Lab 10, Bss, memory pools, malloc

Time to have a look at initial memory initializations.
First we need to initialize BSS (more details: http://en.wikipedia.org/wiki/.bss), statically-allocated variables. We do it in next way:

memset(edata, 0, end-edata);

From Plan9 manual:
“The loaded image has several symbols inserted by the loader: etext is the address of the end of the text segment; bdata is the address of the beginning of the data segment; edata is the address of the end of the data segment; and end is the address of the end of the bss segment, and of the program.”

When it is done, we init with zeros also Mach obejct:

memset(m, 0, sizeof(Mach)); 

Also let’s move pl011 stuff into pl011.c and add signatures into fns.h:

void    pl011_putc(int);
void    pl011_puts(char *);
void    pl011_serputs(char *, int);

Specify amount of Mach objects:

conf.nmach = 1; 

Specify a function for serial console writing:

serwrite = &pl011_serputs;

Next is confinit() call to initialize Conf object:

extern int main_pool_pcnt;
extern int heap_pool_pcnt;
extern int image_pool_pcnt;

void
confinit(void)
{
    ulong base;
    conf.topofmem = 128*MB;

    base = PGROUND((ulong)end);
    conf.base0 = base;

    conf.npage1 = 0;
    conf.npage0 = (conf.topofmem - base)/BY2PG;
    conf.npage = conf.npage0 + conf.npage1;
    conf.ialloc = (((conf.npage*(main_pool_pcnt))/100)/2)*BY2PG;

    conf.nproc = 100 + ((conf.npage*BY2PG)/MB)*5;
    conf.nmach = 1;

    print("Conf: top=%lud, npage0=%lud, ialloc=%lud, nproc=%lud\n",
            conf.topofmem, conf.npage0,
            conf.ialloc, conf.nproc);
}

Plus we need to add ulong npage; and ulong topofmem; into Conf structure
and definition #define PGROUND(s) ROUND(s, BY2PG) into mem.h
Three variable: int main_pool_pcnt; int heap_pool_pcnt; int image_pool_pcnt; we define in rpi config file:

code
    int kernel_pool_pcnt = 10;
    int main_pool_pcnt = 40;
    int heap_pool_pcnt = 20;
    int image_pool_pcnt = 40;

Finally we can initialize memory pools:

static void
poolsizeinit(void)
{
    ulong nb;
    nb = conf.npage*BY2PG;
    poolsize(mainmem, (nb*main_pool_pcnt)/100, 0);
    poolsize(heapmem, (nb*heap_pool_pcnt)/100, 0);
    poolsize(imagmem, (nb*image_pool_pcnt)/100, 1);
}

And in main():

    xinit();
    poolinit();
    poolsizeinit();

As memory pools are ready then malloc() is functional we can do much more in next labs.

FILES:
dat.h
fns.h
mem.h
main.c
pl011.c
rpi
mkfile
bss.pdf