> -----Original Message-----
> From:
> linuxppc-dev-bounces+tiejun.chen=windriver....@lists.ozlabs.or
> g
> [mailto:linuxppc-dev-bounces+tiejun.chen=windriver.com@lists.o
zlabs.org] On Behalf Of Tiejun Chen
> Sent: Friday, July 08, 2011 6:05 PM
> To: b...@kernel.crashing.org; linuxppc-...@ozlabs.org
> Subject: [PATCH 1/2] booke/kprobe: make program exception to
> use one dedicated exception stack
>
> When kprobe these operations such as store-and-update-word for SP(r1),
>
> stwu r1, -A(r1)
>
> The program exception is triggered, and PPC always allocate
> an exception frame as shown as the follows:
>
> old r1 ----------
> ...
> nip
> gpr[2] ~ gpr[31]
> gpr[1] <--------- old r1 is stored.
> gpr[0]
> -------- <--------- pr_regs @offset 16 bytes
> padding
> STACK_FRAME_REGS_MARKER
> LR
> back chain
> new r1 ----------
> Then emulate_step() will emulate this instruction, 'stwu'.
> Actually its equivalent to:
> 1> Update pr_regs->gpr[1] = mem[old r1 + (-A)]
> 2> stw [old r1], mem[old r1 + (-A)]
>
> Please notice the stack based on new r1 may be covered with mem[old r1
> +(-A)] when addr[old r1 + (-A)] < addr[old r1 + sizeof(an
> exception frame0].
> So the above 2# operation will overwirte something to break
> this exception frame then unexpected kernel problem will be issued.
>
> So looks we have to implement independed interrupt stack for
> PPC program exception when CONFIG_BOOKE is enabled. Here we
> can use EXC_LEVEL_EXCEPTION_PROLOG to replace original
> NORMAL_EXCEPTION_PROLOG for program exception if
> CONFIG_BOOKE. Then its always safe for kprobe with independed
> exc stack from one pre-allocated and dedicated thread_info.
> Actually this is just waht we did for critical/machine check
> exceptions on PPC.
Update:
You can understand this problem completely from our previous email thread,
about '[BUG?] 3.0-rc4+ftrace+kprobe: set kprobe at instruction 'stwu' lead to
system crash/freeze'.
>
> Signed-off-by: Tiejun Chen <tiejun.c...@windriver.com>
> ---
> arch/powerpc/include/asm/irq.h | 3 +++
> arch/powerpc/include/asm/reg.h | 4 ++++
> arch/powerpc/kernel/head_booke.h | 12 +++++++++++-
> arch/powerpc/kernel/irq.c | 11 +++++++++++
> arch/powerpc/kernel/setup_32.c | 4 ++++
> 5 files changed, 33 insertions(+), 1 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/irq.h
> b/arch/powerpc/include/asm/irq.h index 1bff591..6d12169 100644
> --- a/arch/powerpc/include/asm/irq.h
> +++ b/arch/powerpc/include/asm/irq.h
> @@ -313,6 +313,9 @@ struct pt_regs;
> extern struct thread_info *critirq_ctx[NR_CPUS]; extern
> struct thread_info *dbgirq_ctx[NR_CPUS]; extern struct
> thread_info *mcheckirq_ctx[NR_CPUS];
> +#if defined(CONFIG_KPROBES) && defined(CONFIG_BOOKE) extern struct
> +thread_info *pgirq_ctx[NR_CPUS]; #endif
> extern void exc_lvl_ctx_init(void);
> #else
> #define exc_lvl_ctx_init()
> diff --git a/arch/powerpc/include/asm/reg.h
> b/arch/powerpc/include/asm/reg.h index c5cae0d..34d6178 100644
> --- a/arch/powerpc/include/asm/reg.h
> +++ b/arch/powerpc/include/asm/reg.h
> @@ -885,6 +885,10 @@
> #endif
> #define SPRN_SPRG_RVCPU SPRN_SPRG1
> #define SPRN_SPRG_WVCPU SPRN_SPRG1
> +#ifdef CONFIG_KPROBES
> +#define SPRN_SPRG_RSCRATCH_PG SPRN_SPRG0
> +#define SPRN_SPRG_WSCRATCH_PG SPRN_SPRG0
> +#endif
> #endif
>
> #ifdef CONFIG_8xx
> diff --git a/arch/powerpc/kernel/head_booke.h
> b/arch/powerpc/kernel/head_booke.h
> index a0bf158..cf6cb1e 100644
> --- a/arch/powerpc/kernel/head_booke.h
> +++ b/arch/powerpc/kernel/head_booke.h
> @@ -79,6 +79,10 @@
> /* only on e500mc/e200 */
> #define DBG_STACK_BASE dbgirq_ctx
>
> +#if defined(CONFIG_KPROBES)
> +#define PG_STACK_BASE pgirq_ctx
> +#endif
> +
> #define EXC_LVL_FRAME_OVERHEAD (THREAD_SIZE -
> INT_FRAME_SIZE - EXC_LVL_SIZE)
>
> #ifdef CONFIG_SMP
> @@ -158,6 +162,12 @@
> EXC_LEVEL_EXCEPTION_PROLOG(DBG, SPRN_DSRR0,
> SPRN_DSRR1) #define MCHECK_EXCEPTION_PROLOG \
> EXC_LEVEL_EXCEPTION_PROLOG(MC, SPRN_MCSRR0, SPRN_MCSRR1)
> +#if defined(CONFIG_KPROBES)
> +#define PROGRAM_EXCEPTION_PROLOG \
> + EXC_LEVEL_EXCEPTION_PROLOG(PG, SPRN_SRR0,
> SPRN_SRR1) #else
> +#define PROGRAM_EXCEPTION_PROLOG NORMAL_EXCEPTION_PROLOG
> +#endif
>
> /*
> * Exception vectors.
> @@ -370,7 +380,7 @@ label:
>
> #define PROGRAM_EXCEPTION
> \
> START_EXCEPTION(Program)
> \
> - NORMAL_EXCEPTION_PROLOG;
> \
> + PROGRAM_EXCEPTION_PROLOG;
> \
> mfspr r4,SPRN_ESR; /* Grab the ESR and
> save it */ \
> stw r4,_ESR(r11);
> \
> addi r3,r1,STACK_FRAME_OVERHEAD;
> \
> diff --git a/arch/powerpc/kernel/irq.c
> b/arch/powerpc/kernel/irq.c index 5b428e3..ff5b8dd 100644
> --- a/arch/powerpc/kernel/irq.c
> +++ b/arch/powerpc/kernel/irq.c
> @@ -397,6 +397,10 @@ struct thread_info
> *critirq_ctx[NR_CPUS] __read_mostly;
> struct thread_info *dbgirq_ctx[NR_CPUS] __read_mostly;
> struct thread_info *mcheckirq_ctx[NR_CPUS] __read_mostly;
>
> +#if defined(CONFIG_KPROBES) && defined(CONFIG_BOOKE)
> +struct thread_info *pgirq_ctx[NR_CPUS] __read_mostly;
> +#endif
> +
> void exc_lvl_ctx_init(void)
> {
> struct thread_info *tp;
> @@ -423,6 +427,13 @@ void exc_lvl_ctx_init(void)
> tp = mcheckirq_ctx[cpu_nr];
> tp->cpu = cpu_nr;
> tp->preempt_count = HARDIRQ_OFFSET;
> +
> +#if defined(CONFIG_KPROBES)
> + memset((void *)pgirq_ctx[i], 0, THREAD_SIZE);
> + tp = pgirq_ctx[i];
> + tp->cpu = i;
> + tp->preempt_count = 0;
> +#endif
> #endif
> }
> }
> diff --git a/arch/powerpc/kernel/setup_32.c
> b/arch/powerpc/kernel/setup_32.c index 620d792..f0c62ae 100644
> --- a/arch/powerpc/kernel/setup_32.c
> +++ b/arch/powerpc/kernel/setup_32.c
> @@ -272,6 +272,10 @@ static void __init exc_lvl_early_init(void)
> __va(memblock_alloc(THREAD_SIZE, THREAD_SIZE));
> mcheckirq_ctx[hw_cpu] = (struct thread_info *)
> __va(memblock_alloc(THREAD_SIZE, THREAD_SIZE));
> +#ifdef CONFIG_KPROBES
> + pgirq_ctx[i] = (struct thread_info *)
^
Next version I should replace 'i' with 'hw_cpu' like
the above usage :)
Tiejun
> + __va(memblock_alloc(THREAD_SIZE,
> THREAD_SIZE)); #endif
> #endif
> }
> }
> --
> 1.5.6
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