From: Russ Cox <rsc@golang.org>
Date: Sat, 19 Sep 2009 01:57:15 +0000 (-0700)
Subject: 8l: step toward native client.
X-Git-Tag: weekly.2009-11-06~530
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=4a4ec238707ac1a7fd83c322c3ab024464d81f20;p=gostls13.git

8l: step toward native client.
  - ELF header bits and addresses
  - do not let instructions span 32-byte boundary
  - align CALLs so return is to 32-byte boundary
  - align indirect jump targets to 32-byte boundary
    (only possible indirect jumps are function entries)

still to do:
  - replace indirect jump, indirect call, and ret with
    nacl-approved instruction sequences
  - switch to GS segment for m-local storage

R=ken
OCL=34818
CL=34818
---

diff --git a/src/cmd/8l/asm.c b/src/cmd/8l/asm.c
index e0cd435290..766349d184 100644
--- a/src/cmd/8l/asm.c
+++ b/src/cmd/8l/asm.c
@@ -132,6 +132,7 @@ asmb(void)
 	int a, np, nl, ns;
 	uint32 va, fo, w, symo;
 	uchar *op1;
+	ulong expectpc;
 
 	if(debug['v'])
 		Bprint(&bso, "%5.2f asmb\n", cputime());
@@ -143,17 +144,39 @@ asmb(void)
 	for(p = firstp; p != P; p = p->link) {
 		if(p->as == ATEXT)
 			curtext = p;
+		curp = p;
+		if(HEADTYPE == 8) {
+			// native client
+			expectpc = p->pc;
+			p->pc = pc;
+			asmins(p);
+			if(p->pc != expectpc) {
+				Bflush(&bso);
+				diag("phase error %lux sb %lux in %s", p->pc, expectpc, TNAME);
+			}
+			while(pc < p->pc) {
+				cput(0x90);	// nop
+				pc++;
+			}
+		}
 		if(p->pc != pc) {
+			Bflush(&bso);
 			if(!debug['a'])
 				print("%P\n", curp);
 			diag("phase error %lux sb %lux in %s", p->pc, pc, TNAME);
 			pc = p->pc;
 		}
-		curp = p;
-		asmins(p);
+		if(HEADTYPE != 8) {
+			asmins(p);
+			if(pc != p->pc) {
+				Bflush(&bso);
+				diag("asmins changed pc %lux sb %lux in %s", p->pc, pc, TNAME);
+			}
+		}
 		if(cbc < sizeof(and))
 			cflush();
 		a = (andptr - and);
+
 		if(debug['a']) {
 			Bprint(&bso, pcstr, pc);
 			for(op1 = and; op1 < andptr; op1++)
@@ -171,6 +194,12 @@ asmb(void)
 		pc += a;
 		cbc -= a;
 	}
+	if(HEADTYPE == 8) {
+		while(pc < INITDAT) {
+			cput(0xf4);	// hlt
+			pc++;
+		}
+	}
 	cflush();
 	switch(HEADTYPE) {
 	default:
@@ -200,6 +229,7 @@ asmb(void)
 		cflush();
 		break;
 	case 7:
+	case 8:
 		seek(cout, rnd(HEADR+textsize, INITRND)+datsize, 0);
 		strtabsize = elfstrtable();
 		cflush();
@@ -254,6 +284,7 @@ asmb(void)
 			symo = rnd(HEADR+textsize, INITRND)+rnd(datsize, INITRND);
 			break;
 		case 7:
+		case 8:
 			symo = rnd(HEADR+textsize, INITRND)+datsize+strtabsize;
 			symo = rnd(symo, INITRND);
 			break;
@@ -485,10 +516,12 @@ asmb(void)
 		break;
 
 	case 7:
+	case 8:
 		np = 3;
 		ns = 5;
 		if(!debug['s']) {
-			np++;
+			if(HEADTYPE != 8)	// no loading of debug info under native client
+				np++;
 			ns += 2;
 		}
 
@@ -497,14 +530,24 @@ asmb(void)
 		cput(1);			/* class = 32 bit */
 		cput(1);			/* data = LSB */
 		cput(1);			/* version = CURRENT */
-		strnput("", 9);
+		if(HEADTYPE == 8) {
+			cput(123);	/* os abi - native client */
+			cput(5);		/* nacl abi version */
+		} else {
+			cput(0);
+			cput(0);
+		}
+		strnput("", 7);
 		wputl(2);			/* type = EXEC */
 		wputl(3);			/* machine = AMD64 */
 		lputl(1L);			/* version = CURRENT */
 		lputl(entryvalue());		/* entry vaddr */
 		lputl(52L);			/* offset to first phdr */
 		lputl(52L+32L*np);		/* offset to first shdr */
-		lputl(0L);			/* processor specific flags */
+		if(HEADTYPE == 8)
+			lputl(0x200000);	/* native client - align mod 32 */
+		else
+			lputl(0L);			/* processor specific flags */
 		wputl(52L);			/* Ehdr size */
 		wputl(32L);			/* Phdr size */
 		wputl(np);			/* # of Phdrs */
@@ -513,13 +556,13 @@ asmb(void)
 		wputl(4);			/* Shdr with strings */
 
 		/* prog headers */
-		fo = 0;
-		va = INITTEXT & ~((vlong)INITRND - 1);
-		w = HEADR+textsize;
+		fo = HEADR;
+		va = INITTEXT;
+		w = textsize;
 
 		elfphdr(1,			/* text - type = PT_LOAD */
 			1L+4L,			/* text - flags = PF_X+PF_R */
-			0,			/* file offset */
+			fo,			/* file offset */
 			va,			/* vaddr */
 			va,			/* paddr */
 			w,			/* file size */
@@ -539,7 +582,7 @@ asmb(void)
 			w+bsssize,		/* memory size */
 			INITRND);		/* alignment */
 
-		if(!debug['s']) {
+		if(!debug['s'] && HEADTYPE != 8) {
 			elfphdr(1,			/* data - type = PT_LOAD */
 				2L+4L,			/* data - flags = PF_W+PF_R */
 				symo,		/* file offset */
@@ -573,7 +616,7 @@ asmb(void)
 
 		stroffset = 1;  /* 0 means no name, so start at 1 */
 		fo = HEADR;
-		va = (INITTEXT & ~((vlong)INITRND - 1)) + HEADR;
+		va = INITTEXT;
 		w = textsize;
 
 		elfshdr(".text",		/* name */
diff --git a/src/cmd/8l/l.h b/src/cmd/8l/l.h
index 3fb79fb1a9..1b61ee14be 100644
--- a/src/cmd/8l/l.h
+++ b/src/cmd/8l/l.h
@@ -288,7 +288,7 @@ EXTERN	uchar	inuxi2[2];
 EXTERN	uchar	inuxi4[4];
 EXTERN	uchar	ycover[Ymax*Ymax];
 EXTERN	uchar*	andptr;
-EXTERN	uchar	and[30];
+EXTERN	uchar	and[100];
 EXTERN	char	reg[D_NONE];
 EXTERN	Prog*	lastp;
 EXTERN	int32	lcsize;
diff --git a/src/cmd/8l/obj.c b/src/cmd/8l/obj.c
index fc15a83e7a..3eacf1ea84 100644
--- a/src/cmd/8l/obj.c
+++ b/src/cmd/8l/obj.c
@@ -150,6 +150,9 @@ main(int argc, char *argv[])
 		else
 		if(strcmp(goos, "darwin") == 0)
 			HEADTYPE = 6;
+		else
+		if(strcmp(goos, "nacl") == 0)
+			HEADTYPE = 8;
 		else
 			print("goos is not known: %sn", goos);
 	}
@@ -225,6 +228,15 @@ main(int argc, char *argv[])
 		if(INITRND == -1)
 			INITRND = 4096;
 		break;
+	case 8:	/* native client elf32 executable */
+		HEADR = 4096;
+		if(INITTEXT == -1)
+			INITTEXT = 0x20000;
+		if(INITDAT == -1)
+			INITDAT = 0;
+		if(INITRND == -1)
+			INITRND = 4096;
+		break;
 	}
 	if(INITDAT != 0 && INITRND != 0)
 		print("warning: -D0x%lux is ignored because of -R0x%lux\n",
diff --git a/src/cmd/8l/span.c b/src/cmd/8l/span.c
index febfc9afdc..d056fecafb 100644
--- a/src/cmd/8l/span.c
+++ b/src/cmd/8l/span.c
@@ -64,6 +64,7 @@ span(void)
 				p->as = ANOP;
 		}
 	}
+
 	n = 0;
 start:
 	do{
@@ -77,20 +78,29 @@ start:
 		}
 		c = INITTEXT;
 		for(p = firstp; p != P; p = p->link) {
-			if(p->as == ATEXT)
+			if(p->as == ATEXT) {
 				curtext = p;
+				if(HEADTYPE == 8)
+					c = (c+31)&~31;
+			}
 			if(p->to.type == D_BRANCH)
 				if(p->back)
 					p->pc = c;
-			if(n == 0 || p->to.type == D_BRANCH) {
+			if(n == 0 || HEADTYPE == 8 || p->to.type == D_BRANCH) {
+				if(HEADTYPE == 8)
+					p->pc = c;
 				asmins(p);
 				m = andptr-and;
+				if(p->mark != m)
+					again = 1;
 				p->mark = m;
 			}
-			if(c != p->pc)
-				again = 1;
-			p->pc = c;
-			c += p->mark;
+			if(HEADTYPE == 8) {
+				c = p->pc + p->mark;
+			} else {
+				p->pc = c;
+				c += p->mark;
+			}
 		}
 		textsize = c;
 		n++;
@@ -1292,9 +1302,35 @@ mfound:
 void
 asmins(Prog *p)
 {
+	if(HEADTYPE == 8) {
+		ulong npc;
 
-	andptr = and;
-	doasm(p);
+		// native client
+		// - pad indirect jump targets (aka ATEXT) to 32-byte boundary
+		// - instructions cannot cross 32-byte boundary
+		// - end of call (return address) must be on 32-byte boundary
+		if(p->as == ATEXT)
+			p->pc += 31 & -p->pc;
+		if(p->as == ACALL)
+			while((p->pc+5)&31)
+				p->pc++;
+		andptr = and;
+		doasm(p);
+		npc = p->pc + (andptr - and);
+		if((p->pc&~31) != ((npc-1)&~31)) {
+			// crossed 32-byte boundary; pad to boundary and try again
+			p->pc += 31 & -p->pc;
+			andptr = and;
+			doasm(p);
+		}
+	} else {
+		andptr = and;
+		doasm(p);
+	}
+	if(andptr > and+sizeof and) {
+		print("and[] is too short - %d byte instruction\n", andptr - and);
+		errorexit();
+	}
 }
 
 enum{