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SubjectRe: [PATCH 4/5] perf probe: Support DW_AT_const_value constant value
Em Tue, Nov 05, 2019 at 09:17:19AM +0900, Masami Hiramatsu escreveu:
> Support DW_AT_const_value for variable assignment instead of location.
> Note that this requires ftrace supporting immediate value.

This one could have come before the other two, depends on the previous
two being applied.

- Arnaldo

> Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
> ---
> tools/perf/util/probe-file.c | 7 +++++++
> tools/perf/util/probe-file.h | 1 +
> tools/perf/util/probe-finder.c | 11 +++++++++++
> 3 files changed, 19 insertions(+)
>
> diff --git a/tools/perf/util/probe-file.c b/tools/perf/util/probe-file.c
> index a63f1a19b0e8..5003ba403345 100644
> --- a/tools/perf/util/probe-file.c
> +++ b/tools/perf/util/probe-file.c
> @@ -1008,6 +1008,7 @@ enum ftrace_readme {
> FTRACE_README_UPROBE_REF_CTR,
> FTRACE_README_USER_ACCESS,
> FTRACE_README_MULTIPROBE_EVENT,
> + FTRACE_README_IMMEDIATE_VALUE,
> FTRACE_README_END,
> };
>
> @@ -1022,6 +1023,7 @@ static struct {
> DEFINE_TYPE(FTRACE_README_UPROBE_REF_CTR, "*ref_ctr_offset*"),
> DEFINE_TYPE(FTRACE_README_USER_ACCESS, "*[u]<offset>*"),
> DEFINE_TYPE(FTRACE_README_MULTIPROBE_EVENT, "*Create/append/*"),
> + DEFINE_TYPE(FTRACE_README_IMMEDIATE_VALUE, "*\\imm-value,*"),
> };
>
> static bool scan_ftrace_readme(enum ftrace_readme type)
> @@ -1092,3 +1094,8 @@ bool multiprobe_event_is_supported(void)
> {
> return scan_ftrace_readme(FTRACE_README_MULTIPROBE_EVENT);
> }
> +
> +bool immediate_value_is_supported(void)
> +{
> + return scan_ftrace_readme(FTRACE_README_IMMEDIATE_VALUE);
> +}
> diff --git a/tools/perf/util/probe-file.h b/tools/perf/util/probe-file.h
> index 850d1b52d60a..0dba88c0f5f0 100644
> --- a/tools/perf/util/probe-file.h
> +++ b/tools/perf/util/probe-file.h
> @@ -72,6 +72,7 @@ bool kretprobe_offset_is_supported(void);
> bool uprobe_ref_ctr_is_supported(void);
> bool user_access_is_supported(void);
> bool multiprobe_event_is_supported(void);
> +bool immediate_value_is_supported(void);
> #else /* ! HAVE_LIBELF_SUPPORT */
> static inline struct probe_cache *probe_cache__new(const char *tgt __maybe_unused, struct nsinfo *nsi __maybe_unused)
> {
> diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
> index 9ecea45da4ca..2e3a468c8350 100644
> --- a/tools/perf/util/probe-finder.c
> +++ b/tools/perf/util/probe-finder.c
> @@ -177,6 +177,17 @@ static int convert_variable_location(Dwarf_Die *vr_die, Dwarf_Addr addr,
> if (dwarf_attr(vr_die, DW_AT_external, &attr) != NULL)
> goto static_var;
>
> + /* Constant value */
> + if (dwarf_attr(vr_die, DW_AT_const_value, &attr) &&
> + immediate_value_is_supported()) {
> + Dwarf_Sword snum;
> +
> + dwarf_formsdata(&attr, &snum);
> + ret = asprintf(&tvar->value, "\\%ld", (long)snum);
> +
> + return ret < 0 ? -ENOMEM : 0;
> + }
> +
> /* TODO: handle more than 1 exprs */
> if (dwarf_attr(vr_die, DW_AT_location, &attr) == NULL)
> return -EINVAL; /* Broken DIE ? */

--

- Arnaldo

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