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bcm, bcm64: preserve memsize across reboots, avoid trashing atags while parsing cmdline

we override atag memory on reboot, so preserve
the memsize learned from atag as *maxmem plan9
variable. the global memsize variable is not
needed anymore.

avoid trashing the following atag when zero
terminating the cmdline string.

zero memory after plan9.ini variables.

--- a/sys/src/9/bcm/bootargs.c

+++ b/sys/src/9/bcm/bootargs.c

@@ -88,34 +88,37 @@

 void

 bootargsinit(void)

 {

+	static char maxmem[11];

+	char x, *e;

 	Atag *a;

-	int n;

-	a = (Atag*)BOOTARGS;

+	e = BOOTARGS;

+	a = (Atag*)e;

 	if(a->tag != AtagCore){

-		plan9iniinit((char*)a, 0);

+		plan9iniinit(e, 0);

 		return;

 	}

-	while(a->tag != AtagNone && a->size != 0){

+	while(a->tag != AtagNone){

+		e += a->size * sizeof(u32int);

+		if(a->size < 2 || e < (char*)a || e > &BOOTARGS[BOOTARGSLEN])

+			break;

 		switch(a->tag){

 		case AtagMem:

-			/* use only first bank */

-			if(conf.mem[0].limit == 0 && a->mem.size != 0){

-				memsize = a->mem.size;

-				conf.mem[0].base = a->mem.base;

-				conf.mem[0].limit = a->mem.base + memsize;

+			if(findconf("*maxmem") < 0){

+				snprint(maxmem, sizeof(maxmem), "%ud", a->mem.base+a->mem.size);

+				addconf("*maxmem", maxmem);

 			}

 			break;

 		case AtagCmdline:

-			n = (a->size * sizeof(u32int)) - offsetof(Atag, cmdline[0]);

-			if(a->cmdline + n < BOOTARGS + BOOTARGSLEN)

-				a->cmdline[n] = 0;

-			else

-				BOOTARGS[BOOTARGSLEN-1] = 0;

+			x = *e;

+			*e = 0;

 			plan9iniinit(a->cmdline, 1);

+			*e = x;

 			break;

 		}

-		a = (Atag*)((u32int*)a + a->size);

+		if(e > &BOOTARGS[BOOTARGSLEN-8])

+			break;

+		a = (Atag*)e;

 	}

 }

@@ -164,6 +167,7 @@

 	if(n >= BOOTARGSLEN)

 		error("kernel configuration too large");

 	memmove(BOOTARGS, p, n);

+	memset(BOOTARGS+n, 0, BOOTARGSLEN-n);

 	poperror();

 	free(p);

 }

--- a/sys/src/9/bcm/dat.h

+++ b/sys/src/9/bcm/dat.h

@@ -227,7 +227,6 @@

 extern register Proc* up;			/* R9 */

 extern uintptr kseg0;

 extern Mach* machaddr[MAXMACH];

-extern ulong memsize;

 extern int normalprint;

 /*

--- a/sys/src/9/bcm/main.c

+++ b/sys/src/9/bcm/main.c

@@ -18,7 +18,6 @@

 uintptr kseg0 = KZERO;

 Mach*	machaddr[MAXMACH];

 Conf	conf;

-ulong	memsize = 128*1024*1024;

 void

 machinit(void)

@@ -241,7 +240,7 @@

 confinit(void)

 {

 	int i, userpcnt;

-	ulong kpages;

+	ulong kpages, memsize = 0;

 	uintptr pa;

 	char *p;

@@ -257,12 +256,10 @@

 	else

 		userpcnt = 0;

-	if((p = getconf("*maxmem")) != nil){

+	if(p = getconf("*maxmem"))

 		memsize = strtoul(p, 0, 0) - PHYSDRAM;

-		if (memsize < 16*MB)		/* sanity */

-			memsize = 16*MB;

-	}

-

+	if (memsize < 16*MB)		/* sanity */

+		memsize = 16*MB;

 	getramsize(&conf.mem[0]);

 	if(conf.mem[0].limit == 0){

 		conf.mem[0].base = PHYSDRAM;

--- a/sys/src/9/bcm/mmu.c

+++ b/sys/src/9/bcm/mmu.c

@@ -304,8 +304,8 @@

 uintptr

 cankaddr(uintptr pa)

 {

-	if(pa < PHYSDRAM + memsize)		/* assumes PHYSDRAM is 0 */

-		return PHYSDRAM + memsize - pa;

+	if(pa < PHYSDRAM+soc.dramsize)

+		return PHYSDRAM+soc.dramsize - pa;

 	return 0;

 }