Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756602AbbHZNCa (ORCPT ); Wed, 26 Aug 2015 09:02:30 -0400 Received: from mail.kernel.org ([198.145.29.136]:45605 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755964AbbHZNC2 (ORCPT ); Wed, 26 Aug 2015 09:02:28 -0400 Date: Wed, 26 Aug 2015 10:02:23 -0300 From: "acme@kernel.org" To: "Wangnan (F)" Cc: =?utf-8?B?5bmz5p2+6ZuF5bezIC8gSElSQU1BVFXvvIxNQVNBTUk=?= , "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: <20150826130223.GN19203@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> <55DD269A.7030408@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <55DD269A.7030408@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: 10653 Lines: 323 Em Wed, Aug 26, 2015 at 10:38:18AM +0800, Wangnan (F) escreveu: > > On 2015/8/26 8:02, 平松雅巳 / HIRAMATU，MASAMI wrote: > >>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? > >It seems that we can do it if we find that the given probe point > >starts with "0x". > > > >Thanks, > > I will change 2/2 as you suggection. > > However, we can only ensure that in kernel side symbol never leading > with '0x'. Although I don't think symbol leading with 0x is useful, > it is still possible for a userspace program compiled and linked by > a language other than C produces such symbol. '+' helps us separate > address and function name semantically, make us don't rely on assumption > on function names. If in future we do meet '0x' symbols, I think we still > need the '+' syntax back. But we can do it at that time. Agreed, I also think that using '+' is better, but will not dwell on this so as to make progress :-) - Arnaldo > Thank you. > > > >>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/