• Lorenzo Pieralisi's avatar
    arm64: kernel: restore HW breakpoint registers in cpu_suspend · 65c021bb
    Lorenzo Pieralisi authored
    When a CPU resumes from low-power, it restores HW breakpoint and
    watchpoint slots through a CPU PM notifier. Since we want to enable
    debugging as early as possible in the resume path, the mdscr content
    is restored along the general purpose registers in the cpu_suspend API
    and debug exceptions are reenabled when cpu_suspend returns. Since the
    CPU PM notifier is run after a CPU has been resumed, we cannot expect
    HW breakpoint registers to contain sane values till the notifier is run,
    since the HW breakpoints registers content is unknown at reset; this means
    that the CPU might run with debug exceptions enabled, mdscr restored but HW
    breakpoint registers containing junk values that can trigger spurious
    debug exceptions.
    
    This patch fixes current HW breakpoints restore by moving the HW breakpoints
    registers restoration to the cpu_suspend API, before the debug exceptions are
    enabled. This way, as soon as the cpu_suspend function returns the
    kernel can resume debugging with sane values in HW breakpoint registers.
    Signed-off-by: default avatarLorenzo Pieralisi <lorenzo.pieralisi@arm.com>
    Acked-by: default avatarWill Deacon <will.deacon@arm.com>
    Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
    65c021bb
hw_breakpoint.c 23.5 KB