Em Thu, Aug 04, 2016 at 04:36:56PM -0300, Arnaldo Carvalho de Melo escreveu: > So: > > int err = debuginfo__get_text_offset(dbg, &baseaddr); > > is returning 0, no relocation, its dwarf_addrdie() that is not finding > SyS_epoll_wait from its address. > > Trying to figure out why dwarf_addrdie(0xffffffffbd295b50) fails...
So, trying to use that vmlinux with objdump to do disassembly I found that I need to do some offsetting, and after calculating it, this made things works for me: diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c index f2d9ff064e2d..9b95754f28ed 100644 --- a/tools/perf/util/probe-finder.c +++ b/tools/perf/util/probe-finder.c @@ -1486,6 +1486,8 @@ retry: /* Find cu die */ if (!dwarf_addrdie(dbg->dbg, (Dwarf_Addr)addr, &cudie)) { if (!reloc && debuginfo__get_text_offset(dbg, &baseaddr) == 0) { + if (baseaddr == 0) + baseaddr = -0x3c000000; addr += baseaddr; reloc = true; goto retry; ---------------- With it, which is not a proper fix, of course, we get: [root@jouet ~]# perf probe sys_epoll_wait Added new events: probe:sys_epoll_wait (on sys_epoll_wait) probe:sys_epoll_wait_1 (on sys_epoll_wait) probe:sys_epoll_wait_2 (on sys_epoll_wait) You can now use it in all perf tools, such as: perf record -e probe:sys_epoll_wait_2 -aR sleep 1 [root@jouet ~]# Which, using -v shows it "finding" the alias: [root@jouet ~]# perf probe -v sys_epoll_wait probe-definition(0): sys_epoll_wait symbol:sys_epoll_wait file:(null) line:0 offset:0 return:0 lazy:(null) 0 arguments Looking at the vmlinux_path (8 entries long) Using /lib/modules/4.7.0+/build/vmlinux for symbols Open Debuginfo file: /lib/modules/4.7.0+/build/vmlinux Try to find probe point from debuginfo. Symbol sys_epoll_wait address found : ffffffffbd295b50 Matched function: SyS_epoll_wait found inline addr: 0xffffffff81295ee7 Probe point found: compat_SyS_epoll_pwait+151 found inline addr: 0xffffffff81295cca Probe point found: SyS_epoll_pwait+138 found inline addr: 0xffffffff81295b50 Probe point found: SyS_epoll_wait+0 Found 3 probe_trace_events. Opening /sys/kernel/debug/tracing//kprobe_events write=1 Writing event: p:probe/sys_epoll_wait _text+2711271 Writing event: p:probe/sys_epoll_wait_1 _text+2710730 Writing event: p:probe/sys_epoll_wait_2 _text+2710352 Added new events: probe:sys_epoll_wait (on sys_epoll_wait) probe:sys_epoll_wait_1 (on sys_epoll_wait) probe:sys_epoll_wait_2 (on sys_epoll_wait) You can now use it in all perf tools, such as: perf record -e probe:sys_epoll_wait_2 -aR sleep 1 [root@jouet ~]# ---------- Now to figure out why baseaddr is returning as zero... - Arnaldo