• Paul Mackerras's avatar
    powerpc/xmon: Fix SPR read/write commands and add command to dump SPRs · 31cdd0c3
    Paul Mackerras authored
    xmon has commands for reading and writing SPRs, but they don't work
    currently for several reasons. They attempt to synthesize a small
    function containing an mfspr or mtspr instruction and call it. However,
    the instructions are on the stack, which is usually not executable.
    Also, for 64-bit we set up a procedure descriptor, which is fine for the
    big-endian ABIv1, but not correct for ABIv2. Finally, the code uses the
    infrastructure for catching memory errors, but that only catches data
    storage interrupts and machine check interrupts, but a failed
    mfspr/mtspr can generate a program interrupt or a hypervisor emulation
    assist interrupt, or be a no-op.
    
    Instead of trying to synthesize a function on the fly, this adds two new
    functions, xmon_mfspr() and xmon_mtspr(), which take an SPR number as an
    argument and read or write the SPR. Because there is no Power ISA
    instruction which takes an SPR number in a register, we have to generate
    one of each possible mfspr and mtspr instruction, for all 1024 possible
    SPRs. Thus we get just over 8k bytes of code for each of xmon_mfspr()
    and xmon_mtspr(). However, this 16kB of code pales in comparison to the
    > 130kB of PPC opcode tables used by the xmon disassembler.
    
    To catch interrupts caused by the mfspr/mtspr instructions, we add a new
    'catch_spr_faults' flag. If an interrupt occurs while it is set, we come
    back into xmon() via program_check_interrupt(), _exception() and die(),
    see that catch_spr_faults is set and do a longjmp to bus_error_jmp, back
    into read_spr() or write_spr().
    
    This adds a couple of other nice features: first, a "Sa" command that
    attempts to read and print out the value of all 1024 SPRs. If any mfspr
    instruction acts as a no-op, then the SPR is not implemented and not
    printed.
    
    Secondly, the Sr and Sw commands detect when an SPR is not
    implemented (i.e. mfspr is a no-op) and print a message to that effect
    rather than printing a bogus value.
    Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
    Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
    31cdd0c3
Makefile 310 Bytes