lkml.org 
[lkml]   [2015]   [Aug]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 2/2] perf probe: Support probing at absolute address
    Date
    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

    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 <wangnan0@huawei.com>
    Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
    Cc: Ingo Molnar <mingo@redhat.com>
    Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
    Cc: Namhyung Kim <namhyung@kernel.org>
    ---
    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


    \
     
     \ /
      Last update: 2015-08-25 15:41    [W:4.189 / U:0.052 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site