linux/tools/perf/arch/powerpc/util/sym-handling.c
Paul Clarke d80406453a perf symbols: Allow user probes on versioned symbols
Symbol versioning, as in glibc, results in symbols being defined as:

  <real symbol>@[@]<version>

(Note that "@@" identifies a default symbol, if the symbol name is
repeated.)

perf is currently unable to deal with this, and is unable to create user
probes at such symbols:

  --
  $ nm /lib/powerpc64le-linux-gnu/libpthread.so.0 | grep pthread_create
  0000000000008d30 t __pthread_create_2_1
  0000000000008d30 T pthread_create@@GLIBC_2.17
  $ /usr/bin/sudo perf probe -v -x /lib/powerpc64le-linux-gnu/libpthread.so.0 pthread_create
  probe-definition(0): pthread_create
  symbol:pthread_create file:(null) line:0 offset:0 return:0 lazy:(null)
  0 arguments
  Open Debuginfo file: /usr/lib/debug/lib/powerpc64le-linux-gnu/libpthread-2.19.so
  Try to find probe point from debuginfo.
  Probe point 'pthread_create' not found.
     Error: Failed to add events. Reason: No such file or directory (Code: -2)
  --

One is not able to specify the fully versioned symbol, either, due to
syntactic conflicts with other uses of "@" by perf:

  --
  $ /usr/bin/sudo perf probe -v -x /lib/powerpc64le-linux-gnu/libpthread.so.0 pthread_create@@GLIBC_2.17
  probe-definition(0): pthread_create@@GLIBC_2.17
  Semantic error :SRC@SRC is not allowed.
  0 arguments
     Error: Command Parse Error. Reason: Invalid argument (Code: -22)
  --

This patch ignores versioning for default symbols, thus allowing probes to be
created for these symbols:

  --
  $ /usr/bin/sudo ./perf probe -x /lib/powerpc64le-linux-gnu/libpthread.so.0 pthread_create
  Added new event:
     probe_libpthread:pthread_create (on pthread_create in /lib/powerpc64le-linux-gnu/libpthread-2.19.so)

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

           perf record -e probe_libpthread:pthread_create -aR sleep 1

  $ /usr/bin/sudo ./perf record -e probe_libpthread:pthread_create -aR ./test 2
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 0.052 MB perf.data (2 samples) ]
  $ /usr/bin/sudo ./perf script
               test  2915 [000] 19124.260729: probe_libpthread:pthread_create: (3fff99248d38)
               test  2916 [000] 19124.260962: probe_libpthread:pthread_create: (3fff99248d38)
  $ /usr/bin/sudo ./perf probe --del=probe_libpthread:pthread_create
  Removed event: probe_libpthread:pthread_create
  --

Committer note:

Change the variable storing the result of strlen() to 'int', to fix the build
on debian:experimental-x-mipsel, fedora:24-x-ARC-uClibc, ubuntu:16.04-x-arm,
etc:

  util/symbol.c: In function 'symbol__match_symbol_name':
  util/symbol.c:422:11: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
     if (len < versioning - name)
             ^

Signed-off-by: Paul A. Clarke <pc@us.ibm.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Link: http://lkml.kernel.org/r/c2b18d9c-17f8-9285-4868-f58b6359ccac@us.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2017-05-02 18:23:11 -03:00

144 lines
3.3 KiB
C

/*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License, version 2, as
* published by the Free Software Foundation.
*
* Copyright (C) 2015 Naveen N. Rao, IBM Corporation
*/
#include "debug.h"
#include "symbol.h"
#include "map.h"
#include "probe-event.h"
#include "probe-file.h"
#ifdef HAVE_LIBELF_SUPPORT
bool elf__needs_adjust_symbols(GElf_Ehdr ehdr)
{
return ehdr.e_type == ET_EXEC ||
ehdr.e_type == ET_REL ||
ehdr.e_type == ET_DYN;
}
#endif
#if !defined(_CALL_ELF) || _CALL_ELF != 2
int arch__choose_best_symbol(struct symbol *syma,
struct symbol *symb __maybe_unused)
{
char *sym = syma->name;
/* Skip over any initial dot */
if (*sym == '.')
sym++;
/* Avoid "SyS" kernel syscall aliases */
if (strlen(sym) >= 3 && !strncmp(sym, "SyS", 3))
return SYMBOL_B;
if (strlen(sym) >= 10 && !strncmp(sym, "compat_SyS", 10))
return SYMBOL_B;
return SYMBOL_A;
}
/* Allow matching against dot variants */
int arch__compare_symbol_names(const char *namea, const char *nameb)
{
/* Skip over initial dot */
if (*namea == '.')
namea++;
if (*nameb == '.')
nameb++;
return strcmp(namea, nameb);
}
int arch__compare_symbol_names_n(const char *namea, const char *nameb,
unsigned int n)
{
/* Skip over initial dot */
if (*namea == '.')
namea++;
if (*nameb == '.')
nameb++;
return strncmp(namea, nameb, n);
}
#endif
#if defined(_CALL_ELF) && _CALL_ELF == 2
#ifdef HAVE_LIBELF_SUPPORT
void arch__sym_update(struct symbol *s, GElf_Sym *sym)
{
s->arch_sym = sym->st_other;
}
#endif
#define PPC64LE_LEP_OFFSET 8
void arch__fix_tev_from_maps(struct perf_probe_event *pev,
struct probe_trace_event *tev, struct map *map,
struct symbol *sym)
{
int lep_offset;
/*
* When probing at a function entry point, we normally always want the
* LEP since that catches calls to the function through both the GEP and
* the LEP. Hence, we would like to probe at an offset of 8 bytes if
* the user only specified the function entry.
*
* However, if the user specifies an offset, we fall back to using the
* GEP since all userspace applications (objdump/readelf) show function
* disassembly with offsets from the GEP.
*/
if (pev->point.offset || !map || !sym)
return;
/* For kretprobes, add an offset only if the kernel supports it */
if (!pev->uprobes && pev->point.retprobe) {
#ifdef HAVE_LIBELF_SUPPORT
if (!kretprobe_offset_is_supported())
#endif
return;
}
lep_offset = PPC64_LOCAL_ENTRY_OFFSET(sym->arch_sym);
if (map->dso->symtab_type == DSO_BINARY_TYPE__KALLSYMS)
tev->point.offset += PPC64LE_LEP_OFFSET;
else if (lep_offset) {
if (pev->uprobes)
tev->point.address += lep_offset;
else
tev->point.offset += lep_offset;
}
}
#ifdef HAVE_LIBELF_SUPPORT
void arch__post_process_probe_trace_events(struct perf_probe_event *pev,
int ntevs)
{
struct probe_trace_event *tev;
struct map *map;
struct symbol *sym = NULL;
struct rb_node *tmp;
int i = 0;
map = get_target_map(pev->target, pev->uprobes);
if (!map || map__load(map) < 0)
return;
for (i = 0; i < ntevs; i++) {
tev = &pev->tevs[i];
map__for_each_symbol(map, sym, tmp) {
if (map->unmap_ip(map, sym->start) == tev->point.address)
arch__fix_tev_from_maps(pev, tev, map, sym);
}
}
}
#endif /* HAVE_LIBELF_SUPPORT */
#endif