mirror of https://gitee.com/openkylin/linux.git
6cecf76b47
MSR_DE is not cleared on entry to the kernel, and we don't clear it explicitly outside of debug code. If we have MSR_DE set in prime_debug_regs(), and the new thread has events enabled in DBCR0 (e.g. ICMP is set in thread->dbsr0, even though it was cleared in the real DBCR0 when the thread got scheduled out), we'll end up taking a debug exception in the kernel when DBCR0 is loaded. DSRR0 will not point to an exception vector, and the kernel ends up hanging at kernel_dbg_exc. Fix this by always clearing MSR_DE when we load new debug state. Another observed source of kernel_dbg_exc hangs is with the branch taken event. If this event is active, but we take a non-debug trap (e.g. a TLB miss or an asynchronous interrupt) before the next branch. We end up taking a branch-taken debug exception on the initial branch instruction of the exception vector, but because the debug exception is DBSR_BT rather than DBSR_IC we branch to kernel_dbg_exc before even checking the DSRR0 address. Fix this by checking for DBSR_BT as well as DBSR_IC, which is what 32-bit does and what the comments suggest was intended in the 64-bit code as well. Signed-off-by: Scott Wood <scottwood@freescale.com> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> |
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