libmach

src/libmach/macho.c

@@ -0,0 +1,128 @@
+#include <u.h>
+#include <libc.h>
+#include <mach.h>
+#include "macho.h"
+
+/*
+http://www.channelu.com/NeXT/NeXTStep/3.3/nd/DevTools/14_MachO/MachO.htmld/
+*/
+
+Macho*
+machoopen(char *name)
+{
+	int fd;
+	Macho *m;
+
+	if((fd = open(name, OREAD)) < 0)
+		return nil;
+	m = machoinit(fd);
+	if(m == nil)
+		close(fd);
+	return m;
+}
+
+static int
+unpackseg(uchar *p, Macho *m, MachoCmd *c, uint type, uint sz)
+{
+	u32int (*e4)(uchar*);
+
+	e4 = m->e4;
+
+	c->type = type;
+	c->size = sz;
+	switch(type){
+	default:
+		return -1;
+	case MachoCmdSegment:
+		if(sz < 56)
+			return -1;
+		strecpy(c->seg.name, c->seg.name+sizeof c->seg.name, (char*)p+8);
+		c->seg.vmaddr = e4(p+24);
+		c->seg.vmsize = e4(p+28);
+		c->seg.fileoff = e4(p+32);
+		c->seg.filesz = e4(p+36);
+		c->seg.maxprot = e4(p+40);
+		c->seg.initprot = e4(p+44);
+		c->seg.nsect = e4(p+48);
+		c->seg.flags = e4(p+52);
+		break;
+	case MachoCmdSymtab:
+		if(sz < 24)
+			return -1;
+		c->sym.symoff = e4(p+8);
+		c->sym.nsyms = e4(p+12);
+		c->sym.stroff = e4(p+16);
+		c->sym.strsize = e4(p+20);
+		break;
+	}
+	return 0;
+}
+
+
+Macho*
+machoinit(int fd)
+{
+	int i;
+	uchar hdr[7*4], *cmdp;
+	u32int (*e4)(uchar*);
+	ulong ncmd, cmdsz, ty, sz, off;
+	Macho *m;
+
+	if(seek(fd, 0, 0) < 0 || readn(fd, hdr, sizeof hdr) != sizeof hdr)
+		return nil;
+
+	if(beload4(hdr) == 0xFEEDFACE)
+		e4 = beload4;
+	else if(leload4(hdr) == 0xFEEDFACE)
+		e4 = leload4;
+	else{
+		werrstr("bad magic - not mach-o file");
+		return nil;
+	}
+
+	ncmd = e4(hdr+4*4);
+	cmdsz = e4(hdr+5*4);
+	if(ncmd > 0x10000 || cmdsz >= 0x01000000){
+		werrstr("implausible mach-o header ncmd=%lud cmdsz=%lud", ncmd, cmdsz);
+		return nil;
+	}
+
+	m = mallocz(sizeof(*m)+ncmd*sizeof(MachoCmd)+cmdsz, 1);
+	if(m == nil)
+		return nil;
+
+	m->fd = fd;
+	m->e4 = e4;
+	m->cputype = e4(hdr+1*4);
+	m->subcputype = e4(hdr+2*4);
+	m->filetype = e4(hdr+3*4);
+	m->ncmd = ncmd;
+	m->flags = e4(hdr+6*4);
+
+	m->cmd = (MachoCmd*)(m+1);
+	off = sizeof hdr;
+	cmdp = (uchar*)(m->cmd+ncmd);
+	if(readn(fd, cmdp, cmdsz) != cmdsz){
+		werrstr("reading cmds: %r");
+		free(m);
+		return nil;
+	}
+
+	for(i=0; i<ncmd; i++){
+		ty = e4(cmdp);
+		sz = e4(cmdp+4);
+		m->cmd[i].off = off;
+		unpackseg(cmdp, m, &m->cmd[i], ty, sz);
+		cmdp += sz;
+		off += sz;
+	}
+
+	return m;
+}
+
+void
+machoclose(Macho *m)
+{
+	close(m->fd);
+	free(m);
+}