Re: [PATCH v2 0/2] perf probe fixes for ppc64le
On 2016/04/12 02:40PM, Naveen N Rao wrote: > This patchset fixes three issues found with perf probe on ppc64le: > 1. 'perf test kallsyms' failure on ppc64le (reported by Michael > Ellerman). This was due to the symbols being fixed up during symbol > table load. This is fixed in patch 2 by delaying symbol fixup until > later. > 2. perf probe function offset was being calculated from the local entry > point (LEP), which does not match user expectation when trying to look > at function disassembly output (reported by Ananth N). This is fixed for > kallsyms in patch 1 and for symbol table in patch 2. > 3. perf probe failure with kretprobe when using kallsyms. This was > failing as we were specifying an offset. This is fixed in patch 1. > > A few examples demonstrating the issues and the fix: > > Example for issue (2): > > # objdump -d vmlinux | grep -A8 \<_do_fork\>: > c00b6a00 <_do_fork>: > c00b6a00: f7 00 4c 3c addis r2,r12,247 > c00b6a04: 00 86 42 38 addir2,r2,-31232 > c00b6a08: a6 02 08 7c mflrr0 > c00b6a0c: d0 ff 41 fb std r26,-48(r1) > c00b6a10: 26 80 90 7d mfocrf r12,8 > c00b6a14: d8 ff 61 fb std r27,-40(r1) > c00b6a18: e0 ff 81 fb std r28,-32(r1) > c00b6a1c: e8 ff a1 fb std r29,-24(r1) > # perf probe -v _do_fork+4 > probe-definition(0): _do_fork+4 > symbol:_do_fork file:(null) line:0 offset:4 return:0 lazy:(null) > 0 arguments > Looking at the vmlinux_path (8 entries long) > Using /proc/kcore for kernel object code > Using /proc/kallsyms for symbols > Opening /sys/kernel/debug/tracing//kprobe_events write=1 > Writing event: p:probe/_do_fork _text+748044 > Added new event: > probe:_do_fork (on _do_fork+4) > > You can now use it in all perf tools, such as: > > perf record -e probe:_do_fork -aR sleep 1 > > # printf "%x\n" 748044 > b6a0c > ^ > This is offset from the LEP. With this, there is also no way to ever > probe between the GEP and the LEP. > > With this patchset: > # perf probe -v _do_fork+4 > probe-definition(0): _do_fork+4 > symbol:_do_fork file:(null) line:0 offset:4 return:0 lazy:(null) > 0 arguments > Looking at the vmlinux_path (8 entries long) > Using /proc/kcore for kernel object code > Using /proc/kallsyms for symbols > Opening /sys/kernel/debug/tracing//kprobe_events write=1 > Writing event: p:probe/_do_fork _text+748036 > Added new event: > probe:_do_fork (on _do_fork+4) > > You can now use it in all perf tools, such as: > > perf record -e probe:_do_fork -aR sleep 1 > > # perf probe -v _do_fork > probe-definition(0): _do_fork > symbol:_do_fork file:(null) line:0 offset:0 return:0 lazy:(null) > 0 arguments > Looking at the vmlinux_path (8 entries long) > Using /proc/kcore for kernel object code > Using /proc/kallsyms for symbols > Opening /sys/kernel/debug/tracing//kprobe_events write=1 > Writing event: p:probe/_do_fork _text+748040 > Added new event: > probe:_do_fork (on _do_fork) > > You can now use it in all perf tools, such as: > > perf record -e probe:_do_fork -aR sleep 1 > > We only offset to the LEP if function entry is specified, otherwise, we > offset from the GEP. > > Example for issue (3): > - > Before patch: > # perf probe -v _do_fork:%return > probe-definition(0): _do_fork:%return > symbol:_do_fork file:(null) line:0 offset:0 return:1 lazy:(null) > 0 arguments > Looking at the vmlinux_path (8 entries long) > Using /proc/kcore for kernel object code > Using /proc/kallsyms for symbols > Opening /sys/kernel/debug/tracing//kprobe_events write=1 > Writing event: r:probe/_do_fork _do_fork+8 > Failed to write event: Invalid argument > Error: Failed to add events. Reason: Invalid argument (Code: -22) > > After patch: > # perf probe _do_fork:%return > Added new event: > probe:_do_fork (on _do_fork%return) > > You can now use it in all perf tools, such as: > > perf record -e probe:_do_fork -aR sleep 1 > > > Concept Acked-by: Michael Ellerman > > Cc: Mark Wielaard > Cc: Thiago Jung Bauermann > Cc: Arnaldo Carvalho de Melo > Cc: Masami Hiramatsu > Cc: Michael Ellerman > Cc: Balbir Singh > Cc: Ananth N Mavinakayanahalli Arnaldo, Can you please pick this up if you're ok with the changes? - Naveen > > Naveen N. Rao (2): > perf tools: Fix kprobe and kretprobe handling with kallsyms on ppc64le > perf tools: Fix kallsyms perf test on ppc64le > > tools/perf/arch/powerpc/util/sym-handling.c | 43 > + > tools/perf/util/probe-event.c | 5 ++-- > tools/perf/util/probe-event.h | 3 +- > tools/perf/util/sy
Re: [PATCH v2 0/2] perf probe fixes for ppc64le
On 12/04/16 19:10, Naveen N. Rao wrote: > This patchset fixes three issues found with perf probe on ppc64le: > 1. 'perf test kallsyms' failure on ppc64le (reported by Michael > Ellerman). This was due to the symbols being fixed up during symbol > table load. This is fixed in patch 2 by delaying symbol fixup until > later. > 2. perf probe function offset was being calculated from the local entry > point (LEP), which does not match user expectation when trying to look > at function disassembly output (reported by Ananth N). This is fixed for > kallsyms in patch 1 and for symbol table in patch 2. > 3. perf probe failure with kretprobe when using kallsyms. This was > failing as we were specifying an offset. This is fixed in patch 1. > > A few examples demonstrating the issues and the fix: > Given the choices, I think this makes sense Acked-by: Balbir Singh ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
[PATCH v2 0/2] perf probe fixes for ppc64le
This patchset fixes three issues found with perf probe on ppc64le: 1. 'perf test kallsyms' failure on ppc64le (reported by Michael Ellerman). This was due to the symbols being fixed up during symbol table load. This is fixed in patch 2 by delaying symbol fixup until later. 2. perf probe function offset was being calculated from the local entry point (LEP), which does not match user expectation when trying to look at function disassembly output (reported by Ananth N). This is fixed for kallsyms in patch 1 and for symbol table in patch 2. 3. perf probe failure with kretprobe when using kallsyms. This was failing as we were specifying an offset. This is fixed in patch 1. A few examples demonstrating the issues and the fix: Example for issue (2): # objdump -d vmlinux | grep -A8 \<_do_fork\>: c00b6a00 <_do_fork>: c00b6a00: f7 00 4c 3c addis r2,r12,247 c00b6a04: 00 86 42 38 addir2,r2,-31232 c00b6a08: a6 02 08 7c mflrr0 c00b6a0c: d0 ff 41 fb std r26,-48(r1) c00b6a10: 26 80 90 7d mfocrf r12,8 c00b6a14: d8 ff 61 fb std r27,-40(r1) c00b6a18: e0 ff 81 fb std r28,-32(r1) c00b6a1c: e8 ff a1 fb std r29,-24(r1) # perf probe -v _do_fork+4 probe-definition(0): _do_fork+4 symbol:_do_fork file:(null) line:0 offset:4 return:0 lazy:(null) 0 arguments Looking at the vmlinux_path (8 entries long) Using /proc/kcore for kernel object code Using /proc/kallsyms for symbols Opening /sys/kernel/debug/tracing//kprobe_events write=1 Writing event: p:probe/_do_fork _text+748044 Added new event: probe:_do_fork (on _do_fork+4) You can now use it in all perf tools, such as: perf record -e probe:_do_fork -aR sleep 1 # printf "%x\n" 748044 b6a0c ^ This is offset from the LEP. With this, there is also no way to ever probe between the GEP and the LEP. With this patchset: # perf probe -v _do_fork+4 probe-definition(0): _do_fork+4 symbol:_do_fork file:(null) line:0 offset:4 return:0 lazy:(null) 0 arguments Looking at the vmlinux_path (8 entries long) Using /proc/kcore for kernel object code Using /proc/kallsyms for symbols Opening /sys/kernel/debug/tracing//kprobe_events write=1 Writing event: p:probe/_do_fork _text+748036 Added new event: probe:_do_fork (on _do_fork+4) You can now use it in all perf tools, such as: perf record -e probe:_do_fork -aR sleep 1 # perf probe -v _do_fork probe-definition(0): _do_fork symbol:_do_fork file:(null) line:0 offset:0 return:0 lazy:(null) 0 arguments Looking at the vmlinux_path (8 entries long) Using /proc/kcore for kernel object code Using /proc/kallsyms for symbols Opening /sys/kernel/debug/tracing//kprobe_events write=1 Writing event: p:probe/_do_fork _text+748040 Added new event: probe:_do_fork (on _do_fork) You can now use it in all perf tools, such as: perf record -e probe:_do_fork -aR sleep 1 We only offset to the LEP if function entry is specified, otherwise, we offset from the GEP. Example for issue (3): - Before patch: # perf probe -v _do_fork:%return probe-definition(0): _do_fork:%return symbol:_do_fork file:(null) line:0 offset:0 return:1 lazy:(null) 0 arguments Looking at the vmlinux_path (8 entries long) Using /proc/kcore for kernel object code Using /proc/kallsyms for symbols Opening /sys/kernel/debug/tracing//kprobe_events write=1 Writing event: r:probe/_do_fork _do_fork+8 Failed to write event: Invalid argument Error: Failed to add events. Reason: Invalid argument (Code: -22) After patch: # perf probe _do_fork:%return Added new event: probe:_do_fork (on _do_fork%return) You can now use it in all perf tools, such as: perf record -e probe:_do_fork -aR sleep 1 Concept Acked-by: Michael Ellerman Cc: Mark Wielaard Cc: Thiago Jung Bauermann Cc: Arnaldo Carvalho de Melo Cc: Masami Hiramatsu Cc: Michael Ellerman Cc: Balbir Singh Cc: Ananth N Mavinakayanahalli Naveen N. Rao (2): perf tools: Fix kprobe and kretprobe handling with kallsyms on ppc64le perf tools: Fix kallsyms perf test on ppc64le tools/perf/arch/powerpc/util/sym-handling.c | 43 + tools/perf/util/probe-event.c | 5 ++-- tools/perf/util/probe-event.h | 3 +- tools/perf/util/symbol-elf.c| 7 +++-- tools/perf/util/symbol.h| 3 +- 5 files changed, 43 insertions(+), 18 deletions(-) -- 2.7.4 ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
