libmach: support reading symbols from Windows .exe for nm

Fixes #979.

R=rsc, alex.brainman
CC=golang-dev, vcc.163
https://golang.org/cl/4894051

include/mach.h

@@ -142,6 +142,7 @@ enum
 	FAMD64B,		/* 6.out bootable */
 	FPOWER64,		/* 9.out */
 	FPOWER64B,		/* 9.out bootable */
+	FWINPE,			/* windows PE executable */
 
 	ANONE = 0,		/* dissembler types */
 	AMIPS,

src/cmd/ld/pe.c

@@ -32,6 +32,11 @@ static char dosstub[] =
 	0x24, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
 };
 
+// Note: currently only up to 8 chars plus \0.
+static char *symlabels[] = {
+	"symtab", "esymtab", "pclntab", "epclntab"
+};
+
 static Sym *rsrcsym;
 
 static char symnames[256]; 
@@ -44,6 +49,7 @@ static int pe64;
 static int nsect;
 static int nextsectoff;
 static int nextfileoff;
+static int textsect;
 
 static IMAGE_FILE_HEADER fh;
 static IMAGE_OPTIONAL_HEADER oh;
@@ -449,20 +455,29 @@ addsymtable(void)
 {
 	IMAGE_SECTION_HEADER *h;
 	int i, size;
+	Sym *s;
 	
-	if(nextsymoff == 0)
-		return;
-	
-	size  = nextsymoff + 4 + 18;
+	fh.NumberOfSymbols = sizeof(symlabels)/sizeof(symlabels[0]);
+	size = nextsymoff + 4 + 18*fh.NumberOfSymbols;
 	h = addpesection(".symtab", size, size);
 	h->Characteristics = IMAGE_SCN_MEM_READ|
 		IMAGE_SCN_MEM_DISCARDABLE;
 	chksectoff(h, cpos());
 	fh.PointerToSymbolTable = cpos();
-	fh.NumberOfSymbols = 1;
-	strnput("", 18); // one empty symbol
-	// put symbol string table
-	lputl(size);
+	
+	// put COFF symbol table
+	for (i=0; i<fh.NumberOfSymbols; i++) {
+		s = rlookup(symlabels[i], 0);
+		strnput(s->name, 8);
+		lputl(datoff(s->value));
+		wputl(textsect);
+		wputl(0x0308);  // "array of structs"
+		cput(2);        // storage class: external
+		cput(0);        // no aux entries
+	}
+
+	// put COFF string table
+	lputl(nextsymoff + 4);
 	for (i=0; i<nextsymoff; i++)
 		cput(symnames[i]);
 	strnput("", h->SizeOfRawData - size);
@@ -532,6 +547,7 @@ asmbpe(void)
 		IMAGE_SCN_CNT_INITIALIZED_DATA|
 		IMAGE_SCN_MEM_EXECUTE|IMAGE_SCN_MEM_READ;
 	chksectseg(t, &segtext);
+	textsect = nsect;
 
 	d = addpesection(".data", segdata.len, segdata.filelen);
 	d->Characteristics = IMAGE_SCN_CNT_INITIALIZED_DATA|

src/libmach/executable.c

@@ -66,6 +66,7 @@ static	int	adotout(int, Fhdr*, ExecHdr*);
 static	int	elfdotout(int, Fhdr*, ExecHdr*);
 static	int	machdotout(int, Fhdr*, ExecHdr*);
 static	int	armdotout(int, Fhdr*, ExecHdr*);
+static	int	pedotout(int, Fhdr*, ExecHdr*);
 static	void	setsym(Fhdr*, vlong, int32, vlong, int32, vlong, int32);
 static	void	setdata(Fhdr*, uvlong, int32, vlong, int32);
 static	void	settext(Fhdr*, uvlong, uvlong, int32, vlong);
@@ -312,6 +313,15 @@ ExecTable exectab[] =
 		sizeof(Exec),
 		beswal,
 		common },
+	{ 0x4d5a9000,    /* see dosstub[] in pe.c */
+		"windows PE executable",
+		nil,
+		FWINPE,
+		0,
+		&mi386,
+		sizeof(Exec), /* TODO */
+		nil,
+		pedotout },
 	{ 0 },
 };
 
@@ -1249,6 +1259,164 @@ armdotout(int fd, Fhdr *fp, ExecHdr *hp)
 	return 1;
 }
 
+/*
+ * Structures needed to parse PE image.
+ */
+typedef struct {
+	uint16 Machine;
+	uint16 NumberOfSections;
+	uint32 TimeDateStamp;
+	uint32 PointerToSymbolTable;
+	uint32 NumberOfSymbols;
+	uint16 SizeOfOptionalHeader;
+	uint16 Characteristics;
+} IMAGE_FILE_HEADER;
+
+typedef struct {
+	uint8  Name[8];
+	uint32 VirtualSize;
+	uint32 VirtualAddress;
+	uint32 SizeOfRawData;
+	uint32 PointerToRawData;
+	uint32 PointerToRelocations;
+	uint32 PointerToLineNumbers;
+	uint16 NumberOfRelocations;
+	uint16 NumberOfLineNumbers;
+	uint32 Characteristics;
+} IMAGE_SECTION_HEADER;
+
+typedef struct {
+	uint32 VirtualAddress;
+	uint32 Size;
+} IMAGE_DATA_DIRECTORY;
+
+typedef struct {
+	uint16 Magic;
+	uint8  MajorLinkerVersion;
+	uint8  MinorLinkerVersion;
+	uint32 SizeOfCode;
+	uint32 SizeOfInitializedData;
+	uint32 SizeOfUninitializedData;
+	uint32 AddressOfEntryPoint;
+	uint32 BaseOfCode;
+	uint32 BaseOfData;
+	uint32 ImageBase;
+	uint32 SectionAlignment;
+	uint32 FileAlignment;
+	uint16 MajorOperatingSystemVersion;
+	uint16 MinorOperatingSystemVersion;
+	uint16 MajorImageVersion;
+	uint16 MinorImageVersion;
+	uint16 MajorSubsystemVersion;
+	uint16 MinorSubsystemVersion;
+	uint32 Win32VersionValue;
+	uint32 SizeOfImage;
+	uint32 SizeOfHeaders;
+	uint32 CheckSum;
+	uint16 Subsystem;
+	uint16 DllCharacteristics;
+	uint32 SizeOfStackReserve;
+	uint32 SizeOfStackCommit;
+	uint32 SizeOfHeapReserve;
+	uint32 SizeOfHeapCommit;
+	uint32 LoaderFlags;
+	uint32 NumberOfRvaAndSizes;
+	IMAGE_DATA_DIRECTORY DataDirectory[16];
+} IMAGE_OPTIONAL_HEADER;
+
+static int
+match8(void *buf, char *cmp)
+{
+	return strncmp((char*)buf, cmp, 8) == 0;
+}
+
+/* TODO(czaplinski): 64b windows? */
+/*
+ * Read from Windows PE/COFF .exe file image.
+ */
+static int
+pedotout(int fd, Fhdr *fp, ExecHdr *hp)
+{
+	uint32 start, magic;
+	uint32 symtab, esymtab;
+	IMAGE_FILE_HEADER fh;
+	IMAGE_SECTION_HEADER sh;
+	IMAGE_OPTIONAL_HEADER oh;
+	uint8 sym[18];
+	uint32 *valp;
+	int i;
+
+	USED(hp);
+	seek(fd, 0x3c, 0);
+	if (readn(fd, &start, sizeof(start)) != sizeof(start)) {
+		werrstr("crippled PE MSDOS header");
+		return 0;
+	}
+	start = leswal(start);
+
+	seek(fd, start, 0);
+	if (readn(fd, &magic, sizeof(magic)) != sizeof(magic)) {
+		werrstr("no PE magic number found");
+		return 0;
+	}
+	if (beswal(magic) != 0x50450000) {  /* "PE\0\0" */
+		werrstr("incorrect PE magic number");
+		return 0;
+	}
+
+	if (readn(fd, &fh, sizeof(fh)) != sizeof(fh)) {
+		werrstr("crippled PE File Header");
+		return 0;
+	}
+	if (fh.PointerToSymbolTable == 0) {
+		werrstr("zero pointer to COFF symbol table");
+		return 0;
+	}
+
+	if (readn(fd, &oh, sizeof(oh)) != sizeof(oh)) {
+		werrstr("crippled PE Optional Header");
+		return 0;
+	}
+
+	seek(fd, start+sizeof(magic)+sizeof(fh)+leswab(fh.SizeOfOptionalHeader), 0);
+	fp->txtaddr = fp->dataddr = 0;
+	for (i=0; i<leswab(fh.NumberOfSections); i++) {
+		if (readn(fd, &sh, sizeof(sh)) != sizeof(sh)) {
+			werrstr("could not read Section Header %d", i+1);
+			return 0;
+		}
+		if (match8(sh.Name, ".text"))
+			settext(fp, leswal(sh.VirtualAddress), leswal(oh.AddressOfEntryPoint), leswal(sh.VirtualSize), leswal(sh.PointerToRawData));
+		if (match8(sh.Name, ".data"))
+			setdata(fp, leswal(sh.VirtualAddress), leswal(sh.SizeOfRawData), leswal(sh.PointerToRawData), leswal(sh.VirtualSize)-leswal(sh.SizeOfRawData));
+	}
+	if (fp->txtaddr==0 || fp->dataddr==0) {
+		werrstr("no .text or .data");
+		return 0;
+	}
+
+	seek(fd, leswal(fh.PointerToSymbolTable), 0);
+	symtab = esymtab = 0;
+	for (i=0; i<leswal(fh.NumberOfSymbols); i++) {
+		if (readn(fd, &sym, sizeof(sym)) != sizeof(sym)) {
+			werrstr("crippled COFF symbol %d", i);
+			return 0;
+		}
+		valp = (uint32 *)&sym[8];
+		if (match8(sym, "symtab"))
+			symtab = leswal(*valp);
+		if (match8(sym, "esymtab"))
+			esymtab = leswal(*valp);
+	}
+	if (symtab==0 || esymtab==0) {
+		werrstr("no symtab or esymtab in COFF symbol table");
+		return 0;
+	}
+	setsym(fp, symtab, esymtab-symtab, 0, 0, 0, 0);
+
+	return 1;
+}
+
 static void
 settext(Fhdr *fp, uvlong e, uvlong a, int32 s, vlong off)
 {