Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932767AbbHZNTw (ORCPT ); Wed, 26 Aug 2015 09:19:52 -0400 Received: from szxga01-in.huawei.com ([58.251.152.64]:10703 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751798AbbHZNTv (ORCPT ); Wed, 26 Aug 2015 09:19:51 -0400 Message-ID: <55DDBCDF.8050607@huawei.com> Date: Wed, 26 Aug 2015 21:19:27 +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: "acme@kernel.org" 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 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> <20150826130223.GN19203@kernel.org> In-Reply-To: <20150826130223.GN19203@kernel.org> 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: 11415 Lines: 336 On 2015/8/26 21:02, acme@kernel.org wrote: > 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 > Maybe we should support both of them, making '+0x1234' the core syntax, and '0x1234' style as a syntax sugar. However I have worked on this problem for nearly a full day but my main work should be BPF related things... Since Masami has acked all of the 6 v3 patches, if we still need '+' I can bring it back with a new patch when I have time. However, same to you, I don't think this should be a blocking problem. 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 -- 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/