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[PATCH perf/core 0/4] perf-probe: Fix and improve module probe events

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  [PATCH perf/core 0/4] perf-probe: Fix and improve module probe events Masami Hiramatsu <mhiramat@kernel.org> - 2017-01-07 06:30 +0100
    [PATCH perf/core 3/4] perf-probe: Fix to probe on gcc generated functions in modules Masami Hiramatsu <mhiramat@kernel.org> - 2017-01-07 06:30 +0100
    [PATCH perf/core 4/4] perf-probe: Find probe events without target module Masami Hiramatsu <mhiramat@kernel.org> - 2017-01-07 06:30 +0100
      Re: [PATCH perf/core 4/4] perf-probe: Find probe events without  target module Masami Hiramatsu <mhiramat@kernel.org> - 2017-01-10 17:00 +0100

#1553589 — [PATCH perf/core 0/4] perf-probe: Fix and improve module probe events

Hello,

This series fixes some issues on offline/online module
probe support and improve perf-probe to probe module
without -m option (Thanks Arnaldo!).
This includes below patches.

 - [1/4] Fix perf-probe --list to show correct probe location
         in module.
 - [2/4] Improve error checking for the probes for offline
         kernel.
 - [3/4] (V2) Fix perf-probe to probe correctly on gcc generated
         functions in module.
 - [4/4] Improve perf-probe to find probe events in module
         without -m option.

Thank you,

---

Masami Hiramatsu (4):
      perf-probe: Fix to show correct locations for events on modules
      perf-probe: Add error checks to offline probe post-processing
      perf-probe: Fix to probe on gcc generated functions in modules
      perf-probe: Find probe events without target module


 tools/perf/util/probe-event.c  |  165 ++++++++++++++++++++++++++++------------
 tools/perf/util/probe-finder.c |   15 ++--
 tools/perf/util/probe-finder.h |    3 +
 3 files changed, 125 insertions(+), 58 deletions(-)

--
Masami Hiramatsu (Linaro)

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#1553590 — [PATCH perf/core 3/4] perf-probe: Fix to probe on gcc generated functions in modules

Fix to probe on gcc generated functions on modules. Since
probing on a module is based on its symbol name, it should
be adjusted on actual symbols.

E.g. without this fix, perf probe shows probe definition
on non-exist symbol as below.

  $ perf probe -m build-x86_64/net/netfilter/nf_nat.ko -F in_range*
  in_range.isra.12
  $ perf probe -m build-x86_64/net/netfilter/nf_nat.ko -D in_range
  p:probe/in_range nf_nat:in_range+0

With this fix, perf probe correctly shows a probe on
gcc-generated symbol.

  $ perf probe -m build-x86_64/net/netfilter/nf_nat.ko -D in_range
  p:probe/in_range nf_nat:in_range.isra.12+0

This also fixes same problem on online module as below.

  $ perf probe -m i915 -D assert_plane
  p:probe/assert_plane i915:assert_plane.constprop.134+0

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 tools/perf/util/probe-event.c  |   45 ++++++++++++++++++++++++++--------------
 tools/perf/util/probe-finder.c |    7 ++++--
 tools/perf/util/probe-finder.h |    3 +++
 3 files changed, 37 insertions(+), 18 deletions(-)

diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index aa8a922..6a6f44d 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -698,18 +698,31 @@ static int add_exec_to_probe_trace_events(struct probe_trace_event *tevs,
 	return ret;
 }
 
-static int add_module_to_probe_trace_events(struct probe_trace_event *tevs,
-					    int ntevs, const char *module)
+static int
+post_process_module_probe_trace_events(struct probe_trace_event *tevs,
+				       int ntevs, const char *module,
+				       struct debuginfo *dinfo)
 {
+	Dwarf_Addr text_offs = 0;
 	int i, ret = 0;
 	char *mod_name = NULL;
+	struct map *map;
 
 	if (!module)
 		return 0;
 
-	mod_name = find_module_name(module);
+	map = get_target_map(module, false);
+	if (!map || debuginfo__get_text_offset(dinfo, &text_offs, true) < 0) {
+		pr_warning("Failed to get ELF symbols for %s\n", module);
+		return -EINVAL;
+	}
 
+	mod_name = find_module_name(module);
 	for (i = 0; i < ntevs; i++) {
+		ret = post_process_probe_trace_point(&tevs[i].point,
+						map, (unsigned long)text_offs);
+		if (ret < 0)
+			break;
 		tevs[i].point.module =
 			strdup(mod_name ? mod_name : module);
 		if (!tevs[i].point.module) {
@@ -719,6 +732,8 @@ static int add_module_to_probe_trace_events(struct probe_trace_event *tevs,
 	}
 
 	free(mod_name);
+	map__put(map);
+
 	return ret;
 }
 
@@ -776,7 +791,7 @@ arch__post_process_probe_trace_events(struct perf_probe_event *pev __maybe_unuse
 static int post_process_probe_trace_events(struct perf_probe_event *pev,
 					   struct probe_trace_event *tevs,
 					   int ntevs, const char *module,
-					   bool uprobe)
+					   bool uprobe, struct debuginfo *dinfo)
 {
 	int ret;
 
@@ -784,7 +799,8 @@ static int post_process_probe_trace_events(struct perf_probe_event *pev,
 		ret = add_exec_to_probe_trace_events(tevs, ntevs, module);
 	else if (module)
 		/* Currently ref_reloc_sym based probe is not for drivers */
-		ret = add_module_to_probe_trace_events(tevs, ntevs, module);
+		ret = post_process_module_probe_trace_events(tevs, ntevs,
+							     module, dinfo);
 	else
 		ret = post_process_kernel_probe_trace_events(tevs, ntevs);
 
@@ -828,30 +844,27 @@ static int try_to_find_probe_trace_events(struct perf_probe_event *pev,
 		}
 	}
 
-	debuginfo__delete(dinfo);
-
 	if (ntevs > 0) {	/* Succeeded to find trace events */
 		pr_debug("Found %d probe_trace_events.\n", ntevs);
 		ret = post_process_probe_trace_events(pev, *tevs, ntevs,
-						pev->target, pev->uprobes);
+					pev->target, pev->uprobes, dinfo);
 		if (ret < 0 || ret == ntevs) {
+			pr_debug("Post processing failed or all events are skipped. (%d)\n", ret);
 			clear_probe_trace_events(*tevs, ntevs);
 			zfree(tevs);
+			ntevs = 0;
 		}
-		if (ret != ntevs)
-			return ret < 0 ? ret : ntevs;
-		ntevs = 0;
-		/* Fall through */
 	}
 
+	debuginfo__delete(dinfo);
+
 	if (ntevs == 0)	{	/* No error but failed to find probe point. */
 		pr_warning("Probe point '%s' not found.\n",
 			   synthesize_perf_probe_point(&pev->point));
 		return -ENOENT;
-	}
-	/* Error path : ntevs < 0 */
-	pr_debug("An error occurred in debuginfo analysis (%d).\n", ntevs);
-	if (ntevs < 0) {
+	} else if (ntevs < 0) {
+		/* Error path : ntevs < 0 */
+		pr_debug("An error occurred in debuginfo analysis (%d).\n", ntevs);
 		if (ntevs == -EBADF)
 			pr_warning("Warning: No dwarf info found in the vmlinux - "
 				"please rebuild kernel with CONFIG_DEBUG_INFO=y.\n");
diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 0278fe1..0d9d6e0 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -1501,7 +1501,8 @@ int debuginfo__find_available_vars_at(struct debuginfo *dbg,
 }
 
 /* For the kernel module, we need a special code to get a DIE */
-static int debuginfo__get_text_offset(struct debuginfo *dbg, Dwarf_Addr *offs)
+int debuginfo__get_text_offset(struct debuginfo *dbg, Dwarf_Addr *offs,
+				bool adjust_offset)
 {
 	int n, i;
 	Elf32_Word shndx;
@@ -1530,6 +1531,8 @@ static int debuginfo__get_text_offset(struct debuginfo *dbg, Dwarf_Addr *offs)
 			if (!shdr)
 				return -ENOENT;
 			*offs = shdr->sh_addr;
+			if (adjust_offset)
+				*offs -= shdr->sh_offset;
 		}
 	}
 	return 0;
@@ -1545,7 +1548,7 @@ int debuginfo__find_probe_point(struct debuginfo *dbg, unsigned long addr,
 	int baseline = 0, lineno = 0, ret = 0;
 
 	/* We always need to relocate the address for aranges */
-	if (debuginfo__get_text_offset(dbg, &baseaddr) == 0)
+	if (debuginfo__get_text_offset(dbg, &baseaddr, false) == 0)
 		addr += baseaddr;
 	/* Find cu die */
 	if (!dwarf_addrdie(dbg->dbg, (Dwarf_Addr)addr, &cudie)) {
diff --git a/tools/perf/util/probe-finder.h b/tools/perf/util/probe-finder.h
index f1d8558..2956c51 100644
--- a/tools/perf/util/probe-finder.h
+++ b/tools/perf/util/probe-finder.h
@@ -46,6 +46,9 @@ int debuginfo__find_trace_events(struct debuginfo *dbg,
 int debuginfo__find_probe_point(struct debuginfo *dbg, unsigned long addr,
 				struct perf_probe_point *ppt);
 
+int debuginfo__get_text_offset(struct debuginfo *dbg, Dwarf_Addr *offs,
+			       bool adjust_offset);
+
 /* Find a line range */
 int debuginfo__find_line_range(struct debuginfo *dbg, struct line_range *lr);
 

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#1553591 — [PATCH perf/core 4/4] perf-probe: Find probe events without target module

Find probe events without -m "module" option. If perf-probe
failed to find given function in kernel image, it tries to
find same symbol and module in kallsyms, and retry search
in the found module. E.g.

  # perf probe -D i915_capabilities
  p:probe/i915_capabilities i915:i915_capabilities+0

Note: without -m option, perf probe can not find inlined
function since there is no symbol information in kallsyms.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Suggested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/probe-event.c |   74 ++++++++++++++++++++++++++++++-----------
 1 file changed, 55 insertions(+), 19 deletions(-)

diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index 6a6f44d..09bd093 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -858,11 +858,7 @@ static int try_to_find_probe_trace_events(struct perf_probe_event *pev,
 
 	debuginfo__delete(dinfo);
 
-	if (ntevs == 0)	{	/* No error but failed to find probe point. */
-		pr_warning("Probe point '%s' not found.\n",
-			   synthesize_perf_probe_point(&pev->point));
-		return -ENOENT;
-	} else if (ntevs < 0) {
+	if (ntevs < 0) {
 		/* Error path : ntevs < 0 */
 		pr_debug("An error occurred in debuginfo analysis (%d).\n", ntevs);
 		if (ntevs == -EBADF)
@@ -2073,8 +2069,10 @@ static int find_perf_probe_point_from_map(struct probe_trace_point *tp,
 	} else {
 		if (tp->symbol && !addr) {
 			if (kernel_get_symbol_address_by_name(tp->symbol,
-						&addr, true, false) < 0)
+						&addr, true, false) < 0) {
+				ret = 0;
 				goto out;
+			}
 		}
 		if (addr) {
 			addr += tp->offset;
@@ -2829,9 +2827,7 @@ static int find_probe_trace_events_from_map(struct perf_probe_event *pev,
 	 */
 	num_matched_functions = find_probe_functions(map, pp->function, syms);
 	if (num_matched_functions == 0) {
-		pr_err("Failed to find symbol %s in %s\n", pp->function,
-			pev->target ? : "kernel");
-		ret = -ENOENT;
+		ret = 0;
 		goto out;
 	} else if (num_matched_functions > probe_conf.max_probes) {
 		pr_err("Too many functions matched in %s\n",
@@ -3233,6 +3229,43 @@ static int find_probe_trace_events_from_cache(struct perf_probe_event *pev,
 	return ret;
 }
 
+static int __convert_to_probe_trace_events(struct perf_probe_event *pev,
+					   struct probe_trace_event **tevs)
+{
+	int ret;
+
+	/* At first, we need to lookup cache entry */
+	ret = find_probe_trace_events_from_cache(pev, tevs);
+	if (ret > 0 || pev->sdt)	/* SDT can be found only in the cache */
+		return ret == 0 ? -ENOENT : ret; /* Found in probe cache */
+
+	/* Convert perf_probe_event with debuginfo */
+	ret = try_to_find_probe_trace_events(pev, tevs);
+	if (ret != 0)
+		return ret;	/* Found in debuginfo or got an error */
+
+	return find_probe_trace_events_from_map(pev, tevs);
+}
+
+static char *find_module_from_kallsyms(const char *symbol_name)
+{
+	struct machine *machine = machine__new_kallsyms();
+	struct symbol *sym;
+	struct map *map;
+	char *module;
+
+	pr_debug("Try to find module for %s\n", symbol_name);
+	sym = machine__find_kernel_function_by_name(machine, symbol_name, &map);
+	if (!sym || map->dso->short_name[0] != '[')
+		return NULL;
+	pr_debug("Found: %s in %s\n", sym->name, map->dso->short_name);
+	module = strdup(map->dso->short_name + 1);
+	if (module)
+		module[strlen(module) - 1] = '\0';
+
+	return module;
+}
+
 static int convert_to_probe_trace_events(struct perf_probe_event *pev,
 					 struct probe_trace_event **tevs)
 {
@@ -3255,17 +3288,20 @@ static int convert_to_probe_trace_events(struct perf_probe_event *pev,
 	if (ret > 0)
 		return ret;
 
-	/* At first, we need to lookup cache entry */
-	ret = find_probe_trace_events_from_cache(pev, tevs);
-	if (ret > 0 || pev->sdt)	/* SDT can be found only in the cache */
-		return ret == 0 ? -ENOENT : ret; /* Found in probe cache */
-
-	/* Convert perf_probe_event with debuginfo */
-	ret = try_to_find_probe_trace_events(pev, tevs);
-	if (ret != 0)
-		return ret;	/* Found in debuginfo or got an error */
+	ret = __convert_to_probe_trace_events(pev, tevs);
+	/* Not found. will retry to check kmodule if possible */
+	if (ret == 0 && !pev->uprobes && !pev->target) {
+		pev->target = find_module_from_kallsyms(pev->point.function);
+		if (pev->target)
+			ret = __convert_to_probe_trace_events(pev, tevs);
+	}
 
-	return find_probe_trace_events_from_map(pev, tevs);
+	if (ret == 0) {
+		pr_warning("Probe point '%s' not found.\n",
+			   synthesize_perf_probe_point(&pev->point));
+		ret = -ENOENT;
+	}
+	return ret;
 }
 
 int convert_perf_probe_events(struct perf_probe_event *pevs, int npevs)

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#1555642 — Re: [PATCH perf/core 4/4] perf-probe: Find probe events without target module

On Sat,  7 Jan 2017 14:28:42 +0900
Masami Hiramatsu <mhiramat@kernel.org> wrote:

> Find probe events without -m "module" option. If perf-probe
> failed to find given function in kernel image, it tries to
> find same symbol and module in kallsyms, and retry search
> in the found module. E.g.
> 
>   # perf probe -D i915_capabilities
>   p:probe/i915_capabilities i915:i915_capabilities+0
> 
> Note: without -m option, perf probe can not find inlined
> function since there is no symbol information in kallsyms.
> 
> Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
> Suggested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
> ---
>  tools/perf/util/probe-event.c |   74 ++++++++++++++++++++++++++++++-----------
>  1 file changed, 55 insertions(+), 19 deletions(-)
> 
> diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
> index 6a6f44d..09bd093 100644
> --- a/tools/perf/util/probe-event.c
> +++ b/tools/perf/util/probe-event.c
> @@ -858,11 +858,7 @@ static int try_to_find_probe_trace_events(struct perf_probe_event *pev,
>  
>  	debuginfo__delete(dinfo);
>  
> -	if (ntevs == 0)	{	/* No error but failed to find probe point. */
> -		pr_warning("Probe point '%s' not found.\n",
> -			   synthesize_perf_probe_point(&pev->point));
> -		return -ENOENT;
> -	} else if (ntevs < 0) {
> +	if (ntevs < 0) {
>  		/* Error path : ntevs < 0 */
>  		pr_debug("An error occurred in debuginfo analysis (%d).\n", ntevs);
>  		if (ntevs == -EBADF)
> @@ -2073,8 +2069,10 @@ static int find_perf_probe_point_from_map(struct probe_trace_point *tp,
>  	} else {
>  		if (tp->symbol && !addr) {
>  			if (kernel_get_symbol_address_by_name(tp->symbol,
> -						&addr, true, false) < 0)
> +						&addr, true, false) < 0) {
> +				ret = 0;
>  				goto out;

Oops, I've found that this is not needed and breaks --list result.
I'll update it.

Thanks.


-- 
Masami Hiramatsu <mhiramat@kernel.org>

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