[lldb-dev] Critique of Linux DoReadMemory implementation

[Piotr Rak]

Hi,

In any case ptrace(PTRACE_PEEKDATA, ) should be left as fallback, at least
for attaching.
Your debugger might CAP_SYS_PTRACE, that would allow it read memory of an
process running with different UID, and it won't be possible with
/proc/<pid>/mem.
It is also very popular for LSM's or hardening patches floating around to
disable access to process memory via proc at all.
So I see that more as optimization rather than replacement.

Cheers,
/Piotr


2014-02-25 10:31 GMT+01:00 Matthew Gardiner <mg11 at csr.com>:

> Folks,
>
> Is there a good reason why the DoReadMemory function of
> Linux/ProcessMonitor.cpp is implemented using multiple calls of
>
> ptrace(PTRACE_PEEKDATA, ...) ?
>
> An easier, and less CPU-intensive way is to read the memory using the proc
> filesystem. The inferior's memory will be available in the file
>
> /proc/<pid>/mem
>
> int fd = open("/proc/<pid>/mem", O_RDONLY);
> ssize_t bytes = read(fd, buf, count);
>
> The read-of-procfs just seems more succinct to me, so I wondered what the
> rationale was for not using this.
>
> Discussion welcomed,
> Matt
>
>
>
> Member of the CSR plc group of companies. CSR plc registered in England
> and Wales, registered number 4187346, registered office Churchill House,
> Cambridge Business Park, Cowley Road, Cambridge, CB4 0WZ, United Kingdom
> More information can be found at www.csr.com. Keep up to date with CSR on
> our technical blog, www.csr.com/blog, CSR people blog, www.csr.com/people,
> YouTube, www.youtube.com/user/CSRplc, Facebook,
> www.facebook.com/pages/CSR/191038434253534, or follow us on Twitter at
> www.twitter.com/CSR_plc.
> New for 2014, you can now access the wide range of products powered by
> aptX at www.aptx.com.
> _______________________________________________
> lldb-dev mailing list
> lldb-dev at cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/lldb-dev
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/lldb-dev/attachments/20140225/63eb0a7c/attachment.html>