riscv: fix reserved memory setup

In the Linux kernel, the following vulnerability has been resolved:

riscv: fix reserved memory setup

Currently, RISC-V sets up reserved memory using the "early" copy of the

device tree. As a result, when trying to get a reserved memory region

using of_reserved_mem_lookup(), the pointer to reserved memory regions

is using the early, pre-virtual-memory address which causes a kernel

panic when trying to use the buffer's name:

Unable to handle kernel paging request at virtual address 00000000401c31ac

Oops [#1]

Modules linked in:

CPU: 0 PID: 0 Comm: swapper Not tainted 6.0.0-rc1-00001-g0d9d6953d834 #1

Hardware name: Microchip PolarFire-SoC Icicle Kit (DT)

epc : string+0x4a/0xea

ra : vsnprintf+0x1e4/0x336

epc : ffffffff80335ea0 ra : ffffffff80338936 sp : ffffffff81203be0

gp : ffffffff812e0a98 tp : ffffffff8120de40 t0 : 0000000000000000

t1 : ffffffff81203e28 t2 : 7265736572203a46 s0 : ffffffff81203c20

s1 : ffffffff81203e28 a0 : ffffffff81203d22 a1 : 0000000000000000

a2 : ffffffff81203d08 a3 : 0000000081203d21 a4 : ffffffffffffffff

a5 : 00000000401c31ac a6 : ffff0a00ffffff04 a7 : ffffffffffffffff

s2 : ffffffff81203d08 s3 : ffffffff81203d00 s4 : 0000000000000008

s5 : ffffffff000000ff s6 : 0000000000ffffff s7 : 00000000ffffff00

s8 : ffffffff80d9821a s9 : ffffffff81203d22 s10: 0000000000000002

s11: ffffffff80d9821c t3 : ffffffff812f3617 t4 : ffffffff812f3617

t5 : ffffffff812f3618 t6 : ffffffff81203d08

status: 0000000200000100 badaddr: 00000000401c31ac cause: 000000000000000d

[<ffffffff80338936>] vsnprintf+0x1e4/0x336

[<ffffffff80055ae2>] vprintk_store+0xf6/0x344

[<ffffffff80055d86>] vprintk_emit+0x56/0x192

[<ffffffff80055ed8>] vprintk_default+0x16/0x1e

[<ffffffff800563d2>] vprintk+0x72/0x80

[<ffffffff806813b2>] _printk+0x36/0x50

[<ffffffff8068af48>] print_reserved_mem+0x1c/0x24

[<ffffffff808057ec>] paging_init+0x528/0x5bc

[<ffffffff808031ae>] setup_arch+0xd0/0x592

[<ffffffff8080070e>] start_kernel+0x82/0x73c

early_init_fdt_scan_reserved_mem() takes no arguments as it operates on

initial_boot_params, which is populated by early_init_dt_verify(). On

RISC-V, early_init_dt_verify() is called twice. Once, directly, in

setup_arch() if CONFIG_BUILTIN_DTB is not enabled and once indirectly,

very early in the boot process, by parse_dtb() when it calls

early_init_dt_scan_nodes().

This first call uses dtb_early_va to set initial_boot_params, which is

not usable later in the boot process when

early_init_fdt_scan_reserved_mem() is called. On arm64 for example, the

corresponding call to early_init_dt_scan_nodes() uses fixmap addresses

and doesn't suffer the same fate.

Move early_init_fdt_scan_reserved_mem() further along the boot sequence,

after the direct call to early_init_dt_verify() in setup_arch() so that

the names use the correct virtual memory addresses. The above supposed

that CONFIG_BUILTIN_DTB was not set, but should work equally in the case

where it is - unflatted_and_copy_device_tree() also updates

initial_boot_params.