On Thu, 2013-06-20 at 18:28 +0800, Tiejun Chen wrote:
> gdb always need to generate a single step properly to invoke
> a kgdb state. But with lazy interrupt, book3e can't always
> trigger a debug exception with a single step since the current
> is blocked for handling those pending exception, then we miss
> that expected dbcr configuration at last to generate a debug
> exception.
What do you mean by "the current is blocked"? Could you explain more
clearly what lazy EE has to do with MSR_DE and DBCR0?
> So here we also update thread's dbcr0 to make sure the current
> can go back with that missed dbcr0 configuration.
>
> Signed-off-by: Tiejun Chen <tiejun.c...@windriver.com>
> ---
> arch/powerpc/kernel/kgdb.c | 13 ++++++++++---
> 1 file changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/arch/powerpc/kernel/kgdb.c b/arch/powerpc/kernel/kgdb.c
> index c1eef24..55409ac 100644
> --- a/arch/powerpc/kernel/kgdb.c
> +++ b/arch/powerpc/kernel/kgdb.c
> @@ -410,7 +410,7 @@ int kgdb_arch_handle_exception(int vector, int signo, int
> err_code,
> struct pt_regs *linux_regs)
> {
> char *ptr = &remcom_in_buffer[1];
> - unsigned long addr;
> + unsigned long addr, dbcr0;
>
> switch (remcom_in_buffer[0]) {
> /*
> @@ -427,8 +427,15 @@ int kgdb_arch_handle_exception(int vector, int signo,
> int err_code,
> /* set the trace bit if we're stepping */
> if (remcom_in_buffer[0] == 's') {
> #ifdef CONFIG_PPC_ADV_DEBUG_REGS
> - mtspr(SPRN_DBCR0,
> - mfspr(SPRN_DBCR0) | DBCR0_IC | DBCR0_IDM);
> + dbcr0 = mfspr(SPRN_DBCR0) | DBCR0_IC | DBCR0_IDM;
> + mtspr(SPRN_DBCR0, dbcr0);
> +#ifdef CONFIG_PPC_BOOK3E_64
This could as well be "CONFIG_PPC64" -- CONFIG_PPC_ADV_DEBUG_REGS
implies booke or 40x. Lazy EE is a CONFIG_PPC64 thing, not specifically
CONFIG_PPC_BOOK3E_64.
> + /* With lazy interrut we have to update thread dbcr0
> here
s/interrut/interrupts/
> + * to make sure we can set debug properly at last to
> invoke
> + * kgdb again to work well.
> + */
> + current->thread.dbcr0 = dbcr0;
> +#endif
> linux_regs->msr |= MSR_DE;
> #else
> linux_regs->msr |= MSR_SE;
Hmm, what happens here if we enable KGDB on booke without
CONFIG_PPC_ADV_DEBUG_REGS? Kconfig doesn't appear to prevent it.
-Scott
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