Prev: [PATCH 20/25] kgdb: Add the ability to schedule a breakpoint via a tasklet
Next: [PATCH 3/7] x86,kgdb: Implement early hardware breakpoint debugging
From: Jason Wessel on 18 May 2010 21:50
If the kernel debugger was configured, attached and started with
kgdbwait, the hardware breakpoint registers should get restored by the
kgdb code which is managing the dr registers.

CC: x86(a)kernel.org
CC: Thomas Gleixner <tglx(a)linutronix.de>
CC: Ingo Molnar <mingo(a)redhat.com>
CC: H. Peter Anvin <hpa(a)zytor.com>
Signed-off-by: Jason Wessel <jason.wessel(a)windriver.com>
---
arch/x86/kernel/cpu/common.c | 29 +++++++++++++++++------------
1 files changed, 17 insertions(+), 12 deletions(-)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 4868e4a..712c1eb 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1084,6 +1084,20 @@ static void clear_all_debug_regs(void)
}
}

+#ifdef CONFIG_KGDB
+/*
+ * Restore debug regs if using kgdbwait and you have a kernel debugger
+ * connection established.
+ */
+static void dbg_restore_debug_regs(void)
+{
+ if (unlikely(kgdb_connected && arch_kgdb_ops.correct_hw_break))
+ arch_kgdb_ops.correct_hw_break();
+}
+#else /* ! CONFIG_KGDB */
+#define dbg_restore_debug_regs()
+#endif /* ! CONFIG_KGDB */
+
/*
* cpu_init() initializes state that is per-CPU. Some data is already
* initialized (naturally) in the bootstrap process, such as the GDT
@@ -1174,18 +1188,8 @@ void __cpuinit cpu_init(void)
load_TR_desc();
load_LDT(&init_mm.context);

-#ifdef CONFIG_KGDB
- /*
- * If the kgdb is connected no debug regs should be altered. This
- * is only applicable when KGDB and a KGDB I/O module are built
- * into the kernel and you are using early debugging with
- * kgdbwait. KGDB will control the kernel HW breakpoint registers.
- */
- if (kgdb_connected && arch_kgdb_ops.correct_hw_break)
- arch_kgdb_ops.correct_hw_break();
- else
-#endif
- clear_all_debug_regs();
+ clear_all_debug_regs();
+ dbg_restore_debug_regs();

fpu_init();

@@ -1239,6 +1243,7 @@ void __cpuinit cpu_init(void)
#endif

clear_all_debug_regs();
+ dbg_restore_debug_regs();

/*
* Force FPU initialization:
--
1.6.3.3

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Prev: [PATCH 20/25] kgdb: Add the ability to schedule a breakpoint via a tasklet
Next: [PATCH 3/7] x86,kgdb: Implement early hardware breakpoint debugging