linux arm中的request_standard_resources()函数

Question

我正在阅读Linux内核(2.6.31)源代码，以了解内存映射。

我的问题是/arch/arm/kernel/setup.c中的这个函数

static void __init request_standard_resources(struct meminfo *mi, struct machine_desc    *mdesc)
{
struct resource *res;
int i;

kernel_code.start   = virt_to_phys(_text);
kernel_code.end     = virt_to_phys(_etext - 1);
kernel_data.start   = virt_to_phys(_data);
kernel_data.end     = virt_to_phys(_end - 1);

for (i = 0; i < mi->nr_banks; i++) {
    if (mi->bank[i].size == 0)
        continue;

    res = alloc_bootmem_low(sizeof(*res));
    res->name  = "System RAM";
    res->start = mi->bank[i].start;
    res->end   = mi->bank[i].start + mi->bank[i].size - 1;
    res->flags = IORESOURCE_MEM | IORESOURCE_BUSY;

    request_resource(&iomem_resource, res);

    if (kernel_code.start >= res->start &&
        kernel_code.end <= res->end)
        request_resource(res, &kernel_code);
    if (kernel_data.start >= res->start &&
        kernel_data.end <= res->end)
        request_resource(res, &kernel_data);
}

if (mdesc->video_start) {
    video_ram.start = mdesc->video_start;
    video_ram.end   = mdesc->video_end;
    request_resource(&iomem_resource, &video_ram);
}

/*
 * Some machines don't have the possibility of ever
 * possessing lp0, lp1 or lp2
 */
if (mdesc->reserve_lp0)
    request_resource(&ioport_resource, &lp0);
if (mdesc->reserve_lp1)
    request_resource(&ioport_resource, &lp1);
if (mdesc->reserve_lp2)
    request_resource(&ioport_resource, &lp2);
}

我不知道变量的值是：_text，_etext，_data，_end。

请帮助我获取这些变量的值以及此函数的用途: request_standard_resources()

Answer 1

这些变量实际上是由组成最终内核映像的链接器脚本定义的。

• _text是内核文本(代码)的开头地址，section.
• _etext是文本的结尾，section.
• _data是数据的开头，section.
• _end是内核的结尾。