Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754237AbbEKN6f (ORCPT ); Mon, 11 May 2015 09:58:35 -0400 Received: from mail.kernel.org ([198.145.29.136]:40774 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754099AbbEKN6b (ORCPT ); Mon, 11 May 2015 09:58:31 -0400 Date: Mon, 11 May 2015 10:58:25 -0300 From: Arnaldo Carvalho de Melo To: He Kuang Cc: masami.hiramatsu.pt@hitachi.com, a.p.zijlstra@chello.nl, jolsa@kernel.org, mingo@redhat.com, wangnan0@huawei.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 2/3] perf probe: Add --range option to show variable location range Message-ID: <20150511135825.GF28183@kernel.org> References: <1431349804-31849-1-git-send-email-hekuang@huawei.com> <1431349804-31849-2-git-send-email-hekuang@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1431349804-31849-2-git-send-email-hekuang@huawei.com> X-Url: http://acmel.wordpress.com User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 11884 Lines: 358 Em Mon, May 11, 2015 at 01:10:03PM +0000, He Kuang escreveu: > It is not easy for users to get the accurate byte offset or the line > number where a local variable can be probed. With '--range' option, > local variables in scope of the probe point are showed with byte offset > range, and can be added according to this range information. Please, when you send a V4 patch like this, state what changed with regards to the previous version, as I already applied this patch :-\ - Arnaldo > For example, there are some variables in function > generic_perform_write(): > > > 0 ssize_t generic_perform_write(struct file *file, > 1 struct iov_iter *i, loff_t pos) > 2 { > 3 struct address_space *mapping = file->f_mapping; > 4 const struct address_space_operations *a_ops = mapping->a_ops; > ... > 42 status = a_ops->write_begin(file, mapping, pos, bytes, flags, > &page, &fsdata); > 44 if (unlikely(status < 0)) > > But we got failed when we try to probe the variable 'a_ops' at line 42 > or 44. > > $ perf probe --add 'generic_perform_write:42 a_ops' > Failed to find the location of a_ops at this address. > Perhaps, it has been optimized out. > > This is because source code do not match assembly, so a variable may not > be available in the sourcecode line where it presents. After this patch, > we can lookup the accurate byte offset range of a variable, 'INV' > indicates that this variable is not valid at the given point, but > available in scope: > > $ perf probe --vars 'generic_perform_write:42' --range > Available variables at generic_perform_write:42 > @ > [INV] ssize_t written @ > [INV] struct address_space_operations* a_ops @ > [VAL] (unknown_type) fsdata @ > [VAL] loff_t pos @ > [VAL] long int status @ > [VAL] long unsigned int bytes @ > [VAL] struct address_space* mapping @ > [VAL] struct iov_iter* i @ > [VAL] struct page* page @ > > Then it is more clearly for us to do the probe with this variable: > > $ perf probe --add 'generic_perform_write+170 a_ops' > Added new event: > probe:generic_perform_write (on generic_perform_write+170 with a_ops) > > Signed-off-by: He Kuang > Acked-by: Masami Hiramatsu > --- > tools/perf/builtin-probe.c | 2 + > tools/perf/util/dwarf-aux.c | 121 +++++++++++++++++++++++++++++++++++++++++ > tools/perf/util/dwarf-aux.h | 2 + > tools/perf/util/probe-event.h | 1 + > tools/perf/util/probe-finder.c | 57 ++++++++++++++----- > 5 files changed, 170 insertions(+), 13 deletions(-) > > diff --git a/tools/perf/builtin-probe.c b/tools/perf/builtin-probe.c > index 7fa2c7a..1272559 100644 > --- a/tools/perf/builtin-probe.c > +++ b/tools/perf/builtin-probe.c > @@ -372,6 +372,8 @@ __cmd_probe(int argc, const char **argv, const char *prefix __maybe_unused) > "Show accessible variables on PROBEDEF", opt_show_vars), > OPT_BOOLEAN('\0', "externs", &probe_conf.show_ext_vars, > "Show external variables too (with --vars only)"), > + OPT_BOOLEAN('\0', "range", &probe_conf.show_location_range, > + "Show variables location range in scope (with --vars only)"), > OPT_STRING('k', "vmlinux", &symbol_conf.vmlinux_name, > "file", "vmlinux pathname"), > OPT_STRING('s', "source", &symbol_conf.source_prefix, > diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c > index 737c9db..afa0971 100644 > --- a/tools/perf/util/dwarf-aux.c > +++ b/tools/perf/util/dwarf-aux.c > @@ -913,3 +913,124 @@ int die_get_varname(Dwarf_Die *vr_die, struct strbuf *buf) > return 0; > } > > +/** > + * die_get_var_innermost_scope - Get innermost scope range of given variable DIE > + * @sp_die: a subprogram DIE > + * @vr_die: a variable DIE > + * @buf: a strbuf for variable byte offset range > + * > + * Get the innermost scope range of @vr_die and stores it in @buf as > + * "@". > + */ > +static int die_get_var_innermost_scope(Dwarf_Die *sp_die, Dwarf_Die *vr_die, > + struct strbuf *buf) > +{ > + Dwarf_Die *scopes; > + int count; > + size_t offset = 0; > + Dwarf_Addr base; > + Dwarf_Addr start, end; > + Dwarf_Addr entry; > + int ret; > + bool first = true; > + const char *name; > + > + ret = dwarf_entrypc(sp_die, &entry); > + if (ret) > + return ret; > + > + name = dwarf_diename(sp_die); > + if (!name) > + return -ENOENT; > + > + count = dwarf_getscopes_die(vr_die, &scopes); > + > + /* (*SCOPES)[1] is the DIE for the scope containing that scope */ > + if (count <= 1) { > + ret = -EINVAL; > + goto out; > + } > + > + while ((offset = dwarf_ranges(&scopes[1], offset, &base, > + &start, &end)) > 0) { > + start -= entry; > + end -= entry; > + > + if (first) { > + strbuf_addf(buf, "@<%s+[%lu-%lu", > + name, start, end); > + first = false; > + } else { > + strbuf_addf(buf, ",%lu-%lu", > + start, end); > + } > + } > + > + if (!first) > + strbuf_addf(buf, "]>"); > + > +out: > + free(scopes); > + return ret; > +} > + > +/** > + * die_get_var_range - Get byte offset range of given variable DIE > + * @sp_die: a subprogram DIE > + * @vr_die: a variable DIE > + * @buf: a strbuf for type and variable name and byte offset range > + * > + * Get the byte offset range of @vr_die and stores it in @buf as > + * "@". > + */ > +int die_get_var_range(Dwarf_Die *sp_die, Dwarf_Die *vr_die, struct strbuf *buf) > +{ > + int ret = 0; > + Dwarf_Addr base; > + Dwarf_Addr start, end; > + Dwarf_Addr entry; > + Dwarf_Op *op; > + size_t nops; > + size_t offset = 0; > + Dwarf_Attribute attr; > + bool first = true; > + const char *name; > + > + ret = dwarf_entrypc(sp_die, &entry); > + if (ret) > + return ret; > + > + name = dwarf_diename(sp_die); > + if (!name) > + return -ENOENT; > + > + if (dwarf_attr(vr_die, DW_AT_location, &attr) == NULL) > + return -EINVAL; > + > + while ((offset = dwarf_getlocations( > + &attr, offset, &base, > + &start, &end, &op, &nops)) > 0) { > + if (start == 0) { > + /* Single Location Descriptions */ > + ret = die_get_var_innermost_scope(sp_die, vr_die, buf); > + return ret; > + } > + > + /* Location Lists */ > + start -= entry; > + end -= entry; > + if (first) { > + strbuf_addf(buf, "@<%s+[%lu-%lu", > + name, start, end); > + first = false; > + } else { > + strbuf_addf(buf, ",%lu-%lu", > + start, end); > + } > + } > + > + if (!first) > + strbuf_addf(buf, "]>"); > + > + return ret; > +} > diff --git a/tools/perf/util/dwarf-aux.h b/tools/perf/util/dwarf-aux.h > index 60676fd..c154c0b8 100644 > --- a/tools/perf/util/dwarf-aux.h > +++ b/tools/perf/util/dwarf-aux.h > @@ -121,4 +121,6 @@ extern int die_get_typename(Dwarf_Die *vr_die, struct strbuf *buf); > > /* Get the name and type of given variable DIE, stored as "type\tname" */ > extern int die_get_varname(Dwarf_Die *vr_die, struct strbuf *buf); > +extern int die_get_var_range(Dwarf_Die *sp_die, Dwarf_Die *vr_die, > + struct strbuf *buf); > #endif > diff --git a/tools/perf/util/probe-event.h b/tools/perf/util/probe-event.h > index 1e2faa3..537eb32 100644 > --- a/tools/perf/util/probe-event.h > +++ b/tools/perf/util/probe-event.h > @@ -9,6 +9,7 @@ > /* Probe related configurations */ > struct probe_conf { > bool show_ext_vars; > + bool show_location_range; > bool force_add; > bool no_inlines; > int max_probes; > diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c > index dcca551..f032329 100644 > --- a/tools/perf/util/probe-finder.c > +++ b/tools/perf/util/probe-finder.c > @@ -177,7 +177,7 @@ static int convert_variable_location(Dwarf_Die *vr_die, Dwarf_Addr addr, > Dwarf_Word offs = 0; > bool ref = false; > const char *regs; > - int ret; > + int ret, ret2 = 0; > > if (dwarf_attr(vr_die, DW_AT_external, &attr) != NULL) > goto static_var; > @@ -187,9 +187,19 @@ static int convert_variable_location(Dwarf_Die *vr_die, Dwarf_Addr addr, > return -EINVAL; /* Broken DIE ? */ > if (dwarf_getlocation_addr(&attr, addr, &op, &nops, 1) <= 0) { > ret = dwarf_entrypc(sp_die, &tmp); > - if (ret || addr != tmp || > - dwarf_tag(vr_die) != DW_TAG_formal_parameter || > - dwarf_highpc(sp_die, &tmp)) > + if (ret) > + return -ENOENT; > + > + if (probe_conf.show_location_range && > + (dwarf_tag(vr_die) == DW_TAG_variable)) { > + ret2 = -ERANGE; > + } else if (addr != tmp || > + dwarf_tag(vr_die) != DW_TAG_formal_parameter) { > + return -ENOENT; > + } > + > + ret = dwarf_highpc(sp_die, &tmp); > + if (ret) > return -ENOENT; > /* > * This is fuzzed by fentry mcount. We try to find the > @@ -210,7 +220,7 @@ found: > if (op->atom == DW_OP_addr) { > static_var: > if (!tvar) > - return 0; > + return ret2; > /* Static variables on memory (not stack), make @varname */ > ret = strlen(dwarf_diename(vr_die)); > tvar->value = zalloc(ret + 2); > @@ -220,7 +230,7 @@ static_var: > tvar->ref = alloc_trace_arg_ref((long)offs); > if (tvar->ref == NULL) > return -ENOMEM; > - return 0; > + return ret2; > } > > /* If this is based on frame buffer, set the offset */ > @@ -250,14 +260,14 @@ static_var: > } > > if (!tvar) > - return 0; > + return ret2; > > regs = get_arch_regstr(regn); > if (!regs) { > /* This should be a bug in DWARF or this tool */ > pr_warning("Mapping for the register number %u " > "missing on this architecture.\n", regn); > - return -ERANGE; > + return -ENOTSUP; > } > > tvar->value = strdup(regs); > @@ -269,7 +279,7 @@ static_var: > if (tvar->ref == NULL) > return -ENOMEM; > } > - return 0; > + return ret2; > } > > #define BYTES_TO_BITS(nb) ((nb) * BITS_PER_LONG / sizeof(long)) > @@ -1268,13 +1278,34 @@ static int collect_variables_cb(Dwarf_Die *die_mem, void *data) > ret = convert_variable_location(die_mem, af->pf.addr, > af->pf.fb_ops, &af->pf.sp_die, > NULL); > - if (ret == 0) { > + if (ret == 0 || ret == -ERANGE) { > + int ret2; > + bool externs = !af->child; > struct strbuf buf; > > strbuf_init(&buf, 64); > - ret = die_get_varname(die_mem, &buf); > - pr_debug2("Add new var: %s\n", buf.buf); > - if (ret == 0) { > + > + if (probe_conf.show_location_range) { > + if (!externs) { > + if (ret) > + strbuf_addf(&buf, "[INV]\t"); > + else > + strbuf_addf(&buf, "[VAL]\t"); > + } else > + strbuf_addf(&buf, "[EXT]\t"); > + } > + > + ret2 = die_get_varname(die_mem, &buf); > + > + if (!ret2 && probe_conf.show_location_range && > + !externs) { > + strbuf_addf(&buf, "\t"); > + ret2 = die_get_var_range(&af->pf.sp_die, > + die_mem, &buf); > + } > + > + pr_debug("Add new var: %s\n", buf.buf); > + if (ret2 == 0) { > strlist__add(vl->vars, > strbuf_detach(&buf, NULL)); > } > -- > 1.8.5.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/