Tiejun Chen wrote:
> 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.
>
> 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/entry_32.S | 15 +++++++++++++++
> arch/powerpc/kernel/head_booke.h | 15 +++++++++++++--
> arch/powerpc/kernel/irq.c | 11 +++++++++++
> arch/powerpc/kernel/setup_32.c | 4 ++++
> 6 files changed, 50 insertions(+), 2 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/entry_32.S b/arch/powerpc/kernel/entry_32.S
> index 56212bc..a99e209 100644
> --- a/arch/powerpc/kernel/entry_32.S
> +++ b/arch/powerpc/kernel/entry_32.S
> @@ -1122,6 +1122,21 @@ ret_from_mcheck_exc:
> RESTORE_xSRR(DSRR0,DSRR1);
> RESTORE_MMU_REGS;
> RET_FROM_EXC_LEVEL(SPRN_MCSRR0, SPRN_MCSRR1, PPC_RFMCI)
> +
> + .globl ret_from_prog_exc
> +ret_from_prog_exc:
> + mfspr r9,SPRN_SPRG_THREAD
> + lwz r10,SAVED_KSP_LIMIT(r1)
> + stw r10,KSP_LIMIT(r9)
> + lwz r9,THREAD_INFO-THREAD(r9)
> + rlwinm r10,r1,0,0,(31-THREAD_SHIFT)
> + lwz r10,TI_PREEMPT(r10)
> + stw r10,TI_PREEMPT(r9)
> + RESTORE_xSRR(SRR0,SRR1);
> + RESTORE_xSRR(CSRR0,CSRR1);
> + RESTORE_xSRR(DSRR0,DSRR1);
> + RESTORE_MMU_REGS;
> + RET_FROM_EXC_LEVEL(SPRN_SRR0, SPRN_SRR1, rfi)
> #endif /* CONFIG_BOOKE */
After a further consideration, to improve the above code fragment with the
following
------
+
+ .globl ret_from_prog_exc
+ret_from_prog_exc:
+#ifdef CONFIG_KPROBES
+ mfspr r9,SPRN_SPRG_THREAD
+ lwz r9,THREAD_INFO-THREAD(r9)
+ rlwinm r10,r1,0,0,(31-THREAD_SHIFT)
+ lwz r10,TI_PREEMPT(r10)
+ stw r10,TI_PREEMPT(r9)
+ RET_FROM_EXC_LEVEL(SPRN_SRR0, SPRN_SRR1, rfi)
+#else
+ b ret_from_except_full
+#endif
Here remove unnecessary restore, and also make sure its still same as normal
program exception when !CONFIG_KPROBES.
Tiejun
>
> /*
> diff --git a/arch/powerpc/kernel/head_booke.h
> b/arch/powerpc/kernel/head_booke.h
> index a0bf158..941be40 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.
> @@ -370,11 +380,12 @@ 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; \
> - EXC_XFER_STD(0x0700, program_check_exception)
> + EXC_XFER_TEMPLATE(program_check_exception, 0x0700, MSR_KERNEL, NOCOPY,\
> + transfer_to_handler_full, ret_from_prog_exc)
>
> #define DECREMENTER_EXCEPTION
> \
> START_EXCEPTION(Decrementer) \
> 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..b872564 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[hw_cpu] = (struct thread_info *)
> + __va(memblock_alloc(THREAD_SIZE, THREAD_SIZE));
> +#endif
> #endif
> }
> }
_______________________________________________
Linuxppc-dev mailing list
Linuxppc-dev@lists.ozlabs.org
https://lists.ozlabs.org/listinfo/linuxppc-dev
