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Date:   Wed, 28 Feb 2018 04:24:40 -0800
From:   Srikar Dronamraju <srikar@linux.vnet.ibm.com>
To:     Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
Cc:     peterz@infradead.org, mingo@redhat.com, acme@kernel.org,
        alexander.shishkin@linux.intel.com, jolsa@redhat.com,
        namhyung@kernel.org, linux-kernel@vger.kernel.org,
        rostedt@goodmis.org, mhiramat@kernel.org,
        ananth@linux.vnet.ibm.com, naveen.n.rao@linux.vnet.ibm.com,
        oleg@redhat.com
Subject: Re: [RFC 2/4] Uprobe: Export few functions / data structures
Reply-To: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
References: <20180228075345.674-1-ravi.bangoria@linux.vnet.ibm.com>
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> @@ -149,6 +155,11 @@ struct uprobes_state {
>  extern bool arch_uprobe_ignore(struct arch_uprobe *aup, struct pt_regs *regs);
>  extern void arch_uprobe_copy_ixol(struct page *page, unsigned long vaddr,
>  					 void *src, unsigned long len);
> +unsigned long offset_to_vaddr(struct vm_area_struct *vma, loff_t offset);
> +void copy_from_page(struct page *page, unsigned long vaddr, void *dst, int len);
> +void copy_to_page(struct page *page, unsigned long vaddr, const void *src, int len);
> +struct uprobe_map_info *free_uprobe_map_info(struct uprobe_map_info *info);
> +
>  #else /* !CONFIG_UPROBES */

If we have to export the above, we might have to work with mm maintainers and
see if we can move them there.

> -static inline struct uprobe_map_info *
> -free_uprobe_map_info(struct uprobe_map_info *info)
> +struct uprobe_map_info *free_uprobe_map_info(struct uprobe_map_info *info)
>  {
>  	struct uprobe_map_info *next = info->next;
>  	kfree(info);
>  	return next;
>  }
> 
> -static struct uprobe_map_info *
> -build_uprobe_map_info(struct address_space *mapping, loff_t offset,
> -		      bool is_register)
> +struct uprobe_map_info *build_uprobe_map_info(struct address_space *mapping,
> +					      loff_t offset, bool is_register)
>  {
>  	unsigned long pgoff = offset >> PAGE_SHIFT;
>  	struct vm_area_struct *vma;

Instead of exporting, did you look at extending the uprobe consumer with
ops. i.e if the consumer detects that a probe is a semaphore and exports
a set of callbacks which can them be called from uprobe
insertion/deletion time. With such a thing, incrementing/decrementing
the semaphore and the insertion/deletion of the breakpoint can be done
at one shot. No?