Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752172AbbEJDVh (ORCPT ); Sat, 9 May 2015 23:21:37 -0400 Received: from mail9.hitachi.co.jp ([133.145.228.44]:56344 "EHLO mail9.hitachi.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752043AbbEJDVf (ORCPT ); Sat, 9 May 2015 23:21:35 -0400 Message-ID: <554ECEB9.2040209@hitachi.com> Date: Sun, 10 May 2015 12:21:29 +0900 From: Masami Hiramatsu Organization: Hitachi, Ltd., Japan User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:31.0) Gecko/20100101 Thunderbird/31.6.0 MIME-Version: 1.0 To: He Kuang , a.p.zijlstra@chello.nl, acme@kernel.org, jolsa@kernel.org, mingo@redhat.com CC: wangnan0@huawei.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 2/3] perf probe: Add --range option to show variable location range References: <1431165306-106463-1-git-send-email-hekuang@huawei.com> <1431165306-106463-2-git-send-email-hekuang@huawei.com> In-Reply-To: <1431165306-106463-2-git-send-email-hekuang@huawei.com> Content-Type: text/plain; charset=iso-2022-jp Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6714 Lines: 192 On 2015/05/09 18:55, He Kuang wrote: > 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. > > 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 @ > Thanks, this looks easier to understand :) [...] > diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c > index dcca551..30a1a1b 100644 > --- a/tools/perf/util/probe-finder.c > +++ b/tools/perf/util/probe-finder.c > @@ -43,6 +43,9 @@ > /* Kprobe tracer basic type is up to u64 */ > #define MAX_BASIC_TYPE_BITS 64 > > +/* Variable location invalid at addr but valid in scope */ > +#define VARIABLE_LOCATION_INVALID_AT_ADDR -10000 Hmm, could you use -ERANGE instead of this? Other part is OK for me. Thank you! > + > /* Dwarf FL wrappers */ > static char *debuginfo_path; /* Currently dummy */ > > @@ -177,7 +180,7 @@ 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 +190,19 @@ 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 = VARIABLE_LOCATION_INVALID_AT_ADDR; > + } 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 +223,7 @@ 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 +233,7 @@ 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 */ > @@ -250,7 +263,7 @@ static_var: > } > > if (!tvar) > - return 0; > + return ret2; > > regs = get_arch_regstr(regn); > if (!regs) { > @@ -269,7 +282,7 @@ 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 +1281,34 @@ 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 == VARIABLE_LOCATION_INVALID_AT_ADDR) { > + 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)); > } > -- Masami HIRAMATSU Linux Technology Research Center, System Productivity Research Dept. Center for Technology Innovation - Systems Engineering Hitachi, Ltd., Research & Development Group E-mail: masami.hiramatsu.pt@hitachi.com -- 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/