linux-kernel - Re: [PATCH V2 03/13] kprobes: Add symbols for kprobe insn pages

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Date:   Wed, 26 Feb 2020 16:21:51 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Adrian Hunter <adrian.hunter@...el.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Leo Yan <leo.yan@...aro.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2 03/13] kprobes: Add symbols for kprobe insn pages

On Wed, Feb 12, 2020 at 02:49:39PM +0200, Adrian Hunter wrote:
> Symbols are needed for tools to describe instruction addresses. Pages
> allocated for kprobe's purposes need symbols to be created for them.
> Add such symbols to be visible via /proc/kallsyms.
> 
> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>

SNIP

> @@ -272,6 +273,8 @@ static inline bool is_kprobe_##__name##_slot(unsigned long addr)	\
>  {									\
>  	return __is_insn_slot_addr(&kprobe_##__name##_slots, addr);	\
>  }
> +#define KPROBE_INSN_PAGE_SYM		"kprobe_insn_page"
> +#define KPROBE_OPTINSN_PAGE_SYM		"kprobe_optinsn_page"
>  #else /* __ARCH_WANT_KPROBES_INSN_SLOT */
>  #define DEFINE_INSN_CACHE_OPS(__name)					\
>  static inline bool is_kprobe_##__name##_slot(unsigned long addr)	\
> @@ -373,6 +376,13 @@ void dump_kprobe(struct kprobe *kp);
>  void *alloc_insn_page(void);
>  void free_insn_page(void *page);
>  
> +int kprobe_get_kallsym(unsigned int symnum, unsigned long *value, char *type,
> +		       char *sym);
> +int kprobe_cache_get_kallsym(struct kprobe_insn_cache *c, unsigned int *symnum,
> +			     unsigned long *value, char *type, char *sym);
> +
> +int arch_kprobe_get_kallsym(unsigned int *symnum, unsigned long *value,
> +			    char *type, char *sym);
>  #else /* !CONFIG_KPROBES: */
>  
>  static inline int kprobes_built_in(void)
> @@ -435,6 +445,24 @@ static inline bool within_kprobe_blacklist(unsigned long addr)
>  {
>  	return true;
>  }
> +static inline int kprobe_get_kallsym(unsigned int symnum, unsigned long *value,
> +				     char *type, char *sym)
> +{
> +	return 0;
> +}
> +static inline int kprobe_cache_get_kallsym(struct kprobe_insn_cache *c,
> +					   unsigned int *symnum,
> +					   unsigned long *value, char *type,
> +					   char *sym)
> +{
> +	return 0;
> +}
> +static inline int arch_kprobe_get_kallsym(unsigned int *symnum,
> +					  unsigned long *value, char *type,
> +					  char *sym)
> +{
> +	return 0;
> +}

there's another arch_kprobe_get_kallsym marked as __weak,
is above function superfluous?

jirka

SNIP

> +int __weak arch_kprobe_get_kallsym(unsigned int *symnum, unsigned long *value,
> +				   char *type, char *sym)
> +{
> +	return -ERANGE;
> +}
> +
> +int kprobe_get_kallsym(unsigned int symnum, unsigned long *value, char *type,
> +		       char *sym)
> +{
> +#ifdef __ARCH_WANT_KPROBES_INSN_SLOT
> +	if (!kprobe_cache_get_kallsym(&kprobe_insn_slots, &symnum, value, type, sym))
> +		return 0;
> +#ifdef CONFIG_OPTPROBES
> +	if (!kprobe_cache_get_kallsym(&kprobe_optinsn_slots, &symnum, value, type, sym))
> +		return 0;
> +#endif
> +#endif
> +	if (!arch_kprobe_get_kallsym(&symnum, value, type, sym))
> +		return 0;
> +	return -ERANGE;
> +}
> +
>  int __init __weak arch_populate_kprobe_blacklist(void)
>  {
>  	return 0;
> -- 
> 2.17.1
>