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Date: Mon, 1 Jul 2019 06:28:25 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Anshuman Khandual <anshuman.khandual@....com>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Cc: akpm@...ux-foundation.org
Subject: Re: [DRAFT] mm/kprobes: Add generic kprobe_fault_handler() fallback
definition
On 7/1/19 2:35 AM, Anshuman Khandual wrote:
> Architectures like parisc enable CONFIG_KROBES without having a definition
> for kprobe_fault_handler() which results in a build failure. Arch needs to
> provide kprobe_fault_handler() as it is platform specific and cannot have
> a generic working alternative. But in the event when platform lacks such a
> definition there needs to be a fallback.
>
> This adds a stub kprobe_fault_handler() definition which not only prevents
> a build failure but also makes sure that kprobe_page_fault() if called will
> always return negative in absence of a sane platform specific alternative.
>
> While here wrap kprobe_page_fault() in CONFIG_KPROBES. This enables stud
> definitions for generic kporbe_fault_handler() and kprobes_built_in() can
> just be dropped. Only on x86 it needs to be added back locally as it gets
> used in a !CONFIG_KPROBES function do_general_protection().
>
> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
> ---
> I am planning to go with approach unless we just want to implement a stub
> definition for parisc to get around the build problem for now.
>
> Hello Guenter,
>
> Could you please test this in your parisc setup. Thank you.
>
With this patch applied on top of next-20190628, parisc:allmodconfig builds
correctly. I scheduled a full build for tonight for all architectures.
Guenter
> - Anshuman
>
> arch/arc/include/asm/kprobes.h | 1 +
> arch/arm/include/asm/kprobes.h | 1 +
> arch/arm64/include/asm/kprobes.h | 1 +
> arch/ia64/include/asm/kprobes.h | 1 +
> arch/mips/include/asm/kprobes.h | 1 +
> arch/powerpc/include/asm/kprobes.h | 1 +
> arch/s390/include/asm/kprobes.h | 1 +
> arch/sh/include/asm/kprobes.h | 1 +
> arch/sparc/include/asm/kprobes.h | 1 +
> arch/x86/include/asm/kprobes.h | 6 ++++++
> include/linux/kprobes.h | 32 ++++++++++++++++++------------
> 11 files changed, 34 insertions(+), 13 deletions(-)
>
> diff --git a/arch/arc/include/asm/kprobes.h b/arch/arc/include/asm/kprobes.h
> index 2134721dce44..ee8efe256675 100644
> --- a/arch/arc/include/asm/kprobes.h
> +++ b/arch/arc/include/asm/kprobes.h
> @@ -45,6 +45,7 @@ struct kprobe_ctlblk {
> struct prev_kprobe prev_kprobe;
> };
>
> +#define kprobe_fault_handler kprobe_fault_handler
> int kprobe_fault_handler(struct pt_regs *regs, unsigned long cause);
> void kretprobe_trampoline(void);
> void trap_is_kprobe(unsigned long address, struct pt_regs *regs);
> diff --git a/arch/arm/include/asm/kprobes.h b/arch/arm/include/asm/kprobes.h
> index 213607a1f45c..660f877b989f 100644
> --- a/arch/arm/include/asm/kprobes.h
> +++ b/arch/arm/include/asm/kprobes.h
> @@ -38,6 +38,7 @@ struct kprobe_ctlblk {
> struct prev_kprobe prev_kprobe;
> };
>
> +#define kprobe_fault_handler kprobe_fault_handler
> void arch_remove_kprobe(struct kprobe *);
> int kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr);
> int kprobe_exceptions_notify(struct notifier_block *self,
> diff --git a/arch/arm64/include/asm/kprobes.h b/arch/arm64/include/asm/kprobes.h
> index 97e511d645a2..667773f75616 100644
> --- a/arch/arm64/include/asm/kprobes.h
> +++ b/arch/arm64/include/asm/kprobes.h
> @@ -42,6 +42,7 @@ struct kprobe_ctlblk {
> struct kprobe_step_ctx ss_ctx;
> };
>
> +#define kprobe_fault_handler kprobe_fault_handler
> void arch_remove_kprobe(struct kprobe *);
> int kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr);
> int kprobe_exceptions_notify(struct notifier_block *self,
> diff --git a/arch/ia64/include/asm/kprobes.h b/arch/ia64/include/asm/kprobes.h
> index c5cf5e4fb338..c321e8585089 100644
> --- a/arch/ia64/include/asm/kprobes.h
> +++ b/arch/ia64/include/asm/kprobes.h
> @@ -106,6 +106,7 @@ struct arch_specific_insn {
> unsigned short slot;
> };
>
> +#define kprobe_fault_handler kprobe_fault_handler
> extern int kprobe_fault_handler(struct pt_regs *regs, int trapnr);
> extern int kprobe_exceptions_notify(struct notifier_block *self,
> unsigned long val, void *data);
> diff --git a/arch/mips/include/asm/kprobes.h b/arch/mips/include/asm/kprobes.h
> index 68b1e5d458cf..d1efe991ea22 100644
> --- a/arch/mips/include/asm/kprobes.h
> +++ b/arch/mips/include/asm/kprobes.h
> @@ -40,6 +40,7 @@ do { \
>
> #define kretprobe_blacklist_size 0
>
> +#define kprobe_fault_handler kprobe_fault_handler
> void arch_remove_kprobe(struct kprobe *p);
> int kprobe_fault_handler(struct pt_regs *regs, int trapnr);
>
> diff --git a/arch/powerpc/include/asm/kprobes.h b/arch/powerpc/include/asm/kprobes.h
> index 66b3f2983b22..c94f375ec957 100644
> --- a/arch/powerpc/include/asm/kprobes.h
> +++ b/arch/powerpc/include/asm/kprobes.h
> @@ -84,6 +84,7 @@ struct arch_optimized_insn {
> kprobe_opcode_t *insn;
> };
>
> +#define kprobe_fault_handler kprobe_fault_handler
> extern int kprobe_exceptions_notify(struct notifier_block *self,
> unsigned long val, void *data);
> extern int kprobe_fault_handler(struct pt_regs *regs, int trapnr);
> diff --git a/arch/s390/include/asm/kprobes.h b/arch/s390/include/asm/kprobes.h
> index b106aa29bf55..0ecaebb78092 100644
> --- a/arch/s390/include/asm/kprobes.h
> +++ b/arch/s390/include/asm/kprobes.h
> @@ -73,6 +73,7 @@ struct kprobe_ctlblk {
> void arch_remove_kprobe(struct kprobe *p);
> void kretprobe_trampoline(void);
>
> +#define kprobe_fault_handler kprobe_fault_handler
> int kprobe_fault_handler(struct pt_regs *regs, int trapnr);
> int kprobe_exceptions_notify(struct notifier_block *self,
> unsigned long val, void *data);
> diff --git a/arch/sh/include/asm/kprobes.h b/arch/sh/include/asm/kprobes.h
> index 6171682f7798..637a698393c0 100644
> --- a/arch/sh/include/asm/kprobes.h
> +++ b/arch/sh/include/asm/kprobes.h
> @@ -45,6 +45,7 @@ struct kprobe_ctlblk {
> struct prev_kprobe prev_kprobe;
> };
>
> +#define kprobe_fault_handler kprobe_fault_handler
> extern int kprobe_fault_handler(struct pt_regs *regs, int trapnr);
> extern int kprobe_exceptions_notify(struct notifier_block *self,
> unsigned long val, void *data);
> diff --git a/arch/sparc/include/asm/kprobes.h b/arch/sparc/include/asm/kprobes.h
> index bfcaa6326c20..9aa4d25a45a8 100644
> --- a/arch/sparc/include/asm/kprobes.h
> +++ b/arch/sparc/include/asm/kprobes.h
> @@ -47,6 +47,7 @@ struct kprobe_ctlblk {
> struct prev_kprobe prev_kprobe;
> };
>
> +#define kprobe_fault_handler kprobe_fault_handler
> int kprobe_exceptions_notify(struct notifier_block *self,
> unsigned long val, void *data);
> int kprobe_fault_handler(struct pt_regs *regs, int trapnr);
> diff --git a/arch/x86/include/asm/kprobes.h b/arch/x86/include/asm/kprobes.h
> index 5dc909d9ad81..1af2b6db13bd 100644
> --- a/arch/x86/include/asm/kprobes.h
> +++ b/arch/x86/include/asm/kprobes.h
> @@ -101,11 +101,17 @@ struct kprobe_ctlblk {
> struct prev_kprobe prev_kprobe;
> };
>
> +#define kprobe_fault_handler kprobe_fault_handler
> extern int kprobe_fault_handler(struct pt_regs *regs, int trapnr);
> extern int kprobe_exceptions_notify(struct notifier_block *self,
> unsigned long val, void *data);
> extern int kprobe_int3_handler(struct pt_regs *regs);
> extern int kprobe_debug_handler(struct pt_regs *regs);
> +#else
> +static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
> +{
> + return 0;
> +}
>
> #endif /* CONFIG_KPROBES */
> #endif /* _ASM_X86_KPROBES_H */
> diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
> index 04bdaf01112c..e106f3018804 100644
> --- a/include/linux/kprobes.h
> +++ b/include/linux/kprobes.h
> @@ -182,11 +182,19 @@ DECLARE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
> /*
> * For #ifdef avoidance:
> */
> -static inline int kprobes_built_in(void)
> +
> +/*
> + * Architectures need to override this with their own implementation
> + * if they care to call kprobe_page_fault(). This will just ensure
> + * that kprobe_page_fault() returns false when called without having
> + * a proper platform specific definition for kprobe_fault_handler().
> + */
> +#ifndef kprobe_fault_handler
> +static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
> {
> - return 1;
> + return 0;
> }
> -
> +#endif
> #ifdef CONFIG_KRETPROBES
> extern void arch_prepare_kretprobe(struct kretprobe_instance *ri,
> struct pt_regs *regs);
> @@ -375,14 +383,6 @@ void free_insn_page(void *page);
>
> #else /* !CONFIG_KPROBES: */
>
> -static inline int kprobes_built_in(void)
> -{
> - return 0;
> -}
> -static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
> -{
> - return 0;
> -}
> static inline struct kprobe *get_kprobe(void *addr)
> {
> return NULL;
> @@ -458,12 +458,11 @@ static inline bool is_kprobe_optinsn_slot(unsigned long addr)
> }
> #endif
>
> +#ifdef CONFIG_KPROBES
> /* Returns true if kprobes handled the fault */
> static nokprobe_inline bool kprobe_page_fault(struct pt_regs *regs,
> unsigned int trap)
> {
> - if (!kprobes_built_in())
> - return false;
> if (user_mode(regs))
> return false;
> /*
> @@ -476,5 +475,12 @@ static nokprobe_inline bool kprobe_page_fault(struct pt_regs *regs,
> return false;
> return kprobe_fault_handler(regs, trap);
> }
> +#else
> +static nokprobe_inline bool kprobe_page_fault(struct pt_regs *regs,
> + unsigned int trap)
> +{
> + return false;
> +}
> +#endif
>
> #endif /* _LINUX_KPROBES_H */
>
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