debug_core: disable hw_breakpoints on all cores in kgdb_cpu_enter()

The slave cpus do not have the hw breakpoints disabled upon entry to
the debug_core and as a result could cause unrecoverable recursive
faults on badly placed breakpoints, or get out of sync with the arch
specific hw breakpoint operations.

This patch addresses the problem by invoking kgdb_disable_hw_debug()
earlier in kgdb_enter_cpu for each cpu that enters the debug core.

The hw breakpoint dis/enable flow should be:

master_debug_cpu   slave_debug_cpu
         \              /
          kgdb_cpu_enter
                |
        kgdb_disable_hw_debug --> uninstall pre-enabled hw_breakpoint
                |
 do add/rm dis/enable operates to hw_breakpoints on master_debug_cpu..
                |
        correct_hw_break --> correct/install the enabled hw_breakpoint
                |
           leave_kgdb

Signed-off-by: Dongdong Deng <dongdong.deng@windriver.com>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>

1 files changed, 5 insertions, 2 deletions

diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c
index 5a3b04d20497..bb9497724808 100644
--- a/kernel/debug/debug_core.c
+++ b/kernel/debug/debug_core.c
@@ -485,6 +485,9 @@ static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs)
         int error;
         int i, cpu;
         int trace_on = 0;
+
+        kgdb_disable_hw_debug(ks->linux_regs);
+
 acquirelock:
         /*
          * Interrupts will be restored by the 'trap return' code, except when
@@ -569,8 +572,6 @@ return_normal:
         if (dbg_io_ops->pre_exception)
                 dbg_io_ops->pre_exception();
 
-        kgdb_disable_hw_debug(ks->linux_regs);
-
         /*
          * Get the passive CPU lock which will hold all the non-primary
          * CPU in a spin state while the debugger is active
@@ -661,6 +662,8 @@ kgdb_restore:
                 else
                         kgdb_sstep_pid = 0;
         }
+        if (arch_kgdb_ops.correct_hw_break)
+                arch_kgdb_ops.correct_hw_break();
         if (trace_on)
                 tracing_on();
         /* Free kgdb_active */