• Max Filippov's avatar
    xtensa: support hardware breakpoints/watchpoints · c91e02bd
    Max Filippov authored
    
    
    Use perf framework to manage hardware instruction and data breakpoints.
    Add two new ptrace calls: PTRACE_GETHBPREGS and PTRACE_SETHBPREGS to
    query and set instruction and data breakpoints.
    Address bit 0 choose instruction (0) or data (1) break register, bits
    31..1 are the register number.
    Both calls transfer two 32-bit words: address (0) and control (1).
    Instruction breakpoint contorl word is 0 to clear breakpoint, 1 to set.
    Data breakpoint control word bit 31 is 'trigger on store', bit 30 is
    'trigger on load, bits 29..0 are length. Length 0 is used to clear a
    breakpoint. To set a breakpoint length must be a power of 2 in the range
    1..64 and the address must be length-aligned.
    
    Introduce new thread_info flag: TIF_DB_DISABLED. Set it if debug
    exception is raised by the kernel code accessing watched userspace
    address and disable corresponding data breakpoint. On exit to userspace
    check that flag and, if set, restore all data breakpoints.
    
    Handle debug exceptions raised with PS.EXCM set. This may happen when
    window overflow/underflow handler or fast exception handler hits data
    breakpoint, in which case save and disable all data breakpoints,
    single-step faulting instruction and restore data breakpoints.
    
    Signed-off-by: default avatarMax Filippov <jcmvbkbc@gmail.com>
    c91e02bd