arm64: use fixmap region for permanent FDT mapping

Currently, the FDT blob needs to be in the same 512 MB region as
the kernel, so that it can be mapped into the kernel virtual memory
space very early on using a minimal set of statically allocated
translation tables.

Now that we have early fixmap support, we can relax this restriction,
by moving the permanent FDT mapping to the fixmap region instead.
This way, the FDT blob may be anywhere in memory.

This also moves the vetting of the FDT to mmu.c, since the early
init code in head.S does not handle mapping of the FDT anymore.
At the same time, fix up some comments in head.S that have gone stale.

Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

1 files changed, 10 insertions, 20 deletions

diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
index 508cca1f8dce..ffd3970721bf 100644
--- a/arch/arm64/kernel/setup.c
+++ b/arch/arm64/kernel/setup.c
@@ -105,18 +105,6 @@ static struct resource mem_res[] = {
 #define kernel_code mem_res[0]
 #define kernel_data mem_res[1]
 
-void __init early_print(const char *str, ...)
-{
-        char buf[256];
-        va_list ap;
-
-        va_start(ap, str);
-        vsnprintf(buf, sizeof(buf), str, ap);
-        va_end(ap);
-
-        printk("%s", buf);
-}
-
 /*
  * The recorded values of x0 .. x3 upon kernel entry.
  */
@@ -326,12 +314,14 @@ static void __init setup_processor(void)
 
 static void __init setup_machine_fdt(phys_addr_t dt_phys)
 {
-        if (!dt_phys || !early_init_dt_scan(phys_to_virt(dt_phys))) {
-                early_print("\n"
-                        "Error: invalid device tree blob at physical address 0x%p (virtual address 0x%p)\n"
-                        "The dtb must be 8-byte aligned and passed in the first 512MB of memory\n"
-                        "\nPlease check your bootloader.\n",
-                        dt_phys, phys_to_virt(dt_phys));
+        void *dt_virt = fixmap_remap_fdt(dt_phys);
+
+        if (!dt_virt || !early_init_dt_scan(dt_virt)) {
+                pr_crit("\n"
+                        "Error: invalid device tree blob at physical address %pa (virtual address 0x%p)\n"
+                        "The dtb must be 8-byte aligned and must not exceed 2 MB in size\n"
+                        "\nPlease check your bootloader.",
+                        &dt_phys, dt_virt);
 
                 while (true)
                         cpu_relax();
@@ -374,8 +364,6 @@ void __init setup_arch(char **cmdline_p)
 {
         setup_processor();
 
-        setup_machine_fdt(__fdt_pointer);
-
         init_mm.start_code = (unsigned long) _text;
         init_mm.end_code   = (unsigned long) _etext;
         init_mm.end_data   = (unsigned long) _edata;
@@ -386,6 +374,8 @@ void __init setup_arch(char **cmdline_p)
         early_fixmap_init();
         early_ioremap_init();
 
+        setup_machine_fdt(__fdt_pointer);
+
         parse_early_param();
 
         /*