	}
 	elfstr[ElfStrShstrtab] = addstring(shstrtab, ".shstrtab");
 
@@ -546,7 +546,7 @@ asmb(void)
 		seek(cout, v, 0);
 		
 		/* index of elf text section; needed by asmelfsym, double-checked below */
-		/* debug['d'] causes 8 extra sections before the .text section */
+		/* !debug['d'] causes 8 extra sections before the .text section */
 		elftextsh = 1;
 		if(!debug['d'])
 			elftextsh += 8;
@@ -627,7 +627,7 @@ asmb(void)
 		lputl(symsize);
 		lputl(lcsize);
 		cflush();
-		if(!debug['s'] && debug['e']) {
+		if(!debug['s']) {
 			elfsymo = symo+8+symsize+lcsize;
 			seek(cout, elfsymo, 0);
 			asmelfsym();
@@ -635,6 +635,11 @@ asmb(void)
 			elfstro = seek(cout, 0, 1);
 			elfsymsize = elfstro - elfsymo;
 			write(cout, elfstrdat, elfstrsize);
+
+                        if(debug['v'])
+                               Bprint(&bso, "%5.2f dwarf\n", cputime());
+
+                        dwarfemitdebugsections();
 		}
 	} else
 	if(dlm){
@@ -911,7 +916,6 @@ asmb(void)
 			sh->addralign = 1;
 			sh->addr = symdatva + 8 + symsize;
 
-			if(debug['e']) {
                         sh = newElfShdr(elfstr[ElfStrSymtab]);
                         sh->type = SHT_SYMTAB;
                         sh->off = elfsymo;
@@ -925,7 +929,8 @@ asmb(void)
                         sh->off = elfstro;
                         sh->size = elfstrsize;
                         sh->addralign = 1;
-			}
+
+                        dwarfaddheaders();
 		}
 
 		sh = newElfShstrtab(elfstr[ElfStrShstrtab]);
@@ -977,6 +982,13 @@ cflush(void)
 	cbc = sizeof(buf.cbuf);
 }
 
+/* Current position in file */
+vlong
+cpos(void)
+{
+        return seek(cout, 0, 1) + sizeof(buf.cbuf) - cbc;
+}
+
 void
 outa(int n, uchar *cast, uchar *map, vlong l)
 {
@@ -1322,4 +1334,3 @@ rnd(vlong v, vlong r)
 	v -= c;
 	return v;
 }
-

src/cmd/6l/l.h

@@ -394,6 +394,7 @@ Prog*	brchain(Prog*);
 Prog*	brloop(Prog*);
 void	buildop(void);
 void	cflush(void);
+vlong   cpos(void);
 void	ckoff(Sym*, int32);
 Prog*	copyp(Prog*);
 double	cputime(void);

src/cmd/6l/obj.c

@@ -33,6 +33,7 @@
 #include	"../ld/lib.h"
 #include	"../ld/elf.h"
 #include	"../ld/macho.h"
+#include	"../ld/dwarf.h"
 #include	<ar.h>
 
 char	*noname		= "<none>";
@@ -575,6 +576,7 @@ loop:
 				histfrogp++;
 			} else
 				collapsefrog(s);
+                        dwarfaddfrag(s->value, s->name);
 		}
 		goto loop;
 	}
@@ -1058,4 +1060,3 @@ doprof2(void)
 		}
 	}
 }
-

src/cmd/ld/dwarf.h

+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+
+/*
+ * Register 'f' symbol file fragments.  Doing this while parsing the
+ * .6 input saves a pass over the symbol table later.
+ */
+void dwarfaddfrag(int n, char* frag);
+
+/*
+ * Add the dwarf section names to the ELF
+ * s[ection]h[eader]str[ing]tab.
+ */
+void dwarfaddshstrings(Sym *shstrtab);
+
+/*
+ * Emit debug_abbrevs, debug_info and debug_line sections to current
+ * offset in cout.
+ */
+void dwarfemitdebugsections(void);
+
+/*
+ * Add ELF section headers pointing to the sections emitted in
+ * dwarfemitdebugsections.
+ */
+void dwarfaddheaders(void);