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Commit 9b239a12 authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Arnaldo Carvalho de Melo
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perf probe: Show correct source lines of probes on kmodules 



Perf probe always failed to find appropriate line numbers because of
failing to find .text start address offset from debuginfo.

e.g.
  ----
  # ./perf probe -m pcspkr pcspkr_event:5
  Added new events:
    probe:pcspkr_event   (on pcspkr_event:5 in pcspkr)
    probe:pcspkr_event_1 (on pcspkr_event:5 in pcspkr)

  You can now use it in all perf tools, such as:

          perf record -e probe:pcspkr_event_1 -aR sleep 1

  # ./perf probe -l
  Failed to find debug information for address ffffffffa031f006
  Failed to find debug information for address ffffffffa031f016
    probe:pcspkr_event   (on pcspkr_event+6 in pcspkr)
    probe:pcspkr_event_1 (on pcspkr_event+22 in pcspkr)
  ----

This fixes the above issue as below.
1. Get the relative address of the symbol in .text by using
   map->start.
2. Adjust the address by adding the offset of .text section
   in the kernel module binary.

With this fix, perf probe -l shows lines correctly.
  ----
  # ./perf probe -l
    probe:pcspkr_event   (on pcspkr_event:5@drivers/input/misc/pcspkr.c in pcspkr)
    probe:pcspkr_event_1 (on pcspkr_event:5@drivers/input/misc/pcspkr.c in pcspkr)
  ----

Reported-by: default avatarArnaldo Carvalho de Melo <acme@kernel.org>
Signed-off-by: default avatarMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Tested-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/20150930164132.3733.24643.stgit@localhost.localdomain


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 9135949d

tools/perf/util/probe-event.c

+23 −12
Original line number Diff line number Diff line
@@ -137,7 +137,8 @@ static struct ref_reloc_sym *kernel_get_ref_reloc_sym(void) 
	return kmap->ref_reloc_sym;

}



static u64 kernel_get_symbol_address_by_name(const char *name, bool reloc)

static int kernel_get_symbol_address_by_name(const char *name, u64 *addr,

					     bool reloc, bool reladdr)

{

	struct ref_reloc_sym *reloc_sym;

	struct symbol *sym;
@@ -146,12 +147,14 @@ static u64 kernel_get_symbol_address_by_name(const char *name, bool reloc) 
	/* ref_reloc_sym is just a label. Need a special fix*/

	reloc_sym = kernel_get_ref_reloc_sym();

	if (reloc_sym && strcmp(name, reloc_sym->name) == 0)

		return (reloc) ? reloc_sym->addr : reloc_sym->unrelocated_addr;

		*addr = (reloc) ? reloc_sym->addr : reloc_sym->unrelocated_addr;

	else {

		sym = __find_kernel_function_by_name(name, &map);

		if (sym)

			return map->unmap_ip(map, sym->start) -

				((reloc) ? 0 : map->reloc);

		if (!sym)

			return -ENOENT;

		*addr = map->unmap_ip(map, sym->start) -

			((reloc) ? 0 : map->reloc) -

			((reladdr) ? map->start : 0);

	}

	return 0;

}
@@ -245,12 +248,14 @@ static void clear_probe_trace_events(struct probe_trace_event *tevs, int ntevs) 
static bool kprobe_blacklist__listed(unsigned long address);

static bool kprobe_warn_out_range(const char *symbol, unsigned long address)

{

	u64 etext_addr;

	u64 etext_addr = 0;

	int ret;



	/* Get the address of _etext for checking non-probable text symbol */

	etext_addr = kernel_get_symbol_address_by_name("_etext", false);

	ret = kernel_get_symbol_address_by_name("_etext", &etext_addr,

						false, false);



	if (etext_addr != 0 && etext_addr < address)

	if (ret == 0 && etext_addr < address)

		pr_warning("%s is out of .text, skip it.\n", symbol);

	else if (kprobe_blacklist__listed(address))

		pr_warning("%s is blacklisted function, skip it.\n", symbol);
@@ -517,8 +522,10 @@ static int find_perf_probe_point_from_dwarf(struct probe_trace_point *tp, 
			goto error;

		addr += stext;

	} else if (tp->symbol) {

		addr = kernel_get_symbol_address_by_name(tp->symbol, false);

		if (addr == 0)

		/* If the module is given, this returns relative address */

		ret = kernel_get_symbol_address_by_name(tp->symbol, &addr,

							false, !!tp->module);

		if (ret != 0)

			goto error;

		addr += tp->offset;

	}
@@ -1884,8 +1891,12 @@ static int find_perf_probe_point_from_map(struct probe_trace_point *tp, 
			goto out;

		sym = map__find_symbol(map, addr, NULL);

	} else {

		if (tp->symbol)

			addr = kernel_get_symbol_address_by_name(tp->symbol, true);

		if (tp->symbol && !addr) {

			ret = kernel_get_symbol_address_by_name(tp->symbol,

							&addr, true, false);

			if (ret < 0)

				goto out;

		}

		if (addr) {

			addr += tp->offset;

			sym = __find_kernel_function(addr, &map);

tools/perf/util/probe-finder.c

+42 −0
Original line number Diff line number Diff line
@@ -1402,6 +1402,41 @@ int debuginfo__find_available_vars_at(struct debuginfo *dbg, 
	return (ret < 0) ? ret : af.nvls;

}



/* 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 n, i;

	Elf32_Word shndx;

	Elf_Scn *scn;

	Elf *elf;

	GElf_Shdr mem, *shdr;

	const char *p;



	elf = dwfl_module_getelf(dbg->mod, &dbg->bias);

	if (!elf)

		return -EINVAL;



	/* Get the number of relocations */

	n = dwfl_module_relocations(dbg->mod);

	if (n < 0)

		return -ENOENT;

	/* Search the relocation related .text section */

	for (i = 0; i < n; i++) {

		p = dwfl_module_relocation_info(dbg->mod, i, &shndx);

		if (strcmp(p, ".text") == 0) {

			/* OK, get the section header */

			scn = elf_getscn(elf, shndx);

			if (!scn)

				return -ENOENT;

			shdr = gelf_getshdr(scn, &mem);

			if (!shdr)

				return -ENOENT;

			*offs = shdr->sh_addr;

		}

	}

	return 0;

}



/* Reverse search */

int debuginfo__find_probe_point(struct debuginfo *dbg, unsigned long addr,

				struct perf_probe_point *ppt)
@@ -1410,9 +1445,16 @@ int debuginfo__find_probe_point(struct debuginfo *dbg, unsigned long addr, 
	Dwarf_Addr _addr = 0, baseaddr = 0;

	const char *fname = NULL, *func = NULL, *basefunc = NULL, *tmp;

	int baseline = 0, lineno = 0, ret = 0;

	bool reloc = false;



retry:

	/* Find cu die */

	if (!dwarf_addrdie(dbg->dbg, (Dwarf_Addr)addr, &cudie)) {

		if (!reloc && debuginfo__get_text_offset(dbg, &baseaddr) == 0) {

			addr += baseaddr;

			reloc = true;

			goto retry;

		}

		pr_warning("Failed to find debug information for address %lx\n",

			   addr);

		ret = -EINVAL;