Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756601AbbHZJCu (ORCPT ); Wed, 26 Aug 2015 05:02:50 -0400 Received: from mail4.hitachi.co.jp ([133.145.228.5]:60712 "EHLO mail4.hitachi.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755863AbbHZJCq (ORCPT ); Wed, 26 Aug 2015 05:02:46 -0400 From: =?utf-8?B?5bmz5p2+6ZuF5bezIC8gSElSQU1BVFXvvIxNQVNBTUk=?= To: "'Wangnan (F)'" , "acme@kernel.org" CC: "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 Thread-Topic: [PATCH 2/2] perf probe: Support probing at absolute address Thread-Index: AQHQ3zni/zBZOhoEh0Oq3boO7ZUBrJ4dZiKQ//+VEgCAAP9rsA== Date: Wed, 26 Aug 2015 09:02:42 +0000 Message-ID: <50399556C9727B4D88A595C8584AAB37524EB465@GSjpTKYDCembx32.service.hitachi.net> 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> In-Reply-To: <55DD269A.7030408@huawei.com> Accept-Language: ja-JP, en-US Content-Language: ja-JP X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.198.219.51] Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from base64 to 8bit by mail.home.local id t7Q92vXd023849 Content-Length: 10832 Lines: 321 > From: Wangnan (F) [mailto:wangnan0@huawei.com] > > 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, if we really find the case, we can add '+' prefix support just for an optional expression :) Thank you! > > 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 > ????{.n?+???????+%?????ݶ??w??{.n?+????{??G?????{ay?ʇڙ?,j??f???h?????????z_??(?階?ݢj"???m??????G????????????&???~???iO???z??v?^?m???? ????????I?