ramdisk.c

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#include <core/system.h>
#include <core/panic.h>
#include <core/arch.h>
#include <core/module.h>
#include <core/string.h>
 
#include <boot/boot.h>
#include <dev/dev.h>
#include <mm/vm.h>
 
static void *rd_addr = NULL;
 
/* the RAM disk's size, which the initramfs code reads too */
size_t rd_size = 0;

static ssize_t rd_read(struct devid *dd __unused, off_t offset, size_t size, void *buf)
{
    if (offset < 0)
        return -EINVAL;
 
    if ((size_t) offset >= rd_size)
        return 0;
 
    /* not past the end */
    size = MIN(size, rd_size - (size_t) offset);
    
    memcpy(buf, (char *) rd_addr + offset, size);
 
    return size;
}

static ssize_t rd_write(struct devid *dd __unused, off_t offset, size_t size, void *buf)
{
    if (offset < 0)
        return -EINVAL;
 
    if ((size_t) offset >= rd_size)
        return 0;
 
    /* not past the end */
    size = MIN(size, rd_size - (size_t) offset);
    
    memcpy((char *) rd_addr + offset, buf, size);
 
    return size;
}

static int rd_probe()
{
    extern struct boot *__kboot;
 
    /* no module: the root is on a disk (root=), there's no RAM disk */
    if (!__kboot->modules_count)
        return 0;
 
    module_t *rd_module = &__kboot->modules[0];
 
    /* the first module, where the boot loader put it */
    rd_size = rd_module->size;
    rd_addr = arch_phys_map(rd_module->paddr, rd_size);
 
    if (!rd_addr)
        panic("ramdisk: no room to map it");
 
    kdev_blkdev_register(1, &rddev);
 
    return 0;
}

static size_t rd_getbs(struct devid *dd __unused)
{
    return 1;
}
 
struct dev rddev = {
    .name  = "ramdisk",
    .probe = rd_probe,
    .bread  = rd_read,
    .bwrite = rd_write,
    .getbs = rd_getbs,
};
 
MODULE_INIT(rd, rd_probe, NULL)