Messages in this thread | | | From | Arnaldo Carvalho de Melo <> | Date | Wed, 6 Nov 2019 17:00:04 -0300 | Subject | Re: [PATCH 5/5] perf probe: Trace a magic number if variable is not found |
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Em Tue, Nov 05, 2019 at 09:17:28AM +0900, Masami Hiramatsu escreveu: > Trace a magic number as immediate value if the target variable > is not found at some probe points which is based on one probe > event. > > This feature is good for the case if you trace a source code > line with some local variables, which is compiled into several > instructions and some of the variables are optimized out on > some instructions. Even if so, with this feature, perf probe > trace a magic number instead of such disappeared variables and > fold those probes on one event.
This too depends on a function introduced in previous patches on hold.
- Arnaldo
> E.g. without this patch, > # perf probe -D "pud_page_vaddr pud" > Failed to find 'pud' in this function. > Failed to find 'pud' in this function. > Failed to find 'pud' in this function. > Failed to find 'pud' in this function. > Failed to find 'pud' in this function. > Failed to find 'pud' in this function. > Failed to find 'pud' in this function. > Failed to find 'pud' in this function. > Failed to find 'pud' in this function. > Failed to find 'pud' in this function. > Failed to find 'pud' in this function. > Failed to find 'pud' in this function. > Failed to find 'pud' in this function. > Failed to find 'pud' in this function. > Failed to find 'pud' in this function. > Failed to find 'pud' in this function. > p:probe/pud_page_vaddr_L0 _text+23480787 pud=%ax:x64 > p:probe/pud_page_vaddr_L0 _text+23808289 pud=%bp:x64 > p:probe/pud_page_vaddr_L0 _text+23558066 pud=%ax:x64 > p:probe/pud_page_vaddr_L0 _text+327957 pud=%r8:x64 > p:probe/pud_page_vaddr_L0 _text+348032 pud=%bx:x64 > p:probe/pud_page_vaddr_L0 _text+23816654 pud=%bx:x64 > > With this patch, > # perf probe -D "pud_page_vaddr pud" | head -n 10 > spurious_kernel_fault is blacklisted function, skip it. > vmalloc_fault is blacklisted function, skip it. > p:probe/pud_page_vaddr_L0 _text+23480787 pud=%ax:x64 > p:probe/pud_page_vaddr_L0 _text+148635 pud=\deade12d:x64 > p:probe/pud_page_vaddr_L0 _text+23808289 pud=%bp:x64 > p:probe/pud_page_vaddr_L0 _text+315510 pud=\deade12d:x64 > p:probe/pud_page_vaddr_L0 _text+23807045 pud=\deade12d:x64 > p:probe/pud_page_vaddr_L0 _text+23557349 pud=%ax:x64 > p:probe/pud_page_vaddr_L0 _text+313681 pud=%di:x64 > p:probe/pud_page_vaddr_L0 _text+313599 pud=\deade12d:x64 > p:probe/pud_page_vaddr_L0 _text+313477 pud=\deade12d:x64 > p:probe/pud_page_vaddr_L0 _text+323667 pud=\deade12d:x64 > > > Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> > --- > tools/perf/util/probe-event.c | 2 + > tools/perf/util/probe-event.h | 3 ++ > tools/perf/util/probe-finder.c | 62 +++++++++++++++++++++++++++++++++++++--- > tools/perf/util/probe-finder.h | 1 + > 4 files changed, 63 insertions(+), 5 deletions(-) > > diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c > index 23db6786c3ea..ceeb75849311 100644 > --- a/tools/perf/util/probe-event.c > +++ b/tools/perf/util/probe-event.c > @@ -46,7 +46,7 @@ > #define PERFPROBE_GROUP "probe" > > bool probe_event_dry_run; /* Dry run flag */ > -struct probe_conf probe_conf; > +struct probe_conf probe_conf = { .magic_num = DEFAULT_PROBE_MAGIC_NUM }; > > #define semantic_error(msg ...) pr_err("Semantic error :" msg) > > diff --git a/tools/perf/util/probe-event.h b/tools/perf/util/probe-event.h > index 96a319cd2378..4f0eb3a20c36 100644 > --- a/tools/perf/util/probe-event.h > +++ b/tools/perf/util/probe-event.h > @@ -16,10 +16,13 @@ struct probe_conf { > bool no_inlines; > bool cache; > int max_probes; > + unsigned long magic_num; > }; > extern struct probe_conf probe_conf; > extern bool probe_event_dry_run; > > +#define DEFAULT_PROBE_MAGIC_NUM 0xdeade12d /* u32: 3735937325 */ > + > struct symbol; > > /* kprobe-tracer and uprobe-tracer tracing point */ > diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c > index 2e3a468c8350..eff6063bebe6 100644 > --- a/tools/perf/util/probe-finder.c > +++ b/tools/perf/util/probe-finder.c > @@ -536,6 +536,14 @@ static int convert_variable_fields(Dwarf_Die *vr_die, const char *varname, > return 0; > } > > +static void print_var_not_found(const char *varname) > +{ > + pr_err("Failed to find the location of the '%s' variable at this address.\n" > + " Perhaps it has been optimized out.\n" > + " Use -V with the --range option to show '%s' location range.\n", > + varname, varname); > +} > + > /* Show a variables in kprobe event format */ > static int convert_variable(Dwarf_Die *vr_die, struct probe_finder *pf) > { > @@ -547,11 +555,11 @@ static int convert_variable(Dwarf_Die *vr_die, struct probe_finder *pf) > > ret = convert_variable_location(vr_die, pf->addr, pf->fb_ops, > &pf->sp_die, pf->machine, pf->tvar); > + if (ret == -ENOENT && pf->skip_empty_arg) > + /* This can be found in other place. skip it */ > + return 0; > if (ret == -ENOENT || ret == -EINVAL) { > - pr_err("Failed to find the location of the '%s' variable at this address.\n" > - " Perhaps it has been optimized out.\n" > - " Use -V with the --range option to show '%s' location range.\n", > - pf->pvar->var, pf->pvar->var); > + print_var_not_found(pf->pvar->var); > } else if (ret == -ENOTSUP) > pr_err("Sorry, we don't support this variable location yet.\n"); > else if (ret == 0 && pf->pvar->field) { > @@ -598,6 +606,8 @@ static int find_variable(Dwarf_Die *sc_die, struct probe_finder *pf) > /* Search again in global variables */ > if (!die_find_variable_at(&pf->cu_die, pf->pvar->var, > 0, &vr_die)) { > + if (pf->skip_empty_arg) > + return 0; > pr_warning("Failed to find '%s' in this function.\n", > pf->pvar->var); > ret = -ENOENT; > @@ -1348,6 +1358,44 @@ static int add_probe_trace_event(Dwarf_Die *sc_die, struct probe_finder *pf) > return ret; > } > > +static int fill_empty_trace_arg(struct perf_probe_event *pev, > + struct probe_trace_event *tevs, int ntevs) > +{ > + char **valp; > + char *type; > + int i, j, ret; > + > + for (i = 0; i < pev->nargs; i++) { > + type = NULL; > + for (j = 0; j < ntevs; j++) { > + if (tevs[j].args[i].value) { > + type = tevs[j].args[i].type; > + break; > + } > + } > + if (j == ntevs) { > + print_var_not_found(pev->args[i].var); > + return -ENOENT; > + } > + for (j = 0; j < ntevs; j++) { > + valp = &tevs[j].args[i].value; > + if (*valp) > + continue; > + > + ret = asprintf(valp, "\\%lx", probe_conf.magic_num); > + if (ret < 0) > + return -ENOMEM; > + /* Note that type can be NULL */ > + if (type) { > + tevs[j].args[i].type = strdup(type); > + if (!tevs[j].args[i].type) > + return -ENOMEM; > + } > + } > + } > + return 0; > +} > + > /* Find probe_trace_events specified by perf_probe_event from debuginfo */ > int debuginfo__find_trace_events(struct debuginfo *dbg, > struct perf_probe_event *pev, > @@ -1366,7 +1414,13 @@ int debuginfo__find_trace_events(struct debuginfo *dbg, > tf.tevs = *tevs; > tf.ntevs = 0; > > + if (pev->event && pev->nargs != 0 && immediate_value_is_supported()) > + tf.pf.skip_empty_arg = true; > + > ret = debuginfo__find_probes(dbg, &tf.pf); > + if (ret >= 0 && tf.pf.skip_empty_arg) > + ret = fill_empty_trace_arg(pev, tf.tevs, tf.ntevs); > + > if (ret < 0) { > for (i = 0; i < tf.ntevs; i++) > clear_probe_trace_event(&tf.tevs[i]); > diff --git a/tools/perf/util/probe-finder.h b/tools/perf/util/probe-finder.h > index 670c477bf8cf..11be10080613 100644 > --- a/tools/perf/util/probe-finder.h > +++ b/tools/perf/util/probe-finder.h > @@ -87,6 +87,7 @@ struct probe_finder { > unsigned int machine; /* Target machine arch */ > struct perf_probe_arg *pvar; /* Current target variable */ > struct probe_trace_arg *tvar; /* Current result variable */ > + bool skip_empty_arg; /* Skip non-exist args */ > }; > > struct trace_event_finder {
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- Arnaldo
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