Messages in this thread |  | | | Date | Wed, 14 Jan 2009 09:25:46 -0500 | | From | Jason Baron <> | | Subject | Re: [PATCH 4/5] ftrace: show ftrace_bprintk()'s formats |
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On Wed, Jan 14, 2009 at 10:49:56AM +0800, Lai Jiangshan wrote: > Jason Baron wrote: > > On Wed, Dec 31, 2008 at 10:56:23AM +0800, Lai Jiangshan wrote: > >> Impact: let user knows the format > >> > >> Create a file on <debugfs-dir>/tracing/ to show ftrace_bprintk()'s formats. > >> > >> This formats will help for these condition: > >> 1) User get binary data from core file.(formats are backup before coredump) > >> 2) User splice ring_buffer to a file. > >> User can use formats for parsing the binary data in userspace. > >> > > > > When I 'cat' trace_bprintk_formats on my system the file is empty. This > > seems to be b/c 'ftrace_bprintk' is not being used in this patchset. It > > can't be used in patch #5 during marker register b/c the format wouldn't > > be known at runtime. Thus, as it currently stands this patch, patch 4/5, > > isn't adding much? > > If you don't use ftrace_bprintk(), the file trace_bprintk_formats is empty. > This file record all formats which ftrace_bprintk() uses. > > You can use ftrace_bprintk() everywhere as another printk(). > > Patch #5 enables binary printk for markers, this is another additional tool > for tracing markers. > > > > > A thought on how this might be resolved would be to have the core marker > > code pass us its address so this could be recorded in the trace buffer. > > Then, also add some debug file that displays the markers and maps marker > > addresses with format strings. > > > > Patch#5 does it as you said. > > >
hmm...i'm still not clear on this. in patch #5 you have:
+static void marker_bprintk_probe(void *probe_private, void *call_private, + const char *fmt, va_list *args) +{ + struct marker_bprintk_struct *p = probe_private; + + if (p->fmt_state == MARKER_FMT_LACK) { + int flen = strlen(fmt); + if (p->fmt - p->name + flen < MARKER_NAME_FMT_LEN) { + memcpy(p->fmt, fmt, flen + 1); + p->fmt_state = MARKER_FMT_OK; + } else + p->fmt_state = MARKER_FMT_INVALID; + } + + if (p->fmt_state == MARKER_FMT_OK) + trace_vbprintk(0, p->name, *args); +} + trace_vbprintk first argument is 'ip'. So I don't see how we are associating instruction pointers with each 'ftrace' record? Aren't we just recording each entry with '0' for the 'ip'?
thanks,
-Jason
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