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Subject[DRAFT] mm/kprobes: Add generic kprobe_fault_handler() fallback definition
Date
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@arm.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.

- 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 */
--
2.20.1
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