On 3/13/15 4:24 AM, He Kuang wrote:
Hi, Alexei
I've followed up your bpf version. In bpf filter, sometimes we need to
get 'pid' and some other context informations to decide whether to
filter or not.
For example, to trace a vfs read procedure, we can insert bpf program to
'__vfs_read(struct file *file, char __user *buf ...)', mark some of
'buf' addresses and only trace the read procedure of these 'buf's. But
this parameter is a userspace pointer, the value is meaningless to other
processes, so we should also record 'pid' to make sense.
To a function like __vfs_read, 'pid' can't be extracted from function
parameters directly. What's your opinion on this issue?
yes. it's the next thing on todo list after this set of patches.
There are several ways to let programs see 'pid'. We'll debate about
the best approach hopefully soon :)
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