Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753084AbbHZCi5 (ORCPT ); Tue, 25 Aug 2015 22:38:57 -0400 Received: from szxga01-in.huawei.com ([58.251.152.64]:11237 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751624AbbHZCiz (ORCPT ); Tue, 25 Aug 2015 22:38:55 -0400 Message-ID: <55DD269A.7030408@huawei.com> Date: Wed, 26 Aug 2015 10:38:18 +0800 From: "Wangnan (F)" User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:31.0) Gecko/20100101 Thunderbird/31.6.0 MIME-Version: 1.0 To: =?UTF-8?B?5bmz5p2+6ZuF5bezIC8gSElSQU1BVFXvvIxNQVNBTUk=?= , "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 References: <1440509256-193590-1-git-send-email-wangnan0@huawei.com> <1440509256-193590-2-git-send-email-wangnan0@huawei.com> <50399556C9727B4D88A595C8584AAB37524EA491@GSjpTKYDCembx32.service.hitachi.net> In-Reply-To: <50399556C9727B4D88A595C8584AAB37524EA491@GSjpTKYDCembx32.service.hitachi.net> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.111.66.109] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 10128 Lines: 318 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. 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/