RPi4B: an example of what RAM u-boot reserves during operation (not necessarily matching what it reports to the next stage) vs. armstub8-gic.bin

U-Boot> bdinfo
boot_params = 0x0000000000000100
. . .
lmb_dump_all:
    memory.cnt             = 0x2
    memory.size            = 0x0
    memory.reg[0x0].base   = 0x0
                   .size   = 0x3e000000
    memory.reg[0x1].base   = 0x40000000
                   .size   = 0xbc000000

    reserved.cnt           = 0x2
    reserved.size          = 0x0
    reserved.reg[0x0].base = 0x0
                     .size = 0x1000
    reserved.reg[0x1].base = 0x3db47b30
                     .size = 0x4b84d0
. . .

That:

    reserved.reg[0x0].base = 0x0
                     .size = 0x1000

means that armstub8-gic.bin is not fully
protected at this point in u-boot's execution.

Basically boot_fdt_add_mem_rsv_regions is all that
is used currently and it does not take into account
CONFIG_RPI_EFI_NR_SPIN_PAGES=2 :

/**
 * boot_fdt_add_mem_rsv_regions - Mark the memreserve and reserved-memory
 * sections as unusable
 * @lmb: pointer to lmb handle, will be used for memory mgmt
 * @fdt_blob: pointer to fdt blob base address
 *
 * Adds the and reserved-memorymemreserve regions in the dtb to the lmb block.
 * Adding the memreserve regions prevents u-boot from using them to store the
 * initrd or the fdt blob.
 */
void boot_fdt_add_mem_rsv_regions(struct lmb *lmb, void *fdt_blob)
{
        uint64_t addr, size;
        int i, total, ret;
        int nodeoffset, subnode;
        struct fdt_resource res;

        if (fdt_check_header(fdt_blob) != 0)
                return;

        /* process memreserve sections */
        total = fdt_num_mem_rsv(fdt_blob);
        for (i = 0; i < total; i++) {
                if (fdt_get_mem_rsv(fdt_blob, i, &addr, &size) != 0)
                        continue;
                boot_fdt_reserve_region(lmb, addr, size);
        }

        /* process reserved-memory */
        nodeoffset = fdt_subnode_offset(fdt_blob, 0, "reserved-memory");
        if (nodeoffset >= 0) {
                subnode = fdt_first_subnode(fdt_blob, nodeoffset);
                while (subnode >= 0) {
                        /* check if this subnode has a reg property */
                        ret = fdt_get_resource(fdt_blob, subnode, "reg", 0,
                                               &res);
                        if (!ret && fdtdec_get_is_enabled(fdt_blob, subnode)) {
                                addr = res.start;
                                size = res.end - res.start + 1;
                                boot_fdt_reserve_region(lmb, addr, size);
                        }

                        subnode = fdt_next_subnode(fdt_blob, subnode);
                }
        }
}


===
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)

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