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kprobes, extable: Identify kprobes trampolines as kernel text area

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Improve __kernel_text_address()/kernel_text_address() to return
true if the given address is on a kprobe's instruction slot
trampoline.

This can help stacktraces to determine the address is on a
text area or not.

To implement this atomically in is_kprobe_*_slot(), also change
the insn_cache page list to an RCU list.

This changes timings a bit (it delays page freeing to the RCU garbage
collection phase), but none of that is in the hot path.

Note: this change can add small overhead to stack unwinders because
it adds 2 additional checks to __kernel_text_address(). However, the
impact should be very small, because kprobe_insn_pages list has 1 entry
per 256 probes(on x86, on arm/arm64 it will be 1024 probes),
and kprobe_optinsn_pages has 1 entry per 32 probes(on x86).
In most use cases, the number of kprobe events may be less
than 20, which means that is_kprobe_*_slot() will check just one entry.

Tested-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/148388747896.6869.6354262871751682264.stgit@devbox
[ Improved the changelog and coding style. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Masami Hiramatsu
2017-01-08 23:58:09 +09:00
committed by Ingo Molnar
parent f913f3a655
commit 5b485629ba
3 changed files with 92 additions and 22 deletions
Download Patch File Download Diff File Expand all files Collapse all files

30
include/linux/kprobes.h
View File

@@ -278,9 +278,13 @@ struct kprobe_insn_cache {
int nr_garbage;
};
#ifdef __ARCH_WANT_KPROBES_INSN_SLOT
extern kprobe_opcode_t *__get_insn_slot(struct kprobe_insn_cache *c);
extern void __free_insn_slot(struct kprobe_insn_cache *c,
kprobe_opcode_t *slot, int dirty);
/* sleep-less address checking routine */
extern bool __is_insn_slot_addr(struct kprobe_insn_cache *c,
unsigned long addr);
#define DEFINE_INSN_CACHE_OPS(__name) \
extern struct kprobe_insn_cache kprobe_##__name##_slots; \
@@ -294,6 +298,18 @@ static inline void free_##__name##_slot(kprobe_opcode_t *slot, int dirty)\
{ \
__free_insn_slot(&kprobe_##__name##_slots, slot, dirty); \
} \
\
static inline bool is_kprobe_##__name##_slot(unsigned long addr) \
{ \
return __is_insn_slot_addr(&kprobe_##__name##_slots, addr); \
}
#else /* __ARCH_WANT_KPROBES_INSN_SLOT */
#define DEFINE_INSN_CACHE_OPS(__name) \
static inline bool is_kprobe_##__name##_slot(unsigned long addr) \
{ \
return 0; \
}
#endif
DEFINE_INSN_CACHE_OPS(insn);
@@ -330,7 +346,6 @@ extern int proc_kprobes_optimization_handler(struct ctl_table *table,
int write, void __user *buffer,
size_t *length, loff_t *ppos);
#endif
#endif /* CONFIG_OPTPROBES */
#ifdef CONFIG_KPROBES_ON_FTRACE
extern void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
@@ -481,6 +496,19 @@ static inline int enable_jprobe(struct jprobe *jp)
return enable_kprobe(&jp->kp);
}
#ifndef CONFIG_KPROBES
static inline bool is_kprobe_insn_slot(unsigned long addr)
{
return false;
}
#endif
#ifndef CONFIG_OPTPROBES
static inline bool is_kprobe_optinsn_slot(unsigned long addr)
{
return false;
}
#endif
#ifdef CONFIG_KPROBES
/*
* Blacklist ganerating macro. Specify functions which is not probed