From da15bd9df4afd2f9f78cf29f85f013e3a38402b5 Mon Sep 17 00:00:00 2001 From: Wang Nan Date: Wed, 26 Aug 2015 10:57:45 +0000 Subject: [PATCH] perf probe: Support probing at absolute address 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. v1 -> v2: Drop the leading '+' in cmdline; Allow uprobing at offset 0x0; Improve 'perf probe -l' result when uprobe at area without debuginfo. v2 -> v3: Split bugfix to a separated patch. Test result: # perf probe 0xffffffff8119d175 %ax # perf probe sys_write %ax # perf probe /lib64/libc-2.18.so 0x0 %ax # perf probe /lib64/libc-2.18.so 0x5 %ax # perf probe /lib64/libc-2.18.so 0xd8e40 %ax # perf probe /lib64/libc-2.18.so __write %ax # perf probe /lib64/libc-2.18.so 0xd8e49 %ax # cat /sys/kernel/debug/tracing/uprobe_events p:probe_libc/abs_0 /lib64/libc-2.18.so:0x (null) arg1=%ax p:probe_libc/abs_5 /lib64/libc-2.18.so:0x0000000000000005 arg1=%ax p:probe_libc/abs_d8e40 /lib64/libc-2.18.so:0x00000000000d8e40 arg1=%ax p:probe_libc/__write /lib64/libc-2.18.so:0x00000000000d8e40 arg1=%ax p:probe_libc/abs_d8e49 /lib64/libc-2.18.so:0x00000000000d8e49 arg1=%ax # cat /sys/kernel/debug/tracing/kprobe_events p:probe/abs_ffffffff8119d175 0xffffffff8119d175 arg1=%ax p:probe/sys_write _text+1692016 arg1=%ax # perf probe -l Failed to find debug information for address 5 probe:abs_ffffffff8119d175 (on sys_write+5 with arg1) probe:sys_write (on sys_write with arg1) probe_libc:__write (on @unix/syscall-template.S:81 in /lib64/libc-2.18.so with arg1) probe_libc:abs_0 (on 0x0 in /lib64/libc-2.18.so with arg1) probe_libc:abs_5 (on 0x5 in /lib64/libc-2.18.so with arg1) probe_libc:abs_d8e40 (on @unix/syscall-template.S:81 in /lib64/libc-2.18.so with arg1) probe_libc:abs_d8e49 (on __GI___libc_write+9 in /lib64/libc-2.18.so with arg1) Signed-off-by: Wang Nan Acked-by: Masami Hiramatsu Cc: Namhyung Kim Cc: Steven Rostedt Cc: Zefan Li Cc: pi3orama@163.com Link: http://lkml.kernel.org/r/1440586666-235233-7-git-send-email-wangnan0@huawei.com Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/probe-event.c | 162 +++++++++++++++++++++++++++++++-- tools/perf/util/probe-event.h | 4 + tools/perf/util/probe-finder.c | 21 +---- 3 files changed, 163 insertions(+), 24 deletions(-) diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c index eaacb58b9b36..eb5f18b75402 100644 --- a/tools/perf/util/probe-event.c +++ b/tools/perf/util/probe-event.c @@ -1204,9 +1204,27 @@ static int parse_perf_probe_point(char *arg, struct perf_probe_event *pev) if (file_spec) pp->file = tmp; - else + else { pp->function = tmp; + /* + * Keep pp->function even if this is absolute address, + * so it can mark whether abs_address is valid. + * Which make 'perf probe lib.bin 0x0' possible. + * + * Note that checking length of tmp is not needed + * because when we access tmp[1] we know tmp[0] is '0', + * so tmp[1] should always valid (but could be '\0'). + */ + if (tmp && !strncmp(tmp, "0x", 2)) { + pp->abs_address = strtoul(pp->function, &tmp, 0); + if (*tmp != '\0') { + semantic_error("Invalid absolute address.\n"); + return -EINVAL; + } + } + } + /* Parse other options */ while (ptr) { arg = ptr; @@ -1804,14 +1822,29 @@ char *synthesize_probe_trace_command(struct probe_trace_event *tev) if (len <= 0) goto error; - /* Uprobes must have tp->address and tp->module */ - if (tev->uprobes && (!tp->address || !tp->module)) + /* Uprobes must have tp->module */ + if (tev->uprobes && !tp->module) goto error; + /* + * If tp->address == 0, then this point must be a + * absolute address uprobe. + * try_to_find_absolute_address() should have made + * tp->symbol to "0x0". + */ + if (tev->uprobes && !tp->address) { + if (!tp->symbol || strcmp(tp->symbol, "0x0")) + goto error; + } /* Use the tp->address for uprobes */ if (tev->uprobes) ret = e_snprintf(buf + len, MAX_CMDLEN - len, "%s:0x%lx", tp->module, tp->address); + else if (!strncmp(tp->symbol, "0x", 2)) + /* 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 ? ":" : "", @@ -1874,8 +1907,8 @@ out: } static int convert_to_perf_probe_point(struct probe_trace_point *tp, - struct perf_probe_point *pp, - bool is_kprobe) + struct perf_probe_point *pp, + bool is_kprobe) { char buf[128]; int ret; @@ -2331,7 +2364,9 @@ static int probe_trace_event__set_name(struct probe_trace_event *tev, if (pev->event) event = pev->event; else - if (pev->point.function && !strisglob(pev->point.function)) + if (pev->point.function && + (strncmp(pev->point.function, "0x", 2) != 0) && + !strisglob(pev->point.function)) event = pev->point.function; else event = tev->point.realname; @@ -2598,6 +2633,98 @@ 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 (!(pev->point.function && !strncmp(pev->point.function, "0x", 2))) + return -EINVAL; + if (perf_probe_event_need_dwarf(pev)) + 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.abs_address; + tp->retprobe = pp->retprobe; + tev->uprobes = pev->uprobes; + + err = -ENOMEM; + /* + * Give it a '0x' leading symbol name. + * In __add_probe_trace_events, a NULL symbol is interpreted as + * invalud. + */ + 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; + tev->args = zalloc(sizeof(struct probe_trace_arg) * tev->nargs); + if (!tev->args) { + err = -ENOMEM; + goto errout; + } + 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, @@ -2614,6 +2741,10 @@ 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) @@ -2784,3 +2915,22 @@ 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 83ee95e9743b..6e7ec68a4aa8 100644 --- a/tools/perf/util/probe-event.h +++ b/tools/perf/util/probe-event.h @@ -59,6 +59,7 @@ struct perf_probe_point { bool retprobe; /* Return probe flag */ char *lazy_line; /* Lazy matching pattern */ unsigned long offset; /* Offset from function entry */ + unsigned long abs_address; /* Absolute address of the point */ }; /* Perf probe probing argument field chain */ @@ -156,4 +157,7 @@ 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 7b80f8cb62b9..29c43c0680a8 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); -- 2.30.2