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SubjectRe: [PATCH v5 5/5] perf: powerpc: choose local entry point with kretprobes
On Wed,  8 Mar 2017 13:56:10 +0530
"Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> wrote:

> perf now uses an offset from _text/_stext for kretprobes if the kernel
> supports it, rather than the actual function name. As such, let's choose
> the LEP for powerpc ABIv2 so as to ensure the probe gets hit. Do it only
> if the kernel supports specifying offsets with kretprobes.

Acked-by: Masami Hiramatsu <mhiramat@kernel.org>

This patch is OK. And I found that most of functions in sym-handling.c
are used only when libelf is supported. (e.g. probe-event.c itself
is not built when we have no libelf)
So, for the next cleanup, this file should not be compiled without
libelf.

Thanks!

>
> Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
> ---
> tools/perf/arch/powerpc/util/sym-handling.c | 14 ++++++++++----
> 1 file changed, 10 insertions(+), 4 deletions(-)
>
> diff --git a/tools/perf/arch/powerpc/util/sym-handling.c b/tools/perf/arch/powerpc/util/sym-handling.c
> index 1030a6e504bb..39dbe512b9fc 100644
> --- a/tools/perf/arch/powerpc/util/sym-handling.c
> +++ b/tools/perf/arch/powerpc/util/sym-handling.c
> @@ -10,6 +10,7 @@
> #include "symbol.h"
> #include "map.h"
> #include "probe-event.h"
> +#include "probe-file.h"
>
> #ifdef HAVE_LIBELF_SUPPORT
> bool elf__needs_adjust_symbols(GElf_Ehdr ehdr)
> @@ -79,13 +80,18 @@ void arch__fix_tev_from_maps(struct perf_probe_event *pev,
> * However, if the user specifies an offset, we fall back to using the
> * GEP since all userspace applications (objdump/readelf) show function
> * disassembly with offsets from the GEP.
> - *
> - * In addition, we shouldn't specify an offset for kretprobes.
> */
> - if (pev->point.offset || (!pev->uprobes && pev->point.retprobe) ||
> - !map || !sym)
> + if (pev->point.offset || !map || !sym)
> return;
>
> + /* For kretprobes, add an offset only if the kernel supports it */
> + if (!pev->uprobes && pev->point.retprobe) {
> +#ifdef HAVE_LIBELF_SUPPORT
> + if (!kretprobe_offset_is_supported())
> +#endif
> + return;
> + }
> +
> lep_offset = PPC64_LOCAL_ENTRY_OFFSET(sym->arch_sym);
>
> if (map->dso->symtab_type == DSO_BINARY_TYPE__KALLSYMS)
> --
> 2.11.1
>


--
Masami Hiramatsu <mhiramat@kernel.org>

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