On Fri, Feb 09, 2018 at 10:47:58AM -0500, Steven Rostedt wrote: > On Fri, 9 Feb 2018 14:13:01 +0900 > Namhyung Kim <[email protected]> wrote: > > > On Fri, Feb 02, 2018 at 06:05:15PM -0500, Steven Rostedt wrote: > > > From: "Steven Rostedt (VMware)" <[email protected]> > > > > > > Allow the function based events to retrieve not only the parameters > > > offsets, > > > but also get data from a pointer within a parameter structure. Something > > > like: > > > > > > # echo 'ip_rcv(string skdev+16[0][0] | x8[6] skperm+16[0]+558)' > > > > function_events > > > > > > # echo 1 > events/functions/ip_rcv/enable > > > # cat trace > > > <idle>-0 [003] ..s3 310.626391: > > > __netif_receive_skb_core->ip_rcv(skdev=em1, skperm=b4,b5,2f,ce,18,65) > > > <idle>-0 [003] ..s3 310.626400: > > > __netif_receive_skb_core->ip_rcv(skdev=em1, skperm=b4,b5,2f,ce,18,65) > > > <idle>-0 [003] ..s3 312.183775: > > > __netif_receive_skb_core->ip_rcv(skdev=em1, skperm=b4,b5,2f,ce,18,65) > > > <idle>-0 [003] ..s3 312.184329: > > > __netif_receive_skb_core->ip_rcv(skdev=em1, skperm=b4,b5,2f,ce,18,65) > > > <idle>-0 [003] ..s3 312.303895: > > > __netif_receive_skb_core->ip_rcv(skdev=em1, skperm=b4,b5,2f,ce,18,65) > > > <idle>-0 [003] ..s3 312.304610: > > > __netif_receive_skb_core->ip_rcv(skdev=em1, skperm=b4,b5,2f,ce,18,65) > > > <idle>-0 [003] ..s3 312.471980: > > > __netif_receive_skb_core->ip_rcv(skdev=em1, skperm=b4,b5,2f,ce,18,65) > > > <idle>-0 [003] ..s3 312.472908: > > > __netif_receive_skb_core->ip_rcv(skdev=em1, skperm=b4,b5,2f,ce,18,65) > > > <idle>-0 [003] ..s3 313.135804: > > > __netif_receive_skb_core->ip_rcv(skdev=em1, skperm=b4,b5,2f,ce,18,65) > > > > > > That is, we retrieved the net_device of the sk_buff and displayed its name > > > and perm_addr info. > > > > > > sk->dev->name, sk->dev->perm_addr > > > > > > Signed-off-by: Steven Rostedt (VMware) <[email protected]> > > > --- > > > > [SNIP] > > > +static unsigned long process_redirects(struct func_arg *arg, unsigned > > > long val, > > > + char *buf) > > > +{ > > > + struct func_arg_redirect *redirect; > > > + int ret; > > > + > > > + if (arg->indirect) { > > > + ret = probe_kernel_read(buf, (void *)val, sizeof(long)); > > > + if (ret) > > > + return 0; > > > + val = *(unsigned long *)buf; > > > + } > > > + > > > + list_for_each_entry(redirect, &arg->redirects, list) { > > > + val += redirect->index; > > > + if (redirect->indirect) { > > > + val += (redirect->indirect ^ INDIRECT_FLAG); > > > + ret = probe_kernel_read(buf, (void *)val, sizeof(long)); > > > + if (ret) > > > + return 0; > > > + } > > > + } > > > + return val; > > > +} > > > + > > > +static long long __get_arg(struct func_arg *arg, unsigned long long val) > > > { > > > char buf[8]; > > > int ret; > > > > > > val += arg->index; > > > > > > - if (!arg->indirect) > > > - return val; > > > + if (arg->indirect) > > > + val += (arg->indirect ^ INDIRECT_FLAG); > > > > > > - val = val + (arg->indirect ^ INDIRECT_FLAG); > > > + if (!list_empty(&arg->redirects)) > > > + val = process_redirects(arg, val, buf); > > > + > > > + if (!val) > > > + return 0; > > > > > > /* Arrays and strings do their own indirect reads */ > > > - if (arg->array || arg->func_type == FUNC_TYPE_string) > > > + if (!arg->indirect || arg->array || arg->func_type == FUNC_TYPE_string) > > > return val; > > > > It seems the indirect is processed twice with redirects. Consider > > "x64 foo[0]+4", the process_redirects() will call probe_kernel_read() > > and then here again. > > > > > Good catch! > > It should have been: > > return process_redirects(arg, val, buf);
But I think you need to consider data type of the arg when dereferencing the last redirect. Thanks, Namhyung
