riscv: additional crash information

riscv: additional crash information

If an exception occurs, the relocated program counter and return address
are required for an analysis.

With this patch you get:

    => exception undefined

    Unhandled exception: Illegal instruction
    EPC: 0000000080595908 RA: 000000008059c0c6 TVAL: 000000008030c01e
    EPC: 0000000080007908 RA: 000000008000e0c6 reloc adjusted

We can use the relocated addresses to find the involved functions in
u.boot.map:

    .text.do_undefined
                0x0000000080007908        0x8 cmd/built-in.o
    .text.cmd_process
                0x000000008000dfcc      0x11a common/built-in.o
                0x000000008000dfcc                cmd_process

If an exception occurs in an UEFI binary additionally the load addresses of
the UEFI binaries are needed. With this patch:

    => setenv efi_selftest exception
    => bootefi selftest

    Unhandled exception: Illegal instruction
    EPC: 000000008042e18a RA: 000000008042e18a TVAL: 000000008030c01e
    EPC: 000000007fea018a RA: 000000007fea018a reloc adjusted

    UEFI image [0x0000000000000000:0xffffffffffffffff] '/\selftest'
    UEFI image [0x000000008042e000:0x000000008042e43f] pc=0x18a '/bug.efi'

The value pc=0x18a matches the position of the illegal instruction in
efi_selftest_miniapp_exception.efi (loaded as /bug.efi);

    asm volatile (".word 0xffffffff\n");

    00000180   93 85 C5 11  1C 64 22 85  82 97 FF FF  FF FF 1C 64

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Sean Anderson <seanga2@gmail.com>
Tested-by: Sean Anderson <seanga2@gmail.com>
Reviewed-by: Bin Meng <bin.meng@windriver.com>
Reviewed-by: Rick Chen <rick@andestech.com>