Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756015AbbHZNAj (ORCPT ); Wed, 26 Aug 2015 09:00:39 -0400 Received: from mail.kernel.org ([198.145.29.136]:45430 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751737AbbHZNAh (ORCPT ); Wed, 26 Aug 2015 09:00:37 -0400 Date: Wed, 26 Aug 2015 10:00:32 -0300 From: "acme@kernel.org" To: =?utf-8?B?5bmz5p2+6ZuF5bezIC8gSElSQU1BVFXvvIxNQVNBTUk=?= Cc: "'Wang Nan'" , "mingo@redhat.com" , "namhyung@kernel.org" , "pi3orama@163.com" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH 2/2] perf probe: Support probing at absolute address Message-ID: <20150826130032.GM19203@kernel.org> References: <1440509256-193590-1-git-send-email-wangnan0@huawei.com> <1440509256-193590-2-git-send-email-wangnan0@huawei.com> <50399556C9727B4D88A595C8584AAB37524EA491@GSjpTKYDCembx32.service.hitachi.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <50399556C9727B4D88A595C8584AAB37524EA491@GSjpTKYDCembx32.service.hitachi.net> 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: 10154 Lines: 315 Em Wed, Aug 26, 2015 at 12:02:40AM +0000, 平松雅巳 / HIRAMATU，MASAMI escreveu: > > From: Wang Nan [mailto:wangnan0@huawei.com] > > > > It should be useful to allow 'perf probe' probe at absolute offset of > > a target. For example, when (u)probing at a instruction of a shared > > object in a embedded system where debuginfo is not avaliable but we > > know the offset of that instruction by manually digging. > > > > This patch enables following perf probe command syntax: > > > > # perf probe +0xffffffff811e6615 > > > > And > > > > # perf probe /lib/x86_64-linux-gnu/libc-2.19.so +0xeb860 > > Why do we need "+" for the absolute address? I guess 'absolute' was the misleading term here, 'offset' would be better, perhaps, or even 'raw' address. > It seems that we can do it if we find that the given probe point > starts with "0x". Which is kinda ok, since that is the most common way of expressing offsets, but i don't know why we would preclude using, say, decimal, octal, etc. - Arnaldo > Thanks, > > > > > In the above example, we don't need a anchor symbol, so it is possible > > to compute absolute addresses using other methods and then use > > 'perf probe' to create the probing points. > > > > Signed-off-by: Wang Nan > > Cc: Arnaldo Carvalho de Melo > > Cc: Ingo Molnar > > Cc: Masami Hiramatsu > > Cc: Namhyung Kim > > --- > > tools/perf/util/probe-event.c | 144 +++++++++++++++++++++++++++++++++++++---- > > tools/perf/util/probe-event.h | 3 + > > tools/perf/util/probe-finder.c | 21 +----- > > 3 files changed, 138 insertions(+), 30 deletions(-) > > > > diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c > > index 6c7e538..59de69a4 100644 > > --- a/tools/perf/util/probe-event.c > > +++ b/tools/perf/util/probe-event.c > > @@ -1194,9 +1194,13 @@ static int parse_perf_probe_point(char *arg, struct perf_probe_event *pev) > > *ptr++ = '\0'; > > } > > > > - tmp = strdup(arg); > > - if (tmp == NULL) > > - return -ENOMEM; > > + if (arg[0] == '\0') > > + tmp = NULL; > > + else { > > + tmp = strdup(arg); > > + if (tmp == NULL) > > + return -ENOMEM; > > + } > > > > if (file_spec) > > pp->file = tmp; > > @@ -1283,11 +1287,6 @@ static int parse_perf_probe_point(char *arg, struct perf_probe_event *pev) > > return -EINVAL; > > } > > > > - if (pp->offset && !pp->function) { > > - semantic_error("Offset requires an entry function.\n"); > > - return -EINVAL; > > - } > > - > > if (pp->retprobe && !pp->function) { > > semantic_error("Return probe requires an entry function.\n"); > > return -EINVAL; > > @@ -1299,6 +1298,11 @@ static int parse_perf_probe_point(char *arg, struct perf_probe_event *pev) > > return -EINVAL; > > } > > > > + if (!pp->function && !pp->offset && !pp->file) { > > + semantic_error("Absolute address should not be zero.\n"); > > + return -EINVAL; > > + } > > + > > pr_debug("symbol:%s file:%s line:%d offset:%lu return:%d lazy:%s\n", > > pp->function, pp->file, pp->line, pp->offset, pp->retprobe, > > pp->lazy_line); > > @@ -1609,7 +1613,7 @@ error: > > static char *synthesize_perf_probe_point(struct perf_probe_point *pp) > > { > > char *buf, *tmp; > > - char offs[32] = "", line[32] = "", file[32] = ""; > > + char offs[32] = "", line[32] = "", file[32] = "", addr[32] = ""; > > int ret, len; > > > > buf = zalloc(MAX_CMDLEN); > > @@ -1622,6 +1626,11 @@ static char *synthesize_perf_probe_point(struct perf_probe_point *pp) > > if (ret <= 0) > > goto error; > > } > > + if (!pp->function) { > > + ret = e_snprintf(addr, 32, "0x%lx", pp->offset); > > + if (ret <= 0) > > + goto error; > > + } > > if (pp->line) { > > ret = e_snprintf(line, 32, ":%d", pp->line); > > if (ret <= 0) > > @@ -1639,9 +1648,11 @@ static char *synthesize_perf_probe_point(struct perf_probe_point *pp) > > goto error; > > } > > > > - if (pp->function) > > - ret = e_snprintf(buf, MAX_CMDLEN, "%s%s%s%s%s", pp->function, > > - offs, pp->retprobe ? "%return" : "", line, > > + if (pp->function || pp->offset) > > + ret = e_snprintf(buf, MAX_CMDLEN, "%s%s%s%s%s", > > + pp->function ? : addr, > > + pp->function ? offs : "", > > + pp->retprobe ? "%return" : "", line, > > file); > > else > > ret = e_snprintf(buf, MAX_CMDLEN, "%s%s", file, line); > > @@ -1786,6 +1797,11 @@ char *synthesize_probe_trace_command(struct probe_trace_event *tev) > > if (tev->uprobes) > > ret = e_snprintf(buf + len, MAX_CMDLEN - len, "%s:0x%lx", > > tp->module, tp->address); > > + else if (tp->symbol[0] == '0' && tp->symbol[1] == 'x') > > + /* Absolute address. See try_to_find_absolute_address() */ > > + ret = e_snprintf(buf + len, MAX_CMDLEN - len, "%s%s0x%lx", > > + tp->module ?: "", tp->module ? ":" : "", > > + tp->address); > > else > > ret = e_snprintf(buf + len, MAX_CMDLEN - len, "%s%s%s+%lu", > > tp->module ?: "", tp->module ? ":" : "", > > @@ -2572,6 +2588,87 @@ err_out: > > goto out; > > } > > > > +static int try_to_find_absolute_address(struct perf_probe_event *pev, > > + struct probe_trace_event **tevs) > > +{ > > + struct perf_probe_point *pp = &pev->point; > > + struct probe_trace_event *tev; > > + struct probe_trace_point *tp; > > + int i, err; > > + > > + if (perf_probe_event_need_dwarf(pev) || pev->point.function) > > + return -EINVAL; > > + > > + /* > > + * This is 'perf probe /lib/libc.so +0xabcd'. Try to probe at > > + * absolute address. > > + * > > + * Only one tev can be generated by this. > > + */ > > + *tevs = zalloc(sizeof(*tev)); > > + if (!*tevs) > > + return -ENOMEM; > > + > > + tev = *tevs; > > + tp = &tev->point; > > + > > + /* > > + * Don't use tp->offset, use address directly, because > > + * in synthesize_probe_trace_command() address cannot be > > + * zero. > > + */ > > + tp->address = pev->point.offset; > > + tp->retprobe = pp->retprobe; > > + tev->uprobes = pev->uprobes; > > + > > + err = -ENOMEM; > > + /* Give it a '0x' leading symbol name */ > > + if (asprintf(&tp->symbol, "0x%lx", tp->address) < 0) > > + goto errout; > > + > > + /* For kprobe, check range */ > > + if ((!tev->uprobes) && > > + (kprobe_warn_out_range(tev->point.symbol, > > + tev->point.address))) { > > + err = -EACCES; > > + goto errout; > > + } > > + > > + if (asprintf(&tp->realname, "abs_%lx", tp->address) < 0) > > + goto errout; > > + > > + if (pev->target) { > > + tp->module = strdup(pev->target); > > + if (!tp->module) > > + goto errout; > > + } > > + > > + if (tev->group) { > > + tev->group = strdup(pev->group); > > + if (!tev->group) > > + goto errout; > > + } > > + > > + if (pev->event) { > > + tev->event = strdup(pev->event); > > + if (!tev->event) > > + goto errout; > > + } > > + > > + tev->nargs = pev->nargs; > > + for (i = 0; i < tev->nargs; i++) > > + copy_to_probe_trace_arg(&tev->args[i], &pev->args[i]); > > + > > + return 1; > > + > > +errout: > > + if (*tevs) { > > + clear_probe_trace_events(*tevs, 1); > > + *tevs = NULL; > > + } > > + return err; > > +} > > + > > bool __weak arch__prefers_symtab(void) { return false; } > > > > static int convert_to_probe_trace_events(struct perf_probe_event *pev, > > @@ -2588,6 +2685,10 @@ static int convert_to_probe_trace_events(struct perf_probe_event *pev, > > } > > } > > > > + ret = try_to_find_absolute_address(pev, tevs); > > + if (ret > 0) > > + return ret; > > + > > if (arch__prefers_symtab() && !perf_probe_event_need_dwarf(pev)) { > > ret = find_probe_trace_events_from_map(pev, tevs); > > if (ret > 0) > > @@ -2758,3 +2859,22 @@ end: > > return ret; > > } > > > > +int copy_to_probe_trace_arg(struct probe_trace_arg *tvar, > > + struct perf_probe_arg *pvar) > > +{ > > + tvar->value = strdup(pvar->var); > > + if (tvar->value == NULL) > > + return -ENOMEM; > > + if (pvar->type) { > > + tvar->type = strdup(pvar->type); > > + if (tvar->type == NULL) > > + return -ENOMEM; > > + } > > + if (pvar->name) { > > + tvar->name = strdup(pvar->name); > > + if (tvar->name == NULL) > > + return -ENOMEM; > > + } else > > + tvar->name = NULL; > > + return 0; > > +} > > diff --git a/tools/perf/util/probe-event.h b/tools/perf/util/probe-event.h > > index 83ee95e..174a3cf 100644 > > --- a/tools/perf/util/probe-event.h > > +++ b/tools/perf/util/probe-event.h > > @@ -156,4 +156,7 @@ int e_snprintf(char *str, size_t size, const char *format, ...) > > /* Maximum index number of event-name postfix */ > > #define MAX_EVENT_INDEX 1024 > > > > +int copy_to_probe_trace_arg(struct probe_trace_arg *tvar, > > + struct perf_probe_arg *pvar); > > + > > #endif /*_PROBE_EVENT_H */ > > diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c > > index 7b80f8c..29c43c068 100644 > > --- a/tools/perf/util/probe-finder.c > > +++ b/tools/perf/util/probe-finder.c > > @@ -553,24 +553,9 @@ static int find_variable(Dwarf_Die *sc_die, struct probe_finder *pf) > > char buf[32], *ptr; > > int ret = 0; > > > > - if (!is_c_varname(pf->pvar->var)) { > > - /* Copy raw parameters */ > > - pf->tvar->value = strdup(pf->pvar->var); > > - if (pf->tvar->value == NULL) > > - return -ENOMEM; > > - if (pf->pvar->type) { > > - pf->tvar->type = strdup(pf->pvar->type); > > - if (pf->tvar->type == NULL) > > - return -ENOMEM; > > - } > > - if (pf->pvar->name) { > > - pf->tvar->name = strdup(pf->pvar->name); > > - if (pf->tvar->name == NULL) > > - return -ENOMEM; > > - } else > > - pf->tvar->name = NULL; > > - return 0; > > - } > > + /* Copy raw parameters */ > > + if (!is_c_varname(pf->pvar->var)) > > + return copy_to_probe_trace_arg(pf->tvar, pf->pvar); > > > > if (pf->pvar->name) > > pf->tvar->name = strdup(pf->pvar->name); > > -- > > 1.8.3.4 > -- 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/