Re: [PATCHv9 2.6.35-rc4-tip 2/13] uprobes: Breakpoint insertion/removal in user space applications.

[Christoph Hellwig <hch@infradead.org>]

> +struct user_bkpt_arch_info {
> +	void (*set_ip)(struct pt_regs *regs, unsigned long vaddr);
> +	int (*validate_address)(struct task_struct *tsk, unsigned long vaddr);
> +	int (*read_opcode)(struct task_struct *tsk, unsigned long vaddr,
> +						user_bkpt_opcode_t *opcode);
> +	int (*set_bkpt)(struct task_struct *tsk,
> +				struct user_bkpt *user_bkpt);
> +	int (*set_orig_insn)(struct task_struct *tsk,
> +				struct user_bkpt *user_bkpt, bool check);
> +	bool (*is_bkpt_insn)(struct user_bkpt *user_bkpt);
> +	int (*analyze_insn)(struct task_struct *tsk,
> +					struct user_bkpt *user_bkpt);
> +	int (*pre_xol)(struct task_struct *tsk,
> +				struct user_bkpt *user_bkpt,
> +				struct user_bkpt_task_arch_info *tskinfo,
> +				struct pt_regs *regs);
> +	int (*post_xol)(struct task_struct *tsk,
> +				struct user_bkpt *user_bkpt,
> +				struct user_bkpt_task_arch_info *tskinfo,
> +				struct pt_regs *regs);
> +};

Just wondering why these are function pointers.  Do we exepect an
architecture to provide different versions of these for say 32 vs 64-bit
binaries?  If not just making these arch provided helpers might be a lot
simpler.  Especially in the current version where only very few of these
are overriden by the architecture at all.

> +unsigned long uprobes_read_vm(struct task_struct *tsk, void __user *vaddr,
> +					void *kbuf, unsigned long nbytes)
> +{
> +	if (tsk == current) {
> +		unsigned long nleft = copy_from_user(kbuf, vaddr, nbytes);
> +		return nbytes - nleft;
> +	} else
> +		return access_process_vm(tsk, (unsigned long) vaddr, kbuf,
> +							nbytes, 0);
> +}
> +
> +unsigned long uprobes_write_data(struct task_struct *tsk,
> +				void __user *vaddr, const void *kbuf,
> +				unsigned long nbytes)
> +{
> +	unsigned long nleft;
> +
> +	if (tsk == current) {
> +		nleft = copy_to_user(vaddr, kbuf, nbytes);
> +		return nbytes - nleft;
> +	} else
> +		return access_process_vm(tsk, (unsigned long) vaddr,
> +						(void *) kbuf, nbytes, 1);
> +}

Any reason for the naming mismatch between _read_vm and _write_data?

Also I wonder if the optimization for tsk == current should be folded
directly into access_process_vm instead of adding these wrappers.