On 11/05, Namhyung Kim wrote:
>
> This is what I have for now:
>
> static void __user *get_user_vaddr(struct pt_regs *regs, unsigned long addr,
> struct trace_uprobe *tu)
> {
> unsigned long base_addr;
> unsigned long vaddr;
>
> base_addr = instruction_pointer(regs) - tu->offset;
> vaddr = base_addr + addr;
>
> return (void __force __user *) vaddr;
> }
>
> When I tested it, it was able to fetch global and bss data from both of
> executable and library properly.
Heh ;) I didn't expect you will agree with this suggestion. But if you
think it can work - great!
Let me clarify just in case. Yes, _personally_ I think we should try
to avoid the vma games, and it looks better to me this way. But I won't
argue if you change your mind, I understand this approach has its own
disadvantages.
As for "-= tu->offset"... Can't we avoid it? User-space needs to calculate
the "@" argument anyway, why it can't also substruct this offset?
Or perhaps we can change parse_probe_arg("@") to update "param" ? Yes,
in this case it needs another argument, not sure...
> But it still doesn't work for uretprobes
> as you said before.
This looks simple,
+ if (is_ret_probe(tu)) {
+ saved_ip = instruction_pointer(regs);
+ instruction_pointer_set(func);
+ }
store_trace_args(...);
+ if (is_ret_probe(tu))
+ instruction_pointer_set(saved_ip);
although not pretty.
> This symbol offset calculation was done in the getsymoff which implemented
> like below (I'm sure there's a much simpler way to do this, but ...).
Perhaps I'll even try to read/understand it later, but this elf stuff is
the black magic to me ;)
Oleg.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
